6 M&E Equipment and Hydraulic Steel Structures

Contents

6 M&E Equipment and Hydraulic Steel Structures ................................................. 6-1

6.1 Hydraulic Machinery ........................................................................................... 6-1

6.2 Main Electric Equipment and Main Electrical Connection ............................... 6-27

6.3 Control, Protection and Instrumentation ............................................................ 6-85

6.4 Hydraulic Steel Structures ................................................................................. 6-96

6.5 Ventilation and Air Conditioning .................................................................... 6-123

6.6 Fire Protection Design ..................................................................................... 6-132

6-1

6 M&E Equipment and Hydraulic Steel Structures

6.1 Hydraulic Machinery

The Paklay Hydropower project (HPP) lies on the junction of Sayaboury Province and

Vientiane Province in Laos, about 50 km away from the border of Thailand. Main function

of the HPP is power generation, followed by development assignment for comprehensive

utilization such as ship transport and fishery. The Paklay HPP has a normal pool level of

240.00 m a.s.l. with a corresponding storage of 890.1 million m3 and a minimum pool level

of 239.00 m a.s.l. with a regulating storage of 58.4 million m3. The HPP has a design

installed capacity of 770 MW, average annual energy output of 4124.8 GW·h, and annual

operating hours of installed capacity of 5,357 h. A small portion of electrical power is

supplied to Laos, and the other portion is supplied to Thailand.

6.1.1 HPP Basic Parameters

a) Upstream water level

Check flood level (0.01%) 240.23 m a.s.l.

Design flood level (0.05%) 238.86 m a.s.l.

Normal pool level 240.00 m a.s.l.

Minimum pool level 239.00 m a.s.l.

b) Tail water level

Check flood level (0.01%) 236.49 m a.s.l.

Design flood level (0.05%) 235.50 m a.s.l.

Tail water level (whole plant in full load) (Q=6101.2m3/s) 224.14 m a.s.l.

c) Hydroenergy

Installed capacity 770 MW

Average annual energy output 4124.8 GW·h

Annual operating hours 5357 h

d) Turbine net head

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Maximum (gross) head 20.00 m

Rated head 14.50 m

Weighted average head 15.9 m

Minimum (gross) head 7.5 m

e) Discharge

Average annual discharge 4100 m3/s

f) Sediment data

Average annual sediment concentration 509 g/m3

6.1.2 Selection of Rated Head

The Paklay HPP has the low head and large discharge, with a reservoir drawdown

depth of only 1 m and relatively small change in reservoir water level. The power

generation head of the HPP is closely related to the change of downstream water level. The

Sanakham HPP is the downstream connection cascade of the Paklay HPP, with a normal

pool level of 220.00 m a.s.l., connecting with the normal pool level of the Paklay HPP. In

view of impact from backwater jacking of the Sanakham HPP, change of the downstream

water level of the Paklay HPP dramatically reduces. The power generation head of the

Paklay HPP mainly ranges from 14.00 m to 18.00 m. The head duration of this range is

about 80% of the total duration. The Paklay HPP is a low-head hydropower project with a

relatively poor regulating performance. Low head generally occurs in the flood period.

Therefore, if the selected rated head is too high, the output of the Paklay HPP will be

decreased dramatically in the flood period. According to simulation results of power

generation operation of the HPP, in flood season, the reservoir water level of the Paklay

HPP is basically kept at the normal pool level, with a head about of 15.50 m corresponding

to power generation at full load. Therefore, in this stage, under the premise that power

generation at full load will not be disabled at the normal pool level, the disabled probability

and capacity in flood season shall be as less as possible. The rated head of the HPP is

selected at 14.50 m based on a head dependability of about 88%.

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6.1.3 Selection of Turbine Type

The head range of the HPP is 7.5 m ~ 20.0 m, and the turbine types suitable for this

head range are axial flow turbine and the tubular turbine. The tubular turbine consists of

shaft-extension tubular turbine, pit turbine, bulb turbine and straight flow turbine. The

shaft-extension tubular turbine is suitable for the HPP with a runner diameter less than 3 m.

The pit turbine is only applicable to the HPP with low head and small capacity, with a

maximum unit capacity of 3,000 kW and runner diameter of 3 m. The straight flow turbine

has an extra high requirement for the sealing technology; therefore, it is only applied to the

small HPPs. The HPP has a medium unit capacity and a runner diameter about of 6.90 m;

therefore, the bulb turbines and axial flow turbines are selected for comparison. According

to the installed capacity of the HPP, two alternatives are preliminarily proposed for

comparison, i.e., fourteen 55 MW bulb turbines and eight 96.25 MW Kaplan turbines.

Main parameters of the above two alternatives are listed in the following table.

Table 6.1-1 Comparison of Turbine Types

Description Bulb Turbine Axial Flow Turbine Difference

Turbine model GZ-WP-690 ZZ-LH-1020

Rated output of turbine (MW) 56.4 98.7

Runner diameter (m) 6.90 10.20

Rated speed (r/min) 93.75 62.5

Rated discharge (m3/s) 435.8 788.6

Unit discharge (m3/s) 2.404 1.99

Efficiency at rated point (%) 91.0 88.0%

Specific speed (m·kW) 787 694

Specific speed coefficient 2997 2643

Weight of a single turbine (t) 756 1550

Weight of a single generator (t) 460 1150

Weight of a single unit (t) 1216 2700

Total weight of all units (t) 17024 21600 -4576

Setting elevation (m) 208.5 217.0 -8.5

Elevation of draft tube base

plate (m) 203.0 186.4 16.6

Clear length of powerhouse (m) 391.0 364.0 27

6-4

Description Bulb Turbine Axial Flow Turbine Difference

Clear width of powerhouse (m) 21.0 31.2 -10.2

Compared with the axial flow turbine, for this project the bulb turbine has advantages

as follows:

a) High efficiency. The bulb turbine has a straight and smooth water passage, with

relatively well-distributed flow fields; therefore, its hydraulic efficiency is relatively high

and its high efficiency area is flat and wide. Optimum efficiency of a bulb turbine model is

about over 1% higher than that of an axial flow turbine model, with HPP weighted average

efficiency about 2% ~ 3% higher.

b) High unit parameter level of turbine. The discharge capacity of a bulb turbine is

greater than that of an axial flow turbine. The unit discharge of the bulb turbine adopted by

the HPP is about 20% higher than that of an axial flow turbine, with specific speed and

specific speed coefficient about 13% higher.

c) Less investment on M & E equipment. Because a bulb turbine has advantages of

high parameter level, high speed, small size, and light weight, total weight of all units in

the plant of bulb turbine alternative is 4,576 t less than that of the axial flow turbine

alternative.

d) Less investment on civil works. If the axial flow turbine alternative is adopted,

length of the powerhouse can be reduced, which is in favor of project layout. However, the

clear width of the powerhouse will be about 50% greater than that of the bulb turbine

alternative and clear plane size of the powerhouse will be about 40% greater than that of

the bulb turbine alternative. Although the setting elevation of a bulb turbine is lower than

that of an axial flow turbine, its draft tube is arranged horizontally and no elbow draft tube

is provided, thus the elevation of draft tube base plate is 16.6 m higher than that of an axial

flow turbine. In this way, the bulb turbine alternative has dramatically less foundation

excavation works. Generally speaking, the bulb turbine alternative can reduce foundation

excavation works and control dimensions of the powerhouse, so as to reduce investment on

civil works.

e) Shorter construction period. Because the bulb turbine alternative has no

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construction of curved passages such as a spiral case and elbow draft tube, its civil

construction period can be shortened. In addition, after the main shaft is installed, the

turbine and the generator can be installed at the same time, which further reduces the

construction period of the HPP.

f) In favor of design of system connection and main electrical connection.

According to the design requirement of grid connection, about 100 MW capacity of the

HPP will supply power to Laos, and the other capacity will supply power to Thailand.

In addition, national power grids of Laos and Thailand are not connected for operation.

For the alternative of fourteen 55 MW bulb turbines, the scheme of output of 12 units

being transmitted to Thailand and that of 2 units to Laos can be adopted. For the

alternative of eight 96.25 MW Kaplan turbines, the scheme of output of 7 units being

transmitted to Thailand and that of 1 unit to Laos can be adopted. In the latter case,

when the unit to supply power to Laos is in maintenance, the HPP cannot supply power

to the Laos power grid, which would affect the power grid greatly.

According to Electrical-Mechanical Design Code of Hydropower Plants (DL/T

5186-2004), tubular turbines should be preferably for a run-of-river hydroelectric plant

with a maximum head less than 20 m.

In conclusion, for this project, the bulb turbine has advantages of high efficiency, high

parameter level, less investment on M & E equipment and civil works, shorter construction

period, being in favor of design of system connection and main electrical connection, etc.

Therefore, it is recommended to select the bulb turbine.

6.1.4 Selection of Turbine Model Parameters

a) Selection of specific speed

Both specific speed and specific speed coefficient of a turbine are the aggregative

indexes for turbine technical parameters. High specific speed and specific speed coefficient

can reduce size of the units and powerhouses and investment, which will enhance

economic benefit of the HPP. However, improvement of the specific speed and specific

speed coefficient is limited by turbine strength, cavitation performance, sediment abrasion,

operational stability and others. To meet safe and reliable operation of a unit, both specific

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speed and specific speed coefficient should be controlled within a rational and practicable

range based on practice; namely, specific speed and specific speed coefficient should not

be set too high.

See Table 6.1-2 for the rated specific speed and specific speed coefficient (K) of a

turbine calculated by the relevant statistical formula. See Table 6.1-3 for the specific speed

and specific speed coefficient of some bulb turbines put into operation, with similar head

section as that of the HPP.

Table 6.1-2 Computation Sheet for Specific Speed and Specific Speed Coefficient

(K)

Common Statistical Formula Specific Speed ns(m-kW)

ns=(2700~3100)/H0.5 709~814 2700~3100

ns=2438.1/Hr0.433 766 2917

702 2672

762 2900

Table 6.1-3 Parameters of Some Bulb Turbines Put into Operation

Description Unit

Output (MW)

Maximum Head

(m)

Rated Head (m)

Rated Speed (r/min)

Rated Specific Speed

(m-kW)

Specific Speed

Coefficient K

Unit Discharge

(m3/s)

Number of

Blades

Hongjiang HPP

45 27.3 20 136.4 695 3107 1.892 5

Qiaogong HPP

57 24.3 13.8 83.3 757 2813 2.254 5

Kangyang HPP

40.75 22.5 18.7 125 655 2831 1.868 5

Julongtan HPP

30 18 14.2 125 798 3005 2.318 4

Bailongtan HPP

32 18 9.7 93.75 995 3099 2.959 4

Nina HPP 40 18.1 14 107.1 801 2996 2.346 4

Changzhou HPP

40 16 9.5 75 931.4 2871 2.873 4

Jirau HPP (DEC)

75 19.6 15.2 85.71 789 3076 2.23 4

Jirau HPP (ALSTOM)

75 19.6 15.6 94.7 872.7 3402 2.46 4

According to Table 6.1-3, the turbines with similar parameters as those of the HPP

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have the specific speed of about 650 m-kW~800 m-kW and specific speed coefficient of

about 2800~3100.

The technical schemes for the HPP prepared by major host equipment manufacturing

plants at home and abroad show that the specific speed is 787 m-kW and corresponding

specific speed coefficient is 2998. According to the experience formula, parameter level of

the similar HPPs constructed or under construction, and parameter level stated in

recommendations from host equipment manufacturing plants, the HPP shall have a specific

speed coefficient of about 3000 and a corresponding specific speed of about 788 m-kW.

b) Selection of unit parameter

Because the bulb turbine has many advantages in the low head range and its

operational stability is constantly proved by practice, in recent years, more and more

research works have been focused on the bulb turbine. The applied head may be extended

up and down based on 5 m to 18 m for 4-bladed runner, i.e., 16 m to 30 m for 5-bladed

runner, and 3 m to 12 m for 3-bladed runner. See Table 6.1-4 for main performance

parameters and applicable head range of a tubular runner.

Table 6.1-4 Main Technical Parameters of Bulb Runner

5-bladed Runner 4-bladed Runner

Operating head 16~30m 5~18m

Optimum operating conditions

n10 ~140r/min ~160r/min

Q10 ~1.7m3/s ~1.8m3/s

η0 ~94.2% ~94%

Rated operating conditions

n11 160r/min~170r/min 180r/min~200r/min

Q11 2.2m3/s~2.3 m3/s 2.9m3/s~3.1 m3/s

η ~90% ~88%

Applicable to the HPP or not Applicable Applicable

The HPP has a maximum gross head of 20 m and proposed unit capacity of 55 MW.

According to Table 6.1-4 as well as investigation and research made for the HPP

constructed and discussion results with host equipment manufacturers, in this stage, it is

recommended to adopt the 4-bladed runners temporarily.

See Table 6.1-5 for the unit speed and unit discharge calculated by the relevant

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statistical formulas.

Table 6.1-5 Computation Sheet for Unit Speed and Unit Discharge

Experience Formula Specific Speed

ns

(m-kW)

Unit Speed n11

(r/min)

Unit Discharge Q11

(m3/s)

Formula I 788 169 2.43

Formula II 788 169 2.35

Formula III

788 170.8 2.41

According to Table 6.1-5, the unit discharge of the turbine at the rated point should be

about 2.35 m3/s ~ 2.43 m 3/s, with a unit speed of about 170 r/min.

For a tubular turbine, its unit discharge (Q11) under the rated operation conditions

shall be a value with the medium efficiency and proper cavitation factor (not too large).

The reason is as follows: selection of unit discharge is directly related to the

turbine-generator unit and civil quantities; when the unit discharge is large, the turbine size

and plan view size of the powerhouse will be small and the turbine construction cost will

be low; in addition, the large unit discharge will increase the cavitation factor, which will

decrease the setting elevation of turbine and increase excavation quantities. By reference to

the similar HPPs and in view of consulting results from the host equipment manufacturers,

the unit discharge at the rated operating point shall be 2.4 m3/s with a unit speed of 170

r/min.

c) Turbine efficiency

By reference to the efficiency level of the bulb model turbine developed at home and

abroad and the prototype turbine put into operation, it is preliminarily proposed to set the

rated turbine efficiency of the HPP not less than 91.0%.

d) Cavitation performance

In comprehensive consideration of the specific speed and unit parameter of turbines of

the HPP and model runner parameter currently applicable to the HPP, the critical cavitation

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factor (to the vertex position of a turbine runner) of turbines should be about 1.3. Because

the HPP has a relatively large sediment concentration, the ratio (k) of cavitation factor of

the HPP to critical cavitation factor of the model shall be 1.13, based on which the

corresponding static suction head and setting elevation can be obtained by calculation.

6.1.5 Number of Units and Unit Capacity

The HPP is proposed to have an installed capacity of 770 MW and adopt the bulb

turbine-generator unit. Because the HPP has a relatively large installed capacity, to reduce

quantity of the units, it should increase the unit capacity as far as possible. The Jirau HPP

(Brazil) has an installed capacity of 4,800 MW, with 64 bulb turbine-generator units of

which the unit capacity is 75 MW and the runner diameters are 7.5 m (7.9 m). These units

are the bulb turbine-generator units with the largest unit capacity at present. The first unit

was put into operation in the end of August 2013. The Guangxi Qiaogong HPP (China) has

8 bulb turbine-generator units with the unit capacity of 57 MW and the runner diameters of

7.45 m, which are the units with the largest unit capacity in China and the second largest in

the world at present. The Changzhou HPP has 15 bulb turbine-generator units with the unit

capacity of 42 MW and the runner diameters of 7.50 m, which are the units in operation

with the largest runner diameter in China at present. In case the HPP is equipped with 12

bulb turbine-generator units with the unit capacity of 64.17 MW, the corresponding runner

diameter will be 7.5 m and the total capacity of 10 units transmitting power to Thailand

will be 641.7 MW. According to the design and manufacturing level of the units at present

and in consideration of the grid connection mode of the HPP (about 100 MW energy

output for Laos and the rest for Thailand), in this stage, it is proposed to compare the

scheme involving 13 the units with the unit capacity of 59.23 MW with the scheme

involving 14 the units with the unit capacity of 55 MW. See Table 6.1-6 for main technical

and economic indexes of the units in both schemes.

Table 6.1-6 Technical and Economic Indexes Corresponding to Schemes of Unit Quantity

Description Unit Number of Units

13 14

Turbine Unit capacity MW 59.23 55

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parameter Rated head m 14.5 14.5

Rated discharge of single unit m3/s 469.3 435.8

Rated Speed r/min 88.24 93.8

Runner diameter m 7.2 6.9

Specific speed m·kW 768.6 786.9

Specific Speed Coefficient - 2927 2997

Energy index

Average annual energy output GW·h 4143.4 4143.4

Primary energy (PE) GW·h 2886.6 2886.6

Secondary energy GW·h 1054.4 1054.4

Excess energy (EE) GW·h 202.4 202.4

Equivalent energy (PE + 0.6 x SE) GW·h 3519.2 3519.2

Utilization ratio of water resource % 85.52 85.52

Annual operating hours of installed capacity h 5381 5381

Economic indexes

Project cost on Hydroproject million yuan 9984.38 9975.89

Project cost per kilowatt Yuan/kW 12967 12955

Project cost per kilowatt hour Yuan/kW·h 2.42 2.42

Project cost per KWH for equivalent energy Yuan/kW·h 2.425 2.422

Total project cost difference million yuan -8.49

In terms of the energy indexes, the Paklay HPP has the same comprehensive

efficiency and basically uniform energy indexes in both schemes.

In terms of the project cost, quantity of the units increases to 14 sets from 13 sets,

which slightly increases the excavation works for the powerhouse but slightly decreases

the total weight of the units. In terms of the total project cost, the scheme involving 14 sets

can save RMB 8.49 million compared to the scheme involving 13 sets, which has better

economical efficiency.

In terms of the manufacturing level and operational conditions of the units, the unit

capacity and runner diameter in both scheme do not exceed those used for the units of the

Jirau HPP (Brazil). However, the scheme involving 13 sets uses a runner diameter of 7.2 m

and unit capacity of 59.23 MW, which is more difficult in unit manufacturing; the scheme

involving 14 sets uses a runner diameter of 6.90 m and unit capacity of 55 MW, which has

successful manufacturing and operating experience in China at present. Therefore, in terms

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of design and manufacturing difficulty of the units, the scheme involving 14 sets will be a

better choice.

Based on the comprehensive comparison, in this stage, it is recommended to adopt the

scheme involving 14 units with the unit capacity of 55 MW for the Paklay HPP.

6.1.6 Unit Parameter of the Recommended Scheme

a) Turbine parameter recommended by manufacturers

In this stage, technical communication has been made with the unit manufacturers;

there are 3 manufacturers provide their preliminary technical schemes with the

recommended turbine parameters as shown in Table 6.1-7.

Table 6.1-7 Turbine Technical Parameters Recommended by Host Equipment

Manufacturers

Manufacturer

Turbine Parameter Manufacturer A Manufacturer B Manufacturer C

Model GZ-WP-690 GZ-WP-690 GZ-WP-690

Rated output of turbine (MW) 56.4 56.4 56.4

Rated head (m) 14.5 14.5 14.5

Runner diameter (m) 6.90 6.90 6.90

Quantity of runner blade 4 4 4

Rated speed (r/min) 93.75 93.75 93.75

Rated discharge (m3/s) 420 424.23 417.7

Unit speed at rated point (r/min) 170 170 170

Unit discharge at rated point (m3/s) 2.32 2.34 2.304

Specific speed (m·kW) 787 787 787

Specific speed coefficient 2998 2998 2998

Efficiency at rated point (%) 94.8 93.9 94.92

Maximum efficiency (%) 95.8 95.33 96.19

Critical cavitation factor at rated

point 1.3

Static suction head (to the unit

centerline) (m) -13.5 -14.5 -13.66

Weight of turbine (t) 731.4 700 860

b) Runner diameter

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According to the unit discharge at the rated operating point (2.4 m3/s) and the

parameters recommended by the manufacturers, in this stage, it is proposed to adopt a

runner diameter of 6.9 m.

c) Rated speed

According to the unit speed at the rated operating point (170 r/min), the HPP has a

calculated speed of 93.81 r/min. In this stage, it is proposed to select three synchronous

speeds, including 88.24 r/min, 93.75 r/min and 100 r/min for comparison. The scheme

involving 88.24 r/min has a corresponding specific speed of 741 m-kW and specific speed

coefficient of 2820. The scheme involving 93.75 r/min has a corresponding specific speed

of 787 m-kW and specific speed coefficient of 2998. The scheme involving 100 r/min has

a corresponding specific speed of 839 m-kW and specific speed coefficient of 3196.

According to the comparison, the scheme involving 93.75 r/min has a relatively suitable

specific speed and specific speed coefficient. In addition, the rated speed of 93.75 r/min is

adopted in the technical schemes provided by 3 manufacturers.

According to the selected specific speed and unit parameter level and in view of the

turbine parameters recommended by the manufacturers, in this stage, it is proposed to

adopt the rated speed of 93.75 r/min for the turbines. Accordingly, the specific speed (ns) at

the rated operating point shall be 787m·kW, the specific speed coefficient (K) shall be

2998, the unit discharge shall be 2.404 m3/s, and the unit speed shall be 170 r/min.

d) Static suction head and setting elevation

According to the selected cavitation factor and safety factor, the static suction head

can be calculated by the rated head. In view of consulting results from the manufacturers,

the HPP shall have a cavitation factor of 1.47, an allowable static suction head (to the

vertex position of a runner blade of a turbine) of -11.61 m, and an allowable static suction

head (to the turbine center) of -15.34 m. The design tail water level shall be the tail water

level (whole plant in full operation) of 224.14 m a.s.l.; the setting elevation of the unit shall

be 209.08 m a.s.l., rounded to 208.50 m a.s.l. in this stage.

e) Turbine parameter of the recommended scheme

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See Table 6.1-8 for main turbine parameters recommended.

Table 6.1-8 Main Turbine Parameters in Recommended Scheme

Description Parameter Value

Turbine model GZ-WP-690

Rated output of turbine (MW) 56.4

Maximum head/rated head/minimum head (m) 20/14.5/7.5

Runner diameter (m) 6.90

Rated speed (r/min) 93.75

Rated discharge (m3/s) 435.8

Unit speed at rated point (r/min) 170

Unit discharge at rated point (m3/s) 2.404

Specific speed under rated operating condition

(m·kW) 787

Specific speed coefficient 2997

Efficiency at rated point (%) 91.0

Static suction head (calculated to the unit

centerline) (m) -15.34

Setting elevation (m) 208.50

Weight of turbine (t) ~756

6.1.7 Governing System

The governing system of the units has an operating oil pressure of 6.3 MPa, and the

DWST-150-6.3 model dual-regulating microcomputer electro-hydraulic governor is

adopted. The counter weight is provided for accident shutdown. In case of accident, the

governing system can adjust oil pressure through the relief valve of the counter weight and

shut down the unit by the dead load of the counter weight. Type of the oil pressure unit is

HYZ-15-6.3 and the pressure level is 6.3 MPa.

6.1.8 Design of Regulation Guarantee

a) Unit information

The HPP adopts the tubular turbine-generator unit, with a runner diameter of 6.9 m,

rated speed of 93.75 r/min, and runaway speed of 290 r/min. The moment of inertia of a

generator is about 5,500 t m2; the moment of inertia of a turbine and water body is about

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2,500 t m2; the moment of inertia of the unit and water body is about 8,000 t·m2 in total;

the inertia time constant of the unit is 3.42 s.

b) Calculation control value for hydraulic transition process

According to the relevant codes, in the HPP, the maximum speed rising rate of the

units should be less than 65%; the guarantee value of the maximum pressure rising rate in

front of a guide vane should be less than 70%~100%; during load dump, the maximum

vacuum guarantee value at the draft tube inlet section shall not be greater than 0.07 MPa.

c) Closure rule

In this stage, the 6s linear closure law shall be used for calculation. After relevant

parameters such as the unit manufacturing plant and turbine model characteristic curve are

determined, recalculation for the hydraulic transition process shall be carried out.

d) Calculation results and analysis of transition process

In this stage, calculation only applies to the transition process with large fluctuation.

The operating conditions of the rated load dump at the rated head and those at the

maximum head shall be used for preliminary calculation. See the table below for the

calculation results.

Table 6.1-9 Calculation Results of Transition Process

Parameter Unit Design Head

Operating Condition

Maximum Head

Operating Condition

Pressure rising absolute value in

front of guide vane mH2O 16.94 22.33

Pressure rising rate in front of

guide vane % 53.8 70.9

Pressure at draft tube inlet section mH2O -2.41 -4.39

Rising speed (β) % 65 50

According to the calculation results, the maximum pressure rising in front of the guide

vane and the minimum pressure at the draft tube inlet section both occur at the rated load

dump at the maximum head, with the maximum pressure rising rate in front of the guide

vane of 70.9% and minimum pressure at the draft tube of -4.39 mH2O. The maximum

speed rising occurs at the rated load dump at the rated head, with the maximum speed

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rising rate of 65%. All of above conditions meet the requirement for calculation control

value for hydraulic transition process.

e) Determination of design value for regulation guarantee

For determination of design value for regulation guarantee, the calculation error and

pressure fluctuation shall be used for correction based on the calculation value of

hydraulic transition process. Based on the above calculations and corrections and

characteristics of the HPP, the design values for regulation guarantee in accordance with

the relevant codes and temporary provisions are as follows:

1) The maximum pressure in front of a guide vane is 58 mH2O;

2) The minimum hydrodynamic pressure at the draft tube inlet is -6 mH2O;

3) The maximum speed rising of the units is 65%.

In this stage, it lacks of relevant parameters such as the characteristic curve of the

units and the moment of inertia of the units and water body, the transition process is

calculated by linear closure law based on relevant experience formulas. After relevant

parameters such as the unit manufacturing plant and turbine model characteristic curve are

determined, recalculation for the hydraulic transition process shall be carried out, in order

to optimize the closure law. In this way, the design value for regulation guarantee of the

HPP can meet requirements for safe and reliable operation.

6.1.9 Transport of Heavy Equipment

The heavy equipment consists of a main transformer, generator rotor, turbine runner,

bridge crane girder and others. The main transformer and generator rotor are the key

equipment in the transport control. See Table 6.1-10 for the transport characteristic values.

Table 6.1-10 Characteristic Values for Transport of Heavy Equipment

Description of

heavy-big piece Unit Qty. Transport Size (m)

Weight of A Single

Piece (t)

Turbine hub Set 14 φ3.0x5.0 (D×H) 65

Inner guide ring Nr. 14 φ5.076×2.695m (D×H) 17.5

Enclosure Nr. 56 10.479×3.9×3.92 m (L×

W×H) 11

6-16

Rotor support Set 14 5.2x5.2x2.2 (L×W×H) 40

Bridge crane girder Pcs. 4 22.0x3.0x3.0 (L×W×H) 60

Main transformer Set 6 6.5x4x6.8 (L×W×H) 100

After dredging and channelized waterway works were carried out to the upstream

basin of the Mekong River, the 71 km long waterway connecting the Jinghong Port with

the China - Myanmar No. 243 boundary monument is Grade V, with a single-ship

navigation capacity of 300 t ~ 500 t. The 331 km long waterway connecting the China -

Myanmar No. 243 boundary monument with Houayxay section, Laos has a perennial

navigation capacity of 200 t ~ 300 t ships, with a navigation period of 10 ~ 11 months. The

section from Houayxay to Luang Prabang is an original river course with a length of about

300 km and navigation capacity of 150 t ships. The waterway at the lower reaches of

Luang Prabang has a relatively poor navigation capacity.

There are two national trunk highways passing through the vicinity of the project site.

One of them is the No. 11 highway from Vientiane, capital of Laos, to Pak Lay, and the

other one is the No. 4 highway connecting the Luang Prabang City with Loei, Thailand.

The above two highways meet each other in the Pak Lay Town. There is a rural road of

about 20 km long connecting the Pak Lay Town to the dam site, in which a section of

about 7 km long has been upgraded and reconstructed so that it can meet transport of large

equipment.

According to the site access conditions of the Project, it is preliminarily proposed that

M & E equipment and heavy-big piece will be transported to the Luang Prabanngd Port via

water transport and then transported to the site via highway. Some equipment can be

transported to the site directly via water transport.

6.1.10 Auxiliary Equipment of Hydraulic Machinery

6.1.10.1 Selection of hoisting equipment for powerhouse

The largest heavy piece inside the powerhouse is the weight of rotor with shaft, with a

hoisting weight of about 230 t. There are 14 units in the whole plant. Given that installation

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and maintenance will be simultaneously applied to 2 units as well as in view of turnover

requirement of large equipment, 2 single-trolley electric double-beam bridge cranes (250

t/30 t/10 t) will be adopted, with the span of 21.0 m. Both bridge cranes are arranged in the

same unit. The main hook has a hoisting height of 30 m while the secondary hook has a

hoisting height of 40 m.

6.1.10.2 Cooling water supply system

Service t water supply of the whole plant consists of cooling water for a generator air

cooler, cooling water for a bearing, sealing water for a main shaft, cooling water for a

water-cooled main transformer, lubricating water for a deep well pump, cleaning water,

domestic water and others.

The generator air cooler uses a closed circulation and secondary cooling water supply

method. It is designed by the unit manufacturers and will not be included to the total

amount of cooling water supply.

According to the preliminary estimate, the water consumption for each part of the

units is as follows:

Cooling water for a bearing: 55m3/h

Sealing water for a main shaft: 6m3/h

Other main cooling water supply in the powerhouse is as follows:

Cooling water for a main transformer: 50m3/h x 5

Utilities water: 25m3/h

Total cooling water of the whole plant 1129 m3/h

The HPP is a low-head and run-of-river hydropower project, with a head range of 7.5

m ~ 20.0 m. According to different requirements for water quality and reliability of water

source, the whole plant is equipped with a cooling water supply system and a cleaning

water supply system.

The cooling water supply system will supply cooling water for unit bearings, cooling

water for main transformers, water for utilities, domestic water and others; meanwhile, it

will serve as the standby water source for sealing of main shafts. The cooling water supply

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system takes its water source from the reservoir and drains the wastewater to the tail water.

It adopts water supply by gravity flow in groups. In one group, 7 units and 3 main

transformers will share 2 routes of intake pipelines in front of dam, standby for each other;

in another group, 7 units and 2 main transformers will share 2 routes of intake pipelines in

front of dam, standby for each other. Each route is provided with an automatic water filter

and a spiral flow filter, with the design discharge of 600 m3/h. To ensure stable hydraulic

pressure of the cooling water supply, the whole plant is provided with 2 pressure

stabilizing pools with an effective volume of 100m3.

The cleaning water supply system will supply cooling water for sealing of main shafts,

water supplement for cooling expansion tank of air cooler, etc. The water source is

upstream reservoir. The wastewater is discharged into the leakage water dewatering pit and

then discharged into the downstream via a leakage drainage pump. Water supply by gravity

flow in groups is adopted. Every 7 units shares 2 water intake pipelines in front of the dam,

standby for each other. Each route is provided with an automatic accurate water filter and a

spiral flow filter, a design discharge of 100 m3/h. To ensure water quality of sealing water

for a main shaft, the water inlet pipe of the main shaft shall be equipped with an accurate

water filter.

See "Paklay-FS-EM-Machinery-01" for details of the Cooling water Supply System

Drawing.

6.1.10.3 Dewatering and drainage system

The dewatering and drainage system of the HPP consists of two parts, including a

dewatering system for unit maintenance and a drainage system for the powerhouse

leakage.

a) Dewatering system

It adopts an indirect dewatering mode. When a unit is under maintenance,

accumulated water in the passage will be drained to the dewatering sump through the

drainage gallery, and then drained to tail water by the deep well pump.

One drain valve will be set at the lowest position of upstream and downstream

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passages in each unit bay. Steel pipes are embedded behind the valves and lead to the

dewatering sump at the erection bay. A sealing head cover is provided on the top of the

sump and an air vent is provided as well.

The water to be discharged involves accumulated water to be drained in the inlet

passage and outlet passage during maintenance. According to the preliminary calculation,

quantity of the accumulated water in the passages is 6000 m3. During unit maintenance, the

total water leakage through upstream and downstream gates is about 90 m3/h.

Dewatering duration shall be calculated based on emptying accumulated water in 4 h

~ 5 h. The pump lift shall be sum of difference between the water level at shutdown of

pump and downstream head and frictional loss in the pipeline. It adopts 4 deep well pumps

with a pump discharge of 370 m3/h and head of 48 m.

To drain out the settled sewage in the sump, 1 submersible sewage pump shall be set,

with a discharge of 90 m3/h and head of 47 m.

After the passages are completely drained out, the dewatering sump will be used for

storing the leakage water from upstream and downstream gates, in order to make the

drainage pump to continuously operate. The effective volume of the sump shall be 90 m3

based on the discharge obtained by a drainage pump operating for 15 min. For leakage

water of the gates, a level controller is used for automatically controlling startup and

shutdown of a drainage pump. A level transmitter is provided in the sump, leading to the

central control room.

b) Drainage system

Leakage water in the powerhouse mainly comes from leakage water of hydraulic

structures in the powerhouse, cooling water for bearings and main transformers, sealing

leakage water for main shafts, valve leakage water of each pipeline, cleaning water etc. By

reference to the similar HPPs, powerhouse leakage water shall be 60 m3/h, and the

maximum discharge for sealing water of main shafts shall be 84 m3/h. In view of other

discharge in the powerhouse, the total discharge shall be 200 m3/h.

A drainage gallery throughout the whole plant is set under the passage base plate. All

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leakage water is drained to the drainage gallery through floor drains and vertical drain

pipes. The leakage water flows into the leakage water dewatering sump by gravity and then

be drained to the downstream tail water through deep well pumps.

The capacity of the leakage water dewatering sump shall be calculated based on the

total leakage water amount in the powerhouse within 37.5 min, with an effective volume of

100 m3.

Four vertical deep well pumps are provided, 2 for use and 2 for standby. The pump

discharge shall be calculated based on the effective volume of the emptying drainage sump

in 20 min. The pump lift shall be determined based on sum of difference between the

maximum tail water level and the water level at shutdown of pump and the frictional loss.

The pump discharge is finally determined as 370 m3/h, with a pump lift of 54 m. Startup or

shutdown of a drainage pumps is automatically controlled by a level controller. A level

transmitter is provided in the sump, leading to the central control room.

To drain out the settled sewage in the sump, 1 submersible sewage pump shall be set,

with a discharge of 90 m3/h and head of 47 m.

See "Paklay-FS-EM-Machinery-02" for Drawing of Dewatering and Drainage

System.

6.1.10.4 Compressed air system

The compressed air system of the HPP consists of a powerhouse mediate-pressure

(MP) compressed air system and a powerhouse low-pressure (LP) compressed air system.

a) Powerhouse MP compressed air system

The MP compressed air system is used for air inflation into a pressure oil tank after

installation or maintenance of a pressure oil supply unit in the governing system and for

supplement of air consumption in the pressure oil tank during operation. Rated oil pressure

of the pressure oil supply unit in the HPP is 6.3 MPa. Air supply under first-stage pressure

is adopted in the design. Air supply of pressure oil tank is carried out via pipelines.

The production rate of a MP air compressor shall be determined based on air inflation

capacity and duration of the pressure oil tank. Three MP air compressors are selected, with

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an air displacement of 1000 L/min and a working pressure of 8.0 MPa. Among them, 2 are

used as the main air compressors and 1 is used for standby.

The compressed air silo volume shall be determined based on the air supplement

quantity required by oil level rising of 150 mm ~ 250 mm in the pressure oil tank.

According to calculations and by reference to the similar HPPs, it is determined that 2 x

3.0m3 compressed air silos with a pressure of 8.0 MPa will be adopted.

b) Powerhouse LP compressed air system

The LP compressed air system of the HPP is 0.7 MPa. The LP compressed air system

supplies air for unit braking, maintenance, purging air, air shroud, etc. Because the HPP

has many units, an air supply system for brake and main shaft sealing and a maintenance

air supply system are provided in the whole plant, in order to prevent each part requiring

air supply of the LP compressed air system from interacting with each other. A non-return

valve is set between the above two systems; the maintenance air supply system can supply

air to the air supply system for brake and main shaft sealing.

According to the main electrical connection mode, the air supply system for brake and

main shaft sealing is configured as follows: 3 units shall brake simultaneously; duration for

restoration of operating pressure of a compressed air silo shall be 10 min; 2 LP air

compressors with an air discharge of 1.4 m3/min and operating pressure of 0.85 MP and 2

x 5.0 m3 compressed air silos with a pressure of 0.8 MPa shall be provided.

Configuration of the maintenance air supply system shall be that 2 air compressors

simultaneously operate to meet requirement of the maximum air demand for maintenance.

By reference to the similar HPPs, the configuration details shall be as follows: 2 LP air

compressors with an air discharge of 10.0 m3/min and operating pressure of 0.85 MPa and

1 x 5.0 m3 compressed air silo with a pressure of 0.8 MPa shall be provided. In addition,

another 1 portable air compressor with an air discharge of 0.28 m3/ min and operating

pressure of 0.7 MPa will be provided as well.

Each air compressor of the MP and LP compressed air systems in the powerhouse will

automatically control startup and shutdown of the air compressors based on the pressure

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settings. A safety valve and pressure signal controller will be installed on the compressed

air silo.

See "Paklay-FS-EM-Machinery-03" for Drawing of MP and LP Compressed Air

Systems in the Powerhouse.

6.1.10.5 Oil system

It consists of a turbine oil system and an insulating oil system.

a) Turbine oil system

The turbine oil system mainly supplies unit lubricating oil and mechanical

hydraulic oil. Based on estimation, the maximum oil consumption of 1 unit is 30.4 m3.

According to requirements of relevant codes and HPP operation, 2 x 20 m3

uncontaminated oil tanks and 2 x 20 m3 operating oil tanks shall be provided.

Each oil pump shall have a capacity of filling up oil for 1 unit within 5 h. Two gear oil

pumps (2CY-6/3.3-1) shall be adopted, with an oil delivery quantity of 6 m3/h and the

maximum operating pressure of 0.33 MPa.

The oil treatment equipment shall have a capacity of filtering oil for 1 unit within 8 h.

One pressure oil filter (LY-100) with production rate of 100 L/min shall be adopted. In

addition, 1 turbine oil filter (ZJCQ-4) with production rate of 4,000 L/h and operating

vacuum (P) not greater than 3,500 Pa shall be adopted.

b) Insulating oil system

It mainly supplies cooling oil for main transformers. Based on estimation, the

maximum oil consumption of 1 main transformer is 56 m3. According to requirements of

relevant codes and HPP operation, 2 x 35 m3 uncontaminated oil tanks and 2 x 35 m3

operating oil tanks shall be provided.

Each oil pump shall have a capacity of filling up oil for 1 unit within 6 h. Two gear oil

pumps (2CY-12/3.3-1) shall be adopted, with an oil delivery quantity of 12 m3/h and the

maximum operating pressure of 0.33 MPa.

The oil treatment equipment shall have a capacity of filtering oil for 1 unit within 24 h.

One pressure oil filter (LY-100) with production rate of 100 L/min shall be adopted. In

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addition, 1 vacuum oil-filter (ZJB-3KY) with production rate of 3,000 L/h and operating

vacuum (P) not greater than 0.5MPa shall be adopted.

See "Paklay-FS-EM-Machinery-04" for Drawing of Oil System

6.1.10.6 Hydraulic monitoring system

Configuration of the hydraulic monitoring system shall meet requirements for safe,

reliable and economic operation, automatic control and test measurement of a

turbine-generator unit. It consists of two parts, including plant monitoring and unit bay

monitoring.

The plant monitoring includes upstream/downstream water level, HPP gross head and

reservoir water temperature.

The unit bay monitoring includes the following items: trash rack differential pressure,

pressure balancing on both sides of the intake gate and draft tube gate, passage inlet

pressure, draft tube outlet pressure, operating head, unit discharge, pressure in front of

guide vane, runner chamber pressure, vibration and throw of units etc.

See "Paklay-FS-EM-Machinery-05" for Drawing of Hydraulic Measuring System.

6.1.10.7 Layout of main hydraulic mechanical equipment

The HPP powerhouse lies at the left bank, including a powerhouse (comprising a host

equipment section and an erection bay) and auxiliary plant. The powerhouse has a total

length of 400.0 m, in which the host equipment section is 301.0 m long. Because the HPP

has many units, 2 erection bays are provided. The main erection bay is 52.0 m long,

arranged at the left side of the powerhouse; the auxiliary erection bay is 41.0 m long,

arranged at the right side of the powerhouse. Area of the erection bays can meet erection

progress that 2 units can be put into operation every 3 months. According to the head cover

of unit passage, turbine lifting holes and equipment layout, the powerhouse has a clear

width of 21.0 m.

Units have a setting elevation of 208.5 m a.s.l. and the ground elevation of the host

equipment floor and auxiliary erection bay is 222.5 m a.s.l.; according to flood control

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requirement of the powerhouse access road, the main erection bay has a ground elevation

of 228.5 m a.s.l.; according to turnover requirement for the largest equipment and outer

gate barrel, a crane has a track top elevation of 240.5 m a.s.l.

The air delivery conduit of the powerhouse is arranged inside the head bay wall of the

powerhouse. The oil-water-air pipeline and the air compressor room are arranged on the

hydraulic mechanical equipment floor at an elevation of 222.50 m a.s.l. in the downstream

auxiliary plant; the governor and oil pressure unit are arranged in the upstream first

quadrant of the host equipment floor of an elevation of 222.5 m a.s.l. in the powerhouse.

The drainage pump house and dewatering pump house are arranged in the auxiliary

plant at an elevation of 216.5 m a.s.l. below the erection bay of the powerhouse.

The turbine oil storage room and its oil treatment room as well as the insulating oil

storage room and its oil treatment room are arranged in the auxiliary plant of an elevation

of 216.5 m a.s.l. at the lower position of the auxiliary erection bay. The insulating oil depot

and the oil treatment room are arranged in the auxiliary plant at an elevation of 228.50 at

the downstream side of the powerhouse.

The instruments and pressure balancing pipeline of draft tube gate are arranged in the

downstream auxiliary plant of an elevation of 219.0 m a.s.l.

6.1.11 List of Main Hydraulic Mechanical Equipment

See Table 6.1-10 for main hydraulic mechanical equipment.

Table 6.1-10 Main Hydraulic Mechanical Equipment.

S/N Description Model, Specification and

Parameter Unit Qty. Remarks

1 Turbine

GZ-WP-690, Hr=14.5m,

N=56.4MW,

nr=93.75r/min, D1=6.9m

Set 14

2 Governor DWST-150-6.3 Set 14

3 Oil pressure unit HYZ-15-6.3 Set 14

4 Crane

4.1 Single-trolley bridge crane 250t/30t/10t, span of

21.0 m Set 2 Powerhouse

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4.2 Single-trolley bridge crane 10t, span of 14.4 m Set 1 500kV GIS room

5 Cooling water supply system

5.1 Vertical centrifugal pump Q=600m3/h, H=20m Set 4 N=55kW

5.2 Full-automatic water filter DN350, Q=600m3/h,

PN1.0 MPa Set 4

5.3 Water treatment equipment Q=10m3/h Set 4

5.4 Pump control valve DN350, PN1.0 MPa Set 4

5.5 Hydrocyclone DN350, Q=600m3/h,

PN1.0 MPa Set 4

6 Unit dewatering system and powerhouse drainage system

6.1 Deep well pump Q=370 m3/h, H=48 m,

N=75 kW Set 4 Dewatering

6.2 Deep well pump Q=370 m3/h, H=48 m,

N=75 kW Set 4 Drainage

6.3 Submersible sewage pump Q=90 m3/h, H=47 m Set 2

6.4 Piezoresistive level transmitter Set 2

6.5 Ball float type level transmitter Set 2

7 MP/LP compressed air system

7.1 MP air compressor Q=1.0 m3/min P=8.0

MPa Set 3 N=11kW

7.2 MP compressed air silo V=3.0 m3 P=8.0 MPa Set 2

7.3 MP freezer dryer 8MPpa Set 3

7.4 Pressure-reducing-stabilizing

valve

DN40 P=8.0MPa/

7.0MPa Set 1

7.5 LP air compressor Q=10.0 m3/min P=0.85

MPa Set 2 N=55kW

7.6 LP air compressor Q=1.4 m3/min P=0.85

MPa Set 2 N=11kW

7.7 LP compressed air silo V=5.0 m3 P=0.8 MPa Set 3

7.8 Portable air compressor Q = 0.28 m3/ min P =

0.7 MPa Set 1 N=2.2kW

7.9 LP freezer dryer 0.8MPa Set 2

8 Oil system

8.1 Indoor oil tank 20m3 Nr. 4 Turbine oil system

8.2 Gear oil pump 2CY6/3.3-1 Q=6 m3/h

H=0.32 MPa N=3kW Set 2 Turbine oil system

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8.3 Pressure oil filter LY-100 Q=100 L/min

N=2.2kW Set 2 Turbine oil system

8.4 Turbine oil filter

ZJCQ-4 Q=4000 L/h,

P≤0.33 MPa

N=30.49kW

Set 1 Turbine oil system

8.5 Indoor oil tank 35m3 Nr. 4 Insulating oil

system

8.6 Gear oil pump 2CY12/3.3-1 Q=12 m3/h

H=0.33 MPa N=4kW Set 2

Insulating oil

system

8.7 Pressure oil filter LY-100 Q=100 L/min

N=2.2kW Set 2

Insulating oil

system

8.8 Two-stage high-vacuum oil filter

ZJA-3KY Q=3000 L/h,

P≤0.5 MPa

N=52.35kW

Set 1 Insulating oil

system

8.9 Filter paper oven 1kW Set 2

9 Hydraulic measurement system

9.1 Water-level gauge Measuring range: 0 m ~

30 m Pcs. 2

For measuring

water level at upper

and lower reaches

9.2 Deep water thermometer Measuring range: 0°C ~

40°C Pcs. 1

For measuring

reservoir water

temperature

9.3 Pressure transmitter Measuring range: 0 MPa

~ 0.6 MPa Pcs. 98

9.4 Vacuum pressure transmitter Measuring range: -0.1

MPa ~ 0.6 MPa Pcs. 48

9.5 Oscillatory pressure transmitter Pcs. 32

9.6 Differential pressure transmitter Pcs. 81

For measuring

gross head and

available head

9.10 Manometer YB-150, PN0~0.6 MPa Set 104

9.11 Vacuum manometer YZ-150,

PN-0.1~0.6MPa Set 48

9.12 Measuring equipment for

vibration and throw of units Set 16

For measuring

vibration and throw

of units

10 "Machine maintenance equipment shall be determined via negotiation with the Employer in the

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future.

6.2 Main Electric Equipment and Main Electrical Connection

6.2.1 Design of Grid Connection

6.2.1.1 Power Supply Range

The Paklay Hydropower Project (HPP) is located in Laos, which lies in the north of

Indo-China Peninsula, bordered by China on the north, Cambodia on the south, Vietnam

on the east, Myanmar and Thailand on the northwest and southwest respectively. The

national territorial area of Laos is 236.8 x 103 km2. Mountains and plateaus account for

80% and most of them are covered by forests. Currently, the population in Laos is about 6

million. Laos' economy is dominated by its agriculture, its industrial base is weak, and its

economic development level is backward. Since 1988, Laos has gradually completed its

market economic system via implementation of reform and opening policies, improvement

of investment environment, and adjustment of economic structure. In addition, its

economic society has developed rapidly. In 2010, Laos' GNP was USD 5.97 billion with a

year-on-year growth of 7.9%, and the GDP per capita was nearly USD 1,000. Although the

level of national economy and social development in Laos has been improved dramatically

in recent years, the power demand in Laos is still not large. Laos enjoys very rich

hydropower resources. According to relevant planning results from the electric power

department in Laos, even without the hydropower resources of main stream of the Mekong

River, the available hydropower resources in Laos still reach 18,000 MW. In addition to 5

HPPs, including Pak Beng HPP, Luang Prabang HPP, Xayaboury HPP, Paklay HPP and

Sanakham HPP, planned on the main stream of the Mekong River, the total available

hydropower resources in Laos are more than 23,000 MW.

In recent years, with the increase of investments from China, Japan, Thailand and other

countries in Laos' hydropower projects, the hydropower development in Laos has entered

an unprecedented development stage. In the next decade, the installed capacity of

hydropower to be put into operation in Laos is expected to be millions kilowatts. The

power demand in Laos cannot consume such rich electrical energy. Therefore, Laos'

electric power will mainly be exported to countries with more developed economy, such as

China and Thailand.

Laos is located in the middle of Southeast Asian countries and bordered by China,

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Myanmar, Thailand, Cambodia and Vietnam. Geographically, it has advantages in electric

power export. According to the relevant planning results, the Lao Government plans to

export about 8,000 MW of electric power to its neighbors in 2020. The main object of

electric power export is Thailand. The Lao Government signed a memorandum of

understanding on power cooperation with the Thai Government in December, 2007. Both

parties agreed that 3,000 MW ~ 5,000 MW of electric power will be supplied from Laos to

Thailand before 2015, and 5,000 MW ~ 7,000 MW of electric power after 2015.

The Paklay HPP is about 50 km away from the borderline of Thailand in a straight-line

distance, so it has geographical advantages in electric power export to Thailand. In view of

the analysis results of electricity market space in Thailand, in 2020, the electricity market

space in Thailand will be large enough to consume the electric power delivered from the

Paklay HPP. Therefore, Thailand is within the power supply range of the Paklay HPP.

6.2.1.2 Scheme of Grid Connection

The Paklay HPP has an installed capacity of 14 × 55 MW and a total installed capacity of

770 MW. For the HPP, it is proposed to connect 2 circuits of 500 kV transmission lines

with a conductor cross-section of LGJ-4×300 to the 500 kV combined switchyard owned

by Laos and located at the Laos ~ Thailand border. Electric power from Laos will be

delivered to Thailand through the combined switchyard. See Fig. 6.2.1-1 for the

connection diagram of Laos power grid in terms of geographical location in 2020.

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Fig. 6.2.1-1 Connection Diagram of Laos Power Grid in Terms of Geographical Location

In 2020

6.2.2 Main Electrical Connection

The main electrical connection shall be safe, reliable, flexible and economical. The

specific design principle is as follows:

(1) Safe and reliable power supply

Because the 500 kV transmission line plays an important role in the electric power

system, it is required to employ a main electrical connection scheme of which the power

supply has high reliability.

(2) Flexible operation, convenient maintenance, and easy startup and shutdown

In the design of main electrical connection, frequent operation of HPP shall be fully

taken into account. When the operation mode changes, startup and shutdown operations

shall be as easy as possible and such operations shall not affect the continuous operation of

the station service system and other elements.

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(3) Easy connection, convenient transition, and compact and clear arrangement

The main electrical connection shall be easy and reliable as far as possible. The

quantity of elements in the main electrical connection shall be as less as possible, and the

arrangement of these elements shall be compact and clear, in favor of operation monitoring,

maintenance and accident handling. Staged transition shall not cause great changes in the

arrangement of electrical equipment or secondary circuit; in addition, the staged transition

shall be in favor of extension.

(4) Simple and reliable relay protection and control

(5) Advanced technology and rational economic efficiency

In model selection of equipment, electrical equipment with mature and advanced

technology shall be adopted as far as possible to minimize the investment and loss of

electric energy as long as the reliability of main electrical connection can be guaranteed.

6.2.2.1 Combination Mode of Generator and Main Transformer

In view of operating characteristics, quantity of units and unit capacity of the HPP,

role of the HPP played in the power system, design requirement and transport conditions

related to connection of the HPP to the electric system, the combination mode of

generators and main transformers shall be one of the following three schemes for technical

and economic comparison. Combination mode of generators and main transformers are as

follows:

a) Scheme 1: Single-bus circuit breaker sectionalized connection of

multi-generator-transformer unit

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Figure 6.2.2-1 Single-bus Circuit Breaker Sectionalized Connection of

Multi-Generator-Transformer Unit

Four generators and two main transformers are connected to form a single-bus

sectionalized circuit-breaker connection. This mode of connection is simple and distinct,

with flexible operation and easy protective relaying and control loop. In case any section of

a bus (or any one of main transformers) fails or is under maintenance, only 2 generators

will be affected, with a small shutdown range and high reliability. Disadvantages of the

scheme are as follows: ① Quantity of incoming lines at the 500 kV side is large and switch

quantity required by the HV side is large, which increases investment on the 500 kV switch

apparatuses; ② Quantity of main transformers is large, which increases investment on the

main transformers. ③ To meet requirements for economic-type generator circuit breaker

(GCB with the rated short-circuit breaking current below 80kA), the section circuit

breakers need to be connected with current limiting reactors in series, which increases

electric energy loss and equipment failure rate. ④ Generator switchgear installation has

many elements, which increases equipment investment and maintenance works.

Paklay Hydropower Project Feasibility Study Report

6-32

b) Scheme 2: connection of multi-generator-transformer unit - united

generator-transformer unit

Figure 6.2.2-2 Connection of Multi-Generator-Transformer Unit - United

Generator-Transformer Unit

Four generators and two main transformers are respectively connected to form

connection of two multi-generator-transformer units; the two expanded unit connections

are in parallel connected with each other at the HV side of the main transformers to form

connection of one multi-generator-transformer unit - united generator-transformer unit.

Compared with the scheme 1, advantages of the scheme are as follows: ① Quantity of

incoming lines at the 500 kV side is less and switch quantity required by the HV side is

②less, which decreases investment on the 500 kV switch apparatuses. Rated short-circuit

breaking current ( 80kA) ≯ can easily meets the demands, no additional current limiting

reactors are required, which decreases electric energy loss and equipment failure rate.

Disadvantages are as follows: in case the bus of united generator-transformer unit

fails or is under maintenance, capacity of 4 generators will be impacted; therefore, the

impact scope is larger; operation flexibility and manipulation convenience both are poorer

than those in scheme 1.

c) Scheme 3: connection of multi-generator-transformer unit


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Figure 6.2.2-3 Connection of Multi-Generator-Transformer Unit

Three generators and one main transformers are connected to form one connection of

multi-generator-transformer unit. Compared with the scheme 1, advantages of the scheme

①are as follows: Quantity of incoming lines at the 500 kV side is less and switch quantity

required by the HV side is less, which decreases investment on the 500 kV switch

②apparatuses. Generator switchgear installation has less elements, which increases

③equipment investment and maintenance works. Rated short-circuit breaking current

( 80kA)≯ of the generator circuit breaker can easily meets the demands, no additional

current limiting reactors are required, which decreases electric energy loss and equipment

④failure rate. Quantity of main transformers is less, which decreases investment on the

main transformers. Disadvantages are as follows: in case the main transformer fails or is

under maintenance, capacity of 3 units will be impacted; therefore, the impact scope is

larger; operation flexibility and manipulation convenience both are poorer than those in

scheme 1.

Compared with the scheme 2, advantage is that this connection mode requires less

main transformer, which reduces investment on the main transformer. Disadvantage is that

quantity of incoming lines at the 500 kV side is large and switch quantity required by the

HV side is large, which increases investment on the 500 kV switch apparatuses.

d) Techno-economic comparison

See Table 6.2.2-1 for the summary of techno-economic comparison between different

combination modes of generator-main transformer.

Table 6.2.2-1 Summary for Technical Comparison Between Different Combination


6-34

Modes of Generator-Main Transformer

S/

N Item

Sectionalize

d Single-bus

Connection

Multi-United

Generator-Transforme

r Unit Connection

Multi-generator-transforme

r Unit Connection

1

Quantity of

main

transformer

7 7 5

2

Quantity of

current-limitin

g reactor

3 / /

3

Quantity of

incoming

circuit at the

500 kV side

7 4 5

4

Investment in

electrical

equipment

Maximum Large Small

5 Reliable power

supply

In case of

failure or

maintenance

of any bus

section (any

main

transformer),

the capacity

of 2 units

will be

restricted

In case of failure or

maintenance of a bus

in the united

generator-transformer

unit connection at the

HV side of main

transformer, the

capacity of 4 units

will be restricted and

the influence is

relatively large.


maintenance of main

transformer, the capacity of

3 units will be restricted

and the influence is

relatively small.


6-35

and the

influence is

smallest.

6 Operation

flexibility Best Poor Good

e) Conclusion

According to the above technical and economic analysis, the scheme 3 has advantages

of high reliability, relatively flexible operation, convenient repair and maintenance. In

addition, this scheme requires less incoming lines at the 500 kV side and less main

transformers; therefore, it is also better in terms of cost. To sum up, the combination mode

of generators and main transformers shall be the scheme 3; namely, the connection of

multi-generator-transformer unit with 3 generators and 1 main transformer.

6.2.2.2 Electrical connection at 500 kV

The 500 kV switchyard of the HPP has 5 incoming circuits and 2 outgoing circuits,

according to the quantity of 500 kV outgoing circuit proposed for the HPP and the

recommended scheme for the combination mode of generator and main transformer

(multi-generator-transformer unit connection). The following 3 connection options are

preliminarily proposed for techno-economic comparison:

Figure 6.2.2-4 Dual-bus Connection


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Figure 6.2.2-5 3/2 Circuit Breaker Connection + Dual Circuit Breaker Connection

Figure 6.2.2-6 Single-bus Sectionalized Connection

a) Scheme 1: dual-bus connection

The dual-bus connection mode has distinct connection; each incoming and outgoing

line will be connected to one group of circuit breakers respectively, free from mutual

impact. In case one group of bus and relevant equipment connected fail, switch over the

circuit connected with the failed bus to another group of bus and then power can be

supplies again, without any influence on the other group of bus; therefore, this mode has

relatively high flexibility. According to line load conditions, switchover of two groups of

bus can basically balance the load distribution on two groups of bus. Switch quantity in

this mode is less than that required by 3/2 connection mode, which decreases equipment

investment.


6-37

Disadvantages are as follows: transfer switching operation of the isolators is very

complicated; in this scheme, in case any one of elements on the bus fails, all elements on

the bus have to be removed; when a bus tie circuit breaker fails, power failure will be

applied to the whole plant in short time.

b) Scheme 2: 3/2 circuit breaker connection + dual circuit breaker connection

The mode of 3/2 circuit breaker connection + dual circuit breaker connection has high

reliability in power supply. Each incoming and outgoing line will be connected to two

groups of circuit breakers respectively. In case a line or a main transformer fails, the failed

element will be deactivated by transfer switching operation and then power supply in other

circuits can be guaranteed. In case any groups of bus or a circuit breaker is under

maintenance, the relevant circuit needs no switchover and operation of isolator is not

frequent, which decreases possibility of misoperation, convenient for operation and

maintenance.

Disadvantages are as follows: protective relaying and control loop are relatively

complicated; switch quantity required is more than that in the scheme of dual-bus

connection, which increases equipment investment.

c) Scheme 3: single-bus sectionalized connection

This mode has simple and distinct connection, with 7 groups of circuit breakers,

simple protective relaying configuration and secondary connection, and distinct equipment

layout. Each incoming and outgoing line will be connected to 1 group of circuit breakers.

In case a main transformer fails, other circuits can properly operate. This mode has flexible

operation and convenient manipulation, which can meet all operating conditions of the

HPP. It is convenient for putting in operation in stages for transition and further expansion.

It has the minimum investment in equipment.

Disadvantages are as follows: in case any one circuit of circuit breakers is under

maintenance or fails, power failure has to be applied to the relevant connected circuit; in

case a bus tie circuit breaker fails or is under maintenance, a short-time shutdown has to be

applied to the whole plant.

d) Techno-economic comparison

See Table 6.2.2-2 for the techno-economic comparison between each connection


6-38

option at the 500 kV side.

Table 6.2.2-2 Techno-Economic Comparison Between Each Connection

Option at the 500 kV Side

Item Name

Option 1:

Double-bus

Connection

Option 2: 3/2

Connection

Option 3:

Sectionalized

Single-bus

Connection

Connection diagram

Quantity of circuit

breaker/disconnectin

g switch

8/23 11/29 8/16

Investment in

electrical equipment Large Maximum Small

Operation

Each circuit is

respectively

connected with 1

group of circuits.

Normal operation is

carried out by a

circuit breaker; in

addition to

maintenance and

isolation, a

disconnecting switch

Each circuit is

respectively

connected with 2

groups of circuit

breakers. Normal

operation is carried

out by a circuit

breaker, and a

disconnecting switch

is only used for

maintenance and

Each circuit is

respectively

connected with 1

group of circuit

breakers. Normal

operation is

carried out by a

circuit breaker,

and a

disconnecting

switch is only


6-39

is also used for

transfer switching;

therefore, operation

in this option is

complex.

isolation. Therefore,

operation in this

option is relatively

simple.

used for

maintenance and

isolation.

Therefore,

operation in this

option is simple.

Arrangement

This option needs

many circuit

breakers and

disconnecting

switches, so the

arrangement is

relatively complex.

This option needs

many circuit breakers

and disconnecting

switches, so the

arrangement is

complex.

This option needs

a few of circuit

breakers and

disconnecting

switches, so the

arrangement is

simple.

Safe power supply

Reliable power supply:


maintenance of one

group of bus and

equipment connected

with the bus, power

supply of another

bus will not be

influenced. After the

circuit connected

with the failed bus is

switched over to

another group of bus,

power restoration is

achieved.


maintenance of any

bus and equipment

connected with the

bus, and in case of

maintenance of any

circuit breaker,

normal power supply

of any circuit will not

be influenced.

In case of failure

or maintenance of

one bus section

and equipment

connected with

the bus section,

power supply of

another bus

section will not be

influenced but 1/2

of the plant

capacity will be

restricted.


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Affected range of power cut:

In case of

maintenance of a

circuit breaker at any

incoming or

outgoing circuit,

power cut will only

be carried out for the

circuit under

maintenance and

other power supply

circuit will work

properly. In case of

failure of bus tie

circuit breaker,

power cut is required

to be carried out for

the whole plant, and

power restoration

will be conducted

after the failure is

eliminated.

In case of failure of

circuit breaker at each

circuit connected with

a bus, only short-time

power supply of the

circuit subjected to

the failure will be

influenced. In case of

failure of

interconnection

circuit breaker

between two circuits,

only short-time power

supply of these two

circuits will be

influenced.

In case of

maintenance of a

circuit breaker at

any incoming or

outgoing circuit,

power cut will

only be carried out

for the circuit

under

maintenance and

other power

supply circuit will

work properly. In

case of failure of

sectionalized

circuit breaker,

power cut is

required to be

carried out for the

whole plant, and

power restoration

will be conducted

after the failure is

eliminated.

Probability for power cut of whole plant:

In case of this

option, the

Power cut of whole

plant will not occur in

When a bus tie

circuit breaker


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probability for power

cut of whole plant is

small.

the following

conditions: a circuit

fails when one bus is

under maintenance (in

the single-bus

operation mode) and

the circuit breaker

fails to operate; a bus

fails in the single-bus

operation mode; two

buses fail at the same

time in the double-bus

operation mode.

fails, power cut

will be carried out

for the whole

plant.

Relay protection

Relay protection and

control circuit are

both complex, not in

favor of automation

or telemechanization.

Relay protection and

control circuit are

relatively complex.

Relay protection

and control circuit

are both simple.

e) Conclusion

According to the above technical and economic comparison, the scheme 1 has

relatively lower investment and flexible operation but its operation and manipulation are

relatively complicated; the scheme 2 has high reliability but its investment is relatively

higher. The scheme 3 has the lowest investment but its reliability is the poorest. In view of

the installed capacity of the HPP and the role and function of the HPP in Thailand power

grid, it is recommended to adopt the scheme 1 for connection at the 500 kV HV side;

namely, the dual-bus connection mode at the 500 kV side.

6.2.3 Station Service System and Power Supply System at Dam Area


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6.2.3.1 Features of Station Service System and Power Supply System at Dam Area

⑴ The range of power supply is wide, load points are decentralized, and the farthest

power supply point is about 1.0 km ~ 2 km away.

⑵ Power supply loads are large and the maximum station service load is about 8,000

kVA.

6.2.3.2 Design Principle

Because the HPP plays an important role in the electric power system, the station

service system of the HPP is required to have high reliability of power supply. According

to Code for Designing Auxiliary Power System of Hydro-power Station (NB/T35044-2014)

and Electrical-mechanical Design Code of Hydropower Plant (DL/T5186-2004), the

design principle for the service power of plant of the HPP is as follows:

a) Arrangement principle for station service power supply

When all units are under operation, at least 3 station service power supplies shall be

provided. When only some units are under operation, at least 2 station service power

supplies shall be provided. When all units are shut down, at least 2 reliable power supplies

shall be provided but one of them is allowed to stand by.

b) Selection principle for voltage class of service power of plant

Loss of electric energy and equipment investment shall be reduced as far as possible,

while considerations shall be given to the voltage class of station service motor with a

large capacity.

c) Design principle for station service connection:

⑴ The connection shall meet the requirements for sectionalized power supply of

each load center.

⑵ The connection shall be as simple as possible, in favor of relay protection system

used for service power of plant and spare power source automatic switch.

⑶ The connection shall meet the power supply requirements in staged construction

or continuous construction and shall be convenient for transition.

⑷ The common power system of the whole plant and the auxiliary power supply


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system of units shall be fed separately. The auxiliary power supplies of units shall be

independent, so that frequent startup or shutdown of units will not influence the continuous

power supply of the common power system of the whole plant, in favor of rapid power

restoration.

⑸ The connection shall meet the power supply requirements for startup and

shutdown of units. Switching operation for service power of plant shall be reduced as far as

possible.

⑹ The lighting power supply system shall be equipped with a lighting transformer

independently.

⑺ In view of flood control by the dam, a diesel generator unit shall be arranged on

the dam crest as the safety emergency power supply when the dam is used for flood

releasing.

⑻ The powerhouse shall be equipped with a diesel generator unit as the safety

emergency power supply of the HPP powerhouse, to prevent the powerhouse from

inundation.

6.2.3.3 Leading of Station Service Power Supply

According to Article 3.1.1 of Code for Designing Auxiliary Power System of

Hydro-power Station (NB/T35044-2014), the leading mode and arrangement of the

working power supply used for the service power of plant shall meet the requirement of

"When the voltage circuit of generator is equipped with a generator circuit breaker, the

working power supply used for service power of plant shall be arranged between the

generator circuit breaker and the LV side of main transformer" in Paragraph 4. Because all

units of the HPP are equipped with a generator circuit breaker, the station service power

supply shall be arranged at the LV side of main transformer. Normally, the units will feed

the service power of plant. In case of shutdown, the electric power system can reversely

feed the service power of plant. This scheme is characterized by highly reliable power

supply, simple connection, convenient arrangement, and good economic efficiency.

Therefore, it can be applied to the main power supply used for service power of plant of


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the HPP.

Because the HPP is a Grade I large (1) scale HPP, an external power supply shall be

arranged and used as the spare station service power supply, so as to improve the reliability

and continuity of the service power of plant. For the HPP, the external power supply can be

provided as follows:

Mode 1: The service power of plant can be supplied reversely from the electric power

system through the main transformer.

Mode 2: A diesel generator unit shall be arranged.

Therefore, the leading scheme for station service power supply is as follows: The

whole plant is equipped with 4 HV station service transformers, and the main power

supplies used for service power of plant are respectively led from the LV sides of main

transformers TM1~TM4. For the spare station service power supply, in addition to reverse

power transmission from the electric power system through main transformers, 1 diesel

generator unit is respectively arranged on the dam crest and in the powerhouse, serving as

the safety emergency power supply for flood releasing by dam and the safety emergency

power supply of powerhouse.

6.2.3.4 Voltage Selection for Service Power of Plant

The HPP is of a water-retaining type powerhouse on the ground. Because the plant

area is relatively large, the power transmission distance is relatively long, and the load

capacity is relatively large, the station service system shall be of the two-stage voltage

power supply. According to the design principle specified in Article 3.2.2 of Code for

Designing Auxiliary Power System of Hydro-power Station (NB/T35044-2014) that "The

HV service power voltage should be 10 kV and the LV service power voltage should be

0.4 kV" and Article 3.3 that "According to Code for Design of AC Electrical Installations

Earthing (GB/T 50065), the grounding mode of LV station service system should be of the

TN-S or TN-C-S system", the station service system of the HPP shall be of the two-stage

voltage power supply (10 kV and 0.4 kV), the LV distribution system shall be of the

three-phase four-wire system, and the neutral point shall be directly grounded.

6.2.3.5 Connection mode for station service power

The Paklay HPP respectively supplies power to the unit service power, common

power demand of plant and lighting power. Connection mode for station service power


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adopts single-bus sectionalized connection.

a) Power supply mode at 10.5 kV voltage level

The bus at 10.5 kV voltage level of the station service power consists of 4 sections, in

① ② ③ ④2 groups. Bus sections and constitute 1 group while sections and constitute

another 1 group. The THA1 HV station service transformer connected to the LV side of the

TM1 main transformer suppl ①ies power to the bus section . The THA2 HV station service

transformer connected to the LV side of the TM2 main transformer supplies power to the

②bus section . ① ②A bus tie switch is set for the bus sections and . The THA3 HV

station service transformer connected to the LV side of the TM3 main transformer supplies

③power to the bus section . The THA4 HV station service transformer connected to the

LV side of the TM4 ④main transformer supplies power to the bus section . A bus tie

switch is set for the bus ③ ④sections and .

During normal operation, 4 HV station service transformers will respectively supply

power to operate the station service loads in the whole plant. In case any one section of bus

① ②in the bus sections and loses its voltage, automatic bus transfer equipment will

automatically operate via the bus tie switch and then 1 HV station service transformer will

① ②drive the bus sections and for operation. In case any one section of bus in the bus

③ ④sections and loses its voltage, automatic bus transfer equipment will automatically

operate via the bus tie switch and then 1 HV station service transformer will drive the bus

③ ④sections and for operation.

See Fig. 6.2.3-1 for the schematic diagram of HV station service connection.

Fig. 6.2.3-1 Schematic Diagram of HV Station Service Connection


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b) Power supply mode at 0.4 kV voltage level

1) Common power system of whole plant

The bus at 0.4 kV voltage level of the common power demand of plant consists of 4

sections, in 2 groups. Bus sections I and III constitute 1 group while sections II and IV

①constitute another 1 group. The bus section I is connected to the bus section at 10.5 kV

voltage level via the TLA1 common transformer. The bus section III is connected to the

bus section ③ at 10.5 kV voltage level via the TLA3 common transformer. A bus tie

switch is set for the bus sections I and III. The bus section II is connected to the bus section

② at 10.5 kV voltage level via the TLA2 common transformer. The bus section IV is

④connected to the bus section at 10.5 kV voltage level via the TLA4 common

transformer. A bus tie switch is set for the bus sections II and IV.

2) Lighting power system

The bus at 0.4 kV voltage level for lighting power consists of 2 sections. Bus section I

②is connected to the bus section at 10.5 kV voltage level via the TL1 lighting transformer.

③Bus section II is connected to the bus section at 10.5 kV voltage level via the TL2

lighting transformer. A bus tie switch is set for the bus sections I and II.

3) Auxiliary power supply system of units

The 0.4 kV bus connected with the main panel of auxiliary power supply of unit

consists of 6 sections, namely, section I, section II, section III, section IV, section V, and

section VI. The 0.4 kV bus is connected with the 10.5 kV bus as follows:

The bus section I of the main panel ①is connected to the bus section at 10.5 kV

voltage level via the TLP1 unit service power transformer; the bus section II of the main

panel is connected to the bus section ③ at 10.5 kV voltage level via the TLP2 unit service

power transformer; the bus section III of the main panel ①is connected to the bus section

at 10.5 kV voltage level via the TLP3 unit service power transformer; the bus section IV of

the main panel is connected to the bus section ③ at 10.5 kV voltage level via the TLP4

unit service power transformer; the bus section V of the main panel is connected to the bus

section ② at 10.5 kV voltage level via the TLP5 unit service power transformer; the bus

section VI of the main panel is connected to the bus section ④ at 10.5 kV voltage level

via the TLP6 unit service power transformer

The connection mode of No. 1 ~ No. 5 multi-generator-transformer units is as


6-47

follows:

⑴ No. 1 multi-generator-transformer unit connection

The bus section I of main panel is connected with the load point of auxiliary power supply

of G1 unit. The bus section II of main panel is connected with the load point of auxiliary

power supply of G2 unit. The bus sections I and II of main panel are equipped with a bus

tie switch to ensure that both G1 and G2 units have 2 main power supply points.

⑵ No. 2 multi-generator-transformer unit connection

The 0.4 kV bus connected with the sub-panel of auxiliary power supply of No. 2

multi-generator-transformer unit consists of 3 sections that are respectively connected with

the load points of auxiliary power supply of G3, G4 and G5 units. The 0.4 kV bus of

sub-panel is equipped with two power supplies that are respectively connected with bus

sections III and IV of main panel, so as to ensure that G3, G4 and G5 units have 2 main

power supply points.

⑶ No. 3 multi-generator-transformer unit connection





sections III and IV of main panel, so as to ensure that G6, G7 and G8 units have 2 main


⑷ No. 4 multi-generator-transformer unit connection





sections V and VI of main panel, so as to ensure that G9, G10 and G11 units have 2 main


⑸ No. 5 multi-generator-transformer unit connection




6-48



sections V and VI of main panel, so as to ensure that G12, G13 and G14 units have 2 main


4) Protective load power system

The bus at 0.4 kV voltage level for protective load consists of 1 section. Dual power

supply is adopted for the bus section for power supply and the bus section is respectively

connected to the bus sections ② and ③ at 10.5 kV voltage level via TLA5 and TLA6

common transformers. In addition, a 0.4 kV 800 kW diesel generator unit shall be provided

for the HPP as the emergency power supply.

5) Power supply system at dam area

According to the dam crest load information upon preliminary estimates, the

utilization voltages of electrical equipment on the dam crest shall all be 380/220 V.

Therefore, the dam crest power supply system shall supply 0.4 kV primary voltage. The

dam crest connection is of single-bus sectionalized connection mode. Bus section I is

connected to the bus section ② at 10.5 kV voltage level via the TLA7 dam crest

transformer. Bus section II is connected to the bus section ④ at 10.5 kV voltage level via

the TLA8 dam crest transformer. A bus tie switch is set for the bus sections I and II, to

ensure 2 main power supply points for the crest power consumption. In addition, a 0.4 kV

800kW diesel generator unit shall be provided as the emergency power supply for flood

releasing on the dam.

6.2.4 Type Selection for 500 kV HV Switchgear Installation

6.2.4.1 Construction Scale for 500 kV Switchyard

The 500 kV switchyard of the Paklay HPP has 5 incoming lines and 2 outgoing lines. See

Table 6.2.4-1 for the construction scale.

Table 6.2.4-1 Construction Scale for 500 kV Switchyard

S/N Item Name Construction Scale (Equipment

Quantity)

1 500 kV incoming line


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1.1 Incoming circuit breaker bay of No. 1 main

transformer 1


transformer 1


transformer 1


transformer 1


transformer 1

2 500 kV outgoing line

2.1 Circuit breaker bay of 500 kV outgoing line I 1

2.2 No. 1 line trap 3

2.3 Capacitor voltage transformer at No. 1 line 3

2.4 Arrester at No. 1 line 3

2.5 Circuit breaker bay of 500 kV outgoing line II 1

2.6 No. 2 line trap 3

2.7 Capacitor voltage transformer at No. 2 line 3

2.8 Arrester at No. 2 line 3

3 Bus tie circuit breaker bay 1

4 Bus PT&LA bay

4.1 1M PT&LA bay 1

4.2 2M PT&LA bay 1

6.2.4.2 Selection Principle for 500 kV Equipment

According to relevant electric power export plan made by the Lao Government, upon the

completion of the Paklay HPP, the electric power will be completely exported to Thailand

and play a very important role in the Thailand power grid. The operation management of


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the HPP is "unmanned-on-duty" (few-on-duty). Selection of 500 kV switchgear installation

shall comply with the following basic principles:

⑴ In the service environment, the equipment shall meet the requirements for proper

operation, maintenance, short circuit and over-voltage; in addition, long-term development

shall also be taken into account.

⑵ The equipment shall have mature operation experience and advanced technology.

⑶ The equipment shall have safe and reliable operation and convenient maintenance,

being adaptive to the management mode of the HPP, which is "unmanned-on-duty"

(few-on-duty).

⑷ In the design level year, the rated short-time withstand current for electrical equipment

at a 500 kV switchyard shall be temporarily considered as 50kA/2s.

6.2.4.3 Preliminary Determination of Switchyard Site

a) Considerations for site selection

With respect to a 500 kV switchyard, the following factors shall be taken into account for

its site selection:

⑴ Topographic conditions: Civil excavation and backfilling shall be carried out as less as

possible to avoid occurrence of a high slope.

⑵ Geological conditions: shall meet the foundation requirements for switchyard

equipment and framework.

⑶ Incoming and outgoing lines: The outgoing line corridor of transmission line shall be

as open as possible, in favor of arrangement of outgoing line.

⑷ 500 kV HV outlet: The length of outlet at the HV side of main transformer shall be as

short as possible.

⑸ The switchyard site shall be convenient for operation management and close to the

powerhouse as much as possible.

⑹ The site shall be away from the vibration area of tailrace platform as far as possible.

b) Preliminarily determined site scheme

According to the combination mode of generator and transformer as well as the quantity of

outgoing circuit of transmission line, the 500 kV switchyard has 5 incoming lines and 2


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outgoing lines in total and its connection at the 500 kV side is of the double-bus connection

mode. The HPP is of a water-retaining type hydroelectric station and the powerhouse is

arranged in a compact manner.

⑴ Option 1: GIS switchyard site for auxiliary plant

According to the arrangement of electromechanical equipment in auxiliary plant, if an SF6

gas insulated switchgear (GIS) is adopted, the GIS switchyard can be arranged at the

downstream auxiliary plant (E.L. 245.50 m) at the No. 3 ~ No. 5 unit bay. Meanwhile, the

GIS is directly connected with main transformers through an SF6 tubular bus.

⑵ Option 2: Right-bank AIS switchyard site

According to topographical conditions of the site area, if the air insulated switchgear (AIS)

is adopted, the AIS switchyard can be arranged on the bottomland on the right bank of the

river. However, main transformers are far away from the switchyard, with limited outgoing

line gallery; the HV side of the main transformers shall be connected to the switchyard via

a 500 kV HV cable. Therefore, it requires an additional 500 kV HV cable of about 7.5 km

in length and 30 cable heads.

6.2.4.4 Equipment model selection and arrangement in GIS option

In the GIS option, the 500 kV GIS circuit breaker is of a horizontal double-break type; the

GIS is connected with main transformers and outgoing bushing through an SF6 tubular bus.

The GIS switchyard is arranged as follows:

The GIS switchyard is arranged in 2 layers. The first layer is the SF6 tubular bus layer and

the second layer contains a GIS room and a 500 kV open-type outgoing line platform.

The plane arrangement dimension of the GIS room and the 500 kV open-type outgoing line

platform is 138.90 m × 21.40 m. The plane dimension of the GIS room at the left side is

68.50 m × 17.40 m. The GIS room is mainly equipped with 5 circuit breaker incoming

bays, 2 circuit breaker outgoing bays, 1 circuit breaker bus tie bay, and 2 PT&LA bays.

The plane dimension of the 500 kV open-type outgoing line platform at the right side is

70.50 m × 21.40 m. The platform is mainly equipped with 6 traps, 6 capacitor voltage

transformers, and 6 arresters.

6.2.4.5 Equipment model selection and arrangement in AIS option

The 500 kV AIS mainly consists of HV distribution equipment and outgoing line


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equipment. The HV distribution equipment includes circuit breaker, disconnecting switch

(including grounding switch), current transformer, voltage transformer, arrester and bus.

The outgoing line equipment includes line arrester, voltage transformer and so on. The

circuit breaker is of the SF6 insulation porcelain stanchion type and the disconnecting

switch is of the single-arm folded structure. The AIS switchyard has a plane arrangement

dimension of 250 m × 100 m and an occupied area of about 25,000 mm2. The 500 kV AIS

is arranged as follows:

A suspended tubular bus is employed, porcelain stanchion circuit breakers are arranged in

a single row, and both the incoming and outgoing lines are arranged at a single side. Facing

the outgoing line side, bays are arranged from left to right as follows: No. 1 incoming bay

(to the TM1 main transformer), No. 2 incoming bay (to the TM2 main transformer), No. 3

outgoing bay, No. 4 incoming bay (to the TM3 main transformer), No. 5 bus tie bay, No. 6

incoming bay (to the TM4 main transformer), No. 7 outgoing bay, and No. 8 incoming bay

(to the TM5 main transformer).

6.2.4.6 Technical Comparison for AIS Option and GIS Option

In conclusion, both AIS switchyard and GIS switchyard can meet the technical

requirements of the Project. Technical analysis and comparison of the GIS switchyard and

AIS switchyard are as follows:

a) Reliability and safety

Generally, a GIS is more reliable and safer than an AIS in terms of operation because

the GIS has a lower failure rate. The GIS has advantages in reliability and safety as

follows:

(1) Electrical equipment in the GIS is more reliable than that in the AIS in terms of

insulating property.

(2) Contact resistance at the connection part of the GIS conductors is less than that of

the AIS conductors.

(3) Personal injury accidents: according to the statistical data, personal injury

accidents caused by the AIS occur every 1,000 station years, while those caused by the GIS

occur every 4,000 station years.

b) Maintenance management and repair

(1) The GIS is nearly free from maintenance, with a small quantity of maintenance


6-53

works.

(2) Most elements of the AIS are susceptible to environmental conditions, with a large

quantity of maintenance works.

(3) The GIS has a heavy maintenance cycle of 15~20 years, with a relatively longer

maintenance time; the AIS has a shorter heavy maintenance cycle, with more frequent

maintenance works. According to the statistical data, the ratio of the AIS maintenance

cycle to the GIS maintenance cycle is 1:5.

c) Installation

Generally, the GIS has complete components and its parts and components are

model-building blocks; therefore, the GIS has convenient site installation and

commissioning. However, the AIS has relatively conditions, with longer installation and

commissioning time.

d) Seismic resistance

The GIS elements are enclosed inside a shell and the whole switchgear installation is

connected to be an integrated structure; in addition, its height is lower than that of the AIS;

therefore, it has better integral rigidity and seismic resistance than the AIS.

e) Electrostatic Induction and radio interference level

Most GIS elements are installed inside an enclosed shell that is grounded. Based on

shielding effect of the shell, it is much better than the AIS in terms of electrostatic

induction and radio interference level.

f) Internal fault test

The structure of GIS equipment is highly intensive; therefore, fault of one element

inside may impact other elements. Compared with the AIS, the GIS has a larger fault

impact scope and it is more difficult to find out the failed element in the GIS.

g) Civil construction period and difficulty of the switchyard

In case of the AIS option, it will be arranged on a bottomland on the right bank of the

river, with an occupied area of about 150.0 m x 70.0 m. In case of the GIS option, the GIS

will be arranged in the auxiliary plant downstream at an elevation of 245.50m in the

section of No. 3~5 units and the GIS room will have an area of 68.50m×17.40. Therefore,

the AIS switchyard has a larger occupied area than the GIS switchyard, with more civil

works. Compared with the GIS switchyard, the AIS has disadvantages as follows:


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(1) The AIS switchyard has a longer civil construction period.

(2) The AIS switchyard has a larger civil works.

(3) The AIS switchyard requires an additional investment on the electrical equipment

such as 500 kV HV cables.

(4) The AIS switchyard is of decentralized layout of equipment, with inconvenient

operation and maintenance.

In conclusion, the GIS scheme is better than the AIS scheme technically.

6.2.4.7 Economic Comparison for AIS Option and GIS Option

According to the quantities of civil works and relevant investment amounts provided

by the powerhouse discipline, the investment comparison for civil works of 500 kV

switchyard is listed in Table 6.2.4-2, the investment comparison for main electrical

equipment is listed in Table 6.2.4-3, and the comparison for comprehensive investment is

listed in Table 6.2.4-4.

Table 6.2.4-2 Investment Comparison for Civil Works of 500 kV Switchyard

S/N Item Name Unit GIS AIS Unit Price

(USD)

Total

Price of

GIS

(USD)

Total

Price of

AIS

(USD)

Differenc

e Value

(USD)

GIS-AIS

1 Open earth

excavation m3 / 221902 3.31 / 734939 -734939

2 Open rock

excavation m3 /

125744

3 9.08 / 11417582

-1141758

2

3 Shotcrete m3 / 3008 201.17 / 605119 -605119

4

Anchor rod

(Ф25, L=6

or 8m)

Nr. / 2228 89.978 / 200471 -200471

5

C20

structure

concrete

m3 / 15000 121.03 / 1815450 -1815450


6-55

6

C25

structure

concrete

m3 5400 / 138.49 747846 / 747846

7 Reinforcem

ent t 648 750 1585.36 1027313 1189020 -161707

8

Drainage

hole (D56,

L=3m)

m / 3759 41.07 / 154382 -154382

9 Total (USD

103) 1775 16117 -14342

Remarks: Investments in the above table are all based on the approximate price in September

2013.


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Table 6.2.4-3 Investment Comparison for Electrical Equipment of 500 kV Switchyard

S/N Description Main Electrical Equipment Unit Qty. Price (USD)

I Option 1: GIS switchyard for auxiliary plant

1 500kV GIS

GIS circuit breaker bay Nr. 8 1.1 million/bay

GIS PT&LA bay Nr. 2 400,000/bay

2 500kV

open-type equipment

Capacitor voltage

transformer Set 6 12,500/set

Zinc oxide arrester Set 6 6,000/set

Trap Set 3 46,000/set

3 Investment in

electrical equipment 9.849 million

II Option 2: Right-bank AIS switchyard

1 500kV AIS

AIS circuit breaker bay Nr. 8 460,000/bay

AIS PT&LA bay Nr. 2 80,000/bay

2 500kV

open-type equipment

Capacitor voltage

transformer Set 6 12,500/set

Zinc oxide arrester Set 6 6,000/set

Trap Set 3 46,000/set

3 500 kV HV cable

500kV XLPE m 7500 385/m

GIS cable terminal Nr. 15 61,500/Nr.

AIS cable terminal Nr. 15 61,500/Nr.

4 500kV GIB 500kV Set 5 230,000/set

5 Investment in

electrical equipment 9.9715 million


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Table 6.2.4-4 Comparison for Comprehensive Investment of 500 kV Switchyard

103 (USD)

S/N Item Name Option 1: GIS Switchyard for

Auxiliary plant

Option 2: Right-bank AIS

Switchyard

1 Investment in civil works 1775.0 16117.0

2 Investment difference in civil

works 0.00 +14342

3 Investment in electrical

equipment 9849.0 9971.5

4 Investment difference in

electrical equipment 0.00 +122.5

5 Total project investment 11624.0 26088.5

6 Total investment difference 0.00 +14464.5

6.2.4.8 Conclusion

According to the above techno-economic analysis and comparison, it is recommended that

the 500 kV HV distribution equipment of the HPP should be of the GIS option and the GIS

switchyard shall be arranged at the downstream auxiliary plant (E.L. 245.50 m). Reasons

①are as follows: The investment in the GIS option is USD 14.4645 million less than that

in the AIS option, because a GIS switchyard occupies less land and has a lower cost of

②civil works. It is easy to implement "unmanned-on-duty" (few-on-duty) management

mode for a GIS, due to its high power supply reliability, small workload of maintenance

work, convenient management and easy centralized monitoring.

6.2.5 Position Selection for 500 kV GIS Switchyard

6.2.5.1 Determination of GIS Arrangement Scheme

The review meeting for the feasibility study report on Paklay HPP at the Mekong River in

Laos was held on April 21~22, 2014. In the meeting, the technical parts of the Project were

reviewed. Review comments on the 500 kV HV distribution equipment are as follows: It is

rational to adopt the GIS scheme for the 500 kV HV distribution equipment. However, it is

suggested that the GIS arrangement position should be further studied to make proper


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adjustment because the tailrace platform will suffer from vibrations when a GIS room is

arranged at the unit bay. According to the review comments from experts, 3 GIS

arrangement options are proposed for technical comparison as follows:

Option 1: The 500 kV GIS room is arranged at the downstream auxiliary plant (E.L.

245.50 m) at the No. 3 ~ No. 5 unit bay, while the 500 kV open-type outgoing line

platform is arranged side by side at the No. 1 ~ No. 2 unit bay ①and at the erection bay of

downstream auxiliary plant (E.L. 245.50 m).

②Option 2: The 500 kV GIS room is arranged at the erection bay of downstream auxiliary

plant (E.L. 245.50 m), while the 500 kV open-type outgoing line platform is arranged side

by side at the downstream auxiliary plant (E.L. 245.50 m) at the No. 11 ~ No. 14 unit bay.

①Option 3: The 500 kV GIS room is arranged at the erection bay of downstream auxiliary

plant (E.L. 245.50 m), while the 500 kV open-type outgoing line platform is arranged on

the roof of GIS room (E.L. 260.50 m).

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6.2.5.2 Technical Comparison

See Table 6.2.5-1 for the summary of technical comparison between each GIS arrangement

option.

Table 6.2.5-1 Technical Comparison for GIS Arrangement Options

Item

Name Option 1 Option 2 Option 3

500 kV

outgoing

line

corridor

The 500 kV open-type

outgoing line platform is

arranged against the left

bank of the Mekong River.

The span and deflection

angle between the outgoing

line framework and the

terminal tower are both

small. The outgoing line

corridor is relatively wide.

To sum up, this option is in

favor of the design of

transmission line.



arranged in the middle of the

riverbed, far away from both

banks. Therefore, a terminal

tower is needed to be

arranged on the retaining

wall at the dredging area.

However, the elevation of the

retaining wall at the dredging

area is relatively low, and it

is difficult to deal with the

tower foundation, and the

quantities of tower are

relatively large. To sum up,

this option is not in favor of

the design of transmission

line.



arranged against the left

bank of the Mekong River.

The span and deflection

angle between the

outgoing line framework

and the terminal tower are

both small. The outgoing

line corridor is relatively

wide. To sum up, this

option is in favor of the

design of transmission

line.

Vibration

Vibration of tailrace platform:

The 500 kV GIS is arranged

at the downstream auxiliary

plant at the No. 3 ~ No. 5

unit bay. When water flow

passes through the units, the

GIS structure will suffer

from vibrations which will

vibrate the electrical

equipment. To sum up,

The 500 kV GIS is arranged

at the ② erection bay of

downstream auxiliary plant.

In flood season, the whole

plant will be shut down when

the bottom discharge orifice

is used for flushing. To sum

up, equipment vibration does

not exist in this option.

The 500 kV GIS is

①arranged at the erection

bay of downstream

auxiliary plant. The

substructure is free of

discharging facilities. To

sum up, equipment

vibration does not exist in

this option.


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equipment will suffer from

vibrations in this option.

Solutions:

1. The 500 kV GIS circuit

breaker should be of the

horizontal type. In addition,

expansion joints in a proper

number shall be provided

for connections of 500 kV

GIS SF6 tubular bus, 13.8

kV isolated-phase bus and

relevant equipment, so as to

improve the anti-vibration

performance of equipment.

2. In the design, a flexible

circuit conductor shall be

used for fixture wire and

equipment connections as

far as possible, and the

flexible circuit conductor

shall be long enough, so as

to improve the anti-vibration


3. A connection terminal

with spring fasteners should

be used as the secondary

connection terminal, to

avoid disconnection of the

secondary connection and to

improve the anti-vibration


Equipment vibration does not

exist in this option.

Equipment vibration does

not exist in this option.

Examples

Refer to the Taoyuan HPP,

the Feilaixia Hydropower

Project, and the Shihutang

Navigation and Hydropower

Examples for arrangement of

switchyard on the tailrace

platform in the middle of

riverbed are seldom.

A tubular HPP complex

generally has a wide

landform. In most cases, a

switchyard is arranged at


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Complex Project for

arrangement of switchyard

on the tailrace platform at

the side of river bank.

the erection bay of

downstream auxiliary

plant at the side of river

bank, and the switchyard

and the outgoing line

platform are arranged at

one elevation.

Structure

pattern

The space of downstream

auxiliary plant is fully used

to arrange the switchyard

and open-type outgoing line

equipment. To sum up, the

structure pattern is relatively

rational.

The space of downstream

auxiliary plant is fully used

to arrange the switchyard and

open-type outgoing line

equipment. To sum up, the

structure pattern is relatively

rational.

For the Project, if the

switchyard is arranged at

①the erection bay of

downstream auxiliary

plant, the switchyard and

the outgoing line platform

shall be arranged in a

stagger manner because

①the end of the erection

bay is a high slope. To

sum up, the structure

pattern is irrational.

6.2.5.3 Conclusion

According to the above technical comparison, option 1 is in favor of the arrangement

of 500 kV outgoing line of switchyard and its structure pattern is rational. Therefore,

option 1 is the recommended GIS arrangement scheme of the HPP.

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6.2.6 Selection of Main Electrical Equipment

6.2.6.1 Estimate of short circuit current

Because of lack of relevant data to connect to the power system, it is temporarily

consider the short circuit current of the HV bus at 500 kV side to be 50 kA and the power

supply to be infinite. Upon estimate, the short circuit current at the generator outlet of the

multi-generator-transformer unit is less than 80 kA.

6.2.6.2 Main electrical equipment

a) Turbo- generator

Model: SFWG55-64/8000

Quantity: 14

Type: Three-phase, horizontal type, bulb, closed forced circulation, air-cooling and

synchronous generator

Rated capacity: 55 MW

Rated voltage: 13.8 kV

Rated current: 2422.1 A

Rated power factor: 0.95

Rated frequency: 50 Hz

Rated speed: 93.8 r/min

Direct-axis subtransient reactance X"d 0.≮ 21 (tentative)

Insulation grade: F

Brake mode: mechanical

Excitation mode: self-shunt thyristor static excitation mode

Fire control method: fixed water spray

b) Generator voltage switchgear installation

(1) Generator voltage bus

From the generator main outlet to the 13.8 kV switchgear, the generator voltage bus is of

the common enclosure bus or the insulating tubular bus with a rated current of 3,150 A and

a thermal stability current/time of 80kA/2s. From the 13.8 kV switchgear to the LV side of


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main transformer, the generator voltage bus is of the isolated-phase bus with a rated

current of 8,000 A and a thermal stability current/time of 80kA/2s. Main technical

parameters are as follows:

Type: common enclosure bus or the insulating tubular bus/isolated-phase bus

Cooling mode: natural cooling

Conductor type: Copper conductor/tubular aluminum conductor

Rated voltage: 13.8kV

Maximum voltage: 15.8kV

Rated current: 3150A/8000A

Rated frequency: 50Hz

Thermal stability current (2s):

Main circuit (effective value) 80kA

Branch circuit (effective value) 125kA

Dynamic stability current:

Main circuit (peak value) 200kA

Branch circuit (peak value) 315kA

⑵ Generator outlet circuit breaker

The HPP is of the multi-generator-transformer unit connection. The generator has a rated

capacity of 55 MW, a rated voltage of 13.8 kV and a rated current of 2422.1 A. The

corresponding generator outlet circuit breaker shall have a rated current of 3,150 A and a

rated short-circuit breaking current of 80 kA, and its main technical parameters shall be as

follows:

Type: SF6 generator circuit breaker

Insulating medium: SF6

Rated voltage: 13.8kV

Rated current: 3150A



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Rated short-circuit making current (peak value): 220kA

Rated peak withstand current: 220kA

Rated short-time withstand current (effective value)/time: 80kA/3s

Rated short-circuit breaking current 80kA

(3) 13.8 kV switchgear installation

The HV station service circuit is proposed to be equipped with an HV current limiting

fuse cabinet. Normal operation (breaking of rated current) is implemented by a load switch.

In case of short circuit, the HV current limiting fuse will provide corresponding protection

for the circuit. A potential transformer, current transformer, surge arrester and others are all

installed inside a fully-closed metal-armored cabinet. All electrical cabinets are of three

phases. Grounding of the generator neutral point is realized by the grounding transformer.

c) Main transformer

The multi-generator-transformer unit connection is adopted for the combination mode of

generator and main transformer. If the multi-generator-transformer unit connection consists

of 3 generators and 1 transformer, in 4 groups, the rated capacity (180 MVA) of main

transformer shall match with the rated capacity of 3 generators. If the

multi-generator-transformer unit connection consists of 2 generators and 1 transformer, in

1 group, the rated capacity (120 MVA) of main transformer shall match with the rated

capacity of 2 generators. Selection for type and parameters of main transformer:

1) Type of main transformer

⑴ Transport of heavy-big piece

Transport scheme of heavy-big piece for the HPP: The transport of heavy-big piece is

carried out by water, rail and road together. Restricted by the load standard of rail tunnel

and road bridge, the transport dimension of the biggest piece shall be within the level-2

over-limit range of railway and the maximum weight shall not exceed 100t.

According to the data on main transformers provided by manufacturers, the transport

weight of common three-phase transformer with nitrogen is beyond the transport

conditions for heavy-big piece of the HPP. Therefore, the following 2 options (i.e.

single-phase transformer bank and combined three-phase transformer) shall be taken into

account for the type of main transformer.


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Option 1: single-phase transformer bank

In this option, three common single-phase transformers are combined into one three-phase

transformer, featuring mature design and fabrication experience, small transport weight

and dimension, short installation period, and rich operation experience. However, the

arrangement area in this option is relatively large.

Option 2: combined three-phase transformer

Upon study and analysis, the combined three-phase transformer composed of three special

single-phase transformers is characterized by mature design and fabrication experience and

wide application. The special single-phase transformer has a structure basically the same as

that of the common one. In combination, independent oil tanks are adopted and only a lead

conduit is used to connect three transformers as a whole. Namely, oil lines of three

independent single-phase transformers are connected as a whole. In this option, the

transport weight, transport dimension and occupied area of arrangement are small, and the

installation period is relatively short.

⑵ Technical analysis

◇ Single-phase transformer bank:

① Reliability

The single-phase transformer bank is composed of three single-phase transformers. In

general, three transformers are respectively arranged in an independent room so their oil

lines are totally separated. Therefore, three-phase short circuit will not occur and reliability

of HPP operation will be improved.

② Arrangement

The single-phase transformer bank is composed of three single-phase transformers. In

general, three phases are arranged separately. According to the typical fire law for

electrical equipment in China, a transformer of which the oil amount is 2,500 kg or above

must be arranged separately; a fire partition shall be used for separation if the interval is

less than 10 m (500 kV). The oil amount of single-phase transformer at an ultra-large type

HPP far exceeds the value specified in the fire law, so the transformers must be arranged

and installed separately and the occupied area is large accordingly.

③ Spare phase


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Application of single-phase transformer bank to a large HPP is to ensure the reliability of

HPP operation. When the quantity of transformer is relatively large, a spare phase shall be

used to improve the reliability of HPP operation and reduce the outage cost. The

replacement of spare phase of single-phase transformer bank shall be convenient.

Specifically, a faulted phase can be taken out from the connecting part between HV side

and LV side and then the spare phase is installed at the connecting part and then the HV

and LV sides are connected again and finally corresponding tests are made.

◇ Combined three-phase transformer:

① Reliability

With the continuous development of design, fabrication and installation technologies of

transformer, the combined three-phase transformer is of independent oil tanks and only a

lead conduit is used to connect three phases as a whole. Namely, oil lines of three

independent single-phase transformers are connected as a whole. In addition, the workload

of site installation is reduced as much as possible. Meanwhile, with the continuous

improvement of construction means and installation process, the reliability of HPP

operation can be guaranteed as long as the field construction management and supervision

are strengthened.

Moreover, after the combined three-phase transformer is assembled on the site, it can work

as a three-phase transformer, sharing one set of oil protection and cooling system.

Therefore, the total quantity of coolers, medium-pressure and low-pressure bushings, and

oil conservators will be reduced, in favor of equipment arrangement and cost reduction. At

present, many HPPs in China have been equipped with the combined three-phase

transformer (such as Lingtan HPP and Xiluodu HPP), and rich experience in both

fabrication and operation has been accumulated.

To sum up, the combined three-phase transformer is inferior to the single-phase

transformer in terms of reliability, but it still can meet the requirements for safe operation

of HPP.

② Arrangement

The combined three-phase transformer has a simplified arrangement mode and less

occupied area. A lead conduit is used to connect three single-phase transformers as a whole.

The single-phase transformers have nearly the same arrangement mode as the three-phase


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transformer. Compared with the single-phase transformer bank, the combined three-phase

transform ① ②er has the following advantages: small occupied area; simple connection

with isolated- ③phase bus at generator outlet; reduction in dimension of auxiliary plant for

arrangement of auxiliary equipment of main transformer, reducing the quantities of civil

works. Therefore, technically and economically, the combined three-phase transformer is

more rational than the single-phase transformer bank in terms of transformer arrangement.

⑶ Conclusion

According to the above factors, in view of reliability and operation and maintenance of

main transformers, the single-phase transformer bank has slightly higher reliability, easier

installation, shorter replacement period of spare phase and easier replacement process than

the combined three-phase transformer. However, the single-phase transformer bank has a

relatively large occupied area and project cost. Therefore, it is recommended that the type

of main transformer of the HPP should be of the combined three-phase transformer to

follow the principle of less project investment.

2) Cooling mode of main transformer

The ODWF and OFAF are both feasible technically for the main transformer. However,

the design of ventilation system will be difficult if the air cooling mode is adopted because

the HPP is of a water-retaining type hydroelectric station and the main transformers are

arranged inside the main transformer room of auxiliary plant. Based on advantages of

convenient water taking at the HPP, mature technology of water cooler and good water

quality of river, it is recommended that the cooling mode of transformers at the HPP

should be of the water cooling mode, so as to simplify the design of ventilation and heat

dissipation and to reduce noise.

3) Technical parameters of main transformer:

The combined three-phase, dual-winding, ODWF, copper winding, non-excitation

voltage-regulation boosting power transformer is selected as the main transformer. Its main


Type: SSP-H-180000(120000)/500

Rated capacity: 180,000 kVA/4 sets

Rated capacity: 120,000 kVA/ 1 set


6-69

Rated transformation ratio: 525±2×2.5%/13.8kV


Connection symbol: YNd11

Short-circuit impedance: Uz=14%

Connection mode of incoming line at the LV side: connected with IPB

Connection mode of outgoing line at the HV side: connected with GIB

Transport weight of biggest piece: ~100t

d) 500 kV HV distribution equipment

1) 500 kV GIS

The indoor SF6 GIS is proposed to be used as the 500 kV switchgear. The GIS

switchyard is arranged at the downstream auxiliary plant (E.L. 245.50 m). Main


Rated voltage: 550kV

Rated current: 3150A


Rated short-circuit breaking current: 50 kA (effective value)

Rated making current: 125kA

Rated short-time withstand current/time 50kA/3s

2) 500 kV open-type outgoing line equipment

The outdoor open-type outgoing line equipment of the HPP mainly includes a capacitor

voltage transformer, an arrester, a trap and so on. The open-type outgoing line

equipment is arranged at the downstream auxiliary plant and its platform has an

elevation of 245.50 m a.s.l.

⑴ Voltage transformer at the 500 kV outgoing line side

It is recommended that the voltage transformer at the 500 kV outgoing line side should

be of the capacitor voltage transformer. Compared with the electromagnetic voltage

transformer, the capacitor voltage transformer is of the capacitor divider and


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characterized by less internal insulating oil, high operation reliability, small workload

of maintenance. In addition, the capacitor voltage transformer can also be used as

carrier coupling capacitor of power line. Main technical parameters of capacitor voltage

transformer are as follows:

Type Capacitive

Transformation ratio 550/ 3 /0.1/ 3 /0.1/ 3 /0.1kV

Accurate degree 0.1/0.5/0.5/3P

Capacity 5VA/50VA/50VA/100VA

⑵ 500 kV line arrester

The line arrester is of the zinc oxide arrester for over-voltage protection against

lightning invasion wave and over-voltage protection against operation. Main technical


Type zinc oxide arrester (MOA)

Rated voltage 444kV

System voltage 500kV

Continuous operating voltage 324kV

Nominal discharge current grade 20kA

DC lmA, reference voltage ≤597kV

Switching impulse-current residual voltage (peak value) ≤907kV

Residual voltage under lightning impulse current (peak value) ≤l106kV

Residual voltage under steep current impulse (peak value) ≤1238kV

2 ms rectangular wave current (peak value) 2,000 A, 20 times

⑶ Line trap

The line trap is of the outdoor seat-type trap, with main technical parameters as

follows:

Model XZF-2000-1.0/50


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Rated voltage 550/ 3 kV

Rated frequency 50Hz

Rated working current 2000A

2s rated thermal stability current (effective value) 50kA

Peak value of short-circuit current 125kA

Rated inductance (it will be adjusted after specific frequency range is determined)

1mH

Allowable deviation ±5%

Bandwidth (it will be adjusted after specific frequency range is determined)

64~464kHz

Wave form: Approximate to sine wave

Quality factor of main coil (at 100 kHz) ≥30

e) Electrical equipment of station service system

The electrical equipment of station service system shall be selected based on the station

service connection and estimated loads of service power of plant.

⑴ HV station service transformer

The HV station service transformer is of 4 dry-type transformers, in 2 groups. The

capacity is under the consideration that 2 transformers back up each other. Namely, the

capacity of each group of transformer is half of the whole plant load (8,000 kVA). Main

technical parameters are as follows:

Type SCB11-4000/13.8

Rated capacity 4000kVA

Transformation ratio 13.8±2×2.5%/10.5kV

Impedance voltage 7%

Type of voltage regulation no-load voltage regulation

⑵ Station service transformer

Type SCB11-2000/10.5


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⑶ Unit service transformer

Type SCB11-1600(500)/10.5

Rated capacity 1,600 kVA (4 in total)/500 kVA (2 in total)




⑷ Lighting transformer

It is recommended that a lighting transformer should be arranged independently and the

on-load voltage regulation should be adopted, so as to prevent lighting quality from

being affected by fluctuation of station service supply voltage cause by drastic changes

in station service loads. Main technical parameters are as follows:

Type SCB11-400/10.5




Type of voltage regulation on-load voltage regulation

⑸ Dam crest transformer

Type SCB11-1000/10.5






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⑹ In-plant emergency transformer

Type SCB11-630/10.5





⑺ Diesel generator unit

A diesel generator unit is arranged on the dam crest to serve as the emergency power

supply for flood control by dam. The capacity of diesel generator unit shall comply

with the maximum quantity of flood gates opened at the same time. A diesel generator

unit is arranged in the powerhouse to serve as the emergency power supply for

powerhouse and to meet the requirements for earthquake resistance and prevention of

powerhouse and leakage water dewatering pump. Main technical parameters are as

follows:

Capacity 800 kW (powerhouse)/800 kW (dam)

Voltage 380V/220V

Frequency 50Hz

⑻ HV station service switchgear

The 10.5 kV station service system will be of the indoor metal armored movable

switchgear inside which a vacuum circuit breaker will be provided.

⑼ LV station service switchgear

The 0.4 kV station service system will be of the MNS drawer type switchgear.

6.2.7 Over Voltage Protection (OVP) and Grounding

6.2.7.1 Principle of Insulation Coordination

The design of over-voltage protection and insulation coordination shall be carried out

according to Insulation Co-ordination — Part 2: Application Guide (GB311.2-2013), Code

for Design of Overvoltage Protection and Insulation Coordination for AC Electrical

Installations (GB/T 50064-2014) [clause explanations are attached], and Overvoltage


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Protection and Insulation Coordination Design Guide for Hydro-power Station (NB/T

35067-2015). The Principle of insulation coordination is as follows:

⑴ Under each over-voltage, the insulation strength of electrical equipment shall be

higher than the voltage level and have proper margins.

⑵ The resonance over-voltage shall be avoided and eliminated during design and

operation.

6.2.7.2 Neutral Point Grounding Mode

⑴ Generator neutral point

The grounding of generator neural point will be achieved by a grounding transformer.

⑵ Main transformer neutral point

Because no special requirements are proposed in the design of grid connection, the

500 kV main transformer neutral point of the HPP is temporarily of the direct grounding

mode.

6.2.7.3 Direct lightning protection

The roof lightning strips of powerhouse and auxiliary plant of the HPP are used to prevent

them from direct lightning. The 500 kV open-type outgoing line platform is equipped with

a framework lightning rod and a lightning conductor, which will work together to prevent

the platform from direct lightning. The whole 500 kV transmission line is equipped with

double lightning conductor to prevent the whole line from direct lightning.

6.2.7.4 Lightning invasion wave OVP1) Arrangement scheme of arrester

According to Overvoltage Protection and Insulation Coordination Design Guide for

Hydro-power Station (NB/T 35067-2015), the arrangement scheme of 500 kV arrester of

the HPP is as follows:

(1) Each circuit of 500 kV outgoing lines shall be equipped with 1 group of zinc

oxide arresters aside;

(2) Each group of 500 kV GIS bus shall be equipped with 1 group of zinc oxide

arresters;

⑶ The 13.8 kV bus at the LV side of each main transformer is equipped with 1 group

of zinc oxide arresters, to prevent the LV winding insulation of main transformer from

being damaged by the electrostatic component of lightning coupling over-voltage


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generated at the HV winding of main transformer.

2) Lightning over-voltage simulation

The calculation for the over-voltage protection against lightning invasion wave is

carried out based on the EMTP software, to check if the arrangement scheme of arrester is

rational or not. According to the diagram of main electrical connection of the HPP, the

operation mode suffering from the severest over-voltage is "single transformer ~ single

line". Therefore, the shortest route is as shown in Fig. 6.2.6-1

(LA1→CVT1→ABS1→CB1→MVT1→LA2→CB2→TR1).

Fig. 6.2.7-1 Simulation Calculation Equivalent Circuit Diagram

The ground capacitance model is applied to a capacitor voltage transformer, a GIS circuit

breaker assembly unit, an electromagnetic voltage transformer, and a main transformer.

The wave impedance model is applied to an overhead transmission line and a GIS SF6

tubular bus.

◇ Parameters of line arrester

Rated voltage 444kV

Maximum continuous operating voltage 324kV

8/20μs residual voltage under lightning impulse (20 kA) 1106kV


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30/60μs residual voltage under switching impulse (2 kA) 907kV

◇ Parameters of GIS bus arrester

Rated voltage 420kV

Maximum continuous operating voltage 318kV

8/20μs residual voltage under lightning impulse (20 kA) 1046kV

30/60μs residual voltage under switching impulse (2 kA) 858kV

See Table 6.2.7-1 for volt-ampere characteristics of arrester.

Table 6.2.7-1 Volt-Ampere Characteristics of 500 kV Zinc Oxide Arrester

I(kA) 0 1 5 10 20 40 1mA(DC)

U(kV) Line side 0 950 1009 1050 1106 1212 597

Bus 0 891 946 984 1046 1136 565

◇ Parameters of lightning invasion wave

In the calculation of traveling wave protection, the lightning invasion wave form is of the

oblique-angled and flat-topped wave, and only lightning stroke within 0.2 km (the first

base tower) is taken into account. The lightning invasion wave has an amplitude of

U0=2450kV and a wave head of τ=2.6μs.

◇ Analysis of calculated results

Under the "single line ~ single transformer" operation mode (the worst case), the

maximum voltage value and equipment insulation level in case of nearby lightning stroke

are listed in Table 6.2.7-2 and the simulation waveform is as shown in Fig. 6.2.7-2.

Table 6.2.7-2 Comparison for Maximum Over-voltage Value and Insulation Level of

Equipment

Node

No. Equipment Name

Equipment

Code

Maximum Voltage In Case of

Nearby Lightning Stroke

Equipment

Insulation Level

(kV)

1 Zinc oxide arrester at the

line side LA1 835 1675


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Node

No. Equipment Name

Equipment

Code

Maximum Voltage In Case of

Nearby Lightning Stroke

Equipment

Insulation Level

(kV)

2 Capacitor voltage

transformer CVT1 840 1675

3 SF6/air bushing + SF6

conduit ABS1 842 1550

4 GIS circuit breaker

assembly unit CB1 846 1550

5 Electromagnetic voltage

transformer MVT1 1036 1550

6 Zinc oxide arrester at the

GIS bus LA2 1048 1675

7 GIS circuit breaker

assembly unit CB2 1112 1550

8 Main transformer TR1 1132 1550

Fig. 6.2.7-2 Simulation Waveform for Lightning Over-voltage

3) Conclusion

Under the "single line ~ single transformer" operation mode suffering from the severest


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lightning over-voltage, the arrangement scheme of arrester meets the requirements as

follows: the lightning over-voltage level on the 500 kV distribution equipment and main

transformer does not exceed the equipment insulation level; both the insulation

coordination and the insulation protection margin comply with relevant design codes and

specifications.

6.2.7.5 Grounding Design of HPP

a) Principle of grounding design

The working grounding, protective grounding and lightning protection grounding of the

HPP share one integral grounding device. The grounding design complies with Ground

Design Guide for Hydro-power Station (NB/T 35050-2015) and Code for Design of AC

Electrical Installations Earthing (GB 50065-2011).

Lacking of relevant data on grid connection, the allowable value of grounding resistance is

temporarily designed as 0.5 Ω. The design principle of grounding system of the HPP is as

follows:

⑴ Make full use of the underwater structural reinforcement for ground connection with a

natural grounding body, and erect a reservoir grounding grid as the main grounding grid.

⑵ Arrange a voltage balancing net to ensure that neither the contact potential difference

nor the step potential difference of the grounding grid will exceed the specified value in

relevant codes and specifications.

⑶ Arrange a centralized grounding device near the grounding point with a large earth

current, such as main transformer neutral point, grounding point of outgoing line portal

framework, grounding point of lightning conductor or grounding point of downlead of

open lightning strip, and grounding point of arrester.

⑷ Take the aperiodic component of short-circuit current into account, to prevent 6 kV ~

10 kV arrester from operation or explosion under the effect of power-frequency transient

reverse over-voltage.

⑸ Carry out corresponding grounding grid treatment if the measured grounding

resistance of the whole plant cannot meet the design requirements for allowable value of

grounding resistance.

b) Constituent parts of grounding grid


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According to the layout of hydroproject of the HPP, the grounding system of the whole

plant is mainly composed of three parts, including reservoir area grounding grid in front of

dam, underwater grounding grid behind dam, and grounding grid used for powerhouse,

auxiliary plant and ship lock. The grounding grids at each position are interconnected with

each other in a multiple manner. According to relevant calculation, the grounding

resistance of the HPP is about 0.48 Ω. The constituent parts of the grounding grid at each

position are as follows:

⑴ The reservoir area grounding grid in front of dam is composed of reservoir grounding

grid in front of dam, grounding grid of dam upstream face and so on.

⑵ The underwater grounding grid behind dam is mainly composed of tailrace grounding

grid, grounding grid at dredging area, stilling basin grounding grid after dam, tailrace

system grounding grid and so on.

⑶ The grounding grid used for powerhouse, auxiliary plant and ship lock is mainly

composed of such natural grounding bodies as grounding steel flat, structural

reinforcement mesh of hydraulic structure, and gate slot.

c) Voltage balancing measures

Because grounding grids at each position have different current divergence effects, current

shunt will be a major means for the grounding system of the HPP. Because grounding grids

are connected via long grounding wires, in case of grounding fault, a large fault current

will pass through grounding wires between grounding grids, generating a relatively large

voltage drop. In this case, reduction in grounding resistance only cannot achieve the

purpose of reduction of grounding grid potential, contact potential and step potential.

Therefore, the calculation of contact potential and step potential must be conducted based

on the arrangement conditions of grounding grids at each position. In addition, various

measures shall be taken to ensure personnel safety of operators at the HPP.

In view of actual conditions of the HPP, the following measures will be taken

comprehensively:

⑴ Design of voltage balancing net

The grounding grid used for powerhouse and auxiliary plant of the HPP is composed of

special grounding sheet flat and structural reinforcement mesh of structures. The structural


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reinforcement meshes are welded with each other to form small mesh openings. The

grounding grid made of special grounding sheet flats is reliably welded and connected with

the structural reinforcement mesh, to connect the grounding grids at each structure as a

whole. In this way, a voltage balancing net with good effects can be obtained without

increase of steel consumption. In addition, the voltage balancing net can reduce the

distribution gradient of potential for each grounding grid.

⑵ Control of transfer potential

The control of transfer potential at the HPP is mainly of the high potential isolation,

focusing on the communication line and neutral line of LV distribution system.

An isolation transformer and equipment with good insulation performance are used for the

communication line, to avoid personal injury or damage of weak current equipment caused

by high voltage of communication equipment and line.

If a metal pipe coming out from a grounding grid is an exposed pipe, insulated isolation

measures shall be taken for the flange connections.

⑶ Fast fault clearing

Fast fault-clearing measures shall be taken to shorten the duration of grounding fault, to

meet the requirements for step potential and contact potential in the guide, to ensure

personnel safety. In addition, such measures can reduce difficulties in grounding design

and material consumption.

⑷ Multipoint grounding protection and equipotential connection

The LV distribution system of the HPP is of the multipoint grounding mode. Namely,

equipotential connection shall be applied to the PE line and neutral line of distribution

equipment, grounding main line of electrical equipment, metal case of equipment, metal

pipe and metal members of structures. The above items shall be connected with the

grounding system. In this way, the personnel safety of operators can be guaranteed.

⑸ Model selection for 10 kV arrester

In model selection of 10 kV arrester, the aperiodic component of short-circuit current

shall be taken into account to prevent 6 kV ~ 10 kV arrester from operation or explosion

under the effect of power-frequency transient reverse over-voltage.


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6.2.8 Layout of Electrical Equipment

The HPP is of a water retaining ground powerhouse, with a powerhouse being 402.0

m in total length and 22.5 m in width, with a main erection bay being 52.0 m in length and

22.5 m in width, with an auxiliary erection bay being 42 m in length and 22.5 m in width,

and with downstream auxiliary plant being 376.0 m in length and 23.4 m in width.

The generator operation floor is at the elevation of 222.50 m a.s.l. in the powerhouse,

with a unit spacing of 21.5 m. It mainly consists of a governor, oil pressure unit and so on.

The main erection bay has an elevation of 228.5 m a.s.l. and the auxiliary erection bay has

an elevation of 222.5 m a.s.l. Both main and auxiliary erection bays are provided with 3

positions for stator field assembly, 2 positions for rotor field assembly, 2 positions for field

assembly of gate operating mechanism, 2 positions for runner field assembly, 2 positions

of field assembly of bulb head, 2 positions for field assembly of cooling jacket, and 2

positions for field assembly of main shaft. The pipeline - bus floor is at the elevation of

219.0 m a.s.l., mainly equipped with such equipment as non-segregated phase enclosed bus

(or insulated tubular bus).

Auxiliary plant is arranged closely to the downstream side of the powerhouse. The

generator voltage switchgear installation floor is at the elevation of 222.5 m a.s.l., mainly

equipped with a VT & LA arrester cabinet, enclosed bus, excitation transformer and others.

The main transformer floor is at the elevation of 228.5 m a.s.l., mainly equipped with a

main transformer room, HV control room of service power, LV control room of service

power, 13.8 kV switch gear and others. The main transformer transport passage is at the

downstream side of the main transformer room. The SF6 pipeline floor is at the elevation

of 240.5 m a.s.l., mainly equipped with an SF6 pipeline. The GIS switchyard and opened

outgoing line platform are set at a floor of an elevation of 245.5 m a.s.l. The outgoing line

platform is mainly equipped with an SF6/air bushing, arrester, high frequency wave trap,

capacitor voltage transformer, outgoing line framework and others.

6.2.9 List of Main Primary Electrical Equipment

See Table 6.2.9-1 for List of Main Primary Electrical Equipment


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Table 6.2.9-1 Main Primary Electrical Equipment

S/N Description Main

Equipment Parameter Unit Qty. Remarks

1

Gen

erat

or a

nd g

ener

ator

vol

tage

sw

itch

gear

ins

tall

atio

n

Generator SFWG55-64/8000 55MW Set 14

Excitation

transformer 13.8kV Set 14

VT cabinet 13.8kV Nos. 14

VT & LA

cabinet 13.8kV Nos. 5

SF6 gas circuit

breaker of

generator

13.8kV 3150A 80kA Set 14

Grounding

transformer 13.8/ 3 kV Set 14

Isolated-phase

enclosed bus

QZFM-13.8/8000

13.8kV 8000A 80kA m 300

HV current

limiting fuse

cabinet

13.8kV Nos. 4

Non-segregated

phase enclosed

bus (or

insulated

tubular bus)

13.8kV 3150A 63kA m 1250

Isolation switch


2

Pow

er

tran

sfor

m

er

Main

transformer

SSP-H-180000/500

180000kVA

525±2×2.5%/13.8kV

Set 4 Combined

3-phase


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Ud=14% YNd11 transformer

Main

transformer

SSP-H-120000/500

120000kVA

525±2×2.5%/13.8kV

Ud=14% YNd11

Set 1

Combined

3-phase

transformer

3

500k

V

GIS

Circuit breaker 500kV 3150A 50kA Set 8

Isolator 500kV 3150A 50kA Group 23

Including

earthing

switch

Electromagnetic

voltage

transformer

500kV Set 6

GIS SF6 arrester YH10W-444/1050 Set 6

4

500

kV o

pene

d ou

tgoi

ng l

ine

equi

pmen

t

SF6/air bushing 500kV 3150A 50kA Nr. 6

High frequency

wave trap 500kV Set 6

Capacitor

potential

transformer

500kV Set 6

Zinc oxide

arrester YH10W-444/1065 Set 6

5

Sta

tion

serv

ice

pow

er

equi

pmen

t HV station

service

transformer

SCB10-4000/13.8

13.8±2x2.5%/10.5kV

Set 4


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Dam crest

transformer

SCB10-1000/13.8

13.8±2x2.5%/0.4kV Set 2

Unit service

power

transformer

SCB10-500/10.5

10.5±2x2.5%/0.4kV

Set 2

Unit service

power

transformer

SCB10-1600/10.5

10.5±2x2.5%/0.4kV

Set 4

Diesel generator

unit at dam 0.4kV 800kW Set 1

Transformer for

common power

demand of plant

SCB10-2000/10.5

10.5±2x2.5%/0.4kV Set 4

Protective load

transformer

SCB10-630/10.5

10.5±2x2.5%/0.4kV Set 2

Transformer

special for

lighting

SCB10-400/10.5

10.5±2x2.5%/0.4kV Set 2

HV switchgear 10.5kV 630A 31.5kA Nos. 35

Isolation


VT & LA


LV switchgear 0.4kV MNS3.0 Nos. 180

Diesel generator

unit for

powerhouse

0.4kV 800kVA Set 1

6 Cable 13.8 kV cable 13.8kV YJV22-3x35 m 4000

LV cable Item 1

7 Grounding Item 1


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8 Lighting Item 1

9 Bridge Item 1

10 Fire

Protection Item 1

6.3 Control, Protection and Instrumentation

6.3.1 Control

The Paklay HPP is the first cascade HPP proposed to be developed on the main

stream of the Mekong River in Laos, with a planned total installed capacity of 770 MW

and 14 sets of 55 MW bulb turbine-generator units. The HPP plays an important role in the

electric power system. Due to lack of relevant data about the electric power system at

present, in the follow-up design, relevant codes and design information of the system

connection shall be used for defining the dispatching management relationship, telecontrol

and other information exchange. At present, it is temporarily determined that the 500 kV

system shall be dispatched by Laos Power Dispatching Center.

6.3.1.1 Plant centralized computer monitoring system

The plant is proposed to operate with no fulltime personnel on duty (a few people on

watch) and be monitored in centralized manner by computer monitoring. The computer

monitoring system shall be of an open network architecture distributed in layers. The

system shall consist of a main control level and a local control level. Ethernet with 100M

redundancy shall be used for communication between the upper and lower levels. The

network topology of the main control level shall be of a twin-stelliform network while that

of the local control level shall be of a double loop network. Main control level equipment

shall use twisted pair cables as its communication media while local control level

equipment shall use optical fibers as its communication media. See attached drawing -

PAKLAY-EM-ES-01 for structural configuration of the computer monitoring system.

The main control level equipment of the computer monitoring system shall consist of

2 historical database servers, 1 set of disk arrays, 2 application program servers, 2 operator

workstations, 1 engineer workstation, 1 training workstation, 1 plant intercommunication

server, 2 remote communication servers, 1 voice alarm and report forms workstation, 1 set

of mimic board and drive device, 2 sets of network equipment, 2 network printer, 1 set of


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clock synchronization system, 2 sets of UPS power supplies and so on. The main control

level equipment shall be used for monitoring the whole plant. Operating crew can monitor

main M & E equipment in the whole plant via the mimic board in the central control room,

liquid crystal display (LCD), keyboard, mouse and others in the operator workstations. The

2 remote communication servers shall be used for communication with Laos Power

Dispatching Department, in order to achieve remote dispatch. The plant

intercommunication server shall be used for communication with fire alarm system, MIS

system of the HPP etc., in order to achieve information exchange. A unit emergency

shutdown button and an emergency incident shutdown button shall be provided for the

mimic board, independent of the monitoring system, in order to achieve manual operation

in case of emergency.

In view of each unit, 500 kV switchyard, station service power, plant utilities and dam

gates, the local control level shall consist of 18 local control units (LCU), including 14

LCUs for the units, 1 LCU for the 500 kV switchyard, 1 LCU for the station service power,

1 LCU for the utilities and 1 LCU for the dam gates. The micro-computer governor,

micro-computer excitation device, micro-computer relay protection device and

micro-computer monitoring instrument of units shall communicate with their

corresponding LCUs.

Unit auxiliary equipment, plant utilities and others shall respectively adopt an

independent programmable logic controller (PLC) so as to independently achieve

automatic control based on their own control programs; in addition, the above items shall

be able to communicate with their corresponding LCUs. The LCU shall be used for

implementing process control for the controlled objects, collecting and processing data,

and carrying out accident detecting and alarming.

Each dam crest flood gate shall be provided with 1 local control cabinet, composed of

a PLC and a motor starter. Ethernet shall be used for communication between the dam

gates and LCU.

The main control level equipment of the whole plant shall be respectively arranged in

the computer room and central control room; the unit control level equipment shall be

respectively arranged beside each unit and in the corresponding relay protection room.

The HPP shall be provided with 1 monitoring system for flooding of powerhouse.


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Both ends of the gallery floor of the powerhouse shall be equipped with one water level

annunciator, which will transmit alerting signals in case of water and shall be connected to

the computer monitoring system.

6.3.1.2 Automation of unit

The self-shunt thyristor rectifier static excitation system is adopted for the excitation

system, which is composed of an excitation transformer, three-phase full-control power

rectifier unit, micro-computer excitation regulator, magnetic field circuit breaker, AC/DC

overvoltage and incomplete phase protection, excitation build-up device current

transformer and potential transformer for measurement, etc. The excitation system is of a

micro-computer excitation regulator with two channels. Each channel is provided with an

automatic voltage regulator (AVR) unit and an automatic current regulator (ACR) unit.

Interface for communication with LCU of the computer monitoring system unit is adopted

for the micro-computer excitation regulator to achieve monitoring and regulation of the

generator excitation via the monitoring system. Normal shutdown is achieved by inverse

de-excitation, while emergency shutdown is achieved by a DC de-excitation switch plus

oxidizing nonlinear resistor de-excitation.

To ensure units, relevant auxiliary equipment and plant utility system can safely

operate, the selected automation elements shall be able to correctly and reliably monitor

the operating parameters and conditions of oil, gas, water and important parts such as

bearing and generator stators, in order to provide reliable and accurate information for the

computer monitoring system and form a reliable hydraulic mechanical protection system.

Non-electric quantity items mainly consist of temperature, discharge, pressure, liquid level,

etc. A resistance temperature detector (RTD) of the computer monitoring system is used

for directly sampling so as to measure the unit temperature. Other non-electric quantity

items are collected by a transmitter and transformed to be 4 ~ 20 mA of analog signals and

finally transmitted to the computer monitoring system.

6.3.2 Protective Relaying

6.3.2.1 Protective relaying of main equipment

Protective relaying of all equipment in the HPP adopts digital protection equipment,

with each level of protection function in accordance with relevant standards and provisions.

In view of specific characteristics of main electrical connection of the Paklay HPP, single


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protection configuration is applied to the generators; electric quantity protection of main

transformers, protection of 500 kV lines, and protection of 500 kV bus all adopt duplex

configuration. See attached drawing - PAKLAY-EM-ES-02 for details.

It is preliminarily to provide the generators with the following protections: completely

longitudinal differential protection, zero-sequence current transverse differential protection,

LV over-current protection with current memory, over-load protection of stator, protection

for loss of excitation, negative-sequence over-current protection, stator grounding

protection, one-point grounding protection of rotor, stator OVP protection, shaft-current

protection, over excitation protection, excitation winding overload protection, reverse

power protection, CT break-wire protection, PT break-wire protection, etc.

It is preliminarily to provide the 500 kV main transformer with the following

protections: longitudinal differential protection, zero-sequence current protection,

over-current protection of compound voltage, CT break-wire protection, PT break-wire

protection and over excitation protection. Non-electric protection of the transformers

includes gas protection, gusty pressure relief protection, temperature protection, abnormal

oil level protection, cooler failure protection, etc.

Bus protection: each 500 kV bus is provided with two sets of bus differential

protection.

Line protection, protection of a 500 kV line shall be configured according to the

relevant provisions and requirements of the electric power system.

Excitation transformer protections consist of cut-off protection, over-current

protection and temperature protection.

Station service transformer protections consist of cut-off protection, over-current

protection and temperature protection.

Protection of station service power: digital protection equipment is provided in

corresponding switchgear and communicates with the LCU of the station service power.

6.3.2.2 Fault recorder and automatic safety device

For the convenience of fault analysis, the 500 kV switchyard is provided with 2 sets

of micro-computer fault recorders, while the 220 kV switchyard is provided with 1 set of

micro-computer fault recorders. Configuration of the automatic safety device shall meet


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requirements of the electric power system.

6.3.3 Secondary Connection

To meet measuring, metering and synchronizing requirements of the HPP, 0.5-level

current transformers for measurement are respectively configured at the HV side of the

excitation transformer and at the HV side of the station service transformer; 0.2-level

current transformers for measurement are configured for the 500 kV circuit breaker etc.; a

0.2-level current transformer for metering and measurement is configured at the generator

terminal; 0.2S-level current transformers for metering are configured at the HV side of

main transformers and 500 kV outgoing lines; corresponding potential transformers are

configured for the generator terminal, generator voltage bus, 500 kV bus and line etc.

6.3.3.1 Measurement

Electric quantity of the station service power, DC system, and switchgear installation

of the HPP is measured by a transmitter and collected by an AC sampling device. The

electric quantity then will be transformed to be 4 mA ~ 20 mA of analog quantity or

transmitted to the computer monitoring system via data communication mode. Water level,

pressure, discharge, temperature etc. of the HPP are measured by a transmitter or directly

collected by a RTD, and then transformed to be 4 mA ~ 20 mA of analog quantity or

directly transmitted to the computer monitoring system via the RTD temperature

measurement module.

6.3.3.2 Synchronization system

Microcomputer-based automatic precise synchronizing device is selected as the main

synchronization method of the HPP. Manual precise synchronization with asynchronous

blocking is provided as a back-up synchronization method. Each generator circuit breaker

and 500 kV circuit breaker will serve as synchronizing points. Each unit is equipped with 1

set of single-object synchronizing device and the 500 kV switchyard is equipped with 1 set

of multiple-object synchronizing device.

6.3.3.3 Signal

No routine central alarm signal is set in the central control room of the HPP. An alarm

is given by voice alarm device of the computer monitoring system and displayed by the

operator workstation. To meet requirements of local control and monitoring, each LCU is


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equipped with a LCD. The local control cabinet of all equipment is equipped with signal

lights for equipment status and monitoring of power supply.

6.3.3.4 Operation and locking

The computer monitoring system in the central control room can be used for

centralized monitoring of all HV circuit breakers, 500 kV isolators and earthing switches,

circuit breakers at the LV side of station service transformers, station service bus

sectionalizing circuit breakers and others of the HPP. Local control is set for other isolators,

earthing switches, outgoing breakers of 400 V station service power, etc.

Status signal indication is set for all circuit breakers on the local control cabinet,

which can be controlled manually. Necessary locking function is set at tripping and closing

circuits of the isolators and earthing switches to prevent from misoperation.

The mimic board in the central control room is equipped with simply measuring

meters, equipment status signal device and emergency operation button, etc.

6.3.4 Control Power Supply System

The HPP has a large powerhouse area and decentralized layout of M & E equipment.

To reduce distance and scope of power supply, the control power supply system shall be

arranged in a properly decentralized manner, so as to reduce the impact scope related to

power failure or maintenance, and improve reliability of the control power supply system.

The HPP is proposed to employ 4 sets of 220 V AC/DC control power supply systems.

Fourteen units, accident lighting, utilities and station service power system will share 2 sets

of the control power supply systems. Unit control, protection and operation, station service

power, utilities control and accident lighting in the No. 1 ~ No. 7 unit bays will share 1 set

of control power supply system. Unit control, protection and operation, station service

power, utilities control and accident lighting in the No. 8 ~ No. 14 unit bays will share 1

set of control power supply system. Switchyard and central control room will share 1 set of

control power supply system. In addition, dam site will be provided with 1 set of control

power supply system. Each set of DC power supply system shall employ two groups of

batteries, in order to ensure safe operation of the HPP and be convenient for maintenance.

All DC systems shall adopt single-bus sectionalized connection. Each section of bus shall

be connected with one group of battery and one set of float charging device. Normally, a

battery operates in float charging mode and two groups of batteries stand up for each other.


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The battery shall be valve-controlled sealed lead-acid battery, with a rated voltage of 2 V.

Each group of batteries of the 4 sets of control power supply systems respectively has a

capacity of 600 Ah, 600 Ah, 600 Ah and 200 Ah. See attached drawing -

PAKLAY-EM-ES-03 for the control power supply system.

6.3.5 Communication

The HPP communication consists of dispatching communication of the electric power

system, HPP internal dispatching and administrative management communication,

communication with local telephone department, etc.

The dispatching communication of the electric power system shall be set according to

requirements of the electric power system. Due to lack of relevant data about the electric

power system at present, it is temporarily considered to use two types of communication

channels, with a main communication channel using the OPGW optical fiber and a standby

communication channel using the power line carrier.

The HPP internal dispatching and administrative management communication shall

use 1 set of dispatching communication equipment and 1 set of administrative

communication equipment, equipped with corresponding intelligent dispatching console,

attendant desk, digital recording system, maintenance and charging terminal, wiring

devices, etc. It shall also be equipped with 1 set of in-plant addressable broadcast system

and 1 set of in-plant wireless intercom system.

Communication with the local telephone department shall be set according to the

existing local conditions. At present, it is temporarily proposed to use digital relay lines for

connecting the digital program-controlled exchangers with program-controlled switching

equipment of the local telephone department.

The HPP is equipped with 2 sets of power supply units for communication. Each set

consists of 2 groups of high-frequency switch rectifiers, 2 groups of valve-controlled

sealed lead-acid battery of 48 V/200 Ah, etc. AC power of the high-frequency switch

rectifiers comes from the station service power.

Emergency communication of the HPP is temporarily proposed to use 2 satellite

phones.

6.3.6 Industrial Television Monitoring System


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One set of all-digital industrial television monitoring system shall be provided, which

includes two areas - the HPP area and navigation lock area. Each area shall be equipped

with an independent server, hard disk video, monitoring terminal, camera, switching

control device, exchanger, etc., which will form two area systems operating independently.

Network shall be used for communication between the two systems; important video

images can be uploaded to the central control room of the HPP. The industrial television

monitoring scope involves the powerhouse, switchyard, control building, dam crest,

navigation lock, important safety exits, etc. The system transmits the camera video signal

and control signal via Ethernet. It is able to carry out digital coding, compressing, picture

recording, monitoring, multi-picture separating and controlling for video signals. In

addition, it is also able to interlock with the fire alarm system and monitoring system for

flooding of powerhouse.

At present, the HPP is proposed to employ 80 cameras, a hard disk video with

128-channel capacity, 2 serves, 1 monitoring terminal and 1000M backbone network. The

ship lift is proposed to employ 20 cameras, a hard disk video with 32-channel capacity, 1

serve, 1 monitoring terminal and 100 M backbone network. A 100M Ethernet is used for

connecting the HPP with the ship lift area.

The monitoring terminals are installed in the central control room and navigation lock

control room. The servers, hard disk videos and main network equipment panels are

installed in the relay protection room. The cameras and front-end accessory equipment etc.

are installed on site. Power supply of all cameras and front-end accessory equipment is

taken nearby where they are installed.

6.3.7 Electrical testing laboratory

Electrical testing consists of HV test, relay protection test, automation test,

electrotechnical instrument verification, etc. Selected instrument and testing apparatuses

shall meet requirements of operation and maintenance, acceptance and preventive test,

general test, supervising verification and adjustment test, repair, element test, etc.

Equipment for electrical testing laboratory shall be provided as per Grade-I electrical

testing laboratory.

6.3.8 Navigation Control System of Navigation Lock

Navigation control of the navigation lock is achieved by a navigation lock control


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system focused on a computer. The system consists of 1 set of upstream gate control unit, 1

set of downstream gate control unit, and 1 set of centralized control unit. Ethernet with

100M redundancy is used for communication between each unit. The network topology is

of a twin-stelliform network and equipment communication media is optical fiber. The

control system and gate hoisting device are equipped with 1 set of independent AC/DC

control power supply system.

The fire alarm and joint control devices as well as communication devices in the

navigation lock area are all included in the fire fighting system and communication system

of the HPP.


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6.3.9 List of Main Secondary Electrical Equipment

See Table 6.3.9-1 for List of Main Secondary Electrical Equipment

Table 6.3.9-1 Main Secondary Electrical Equipment

S/N Description of Equipment Qty. Remarks

I Automatic system of unit

1 Control cabinet for unit governor and oil pressure unit 14 x 1 Included in the unit governor

2 Unit excitation system 14 x 1

3 Control system of auxiliary equipment 14 x 1 Included in the unit

II Computer monitoring system

1 Historical database server 2

2 Disk array 1

3 Application server 2

4 Operator workstation 2

5 Engineer workstation 1

6 Simulation training workstation 1

7 Voice alarm and report forms workstation 1

8 Mimic board and drive device 1

9 Remote communication server 2

10 In-plant communication server 1

11 Network printer 2

12 Double-seat console 1

13 Ethernet network device 2

14 Clock synchronization system 1

15 LCU for unit (including synchronizing devices, etc.) 14 x 1

16 LCU for switchyard (including synchronizing devices,

etc.) 1

17 LCU for dam gate 1

18 LCU for utilities 1

19 LCU for station service power 1

20 Utilities control system (including drainage and

compressed air system, etc.) 1

21 Monitoring system for vibration and throw of unit 14 x 1 Included in the unit

22 Local control cabinet of dam flood gate Included in the complete hoist equipment

23 Ventilation control system 1 III Relay protection and automatic safety device


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S/N Description of Equipment Qty. Remarks

1 Generator protective equipment 14 x 1 2 Transformer protective equipment 5 x 2 3 500 kV line protective equipment 2 x 2 4 500 kV bus protective equipment 2 5 500 kV fault recorder 1

6 Automatic safety device for 500 kV system 1 Configured as per requirements of the electrical power system

7 10 kV protective equipment and automatic bus transfer equipment

Included in the switchgear

8 400 V protective equipment and automatic bus transfer equipment

Included in the switchgear

IV Control power supply system

1 AC/DC control power supply in No. 1 ~ No. 7 unit bays 1 With 2 groups of batteries being 600 Ah and 2 groups of float charging devices

2 AC/DC control power supply in No. 8 ~ No. 14 unit bays

1 With 2 groups of batteries being 600 Ah and 2 groups of float charging devices

3 220 V control power supply for GIS switchyard and central control room

1 With 2 groups of batteries being 600 Ah and 2 groups of float charging devices

4 220 V control power supply of dam gate 1 With 2 groups of batteries being 200 Ah and 2 groups of float charging devices

5 UPS for Main control level of computer monitoring system

2 30 kVA, free of battery

V Communication system 1 Carrier communication equipment 2 2 Optical fiber communication equipment 1

3 In-plant administrative communication equipment 1 Including navigation lock part

4 Dispatching communication equipment 1 5 In-plant addressable broadcast equipment 1 6 In-plant wireless intercom equipment 1 7 Communication power supply equipment 2 8 Communication cable 50km 9 Emergency communication equipment 1 2 hand-held satellite phones

VI Industrial TV system 1 Equipped with 100 cameras (including navigation lock part)

VII Automatic fire control and alarm system 1 Including navigation lock part

VIII Electric energy metering system 1 Including 4 gateway energy meters

IX Navigation lock control system 1

X AC/DC control power supply system for navigation lock

1

XI Control cable

Estimated as per 8 x 1.5 cables 500km Armored, fire-proof and overall shield

XII Others Electrical testing equipment 1


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6.4 Hydraulic Steel Structures

Hydraulic steel structure equipment of the Paklay HPP is mainly distributed in the

flood discharging system, headrace and power generation system, navigation lock system

and fish pass structure. Work amount of the hydraulic steel structures is 23,170 t in total.

See Table 6.4-1 - Summary Sheet of Main Metal Structure Equipment of the Paklay HPP

for details.

6.4.1 Metal Structure Equipment of Flood Release System

According to project layout, the flood releasing and flushing system structures are

provided with 2 flushing bottom outlets, 3 low-level surface bays (the low-level surface

bays are set for the purpose of flood releasing and sediment discharge) and 11 high-level

surface bays in sequence from left to right.

The hydraulic steel structure equipment of the flood releasing and flushing system is

composed of the upstream bulkhead gate and service gate of the release sluice, downstream

bulkhead gate of the release sluice, the emergency bulkhead gate, service gate and outlet

bulkhead gate of the flushing bottom outlets, as well as the corresponding hoists. For the

details of arrangement, please refer to the Layout Plan for Gates and Hoists of the Flood

Releasing & Flushing System (Drawing No.: Paklay-FS-MS-01 (1/5)), the Layout for

Gates and Hoists of Low-level Surface Bays of the Flood Releasing & Flushing System

(Drawing No.: Paklay-FS-MS-01 (2/5)), the Layout for Gates and Hoists of High-level

Surface Bays (with stilling basin) of the Flood Releasing & Flushing System (Drawing No.:

Paklay-FS-MS-01 (3/5)), the Layout for Gates and Hoists of High-level Surface Bays

(without stilling basin) of the Flood Releasing & Flushing System (Drawing No.:

Paklay-FS-MS-01 (4/5)) and the Layout for Gates and Hoists of Flushing Bottom Outlets

of the Flood Releasing & Flushing System (Drawing No.: Paklay-FS-MS-01 (5/5)).

6.4.1.1 Upstream Bulkhead Gate for Low-Level Surface Bay of Flood Discharge Gate

The upstream bulkhead gate for the low-level surface bay of the flood discharge gate


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is set at the upstream side of the service gate for the low-level surface bay. There are 3

outlets in total. For the bulkhead gate, the orifice width is 16.0m, the normal pool level is

240.000m, the design flood level is 239.020m, the check flood level is 240.530m. For the

low-level surface bay, the crest elevation is 212.000m, the elevation of sill is 212.000m,

the design water head is 28.0m and the gate height is about 29.0m. The gate shall be the

emerged plane stoplog sliding gate supported by a high-strength and low-friction

composite slide block. The gate is closed in static water and lifted by filling water between

segments. The gate is operated by the gantry crane main hook on the dam crest of release

sluice dam monolith through the automatic hydraulic pick-up beam. The gate is normally

locked at the top of gate slot with flashboard locking device. One segment is locked in

each orifice. The gate leaves exceeding the number of gate slot orifices shall be locked on

the dam crest between oil cylinder trunnion of high-level surface bays and downstream

pedestrian bridge.

6.4.1.2 Upstream Bulkhead Gate for High-Level Surface Bay of Release Sluice

The upstream bulkhead gate for the high-level surface bay of release sluice is set at

the upstream side of the service gate for the high-level surface bay. There are 11 outlets in

total. For the bulkhead gate, the orifice width is 16.0m, the normal pool level is 240.000m,

the design flood level is 239.020m, the check flood level is 240.530m. For the high-level

surface bay, the crest elevation is 220.000m, the elevation of sill is 220.000m, the design

water head is 20.0m and the gate height is about 20.3m. The gate shall be the emerged

plane stoplog sliding gate supported by a high-strength and low-friction composite slide

block. The gate is closed in static water and lifted by filling water between sections. The

gate is operated with the gantry crane main hook on the dam crest of the release sluice dam

monolith through the automatic hydraulic pick-up beam. One upstream bulkhead gate is set

for the high-level surface bay and the gate is normally locked at the top of gate slot with

flashboard locking device. Each gate segment leaf is exchangeable with each segment leaf

of the upstream bulkhead gate for the low-level surface bays. The 14 crest overflowing


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outlets share 2 bulkhead gates. The gate is normally locked at the top of gate slot with

flashboard locking device.

6.4.1.3 Dam Crest Gantry Crane of Release Sluice

One two-way gantry crane with a downstream cantilever is provided on the top of

flood releasing dam monolith. It is mainly used to hoist the upstream and downstream

bulkhead gates of the release sluice and for the erection, examination and repairing of the

service gate of the release sluice and its hoists. The main hook capacity of the dam crest

two-way gantry crane is 2×800kN. An auxiliary trolley, with hoisting capacity of 2×400kN,

is provided on the downstream cantilever of the gantry crane. The track gauge of the gantry

crane is 32.5m, the main hook lift is 50.0m and the secondary hook lift is 58.0m.

6.4.1.4 Service Gate for Low-level Surface Bay of Release Sluice

The low-level surface bay of the release sluice is provided with 3 service gates, each

outlet is provided with 1 service gate. There are 3 service gates in total. Given the radial

gate of the release sluice has no gate slot, with good flowing condition and small vibration

upon partial lifting of the gate, the radial gate is adopted as the service gate. The width of

gate orifice is 16.0m, the normal pool level is 240.000m, the design flood level is

239.020m and the check flood level is 240.530m. For the low-level surface bay, the crest

elevation is 212.000m. And for the service gate, the elevation of sill is 212.000m, the

design water head is 28.0m, the gate height is about 28.5m and the panel curvature radius

is 31.0m. The elevation of the radial gate trunnion is decided as 235.000m as per the

principle that the trunnion shall not be impacted while discharging a 100-year flood. Three

main beam and oblique supporting arms structure is employed for the radial gate structure.

And the spherical sliding bearing is adopted for trunnion bearing. It is designed to be lifted

and closed in dynamic water and to allow partially lifting for flow regulation. When the

radial gate is fully opened, the bottom edge of the gate is preliminarily considered to be at

an elevation of 241.000m; this ensures that the radial gate will not be subject to the strike

of the water flow or the floating debris during flood release at check flood level.


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6.4.1.5 Service Gate Hoist for the Low-level Surface Bay of the Release Sluice

Each service gate with the low-level surface bay is provided with 1 set of hoist. Since

the hydraulic hoist is characterized by simple structure, small volume, stable transmission,

such advantages as no adoption of high bent frame, convenience of remote control and

good-looking arrangement of dam surface, it is used for the service gate. The hoist for the

radial gate with the low-level surface bay has a capacity of 2×6500kN with an operating

stroke of about 13.0 m. The hoist for the radial service gate with the low-level surface bay

is suspended, with the upper bearings of the two oil cylinders being respectively fixed onto

the side walls of the left and right gate piers and the lower ends being connected to the gate

lifting eye on the rear flange of the lower main beam. Each set of hydraulic hoist shall be

provided with a pump station and the hoist shall be controlled both locally and remotely.

6.4.1.6 Service Gate for the High-level Surface Bay of the Release Sluice

At the right side of the low-level surface bay of the release sluice, 11 high-level

surface bays are provided, each outlet is provided with 1 service gate. There are 11 service

gates in total. The crest elevation is 220.000m. And for the gate, the elevation of sill is

220.000m, the design head is 20.0m, the gate height is about 20.5m and the panel curvature

radius is 25.0m. The elevation of the radial gate trunnion is decided as 235.000m as per the

principle that the trunnion shall not be impacted while discharging a 100-year flood.

Double main beam and oblique supporting arms structure is employed for the radial gate

structure. And the spherical sliding bearing is adopted for trunnion bearing. It is designed

to be lifted and closed in dynamic water and to allow partially lifting for flow regulation.

When the radial gate is fully opened, the bottom edge of the gate is preliminarily

considered to be at an elevation of 241.000m; this ensures that the radial gate will not be

subject to the strike of the water flow or the floating debris during flood release at check

flood level.

6.4.1.7 Service Gate Hoist for the High-level Surface Bay of the Release Sluice

One set of hydraulic hoist with hoisting capacity of 2×3800kN and working stroke of


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about 10.0m is provided for each service gate. The radial service gate hoist for the

high-level surface bay shall be hanging mounted. The upper bearings of the two oil

cylinders shall be fixed on the side walls of the left and right gate piers of the gate,

respectively, while the lower ends shall be connected with the gate hoist eye of the lower

main beam rear wing plate of the gate. Every set of hydraulic hoist shall be equipped with

1 pump station. The hoist shall be controlled by the combination of local control and

remote control.

6.4.1.8 Downstream Bulkhead Gate of the Release Sluice

At the downstream of each service gate for release sluice, a 1-orifice bulkhead gate

slot shall be provided. There are 14 orifices in total. The orifice width of the bulkhead gate

is 16.0m. The elevation of sill for the downstream bulkhead gate of the low-level surface

bay is 204.201m, while that for the 5 high-level surface bays at left is 212.206m and that

for the 6 high-level surface bays at the right is 220.000m. One downstream bulkhead gate

is provided by taking the tailwater level of 224.140m when the unit is at full load as the

downstream service level. The bulkhead gate, with a height of about 20.9m and design

water head of about 19.939m, is provided for service gate and gate slot repairing and

maintenance. For low-level surface bays, 11 segments shall be used; for high-level surface

bays with stilling basin, 7 segments shall be used; for high-level surface bays without

stilling basin, 3 segments shall be used. The gate shall be the emerged plane stoplog sliding

gate. It is supported by a high-strength and low-friction composite slide block. Each leaf of

gate segments are exchangeable and 1 bulkhead gate is shared by 14 outlets. The gate is

closed in static water and lifted by filling water between sections. The gate is normally

locked by segment on the platform with an elevation of 245.000m above the downstream

side orifice of the downstream track of the dam crest gantry crane at the high-level surface

bay dam monolith.

6.4.1.9 Downstream Bulkhead Gate Hoist of the Release Sluice

The downstream bulkhead gate of the release sluice is operated with the secondary


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hook of downstream cantilever on the dam crest two-way gantry crane at the release sluice

dam monolith through the hydraulic automatic pick-up beam.

6.4.1.9 Emergency Bulkhead Gate of the Flushing Bottom Outlet

Two flushing bottom outlets share 1 emergency bulkhead gate. The emergency

bulkhead gate is of plane fixed wheel gate for closing in dynamic water in case of service

gate accident, and for orifice closing during service gate and gate slot maintenance; for the

gate, the orifice size is 10.0m×12.1m, the elevation of sill is 205.000m and the design

water head is 35.0m. The emergency bulkhead gate adopts the form of upstream board and

upstream water stop. And the gate is closed by dead weight of itself. A filling valve is

equipped at the top of the gate for gate lifting in static water after the pressure is balanced

by water filling of the filling valve. The gate is normally locked at the top of the gate slot.

6.4.1.10 Emergency Bulkhead Gate Hoist of the Flushing Bottom Outlet

The emergency bulkhead gate of the flushing bottom outlet is operated with the

platform hoist set on the dam crest bent. For the platform hoist, the hoisting capacity is

2500kN and the lift is about 42.0m.

6.4.1.11 Service Gate of the Flushing Bottom Outlet

The service gate is arranged at the downstream outlet of the flushing bottom outlet

with 1 service gate for each flushing bottom outlet. There are 2 service gates in total. The

gate is of plane fixed wheel gate with an orifice dimension of 10.0m×10.0m, the elevation

of sill of 205.000m and the design water head of 35.0m; to prevent sediment deposition in

the tunnel and beam grillage of the gate, the service gate adopts the form of upstream

board and upstream water stop. The gate is lifted and closed in dynamic water and the

maximum head difference during operation in dynamic water is about 20m.

6.4.1.12 Service Gate Hoist of the Flushing Bottom Outlet

The service gate of the flushing bottom outlet is operated with the stationary winch

hoist set on the dam crest bent. For the hoist, the hoisting capacity is 3200kN and the lift is


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about 34.0m. A bridge crane with capacity of 30kN shall be set on the top of the hoist

room for maintenance of the hoisting equipment for the service gate of the flushing bottom

outlet.

6.4.1.13 Outlet Bulkhead Gate of the Flushing Bottom Outlet

As the sill is submerged in the downstream water level of the flushing bottom outlet

for a long time, for the maintenance of the waterway, tunnel and embedded parts of the slot,

1 bulkhead gate slot shall be provided at the downstream side of the service gate slot at the

outlet of each flushing bottom outlet. There are 2 outlets in total which share 1 bulkhead

gate. For the gate, the orifice dimension is 10.0m×10.0m, the elevation of sill is 205.000m,

the design water level is 235.600m which is also the downstream design flood level and the

design water head is 30.6m. The gate is of plane sliding gate supported by a high-strength

and low-friction composite slide block. And the simple supporting side wheels are used to

serve as the lateral support. The gate closed in static water is lifted when the pressure is

balanced by water filling of the filling valve set on the top of the gate. The gate is normally

locked on the top of the gate slot in two segments.

6.4.1.14 Outlet Bulkhead Gate Hoist of the Flushing Bottom Outlet

Lifting and closing of the outlet bulkhead gate of the flushing bottom outlet are

realized by tailrace 2×1600kN gantry crane through the hydraulic automatic pick-up beam.

6.4.2 Hydraulic steel Structure Equipment of Headrace and Power Generation System

The headrace and power generation system is equipped with 14 units in total and each

unit is equipped with a single headrace tunnel and a single draft tube. Hydraulic steel

structure equipment of headrace and power generation system mainly consists of an intake

trashrack, intake trash rack, intake bulkhead gate, tailrace emergency gate and

corresponding hoists. For the details of arrangement, please refer to the Layout Plan for the

Trashrack of the Headrace and Power Generation System (Drawing No.:

Paklay-FS-MS-02(1/2)) and Layout for Gates and Hoists of the Headrace and Power

Generation System (Drawing No.: Paklay-FS-MS-02(2/2)).

6.4.2.1 Intake trashrack and embedded parts


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One trashrack guide slot column is provided on the guide wall between the flushing

outlet dam monolith and the power station dam monolith and one provided at the place

about 610m upstream of the power station on the left bank. Between the aforementioned

two trashrack guide slot columns, another two trashrack guide slot columns are arranged to

divide the whole trashrack into 3 sections. 3 sets of trashracks are furnished. Each set of

trashrack is composed of the pedestals with floating camel at both ends and several floating

caissons which are interconnected with tie bars. Pedestals with floating camel at both ends

shall be restrained in the guide slot arranged in vertical and lifted up and down along the

guide slot track through rollers. Grids are welded at the upstream face of the floating

caisson, allowing the whole trashrack to go up and down along with the water. The trash

before the trashrack shall be cleaned manually with wastes cleaning boats.

The reason why trash cleaning boat is used to remove the trashes in front of the trash

boom rather than setting a flap gate in the radial service gate of flood discharging for

surface trash discharging is mainly based on the following consideration: during the

non-flood season, the surface trashes are comparatively of small quantity and frequent

discharge of the trashes is not good for concentrative cleaning and will affect the

downstream environment. Besides, the discharge of the trashes from the trash boom does

not ensure the thorough cleaning and trash cleaning boat may still be needed. During the

flood season, in case of the occurrence of a 2-year flood or flood with longer return period,

there will be a lot of surface trashes. For this case, as the flood discharge is realized by

fully opening the gate, the trashes could be discharged to the downstream as well with the

fully-opened radial gate.

6.4.2.2 Intake trash rack

An intermediate pier is set at the water intake of each unit, which evenly divides the

water intake to be 2 orifices and 2 trash racks are provided. The 14 units are corresponding

to 28 orifices; therefore, 28 trash racks are required in total. The trash rack has an orifice

width of 6.65 m and orifice height of 28.0 m, all of which are arranged vertically. All trash

racks are designed as per a head difference of 4.0 m. The composite sliding block is

employed for both reverse guide and support of the trash rack, connected to the dam crest

by a tie bar for locking. A cleaning guide slot is set in front of a trash rack slot. The

cleaning grab bucket is operated by the dam crest gantry crane at the intake monolith to


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remove trash of the trash rack. When a trash rack needs to be maintained, a dam crest

gantry crane at the intake monolith is used for hoisting the trash rack onto the dam crest.

6.4.2.3 Intake bulkhead gate

Behind each intake trash rack slot, 1 intake bulkhead gate slot is set. The 14 units are

corresponding to 14 orifices in total; after power generation by the first generator unit,

intakes shall be closed for installation of other units; therefore, 14 bulkhead gates are

needed in total, including 4 permanent bulkhead gates and 10 gates for temporary water

retaining during construction. The bulkhead gates have an orifice width of 15.1 m, height

of 16.3 m, sill elevation of about 201.020 m a.s.l., normal pool level of 240.000 m a.s.l.,

design flood level of 239.020 m a.s.l., and design head of 38.98m. The gate type is of the

down-hole plane sliding stoplog gate, supported by high-strength low-friction composite

steel slide blocks. Gates are opened and closed in still water. Pressure balancing method of

gates is that a filling valve on the top of gate is used for filling water so as to balance

pressure. Pressure balancing is carried out by the automatically hydraulic pick-up beam

operated by the dam crest gantry crane at the intake monolith. At ordinary times, gates are

placed inside a gate chamber.

6.4.2.4 Temporary Water Retaining Gate at the Intake

Given that water inlets shall be sealed for installation of other units after power

generation of the first unit, 10 temporary water retaining gates are provided for water

retaining during project construction. For the temporary water retaining bulkhead gate, the

orifice width is 15.1m, the height is 16.3m, the elevation of sill is 201.020m, the normal

pool level is 240.000m, the design flood level is 239.020m and the design water head is

38.98m. The gate shall be the down-hole sliding plane stoplog gate supported by a

high-strength and low-friction composite slide block. The gate is lifted and closed in static

water. The pressure is balanced by water filling of the filling valve provided on the top of

the gate. The operation is carried out with the dam crest gantry crane at the intake dam

monolith through the hydraulic automatic pick-up beam. Gates are normally stored in the


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gate chamber. After the gate is used, it is properly stored in some place at the station or

will be recycled.

6.4.2.5 Dam crest gantry crane at intake monolith

One two-way gantry crane is installed on the dam crest at the intake monolith, mainly

used for hoisting the intake trash rack and intake bulkhead gate as well as cleaning the

intake trash rack. The two-way gantry crane has a main hook capacity of 2 x 1000 kN,

auxiliary hook capacity of 2 x 400kN, gantry crane track gauge of 15.0 m, and head of

main and auxiliary hooks is about 55 m.

6.4.2.6 Tailrace emergency gate

Draft tube outlet of each unit is equipped with 1 tailrace emergency gate slot. The 14

units are corresponding to 14 orifices in total; after power generation by the first generator

unit, draft tubes shall be closed for installation of other units; therefore, 14 tailrace

emergency gates are needed in total, including 5 permanent emergency gates and 9 gates

for temporary water retaining during construction. The gates have an orifice width of 13.6

m, orifice height of 10.88 m, sill elevation of 203.060 m a.s.l., downstream design flood

level of 235.600 m a.s.l. and design head of 32.54 m. The above permanent gates are

down-hole plane gates, with two-way water seal. The gates are supported by high-strength

low-friction composite steel slide block on the upstream side and fixed roller on the

downstream side, closed in flowing water (maximum head difference at lowering of gate is

20 m) and opened in still water. The gates used for temporary water retaining are

down-hole plain sliding gates, supported by high-strength low-friction composite steel

slide blocks, opened and closed in still water. Pressure balancing method of gates is that a

filling valve on the top of gate is used for filling water so as to balance pressure. Pressure

balancing is carried out by the automatically hydraulic pick-up beam operated by the

tailrace gantry crane. At ordinary times, gates are locked at the top of gate slots.

6.4.2.7 Temporary Water Retaining Gate of the Tail Water

For the temporary water retaining gate, the orifice width is 13.6m, orifice height is

10.88m and the elevation of sill is 203.060m. And the design level is 232.980m as per the

downstream flood level specified in the construction and flood control standard of

100-year flood, while the design water head is 29.92m. The temporary water retaining gate


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shall be the down-hole plane sliding gate supported by a high-strength and low-friction

composite slide block. The gate is lifted and closed in static water. The pressure of the gate

is balanced by water filling of the filling valve provided on the top of the gate. The

operation is carried out through the hydraulic automatic pick-up beam of the tailrace gantry

crane. The gate is normally locked on the top of the gate slot. After the gate is used, it is

properly stored in some place at the station or will be recycled.

6.4.2.8 Tailrace gantry crane

One single-way gantry crane is installed on the tailrace platform, with a capacity of 2

x 1600 kN, track gauge of 6.5 m, and head of about 36.0 m. It is mainly used for hoisting

the permanent tailrace emergency gates, gates used for temporary water retaining and

bulkhead gate at the sediment releasing bottom outlet.

6.4.3 Hydraulic steel Structure Equipment of Navigation Lock System

The navigation lock is the one-stage type, arranged on the right side of riverbed, with

a lock chamber width of 12.00 m, upstream check flood level of 240.530m m a.s.l.,

upstream maximum stage of waterway of 240.000 m a.s.l., upstream minimum stage of

waterway of 239.000 m a.s.l., downstream maximum stage of waterway of 229.600 m a.s.l.,

and downstream minimum stage of waterway of 219.000 m a.s.l. The navigation lock is

composed of an upstream approach channel, upper lock head, lock chamber, lower lock

head, downstream approach channel, etc. The main hydraulic steel structure equipment of

navigation lock system mainly includes emergency bulkhead gate and service gate of the

upstream lock head, service gate and bulkhead gate of the downstream lock head, bulkhead

gate and service gate for water conveyance gallery at upstream and downstream lock heads,

corresponding hoists and floating makefast in the gate chamber. For the details of

arrangement, please refer to the Layout for the Gates and Hoists of the navigation lock

system (Drawing No.: Paklay－FS－MS－03).

6.4.3.1 Gates and Hoists of the Upstream Lock Head

a) Emergency bulkhead gate of the upstream lock head

One emergency bulkhead gate of upper lock head is set at the upstream side of the

upper lock head, with an orifice width of 12.0 m, height of about 5.73 m, sill elevation of

235.000 m a.s.l., and design head of 5.53 m. The gate type is of the emersed plane sliding

gate, supported by steel-based high-strength low-friction composite sliding blocks. The

gates are opened and closed in still water. In case of emergency, the gates can be closed in


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flowing water as well. At ordinary times, the gates are placed inside the gate chamber for

the bulkhead gate of upper lock head.

b) Emergency bulkhead gate hoist of the upstream lock head

The emergency bulkhead gate for the upstream lock head is operated with the

platform hoist with capacity of 2×400kN at the dam crest of the upstream lock head dam

monolith through the hydraulic automatic pick-up beam.

c) Service gates of the upstream lock head

Miter gates or submergence gates are adopted as service gates of the lock head. At

present, the service gates for domestic medium-high water head navigation lock are

generally miter gates, while the service gates for the low water head navigation lock are

generally miter gates, lateral drawing gates and submergence gates. However, most of the

service gates are miter gates. When the miter gate is adopted, small capacity of the hoist is

required with easy control and convenient maintenance, while the hoist for submergence

gate requires large capacity, high degree of synchronization and complicated control. The

miter gate basically adopts rigid water seal as it show excellent water stop effect, long

service life and short navigation interference time. The water seal of the submergence gate

has short service life and overall poor sealing and water stop effect. It also shows high

maintenance frequency, long maintenance duration and long navigation interference time.

The miter gates are generally arranged horizontally with relatively complicated civil

structure and relatively large gate structure weight. The hoist of the submergence gate is

set on the top of the gate with simple civil structure, gate structure and low construction

cost. For the convenience of future maintenance and minimize the influence of equipment

maintenance on navigation, the service gates of the upstream lock head of navigation lock

shall adopt miter gate. For the miter gate, the orifice width shall be 12.0m and the height

shall be about 6.0m. Pedestrian steel bridge and guardrail shall be provided on the top of

gate. The elevation of threshold is 235.000m and the design water head is 5.0m. The miter

gate adopts the beam structure with the fixed bottom pintle hinged with the frame-type top

pintle. The continuous support pillow spacers serve as support and water stop. And


6-108

prestress diagonal tie bars are adopted for torsion resistance.

d) Service gate hoist of the upstream lock head

The miter gate of the upstream lock head shall be lifted and closed in static water with

the 2×320kN horizontal hydraulic hoist (a water head difference of 0.2m is allowed during

operation).

6.4.3.2 Hydraulic steel structure equipment of lower lock head

a) Service gates of the downstream lock head

The service gate of lower lock head is a mitre gate, with an orifice width of 12.0 m,

height of about 26.0 m, sill elevation of 215,000 m a.s.l., and design head difference of

21.0 m. The mitre gate is of a cross beam structure, with the pedestrian steel bridge and

guardrail on the top, as well as a fixed bottom pintle, and a top pintle in hinged frame

manner. Bolsters and cushion blocks are continuously used for support and water seal. A

pre-stressed diagonal draw bar is used for torsion resistance.

b) Service gate hoist of the downstream lock head

The miter gate of the downstream lock head shall be lifted and closed in static water

with the 2×1250kN horizontal hydraulic hoist (a water head difference of 0.2m is allowed

during operation).

c) Bulkhead gate of the downstream lock head

At the downstream side of the downstream lock head, 1 bulkhead gate of the

downstream lock head shall be provided. For the bulkhead gate, the orifice width is 12.0m,

the height is about 9.64m, the elevation of the sill is 215.000m, the downstream

maintenance water level is 224.140m and the design water head is 9.14m. The gate shall be

the emerged plane sliding gate supported by a high-strength and low-friction composite

slide block. The gate shall be lifted and closed in static water. The gate is normally locked

on the dam crest of the downstream lock head with flashboard locking device. The bottom

elevation of the gate leaf shall not affect ship navigation. The control elevation is

238.000m.

d) Bulkhead gate hoist of the downstream lock head

The bulkhead gate of downstream lock head shall be operated through the stationary


6-109

winch hoist with capacity of 2×630kN on the dam crest bent of the downstream lock head.

6.4.3.3 Gates and Hoists of the Water Conveyance Gallery

a) Trash racks of the water conveyance gallery of the upstream lock head

Trash racks are provided at the left and right inlets of the water conveyance gallery of

the upstream lock head. Every water conveyance gallery inlet is divided into 5 sections

with separating piers. There are 10 sections in the left and right water conveyance galleries.

And 10 stationary trash racks are provided. For the trash racks, the orifice width is 2.3m,

the orifice height is 3.3m and the design water head difference is 5.0m.

b) Bulkhead gates of the water conveyance gallery of the upstream lock head

One set of bulkhead gate for water conveyance gallery is arranged at the downstream

side of trash rack at the left and right water conveyance gallery of the upstream lock head,

respectively. There are 2 sets in total. For the gate, the orifice width is 2.2m, the height is

3.3m, the elevation of sill is 226.200m and the design water head is 14.33m. The gate shall

be the down-hole plane sliding gate which is closed in static water and lifted in static water

after small lifting of the gate for water filling and pressure balancing. The gate is normally

locked on the top of the gate slot.

c) Bulkhead gates hoist of the water conveyance gallery of the upstream lock head

The bulkhead gate for the left and right water conveyance galleries of the upstream

lock head is operated with the platform hoist with capacity of 2×400kN at the dam crest of

the upstream lock head dam monolith through tie bars.

d) Service gates of the water conveyance gallery of the upstream lock head

One set of service gate is arranged for the left and right water conveyance galleries of

the upper lock head, respectively. There are 2 sets in total. Service gates commonly used

for the water conveyance gallery are of two types, i.e. reverse radial gates and plane gates.

For water head larger than 15m, the adoption of plane gates may cause gate vibration and

slot cavitation. The reverse radial gates are normally provided as the service gates for the

water conveyance gallery of navigation lock with higher water head. Without the


6-110

interference of gate slot, it provides relatively good hydraulic conditions. With small

hoisting force, light water fluctuation and vibration, the water entering the gate chamber is

in good state of flow. Therefore, reverse radial gates are adopted as the service gates of the

water conveyance gallery. The orifice width of the gate is 2.2m, the height is 2.6m, the

elevation of sill is 209.700m, the design retaining water head is 30.83m and the dynamic

operation water head is 30.3m. The gate is lifted in dynamic water and closed in static

water (closing in dynamic water is allowable in emergency conditions).

e) Service gate hoists of the water conveyance gallery of the upstream lock head

The water conveyance gallery of the upstream lock head shall be operated with the

630kN hydraulic hoist through tie bars.

f) Bulkhead gates beside the service gate chamber for the water conveyance gallery

One bulkhead gate slot is provided beside the upstream and downstream service gate

chambers of the left and right water conveyance galleries, respectively. There are 4

bulkhead gate slots in total. For the convenience of repair and maintenance of the service

gates for the water conveyance gallery, 2 bulkhead gates are provided beside the service

gate chamber of the water conveyance galleries. For the gate, the orifice width is 2.2m, the

height is 3.3m and the elevation of sill is 211.90m. The design water level of the gate is

240.000m, which is also the maximum upstream stage of waterway. The design water head

for the gate is 28.1m. The gates shall be the down-hole plane sliding gates supported by a

high-strength and low-friction composite slide block. The gates are closed in static water

and lifted in static water after small lifting of the gate for water filling and pressure

balancing. The gate is normally locked on the top of the gate slot.

g) Bulkhead gate hoists beside the service gate chamber for the water conveyance

gallery

The bulkhead gate beside the service gate chamber of the water conveyance gallery

shall be operated with a temporary floating crane with a hoisting capacity equal to or larger

than 400kN.


6-111

h) Service gates of the water conveyance gallery of the downstream lock head

Left and right water conveyance galleries of lower lock head are respectively equipped

with 1 service gate of water conveyance gallery, 2 in total. The gate has an orifice width of

2.2 m, height of 2.6 m, sill elevation of 209.700 m a.s.l., and design head difference of 21.0

m. The gate type is of reversed radial gate and is opened in flowing water and closed in

still water. In case of emergency, it can also be closed in flowing water.

i) Service gate hoists of the water conveyance gallery of the downstream lock head

The service gate of the water conveyance gallery for the downstream lock head shall be

operated with the 630kN hydraulic hoist through tie bars.

j) Bulkhead gates of the water conveyance gallery of the downstream lock head

Downstream sides of the service gates of the left and right water conveyance galleries of

lower lock head are respectively equipped with 1 bulkhead gate of water conveyance

gallery, 2 in total. The gate has an orifice width of 2.2 m, height of 3.3 m, sill elevation of

209.700 m a.s.l., downstream water level during maintenance of 224.140 m a.s.l., and

design head of 14.44 m. The gate type is of down-hole plain sliding gate. The operating

condition of the gate is as follows: the gate is closed in still water; the gate is then slightly

opened for water filling and pressure balancing, after which the gate is completely opened

in still water. At ordinary times, gates are locked at the top of the gate slot.

k) Bulkhead gate hoists of the water conveyance gallery of the downstream lock head

The bulkhead gates of the left and right water conveyance galleries for the downstream

lock head shall be operated with a stationary winch hoist with capacity of 250kN on the

bent at the top of gate chamber.

6.4.3.4 Floating makefast of lock chamber

There are 12 floating makefasts in total at both sides of the lock chamber. The floating

makefast is of floating camel structure. Upper part of the floating camel is equipped with a

double-deck floating makefast. There are 6 sets of rollers provided respectively at three

positions including upper, intermediate and lower parts. The floating camel can go up and

down along the guide slot based on change of water level.

6.4.3.5 Anticollision device and hoisting equipment of gate chamber

To avoid the clash on the service gate of lower lock head by the ships due to their

failure in speed control, a set of anticollision device is provided in front of the service gate.

This anticollision device uses steel wire rope as the ship holding rope, which goes across


6-112

the gate chamber, with both ends of the rope tied to the buffering device of the butterfly

spring at the lifting platform in both sides of the gate wall slot. The anticollision device

could withstand a max. striking energy of 250kNm from the ships, having a max. buffering

distance of around 2.32m. The anticollision device is operated by the 2×200kN (lifting

force)/2×300kN (holding force) stationary winch-type hoist set on the bent frame at the top

of the gate wall.

6.4.4 Hydraulic steel Structure Equipment of Fish Pass Structure

The fish pass structures shall be arranged at the left side of the powerhouse dam

monolith. The hydraulic steel structure equipment for the fish pass structures include

upstream flood control service gates, downstream flood control gates and corresponding

hoists.

6.4.4.1 Service Gates of Upstream Flood Control

One service gate slot for flood control and one service gate for flood control shall be

provided at the fishway entrance in front of the dam. For the service gate, the orifice width

is 6.0m, the height is 3.3m, the elevation of sill is 237.240m and the design water head is

about 3.29m. The gate shall be emerged plane sliding gate supported by a high-strength

and low-friction composite slide block. The gate shall be lifted and closed in dynamic

water. For maintenance of service gate slot for flood control, water retaining shall be

carried out by sandbag cofferdams.

6.4.4.2 Service Gate Hoists of Upstream Flood Control

The service gate for upstream flood control shall be operated through the stationary

winch hoist with capacity of 2×100kN set on the dam crest bent.

6.4.4.3 Service Gates and the Hoists for Downstream Flood Control

According to the requirements of the fish pass structure arrangement, 1 flood control

gate is arranged at the middle section of the fishway close to the access road on the left

bank of the power station. For the gate, the orifice width is 6.0m, the height is 3.0m, the

elevation of sill is 232.140m, the downstream design flood level is 235.500m and the

design water head is about 3.46m. The gate shall be the down-hole plane sliding gate


6-113

supported by a high-strength and low-friction composite slide block. The gate shall be

lifted and closed in dynamic water.

6.4.4.4 Service Gate Hoists of the Downstream Flood Control

The service gate for downstream flood control shall be operated through the stationary

winch hoist with capacity of 2×100kN set on the bent of the platform with an elevation of

237.500m on the top of gate slot.

6.4.5 Correction Protection Scheme for Hydraulic steel Structure Equipment

The correction protection scheme for hydraulic steel structure equipment of the

Project mainly consists of four classifications as follows:

a) Except structural components for the temporary gates, all other structural

components for trash racks, gates, exposed surface (unfinished surface) of embedded parts,

and hoists shall be sprayed with zinc for corrosion prevention. The minimum partial

thickness of zinc spraying shall be 120 μm. After zinc spraying, seal coat, intermediate

coat and finishing coat shall also be painted. The seal coat is 30 μm thick epoxy primer, the

intermediate coat is 50 μm thick epoxy micaceous iron antirust paint and the finishing coat

is 60 μm ~ 100 μm thick chlorinated rubber pain.

b) Structural components for the temporary gates shall be applied with coatings for

corrosion prevention. The coatings consist of epoxy asphalt antirust primer with a

thickness of 125 μm and epoxy asphalt antirust finishing coat with a thickness of 125 μm.

c) Surface of non-fit mechanical components of hoists shall be applied with coatings

for correction prevention. The coatings consist of epoxy zinc-rich primer with a thickness

of 70 μm at the bottom course, epoxy micaceous iron antirust paint with a thickness of 80

μm at the intermediate course, and chlorinated rubber paint with a thickness of 70 μm at

the surface course.

d) Embedded parts of all gate slots, rack slots and guide slots in concrete shall be

painted with cement mortar for corrosion prevention.

6.4.6 Summary Sheet of Main Hydraulic steel Structure Equipment of Paklay HPP


6-114

Table 6.4-1 Summary Sheet of Main Hydraulic steel Structure Equipment of Paklay HPP

S/N Description Type Specification Qty. Unit Unit

Qty. Subtotal Remarks

(t) (t)

1. Flood Releasing System

10458

1.01

Upstream

Bulkhead Gate

of the Release

Sluice (I)

Plane

stoplog

sliding gate

16.0m×29.0m-28.000m 1 Set 500 500

1.02

Embedded

Parts of

Upstream

Bulkhead Gate

of the Release

Sluice (I)

3 Orifice 30 90

1.03

Upstream

Bulkhead Gate

of the Release

Sluice (II)

Plane

stoplog

sliding gate

16.0m×20.3m-20.00m 1 Set 350 350

1.04

Embedded

Parts of

Upstream

Bulkhead Gate

of the Release

Sluice (II)

11 Orifice 23 253

1.05

Upstream

Bulkhead Gate

Hoist of the

Release Sluice

Two-way

gantry crane 2×800kN/2×400kN 1 Set 650 650

1.06

D a m C r e s t

Gantry Crane

Track of the

Release Sluice

QU120 1 Set 105 105

Single track has a

length about 285m,

two tracks

1.07

Service Gate

for the

Low-level

Surface Bay of

Radial gate 16.0m×28.50m-28.000m 3 Set 550 1650


6-115

the Release

Sluice

1.08

Embedded

Parts of the

Service Gate

for the

Low-level

Surface Bay of

the Release

Sluice

3 Orifice 40 120

1.09

Service Gate

Hoist for the

Low-level

Surface Bay of

the Release

Sluice

Hydraulic

hoist 2×6500kN 3 Set 110 330

1.10

Service Gate

for the Surface

Outlet of the

Release Sluice

Radial gate 16.0m×20.5m-20.000m 11 Set 330 3630

1.11

Embedded

Parts of the

Service Gate

for the Surface

Outlet of the

Release Sluice

11 Orifice 29 319

1.12

Service Gate

Hoist for the

Surface Outlet

of the Release

Sluice

Hydraulic

hoist 2×3800kN 11 Set 70 770

1.13

Downstream

Bulkhead Gate

of the Release

Sluice

Plane

stoplog

sliding gate

16.0m×20.9m-19.939m 1 Set 330 330

1.14

Embedded

Parts of

Downstream

Bulkhead Gate

of the Release

3 Orifice 29 87


6-116

Sluice (I)

1.15

Embedded

Parts of

Downstream

Bulkhead Gate

of the Release

Sluice (II)

5 Orifice 23 115

1.16

Embedded

Parts of

Downstream

Bulkhead Gate

of the Release

Sluice (III)

6 Orifice 15 90

1.17

D o w n s t r e a m

Bulkhead Gate

Ho i s t o f th e

Release Sluice

Two-way

gantry crane

Shared dam crest

gantry crane

1.18

Emergency

Bulkhead Gate

of the Flushing

Bottom Outlet

Plane

fixed-roller

gate

10.0m×12.1m-35.0m 1 Set 165 165

1.19

Embedded

Parts of

Emergency

Bulkhead Gate

of the Flushing

Bottom Outlet

2 Orifice 50 100

1.20

Emergency

Bulkhead Gate

Hoist of the

Flushing

Bottom Outlet

Platform

hoist 2500kN 1 Set 110 110 Including track

1.21

Service Gate of

t h e F lu sh in g

Bottom Outlet

Plane

fixed-roller

gate

10.0m×10.0m-35.0m 2 Set 140 280

1.22

Embedded

Parts of Service

Gate of the

Flushing

2 Orifice 42 84


6-117

Bottom Outlet

1.23

Service Gate

Hoist of the

Flushing

Bottom Outlet

Stationary

winch hoist 3200kN 2 Set 75 150

1.24

Maintenance

Crane of the

Service Gate

Hoist Room of

the Flushing

Bottom Outlet

Electric

block 30kN 1 Set 10 10

1.25

Bulkhead Gate

of the Flushing

Bottom Outlet

Plane

sliding gate 10.0m×10.0m-30.6m 1 Set 110 110

1.26

Embedded

Parts of

Bulkhead Gate

of the Flushing

Bottom Outlet

2 Orifice 30 60

1.27

Bulkhead Gate

Hoist of the

Flushing

Bottom Outlet

One-way

gantry crane

Shared tailrace gantry

crane

2. Headrace and power generation system

11354

2.01 Intake

Trashrack 3 Set 300 900

2.02

Guide Slot of

the Intake

Trashrack

3 Set 20 60

2.03 Intake trash

rack

Plane

vertical

trash rack

6.65m×28.0m-4.0m 28 Set 55 1540

2.04

Embedded

Parts of the

Intake Trash

Rack and

Embedded

Parts of the

28 Orifice 25 700


6-118

Cleaning Guide

Slot

2.05 Intake

Bulkhead Gate

Plane

stoplog

sliding gate

15.1m×16.3m-38.98m 4 Set 260 1040

2.06

Temporary

Water

Retaining Gate

at the Intake

Plane

stoplog

sliding gate

15.1m×16.3m-38.98m 10 Set 260 2600

2.07

Embedded

Parts of the

Intake

Bulkhead Gate

14 Orifice 33 462

2.08

Embedded

Parts of Intake

Bulkhead Gate

Chamber

14 Orifice 5 70

2.09

Dam Crest

Gantry Crane at

Intake

Two-way

gantry crane 2×1000kN/2×400kN 1 Set 360 360

Including cleaning

equipment

2.10 Intake Gantry

Crane Track QU100 1 Set 100 100

Single track has a

length about 345m,

two tracks

2.11

Tail Water

Emergency

Gate

Plane

fixed-roller

gate

13.6m×10.88m-32.54m 5 Set 190 950 Maximum gate closing

water head 20m

2.12

Temporary

Water

Retaining Gate

of the Tail

Water

Plane


2.13

Embedded

Parts of the Tail

Water

Emergency

Gate

14 Orifice 41 574

2.14 Tailrace Gantry

Crane

One-way

gantry crane 2×1600kN 1 Set 320 320


6-119

2.15

Tail Water

Gantry Crane

Track

QU120 1 Set 130 130

Single track has a

length about 345m,

two tracks

3. Navigation Lock System

1328

3.01

Emergency

Bulkhead Gate

of the Upstream

Lock Head

Plane


3.02

Embedded

Parts and

Chamber of the

Emergency

Bulkhead Gate

of the Upstream

Lock Head

1 Orifice 15 15

3.03

Emergency

Bulkhead Gate

Hoist of the

Upstream Lock

Head

Platform

hoist 2×400kN 1 Set 70 70

3.04

Platform Hoist

Track of the

Upstream Lock

Head

QU80 1 Set 12 12

Single track has a

length about 44m, two

tracks

3.05

Service Gates

of the Upstream

Lock Head

Mitre gate 12.0m×6.0m-5.0m 1 Set 70 70

3.06

Embedded

Parts of the

Service Gate of

the Upstream

Lock Head

1 Orifice 8 8

3.07

Service Gate

Hoist of the

Upstream Lock

Head

Hydraulic

hoist 2×320kN 1 Set 8 8

3.08

Service Gates

of the

Downstream

Mitre gate 12.0m×26.0m-21.0m 1 Set 290 290


6-120

Lock Head

3.09

Embedded

Parts of the

Service Gate of

the

Downstream

Lock Head

1 Orifice 25 25

3.10

Service Gate

Hoist of the

Downstream

Lock Head

Hydraulic

hoist 2×1250kN 1 Set 25 25

3.11

Bulkhead Gate

of the

Downstream

Lock Head

Plane


3.12

Embedded

Parts of the

Bulkhead Gate

of the

Downstream

Lock Head

1 Orifice 20 20

3.13

Bulkhead Gate

Hoist of the

Downstream

Lock Head

Stationary

winch hoist 2×630kN 1 Set 25 25

3.14

Trash Racks

and Embedded

Parts of the

Water

Conveyance

Gallery Inlet of

the Upstream

Lock Head

Stationary

type 2.3m×3.3m-5.0m 10 Set 2.5 25

3.15

Bulkhead Gates

of the Water

Conveyance

Gallery of the

Upstream Lock

Head

Plane



6-121

3.16

Embedded

Parts of the

Bulkhead Gates

of the Water

Conveyance

Gallery of the

Upstream Lock

Head

2 Orifice 6 12

3.17

Bulkhead Gates

beside the Gate

Chamber for

the Water

Conveyance

Gallery

Plane


3.18

Embedded

Parts of the

Bulkhead Gates

beside the Gate

Chamber for

the Water

Conveyance

Gallery

4 Orifice 9 36

3.19

Bulkhead Gates

of the Water

Conveyance

Gallery of the

Downstream

Lock Head

Plane

sliding gate 2.2m×3.3m-14.44m 2 Set 8.5 17

3.20

Embedded

Parts of the

Bulkhead Gates

for the Water

Conveyance

Gallery of the

Downstream

Lock Head

2 Orifice 9 18

3.21

Bulkhead Gate

Hoists of the

Water

Conveyance

Gallery of the

Stationary

winch hoist 250kN 2 Set 5 10


6-122

Downstream

Lock Head

3.22

Service Gates

of the Water

Conveyance

Gallery of the

Upstream and

Downstream

Lock Head

Reverse

radial gate 2.2m×2.6m-30.83m 4 Set 32 128

3.23

Embedded

Parts of the

Service Gates

for the Water

Conveyance

Gallery of the

Upstream and

Downstream

Lock Head

4 Orifice 50 200

3.24

Service Gate

Hoist of the

Water

Conveyance

Gallery of the

Upstream and

Downstream

Lock Head

Hydraulic

hoist 630kN 4 Set 8 32

3.25 Floating

Makefast 12 Set 2.5 30

3.26

Embedded

Parts of the

Floating

Makefast

12 Orifice 6.5 78

3.27

Anticollision

device of gate

chamber

Butterfly

spring

buffering

type ship

holding

rope

1 Set 25 25

3.28

Embedded

parts of

anticollision

device of gate

chamber

1 Set 6 6


6-123

3.29

Hoist of

anticollisio

n device of

gate chamber

Stationary

winch type

hoist

2×200kN (lifting force)/2×300kN (holding force)

1 Set 9 9

4. Fish Pass System 30

4.01

Service Gates

of Upstream

Flood Control

Plane


4.02

Embedded

Parts of the

Service Gates

for Upstream

Flood Control

1 Set 4 4

4.03

Service Gate

Hoists of

Upstream Flood

Control

Stationary

winch hoist 2×100kN 1 Orifice 5 5

4.04

Service Gates

of Downstream

Flood Control

Plane


4.05

Embedded

Parts of the

Service Gates

for

Downstream

Flood Control

1 Orifice 4 4

4.06

Service Gate

Hoists of the

Downstream

Flood Control

Stationary

winch hoist 2×100kN 1 Set 5 5

5. Total 23170

6.5 Ventilation and Air Conditioning

6.5.1 Overview

The Paklay HPP is in Laos, where the climate is hot, and annual average temperature

is 25.3 °C, extreme maximum temperature is 40.5 °C, and extreme minimum temperature

is 1.3 °C.


6-124

The HPP is of a water retaining powerhouse. Main auxiliary plant is composed of

powerhouse and downstream auxiliary plant. Generator floor, busbar floor, and operation

gallery floor are set for the powerhouse only. Floors of the downstream auxiliary plant

from bottom to top are busbar cable floor, power distribution device floor, SF6 pipeline

floor, GIS floor, outgoing line platform floor. Two erection bays, which are 1# erection

bay (at left side of the powerhouse) and 2# erection bay (between the 11# 12# units), are

set for the HPP. The central control building is at left side of the downstream auxiliary

plant and downstream side of the 1# erection bay.

6.5.2 Design Parameters of Indoor Air

a) Summer

Generator floor ≤33 °C 75%

Main transformer room <40 °C

Station service transformer room ≤35 °C

Turbine oil depot and insulating oil depot ≤33 °C 80%

Air compressor room ≤35 °C 75%

Cable room (passage) ≤35 °C

Central control room and computer room ≤28 °C 60%±5%

Local panel room, relay protection room, storage room, etc. ≤28 °C 60%±5%

Office, meeting room, etc. ≤28 °C 60%±5%

b) Winter

Generator floor ≥10 °C

Main transformer room ≥10 °C

Central control room and computer room ≥20 °C

Oil disposal room ≥10 °C

Air compressor room ≥12 °C

Office, meeting room, etc. ≥18 °C


6-125

6.5.3 Preparation of System Scheme

Location of the HPP is of a hot climate. According to meteorological and local

conditions, etc., method of mechanical ventilation (the major part) supported by multi-split

air condition is adopted for design scheme of ventilation and air conditioning of the whole

plant. Mechanical ventilation is adopted for the powerhouse, electrical equipment room for

the main transformer, station service transformer, etc. Multi-split central air conditioning

system is adopted for rooms of the central control building and equipment rooms (such as

local panel room) which are within the unit bay scope and have high requirement for

temperature and moisture while holding a heavy thermal load. Ventilation method of

natural air intake and mechanical air exhaust is adopted for GIS room and pipeline floor.

Independent air exhaust system of natural air intake and mechanical air exhaust is adopted

for the battery room, which is of maintenance-free type.

6.5.4 Organization and Systematic Design of Ventilation Air

According to layout of the electromechanical equipment, method of air blown from

upstream and exhausted from d ①ownstream is adopted for the whole plant. Blower room

② ③is set at upstream side at left of the powerhouse, and blower rooms and are set at

②upstream side of the erection bay . Unit bay ⑫~⑭ ①is air supply area of blower room

and unit bay ①s ~⑪ is air su ② ③pply area of blower rooms and . One air blow gallery of

powerhouse is set in wall at upstream of the powerhouse as channel to blow outdoor fresh

air to operation floor and busbar floor by centrifugal fan. An air exhaust interlayer is set at

downstream side of the downstream auxiliary plant as channel to exhaust the air to outside

by 5 exhaust fans set at downstream side of the main transformer floor.

As the GIS and pipeline floor is above ground outside, wall axial flow fan is adopted

to exhaust the air to outside of downstream.

Unit battery room is at downstream side with an elevation of 228.50 m a.s.l. of the

downstream auxiliary plant. Natural air flows into the lower auxiliary access gallery and is

exhausted outside by explosionproof axial flow fan set in the battery room via


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umbrella-shaped vent cap at roof.

Multi-split central air conditioning system is adopted for rooms of the central control

building and equipment rooms (such as local panel room) which are within the unit bay

scope while holding a heavy thermal load. The outside unit is set at an elevation of 236.50

m a.s.l. of the tailrace platform.

a) Air blow system of powerhouse

Outside air is induced and sent to operation floor and busbar floor of powerhouse

via upstream air blow gallery by blower. Total air capacity of the system is 320000 m3/h;

air capacity of the operation floor and busbar floor are 160000 m3/h respectively.

The 1# blower room is provided with 1 dual-inlet centrifugal fan of 4-79No.2-12E

model with air capacity of 80000 m3/h; 2# and 3# blower rooms are provided respectively

with 1 dual-inlet centrifugal fan of 4-79No.2-14E model with air capacity of 120000 m3/h.

b) Air exhaust system of downstream auxiliary plant

Air of busbar floors of powerhouse and downstream auxiliary plant, as well as

downstream equipment rooms (water supply room and circuit breaker room) of operation

floor of the downstream powerhouse are all exhausted to the air exhaust interlayer of

downstream auxiliary plant, which has a total air capacity of 215000 m3/h and exhausts air

to outside via its downstream exhaust fan of the operation floor (elevation of 228.50 m

a.s.l.). There are 5 blower rooms in total and 1 dual-inlet centrifugal fan of 4-79No.2-10E

model is set for each blower room.

c) Air exhaust system of oil depot and oil disposal room

Blower rooms are set at downstream side of the insulation oil room and oil disposal

room, and turbine oil depot and oil disposal room. Air ducts are embedded in upstream

wall of the oil depot as channel to exhaust air of the oil depot and oil disposal room outside

via blower room. Air capacities of air exhaust systems of the insulating oil and turbine oil

are both 10000 m3/h, with blower model of B4-79 No.8D, and each system has 1 blower.

d) Air exhaust system of GIS room

Ventilation method of natural air intake and mechanical air exhaust is adopted for the


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GIS room. Lower part of the upstream wall is set with air intake window and axial flow

fans are set for upper and lower parts of the downstream wall. The upper axial flow fan is

used for ventilation and the lower one is used for emergency ventilation. Total air capacity

of the system is 100000 m3/h and 20 axial flow fans of BFT35-11No.5 model are adopted.

e) Air exhaust system of pipeline floor

Ventilation method of natural air intake and mechanical air exhaust is adopted for the

pipeline floor. Air is taken from upper large space of the generator floor. Lower part of the

upstream wall of pipeline floor is set with air intake window and upper part of the

downstream wall is set with axial flow fan. Total air capacity of the system is 35000 m3/h

and 12 axial flow fans of T35-11 No.4 model are adopted.

f) Air exhaust system of main transformer and station service transformer room

Ventilation method of natural air intake and mechanical air exhaust is adopted. Air

flows from operation floor of the powerhouse and exhausted to outside of the downstream

side via axial flow fan. Total air capacity of the system is 150000 m3/h and 20 axial flow

fans of T35-11 No.5.6 model are adopted.

g) Air exhaust of switchgear room, DC panel room, etc. of downstream auxiliary

plant

Ventilation method of natural air intake and mechanical air exhaust is adopted. Air

flows from transportation channel of the main transformer and exhausted to outside of the

downstream side via axial flow fan. Total air capacity of the system is 50000 m3/h and 5

axial flow fans of T35-11 No.6.3 model are adopted.

h) Air exhaust from battery room

No. 1, No. 2, and No. 3 batteries of the unit are all at downstream side with an

elevation of 228.50 m a.s.l. of the downstream auxiliary plant. Natural air flows into the

lower auxiliary access gallery and is exhausted outside by explosionproof axial flow fan

set in the battery room via umbrella-shaped vent cap at roof. Air capacity of each battery

room is 2000 m3/h and each room is provided with 1 axial flow fan of BT35-11 No.3.55

model.


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6.5.5 Dehumidification in Plant

Inside of the plant is set with 10 mobile dehumidifiers for dehumidification of wet

districts (such as operation gallery) in the plant. Dehumidifying capacity of the

dehumidifier is 5 kg/h. The dehumidifiers can be set in flexible way as required and can be

moved.

6.5.6 Smoke Exhaust of Main and Auxiliary plants

According to requirements of the specification, smoke exhaust system should be set

for generator floors of the main and auxiliary plants and transportation channel of main

transformer.

Smoke exhaust system of generator floor: smoke exhaust pipes are set in central part

of the upper part of generator floor; smoke exhaust holes are set on the pipes, which are

closed under common condition and opened automatically upon fire. Axial flow fan for

smoke exhaust connects with the smoke exhaust pipe directly and are mounted under the

arc crown. Smoke is directly exhausted to upstream outside of 2# erection bay when there

is a fire. Smoke exhaust capacity of the system is 60000 m3/h. There are only 1 smoke

exhaust fan with model of HTF-11.2-I.

Smoke exhaust system of transportation channel of main transformer: smoke exhaust

pipes are set at upper part of transportation channel of the main transformer; smoke

exhaust holes are set on the pipes, which are closed under common condition and opened

automatically upon fire. Axial flow fan for smoke exhaust connects with the smoke

exhaust pipe directly. Smoke is directly exhausted to downstream outside when there is a

fire. Smoke exhaust capacity of the system is 15000 m3/h. There are only 1 smoke exhaust

fan with model of HTF-8-I.

6.5.7 Main Equipment of HVAC System

Refer to Table 6.5-1 for main equipment of the HVAC system.

Table 6.5-1 Main Equipment of HVAC System

S/N Description Model Specifications Unit Qty. Remarks


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1 Centrifugal fan 4-79No.2-14E

L=123000m3/h

H=431Pa

n=460rpm

N=22kW

Set 2 Air blown to

powerhouse


L=82600m3/h

H=451Pa

n=520rpm

N=15 kW

Set 1 Air blown to

powerhouse


L=45000m3/h

H=657Pa

n=660rpm N=15

kW

Set 10

Air exhausted

from

downstream

auxiliary plant

4 Centrifugal fan B4-72-8D

L=11000m3/h

H=480Pa

n=730rpm N=3 kW

Set 2 Air exhausted

from oil depot

5 Axial flow fan T35-11No.6.3

L=11534m3/h

H=114Pa

n=960rpm N=0.75

kW

Set 5

Air exhausted

from switchgear

room


L=8100m3/h H=90Pa

n=960rpm N=0.37

kW

Set 20

Air exhausted

from

transformer

room

7 Axial flow fan T35-11No.4

L=3505m3/h

H=76.2Pa

n=1450rpm

N=0.18 kW

Set 12

Air exhausted

from pipeline

floor

8 Axial flow fan T35-11No.5

L=5235m3/h

H=63.5Pa

n=960rpm N=0.37

kW

Set 20 Air exhausted

from GIS room


L=2692m3/h

H=69.7Pa

n=1450rpm

N=0.09 kW

Set 30 Air blown to

busbar floor


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L=2692m3/h

H=69.7Pa

n=1450rpm

N=0.09 kW

Set 30

Air blown to

water supply

room and

circuit breaker

room


L=2078m3/h

H=61.7Pa

n=1450rpm

N=0.09 kW

Set 14

Air blown to

operation

gallery

12

High-temperature

smoke exhaust fan

box

HTF-11.2-Ⅰ

L=59007m3/h

H=593Pa

n=1450rpm N=22

kW

Set 1

Smoke

exhausted from

generator floor

of powerhouse

13

High-temperature

smoke exhaust fan

box

HTF-8-Ⅰ

L=14336m3/h

H=508Pa

n=1450rpm N=4

kW

Set 1

Smoke

exhausted from

transportation

channel of main

transformer

14 Explosionproof

axial flow fan BT35-11No.3.55

L=2683m3/h H=75Pa

n=1450rpm

N=0.12kW

Set 3

Air exhausted

from battery

room


L=2692m3/h

H=69.7Pa

n=1450rpm

N=0.09 kW

Set 30 Auxiliary fan

16 Mobile

dehumidifier 5 kg/h Set 10

17

Outdoor machine

of multi-split air

conditioning unit

Refrigerating

capacity QL: 75 kW Set 4

Air condition of

central control

room

18

Outdoor machine

of multi-split air

conditioning unit

Refrigerating


Air conditions

of equipment

rooms such as

local panel

room


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19

Outdoor machine

of multi-split air

conditioning unit

Refrigerating


Air conditions

of equipment

rooms such as

local panel

room

20 Indoor unit Set

Air conditions

of areas of

central control

room, local

panel room, etc.

21 Fire damper Pcs.

22 Smoke exhaust

damper Pcs.

23

Opposed

multi-blade

damper

Pcs.

24

Aluminium air

hole of window

blind

Pcs.

25 Galvanized iron air

duct m2

Manufacturing

including the

air duct

18

Outdoor machine

of multi-split air

conditioning unit

Refrigerating


Air conditions

of equipment

rooms such as

local panel

room

19 Indoor unit Set

Air conditions

of areas of

central control

room, local

panel room, etc.

20 Fire damper Pcs.

21 Smoke exhaust

damper Pcs.


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22

Opposed

multi-blade

damper

Pcs.

23

Aluminium air

hole of window

blind

Pcs.

24 Galvanized iron air

duct m2

Manufacturing

including the

air duct

6.6 Fire Protection Design

6.6.1 Project Overview

6.6.1.1 Overview

The Paklay HPP has storage of 0.89×109 m3 corresponding to normal pool level of

240.00 m a.s.l. and of 904.4×106 m3 corresponding to check flood level of 240.23 m a.s.l.,

with total installed capacity of 770 MW (14×55 MW). The hydraulic structures mainly

consist of the flood releasing and energy dissipation (sediment releasing) structure, water

retaining structure, powerhouse, navigation lock and fish way. The non-overflow dam

section on the left bank, water retaining powerhouse dam section, sediment releasing

bottom outlet dam section, low-level surface bay, overflow surface bay dam section (11 in

total, with underflow for the energy dissipation downstream for the 5 bays on the left),

navigation lock dam section and the non-overflow dam section on the right bank are

arranged in sequence from left to right.

6.6.1.2 General Layout of Powerhouse

a) Layout of powerhouse area

Main structures in the powerhouse area include the powerhouse, auxiliary plant, GIS

room of main transformer switchyard, outgoing line platform, central control building,

entrance channel, tailwater canal, access road, etc.

Main unit bay of the powerhouse is located on the main riverbed of the left bank with


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a total length of 301.00 m. For the main unit bay, its left end is connected with the

non-overflow dam section and its right end is connected with the bottom outlet dam section.

The total width of the powerhouse dam section along the water flow direction is 83.05m.

Water retaining type intake is arranged on the upstream side of the generator hall, while the

downstream side of the generator hall is provided with downstream auxiliary plant. The

GIS switchyard and outgoing line platform are provided on the top of unit ① ~ unit ⑤

in downstream auxiliary plant. One erection bay is provided on the left and the right ends

of the generator hall respectively. Auxiliary erection bay is located on the sediment

releasing bottom outlet at the right end of generator hall, while the main erection bay is

located on the left end of generator hall. Auxiliary plant of central control building is

located 26 m downstream of the main erection bay on the right side, and turnaround is

located 26 m on the left side. Powerhouse access road leads to the site horizontally from

the downstream and connects with the turnaround. Direct access to the floor of main

erection bay can be realized through the turnaround.

Sand-guide sill and trashrack are arranged in front of the powerhouse dam section.

Upstream guide wall is arranged on the right side slope of the entrance channel. After

extending upstream 60.00 m, the upstream guide wall will extend upstream 50.00 m

along the sand-guide sill.

b) Layout of intake

Each unit is set with 1 intake. Elevation of foundation surface of the intake is 194.02

m a.s.l.; dam crest elevation of the intake is 245.20 m a.s.l.; height of the intake is 50.98 m.

Width of each intake front is 21.50 m and thickness of abutment pier is 3.20 m. To reduce

span of trash rack, an intermediate pier which is 1.80 m thick is set at the intake. Abutment

pier at intake and water retaining wall at upstream of the generator hall integrate as a whole.

Thickness of the water retaining wall is 6.00 m. Air delivery conduit and air vents for

emergency gate are set in the wall. Platform at top of the intake is 30.05 m long along the

flow direction, which is set with an 8-meter-wide road, upstream track of gantry, trash rack,

emergency gate chamber and slot, and downstream track of gantry. A breast wall


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connecting the abutment piers and intermediate pier is set between trash rack slot and

emergency gate slot. Base plate elevation of the intake is 201.02 m a.s.l. Grouting and

drainage gallery is set in the base plate of the intake.

One gantry is set at top of the intake to lift the trash rack and emergency gate. A

highway bridge of dam crest connecting the overflow monolith and non-overflow monolith

is set at front of the dam crest.

c) Layout of powerhouse

The powerhouse consists of generator hall and erection bay, with a dimension of

400.00m×22.50m×52.44m (length×width×height). The distance between generator units is

21.50m. Two single-trolley bridge cranes are set in the powerhouse, with the rated lifting

capacity per crane of 2500 kN; the span is 21.00 m, and elevation of rail top is 240.50 m.

The crane can operate between erection bay and generator hall. In the powerhouse, bottom

elevation of the roof is 246.50 m a.s.l, and elevation of the foundation surface is 194.06 m

a.s.l.

The generator hall has a length of 301.00 m and a net width of 21.00 m. The generator

hall consists of operation floor, pipeline floor, and flow passage floor from top to bottom.

Ground elevation of operation floor is 222.50 m a.s.l. and this floor is set with oil pressure

apparatus, governor, generator and turbine lifting holes at the upstream and downstream

sides. The pipeline floor has a ground elevation of 219.00 m. Pipe gallery and cable gallery

are set respectively at both sides of the pipeline floor to connect with the generator lifting

hole and turbine lifting hole. Setting elevation of the unit is 208.50 m a.s.l. An access

gallery running through the whole powerhouse is set below the runner room. Bottom

elevation of the gallery is 198.06 m a.s.l., and the gallery connects with tubular shaft of the

unit.

The auxiliary erection bay has a length of 47.00 m, a net width of 21.00 m and a

ground elevation of 222.50 m, same as that of the operation floor. It is the place for unit

installation and maintenance. Two sand releasing bottom outlets are arranged at the lower

part of the auxiliary erection bay.


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The main erection bay has a length of 52.00 m, a net width of 21.00 m and a ground

elevation of 228.50 m, 6.00m higher than that of the operation floor. At 26.00m on the left

end of main erection bay, the lower part is solid concrete. The place of 26.00m on the right

end is a 3-layer reinforced concrete structure. The top floor is the place for unit installation

and maintenance. Middle floor with a ground elevation of 222.50 m is equipped with an air

compressor room. The ground floor with an elevation of 216.50 m is equipped with a

turbine oil depot and a pump house for leakage water drainage sump and maintenance

drainage sump. Such two drainage sumps are arranged below the pump house. The

elevation of drainage sump bottom is 192.00 m.

d) Layout of auxiliary plant

The auxiliary plant consists of downstream auxiliary plant and auxiliary plant of the

central control building. The downstream auxiliary plant, which is 21.40 m wide, is set at

downstream side of generator hall and is a 5-storey reinforced concrete structure. The

bottom is pipeline floor with an elevation of 219.50 m a.s.l. Local panel room and power

distribution room are set at the elevation of 222.50 m a.s.l. The generator floor consisting

of main transformer room, switchgear room, station service transformer room, exhaust fan

room, and main transformer transportation rail, etc. is set at the elevation of 228.50 m a.s.l.

SF6 pipeline floor is set at the elevation of 240.50 m a.s.l. with the roof elevation of 245.50

m. 500 kV GIS room with a plan size of 64.50m×17.40m (L×W) is arranged at the section

of units ③~⑤, and 1 bridge crane of 150 kN is set indoor. The GIS room has a roof

elevation of 260.50 m and outgoing line platform with a plan size of 69.00 m×23.40 m

(L×W) ① ②is formed jointly by section of units ~ and roof of auxiliary plant of central

control building.

Auxiliary plant of central control building is arranged at downstream of the main

erection bay, with the plan size of 26.00 m×21.40 m (L×W); it is of a 5-storey reinforced

concrete structure. Elevation of the ground floor is 216.50 m a.s.l. with turbine oil

treatment room, powerhouse drainage sump and sewage pool arranged. Drainage pump

room, sewage pump room, air conditioning equipment room and HV laboratory, etc. are


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arranged at an elevation of 222.50 m a.s.l. Relay protection room and diesel engine room

are arranged at an elevation of 228.50 m a.s.l. Central control room and computer room are

arranged at an elevation of 234.50 m a.s.l. Battery room, tool room, communication

equipment room and communication power supply room of the central control building are

set at an elevation of 240.50 m a.s.l.; and the outgoing line platform is arranged at the roof

elevation of 245.50 m.

Exhaust fan room is arranged in the space between main erection bay and upstream

non-overflow dam, with a plan dimension of 11.00 m×7.00 m (length×width) and a ground

elevation of 228.50m. Fire pump house and public auxiliary panel cabinet are arranged in

the space at the downstream part of auxiliary erection bay.

e) Internal and external access of the powerhouse

Internal access of the powerhouse: 1 staircase is set at upstream of main erection bay

of the powerhouse to connect with each floor and the deep well pump house. Manholes for

dewatering sump and leakage drainage sump are set in the deep well pump house at the

lower part. At the downstream auxiliary plant, 1 staircase is arranged respectively at ③,

⑥, ⑨, ⑪, ⑭ unit bays and bottom outlet dam section end, to connect to each floor.

Staircase and elevator are set at the downstream side of the central control room to connect

to each floor. Meanwhile, door opening is set for foundation wall at downstream between

the powerhouse and auxiliary plant for horizontal transportation of each floor and ensure

easy operation management.

External access of the powerhouse: horizontal access to the powerhouse is adopted.

Access road of the powerhouse is set along hillside toe at left bank of downstream of the

powerhouse. One end of the access road connects with downstream of the turnaround loop

and the other end connects with outside highway at downstream of the powerhouse. The

access road is 8 m wide and about 150 m long, with average longitudinal slope of 6.07%.

Drainage ditches are set at both sides of the road; the left side is excavated side slope, and

the right side is gravity retaining wall.


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6.6.2 Design Basis and Principle for Fire Protection

6.6.2.1 Overview

a) Scope and key point of design

Fire protection design of the Paklay HPP includes the powerhouse area (including

powerhouse, auxiliary plants, 500 kV switchyard, insulating oil disposal room, and tailrace

platform) and head structure (including dam crest at intake and dam crest of spillway).

Design of the powerhouse area is key point of fire protection of the Project.

b) Fire extinguishment method

Fire hydrant, water spray, and dry powder fire extinguisher are adopted for fire

protection of the station. As water yield of the HPP is sufficient, fire extinguishment with

water is the main fire protection way.

Fire hydrant is adopted for fire extinguishment with water and ammonium phosphate

dry powder extinguisher (MFA type) is adopted.

c) Design of fire protection of powerhouse area

Design of fire protection of powerhouse area includes buildings such as powerhouse,

auxiliary plants, 500 kV switchyard, insulating oil disposal room, and tailrace platform, as

well as their electromechanical equipment inside. Fire hydrant is adopted for fire

protection of buildings of the plant area; fixed system for fire extinguishment of water

spray is adopted for fire protection of the generator; ammonium phosphate dry powder

extinguisher is adopted for fire protection of the central control room, relay protection

panel room, computer room, tailrace hoist room, etc.

d) Head works

Fire protection of head works includes buildings and electromechanical equipment.

Dry powder extinguisher is adopted for fire protection of electromechanical equipment of

power distribution room at dam crest of the head, diesel engine room, hydraulic hoist room,

etc.

e) Design basis

Design for fire protection of the Paklay HPP is based on following latest rules and


6-138

codes issued by the People’s Republic of China and the industry.

1) Fire Control Law of the People's Republic of China

2) Code of Design on Building Fire Protection and Prevention

3) Code for Design of Fire Protection of Hydraulic Engineering

4) Typical Rules of Fire Protection for Electric Power Installations

5) Code of Design for Water Spray Extinguishing Systems

6) Code of Design for Carbon Dioxide Fire Extinguishing Systems

7) Code for Design of Extinguisher Distribution in Buildings

8) Code for Design of Automatic Fire Alarm Systems

9) Code for Design of Heating, Ventilation, and Air Conditioning

10) Design Code for Heating, Ventilation and Air Conditioning of Power House of

Power station

11) Electrical-mechanical Design Code of Hydropower Plant

6.6.2.2 Design Principle

Fire control design of the Project should be implemented on the basis of "prevention

first, combination of prevention and elimination", ensuring key points, giving

consideration to general points, easy management, and economical and practical.

Provisions of current regulations and specifications should be strictly followed during the

design. Comprehensive fire control technical measures should be adopted for the fire

control. Functions of the fire control system requires complete consideration of fire control,

monitoring, alarm, control, fire extinguishment, fume exhaust, life saving, etc. to achieve

“prevention before a fire starts”. And fire can be extinguished in short time once it happens

to minimize fire damage.

Allocation of fire control facilities is based on fire self-rescue. In general layout of the

project, fire lane, fire separation distance, emergency exits and signs should all be arranged

to meet the requirements of specifications. Fire protection devices and apparatuses should

be allocated according to production significance and risk level of the fire. Special fire

control measures should be adopted for special parts according to fire control specification.


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Monitoring apparatus of automatic fire alarm system should be set in the central control

room.

Fire control products to be used should all be safe and reliable, easy for use,

economical, with advanced technology, and meet special requirements of the Project. All

the products should be qualified by related national quality supervision and inspection

departments. Water spray, fire hydrant, dry powder fire extinguisher, and CO2 fire

extinguishment are adopted. Fire protection water is taken from the upstream reservoir

with sufficient and reliable water. Double-circuit independent power supply is used as the

fire protection power supply. Ventilation and smoke exhaust system after fire protection

should be set. Electrical equipment using nonflammable or flame-retardant materials as

insulating medium should be used if possible. Apparatus rooms with fire risk should be

insulated by fire-proof materials; holes and cable channels should be blocked by fire-proof

materials. Fire separation zones should be set to prevent fire spreading.

6.6.3 Design for Fire Protection of the Project Buildings

6.6.3.1 Fire Risk Classification and Fire Resistance Rating of Workshop

a) Fire risk of workshops is classified as Class C, Class D, or Class E according to

principles of Code of Design on Building Fire Protection and Prevention (GB

50016—2006).

b) According to the hydro-project layout and production characteristics, fire

protection zones of buildings and structures of the workshops are naturally divided to the

powerhouse and erection bay, auxiliary plant, busbar floor, main transformer floor, 500 kV

switchyard, inlet and water intake of flood release and desilting buildings, dam area, etc.

c) According to stipulations of Code for Design of Fire Protection of Hydraulic

Engineering (GB50872-2014), fire risk classification, fire resistance rating, and fire

protection measures of buildings and structures are classified as what are shown in Table

6.6-l.

Table 6.6-1 Fire Risk Classification, Fire Resistance Rating, and Fire Protection


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Measures of Buildings and Structures

S/N

Buildings, Structures,

and Electromechanical

Equipment

Fire Risk

Classification

Fire

Rating Fire Protection Measures

1 Powerhouse and erection bay

1.1 Generator floor and

erection bay Class D II

Wheeled and portable fire

extinguisher and fire hydrant

1.2 Hydraulic generator Class D II System for fire extinguishment of

water spray

1.3 Busbar floor Class D II Portable fire extinguisher and fire

hydrant

1.4 Cable floor Class C II

Layered arrangement of cables;

fireproof bulkhead, coating, gas

mask, cable-type thermal detector,

portable fire hydrant, system for fire

extinguishment of water spray

1.5 HV cable adit and shaft Class D II Portable fire extinguisher and fire

hydrant

1.6 Turbine floor Class D II Portable fire extinguisher and fire

hydrant

1.7 Operation gallery Class D II Portable fire extinguisher

1.8 Air compressor room Class D II Portable fire extinguisher

1.9 Deep-well pump house of

powerhouse Class D III Portable fire extinguisher

1.10 Bridge crane of

powerhouse Class D II Portable fire extinguisher

2 Auxiliary plant

2.1

Central control room,

relay protection room,

computer room, etc.

Class C II

Automatic alarm, fire extinguishing

system of IG541 mixed gas, and

portable fire extinguisher

2.2 10 kV station service HV

switchgear room Class D II Portable fire extinguisher

2.3 0.4 kV station service LV

switchgear room Class D II Portable fire extinguisher

2.4

Generator voltage

distribution equipment

room

Class D II Portable fire extinguisher


6-141

S/N



Equipment

Fire Risk

Classification

Fire


2.5 Power cable floor Class C II






2.6 Control cable floor Class C II






2.7 Turbine oil depot and oil

treatment room Class C II

Automatic alarm, portable fire

extinguisher, sand box, and system

for fire extinguishment of water

spray

3 Isolated-phase enclosed

bus Class D II

Portable fire extinguisher and fire

hydrant

4 Main transformer

4.1 Main transformer room Class C I Water spray extinguishing system

5 Insulating oil tank room,

oil disposal room Class C II

Portable fire extinguisher, system for

fire extinguishment of water spray,

fire hydrant, and sand box

6 Oil testing room Class C II Portable fire extinguisher and sand

box

7 500 kV cable adit and

cable shaft Class D II


hydrant

8 500KV switchyard

8.1 Indoor switchgear of

500kV SF6 GIS Class D II

Ammonium phosphate fire

extinguisher of trolley type, gas

mask, and fire hydrant

8.2 500 kV cable floor Class D II

Automatic alarm, portable fire

extinguisher, and water spray

extinguishing system

8.3 Outgoing line platform Class D II

Ammonium phosphate fire

extinguisher of trolley type, and fire

hydrant


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S/N



Equipment

Fire Risk

Classification

Fire


9 Dam area and parts outside the plant

9.1 Power distribution room

at dam crest Class D II Portable fire extinguisher

9.2 Diesel generator room Class C I Portable fire extinguisher and fire

hydrant

9.3 Hoist room Class D II Portable fire extinguisher

10 Equipment repairing

workshop Class D III


hydrant

6.6.3.2 Fire Protection Zones and Emergency Exit

According to stipulation of Article 3.2.1 of Code of Design on Building Fire

Protection and Prevention, there is on limit for maximum allowable floor area of fire

protection zones with production category of Class D, fire resistance rating of Grade II,

and multilayer. Thus, powerhouse of the Paklay HPP can be divided to 2 fire protection

zones. The powerhouse and auxiliary plant are set as two independent fire protection zones;

firewalls, fireproof doors, and wall-type fire dampers are adopted to segregate the big

space in the powerhouse.

According to stipulations of clauses of Article 4.2 of Code for Design of Fire

Protection of Hydraulic Engineering, two emergency exits are set for operation floor of the

powerhouse, and at least two evacuation exits are set for each floor such as generator floor,

cable floor, and operation gallery. Only 1 evacuation exit is set for the central control

building as the floor area of each floor is less than 800 m2 and number of staff on duty is

not more than 15.

For each floor, distance between the farthest work place and nearest evacuation exit

should be not more than 60.0 m. Net width of evacuation door, which opens towards

evacuation direction, is not less than 0.9 m. Net width of corridor is not less than 1.2 m.


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Net width of staircase is not less than 1.1 m and slope gradient of the staircase is not more

than 45°. Fireproof doors and firewalls are set between the underground buildings and

ground buildings for segregation.

Number of staircase and safe evacuation distance should both meet requirements of

the Codes.

6.6.3.3 Fire Lane

a) Fire lane outside the plant

Permanent access road can lead to the generator floor and head structures. Both the

permanent access road and dam crest road can be used as fire lane.

b) Fire lane inside the powerhouse

The station is of a ground-type powerhouse; the fire truck can reach to powerhouse

via access road and do fire protection operation. Turnaround loop, which can also be used

as turnaround loop for fire truck, is set before the plant gate.

6.6.3.4 Fire Water Supply and Design of Water Supply System

Water source of the HPP is abundant. Upstream reservoir is the source of fire water

supply and direct water supply system of pressurization of water pump is adopted.

Capacity of fire pump is not less than sum of maximum water yield of water spray and fire

water yield of hydrant; the sum is 360 m3/h by calculation. Elevation of the water pump

should ensure that pressure at outlet of water sprayer at highest place should be not less

than 0.35 MPa (35.7 mH2O) stipulated in the Code, and that value is 50 mH2O by

calculation. Two water supply pumps are provided (one for use and one for standby).

Circular pipe for water supply of fire protection should be set crossing the whole plant.

Water is led by branch pipes of the circular pipe to each water consumption system.

According to requirement of the Code, sectionalized valves should be set on the circular

pipe. When a section is damaged, fire hydrants out of work should be not more than 5 in

same floor.


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6.6.3.5 Design for Fire Control of Main Electromechanical Equipment

a) Turbine generator

Water spray should be adopted for fire extinguishment of generators according to the

capacity, scale, and fire protection technology at present. Detectors for temperature sensing

and smoke sensing should be set in foundation pit of generators. When the fire alarm of

generator gives alarm signal to fire control centers of whole plant, staff on duty should

confirm the alarm and then connect the separated hoses of fire hydrant of the generator

manually to open the water supply valve to put out fire.

b) Main transformer

Independent water spray extinguishing system should be adopted for each main

transformer. When the transformer is on fire, the sprayer seals both its body and oil sump

in the water spray, and extinguishes fire by cooling down and asphyxiating effects. Oil

discharging pipe is set at bottom of the oil storage pit to discharge fire protection water and

transformer oil which may overflow to the emergency oil pool. Capacity of emergency oil

pool is sum of transformer oil capacity and water yield of fire protection for 24 min. The

sum is 195.4 m3. Capacity of emergency oil pool of main transformer is 200 m3.

c) Turbine oil depot and oil disposal room, insulating oil depot and oil disposal room

The turbine oil depot and oil disposal room, and insulating oil depot and oil disposal

room are all set at the floor with an elevation of 216.500 m a.s.l. below the central erection

bay. Two fireproof doors opening outward are set at that floor. Firewalls with fire

endurance of 4 h are set for the oil depots and oil disposal rooms. Explosionproof electric

appliances are provided for the oil disposal room.

Fixed fire extinguishment appliance for water spray is adopted for fire protection of

the oil depot and oil disposal room. Complete set of deluge valves, which are set outside

the turbine oil depot, is adopted as operation valves for inflow of fire protection water.

Detectors for temperature sensing and smoke sensing are set in the oil depots to send alarm

to the fire control center automatically when there is a fire. At that time, the fire damper

will close automatically, the exhaust fan stops exhausting immediately, deluge valves start


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spraying water to put out fire, and the exhaust fan starts exhausting after the fire is put out.

d) Central control room, computer room, and relay protection room

Fixed fire extinguishment system of CO2 is adopted for this part. Combined and

distributed pipeline system is adopted and one set of storage vessel is adopted. Design

capacity of the system is determined as per demand capacity of the biggest central control

room and a standby capacity of 8% should be considered. By calculation, 22 storage

cylinders are adopted. The cylinders are controlled by fire alarm control panel. Point-type

temperature and smoke sensing detectors as well as audible and visual alarms should be set

in fire extinguishing districts. Gas indicators should be set at upper parts outside the doors,

which should be provided with emergency interrupting boxes. When the temperature and

smoke sensing detectors give alarms simultaneously, the controller will stop air

conditioners and fans of the district immediately, and the audible and visual alarms give

alarms to alert people to evacuate immediately. After a time delay of 30 s (adjustable), the

fire protection door will be closed and fire extinguishing apparatus will be used. Cylinders

will be started by solenoid valve to start the CO2 storage cylinders. When the gas indicators

are on, it means that the fire extinguishing system is working. Supporting sprayers of the

fire extinguishment system are adopted as sprayers of the protection zone. Number of both

kinds sprayers are 8 respectively. When the staff on duty finds a fire, he must press the

emergency interrupting box, and then the fire extinguishment appliance will start to work

immediately. Or if the staff finds that the alarm is a false one during time delay before

the gas is emitted, he can press the emergency interrupting box to stop the fire

extinguishment appliance.

e) Cable

Flame retardant cables should be adopted to prevent and reduce occurrence and

spreading of fire disasters. Temperature sensing cables are laid for each floor of enclosed

cable bridge.

Fire resistant plates should be set for spaces between the power cable floors and

control cable floors in the enclosed cable bridge. Fire retardant sections should be set at


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appropriate position. Fire proof materials should be adopted to seal holes on walls, floors,

etc. those are crossed by cables, and ends of cables.

Fire extinguishment appliances of water spray are set for main cable channels such as

those of the central control room, cables of the powerhouse, etc.

Combining layout of equipment and cables, cable zones without fixed fire

extinguishment systems of water spray should be set with portable fire extinguishers at

certain interval distances. Fire protection sealing measure, as well as sand boxes and

portable fire extinguishers, etc. is set at entrances and outlets where cables are centralized.

6.6.3.6 Electrical Works for Fire Control

a) Power Distribution for Fire Fighting

Electrical fire fighting equipment includes smoke exhaust fans, fire dampers, fire and

smoke exhaust dampers, automatic fire alarm control system, safety evacuation

identifications and emergency lightening, etc.

Power supply for the electrical fire fighting equipment is provided with second class

load through independent power supply circuit. The arrangement ensures the availability of

fire fighting power supply in case of a fire. And the power distribution equipment is

provided with the sign of “Dedicated Equipment for Fire Fighting”.

The power station is equipped with dedicated fire fighting power panel. The power

supplies come from the II-section and III-section bus of the public power supply for the

whole powerhouse, respectively to ensure 2 reliable power supplies for the electrical fire

fighting equipment.

The emergency system is powered by the AC and DC switching system. In normal

conditions, AC power supply shall be used for supplying power. If the AC power supply is

out of service, switch to the DC power supply system to convert DC power supply into AC

power supply. Under normal conditions, AC power supply shall be used for supplying

power for evacuation indicator lights. If the AC power supply is out of service, batteries of

the lights shall be used for supplying power.


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Evacuation indication lighting and emergency lighting are also the emergency lighting

in case of fire. Continuously supplying power of the fire emergency lighting and

evacuation signs shall not be less than 30 min.

Cables for power supply of the fire fighting power supply system, emergency lighting

system and evacuation indication lighting shall adopt fire resisting cables and be laid in

conduit.

b) Fire emergency lighting, evacuation sign indication and lamps

Main evacuation exits, staircases, emergency exits are provided with fire

emergency lighting and emergency sign indication lighting with minimum illumination

no less than 0.5Lux.

The emergency lighting lamps are mounted on wall or ceiling. Evacuation lighting of

the emergency exits shall be mounted on the top. Evacuation indication signs of the

evacuation corridor shall be mounted on the wall with a distance of 0.5m to the ground

(floor). The distance between the signs shall not be larger than 20m.

The emergency lighting and evacuation indicator lights shall be equipped with

protection covers made of glass or other refractory materials.

6.6.3.7 Smoke Prevention and Exhaust System

a) Fire protection plan for ventilation system

According to requirements of fire protection code, fire protection design of ventilation

system of the whole plant conforms to the following principles.

Open fire heating is prohibited at parts such as oil depots, oil disposal room, places

neat to the oil pipes and their accessories, battery room, etc.

Fire dampers are set for spaces of different fire protection zones, for spaces between

important equipment rooms and the outside, and for areas among different fire ratings for

segregation.

Independent exhaust systems are set for equipment rooms with superior fire ratings,

such as oil depots, battery rooms, etc.


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Based on the above principles, fire dampers are adopted for exhaust outlets set at

exhaust interlayer of the downstream auxiliary plant to complete fire protection function of

the ventilation system, for exhaust inlets for fire protection, alarm, and air volume

regulation, for air inlets and exhaust outlets of main transformer room of the exhaust

system for main transformers to separate the main transformers with other zones, separate

the transformers with each other to prevent spreading of fire, for air inlets and exhaust

outlets of oil depots and battery room to prevent and cut off fire. The exhaust fan is of

direct-connection explosionproof type and axial exhaust fan of SF6 switchyard is of

explosionproof type.

Galvanized iron-sheet air hose with good fireproof performance is adopted for all air

ducts of the plant to eradicate fire risk.

Joint control is carried out for the fire dampers and their corresponding exhaust fans.

When there is a fire, the fire damper will start to work and send electric signal to stop its

corresponding exhaust fan. After the fire is put out, fire damper will open again to start the

exhaust fan to exhaust smoke after the fire.

b) Design of smoke prevention and exhaust of whole plant

According to requirements of the Code, mechanical smoke exhaust system is set for

generator floor of the powerhouse and transportation channel of main transformer, as the

HPP is of a ground-type powerhouse.

Smoke exhaust system of generator floor: smoke exhaust pipes are set in central part

of the upper part of generator floor; smoke exhaust holes are set on the pipes, which are

closed under common condition and opened automatically upon fire. Axial flow fan for

smoke exhaust connects with the smoke exhaust pipe directly and are mounted under the

arc crown. Smoke is directly exhausted to upstream outside of 2# erection bay when there

is a fire. Smoke exhaust capacity of the system is 60000 m3/h. There are only 1 smoke

exhaust fan with model of HTF-11.2-I.

Smoke exhaust system of transportation channel of main transformer: smoke exhaust

pipes are set at upper part of transportation channel of the main transformer; smoke


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exhaust holes are set on the pipes, which are closed under common condition and opened

automatically upon fire. Axial flow fan for smoke exhaust connects with the smoke

exhaust pipe directly. Smoke is directly exhausted to downstream outside when there is a

fire. Smoke exhaust capacity of the system is 15000 m3/h. There are only 1 smoke exhaust

fan with model of HTF-8-I.

Air exhaust system of downstream auxiliary plant exhausts smoke as well. When

there is a fire, fans of related parts should be stopped; after the fire disaster, fans should be

started to exhaust smoke. Twenty axial flow fans with model of T35-11No.5 are set at

upper and lower parts (10 for the upper part and 10 for the lower part) of downstream wall

of GIS room. The upper fans can exhaust smoke and the lower fans can exhaust SF6 gas

leaked when putting out the fire.

For areas such as generator floor of powerhouse and transportation channel of main

transformer that are set with immediate smoke exhaust facilities, their smoke exhaust

dampers are interlocked with corresponding exhaust fans so that when the smoke exhaust

damper is started (via the fire control center), the exhaust fan will operate automatically.

For areas set with emergency exhaust facilities, fire alarm controller will automatically

close the corresponding fire dampers and stop corresponding exhaust fans via joint module

when there is a fire. Fire dampers will be open to start smoke exhaust fan after the fire is

put out.

6.6.3.8 Fire Alarm Control System

A set of automatic fire alarm and fire joint control cabinet and fire monitoring

computer (including professional fire monitoring software) is set in the control room to

achieve fire detection, audible and visual alarm, joint control of fans and air conditioners,

join control of smoke prevention and exhaust, joint control of fire extinguishment, etc. of

the HPP and monitoring scope within the navigation lock. The fire monitoring computer

can monitor, deal with, store, and print all alarm information to display the system status

via plane graph, as well as control all controllable fire extinguishment apparatuses. Each

one regional fire alarm and fire joint control cabinet is set for the dam area and navigation


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lock. Coaxial cables or optic fiber communication is adopted for all control cabinets.

The alarm and joint control apparatus connects with the fire monitoring computer via

communication interface, connects with the computer monitoring system via I/O interface

to send general alarm information to the computer monitoring system, and connects with

industrial television monitoring system via I/O interface and communication interface to

link with facility of the industrial television monitoring system to achieve automatic

tracking and video recording of the alarm site. Operators in the control room can operate

the facility of the industrial television monitoring system to carry out remote monitoring to

area with the scope of fire protection monitoring of the HPP and facilities.

Detectors are installed at areas where important facilities are set and places where fire

may occur easily. Detectors, manual fire alarm buttons, etc. are set according to Code for

Design of Automatic Fire Alarm Systems (GB50116-98) and actual layout of the HPP.

Joint control modules are provided according to requirement of automatic control of fire

extinguishment apparatus. Point-type smoke sensing detectors are provided for areas (such

as hydraulic generator room, central control room, relay protection panel room, computer

room, communication facility room, and main transformer room) where important and

common facilities are set. Explosionproof infrared-beam smoke sensing detectors are

provided for turbine oil depot and oil disposal room. Point-type and cable-type temperature

sensing detectors are provided for areas where fixed fire extinguishment apparatus of water

spray are set. Manual alarm buttons, audible and visual alarms are provided for important

transportation channels, evacuation channels, galleries, stairs, and main facilities.

Complete administration and dispatching communication facilities are set in the HPP

to cover the area of fire monitoring system, thus, there is no need to set fire protection

communication facilities. Fireproof treatment is carried out to communication line

according to laying requirement of fire protection line. Meanwhile, a number of wireless

intercoms are provided for the HPP as standby communication for the wire

communication.


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6.6.4 Fire Protection Design for Finishing Works of Buildings

6.6.4.1 Overview

Design for finishing works of the HPP should not only meet the requirement of

operation function, pay attention to appearance, but also meet the requirement of durability,

anti-corrosion ability, and good fireproof performance. Therefore, materials which are

non-inflammable and fire-retardant should be used as finish to meet the architectural effect

and prevent flame. In addition, fire protection zones should be set reasonably at the same

time.

Suspended ceiling is an important part of the finishing. As many lighting lines are set,

the suspended ceiling is a part where fire may occur easily. Therefore, suspended ceilings

of important places and provided with light-steel keel and aluminium alloy perforated plate

(with requirement of sound absorption) should be paved with mineral cotton with thickness

of 50 mm. Thus, requirement of sound absorption and flame prevention can be met. In

addition, constant temperature sensing detectors should be laid at the suspended ceiling.

Interior wall is plastered by cement mortar, whitened after leveling, and finished by

environmental wall paint.

Except the computer room, communication room, etc. which are paved by aluminium

alloy antistatic floor, other grounds are paved by granite, floor tile, cement floor, cement

mortar, and terrazzo.

Class A or Class B fireproof doors are adopted for windows and doors of partition

walls according to fire ratings of rooms. Fireproof materials are adopted to seal facility

holes which cross the walls.

6.6.4.2 Powerhouse

Generator hall and erection bay are key places of interior safety design of the

powerhouse. White wall paints are adopted as finish of the wall. Magenta marble boards

which are 2000 mm high are adopted for wainscot. The 1000×1000 copper bar frames of

cast-in-situ terrazzo are adopted for the generator hall and erection bay. Color plate

arc-shaped roof is adopted as the roof. Stainless-steel metal guard rods which are 1050

mm high are adopted for interior surrounding of the generator hall. Cover plates are

adopted to seal the lifting holes.


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6.6.4.3 Downstream Auxiliary plant and Central Control Building

Class A fireproof doors are adopted for power distribution room, 10 kv switchgear

room, central control room, communication power supply room, communication facility

room, relay protection room, and battery room of the downstream auxiliary plant and

central control building as safety design measure of fire protection. Double-layer

fireproof glass windows are adopted for windows of the central control room.

Architectural finishing: white wall paints are adopted for walls of the power

distribution facility room, station-service power distribution panel room, 10 kv

switchgear room, local small room, duty room, office, galleries, relay protection room,

and shift room as finish. In addition, tiles with skirting which is 150 mm high, 600×600

anti-skidding floor tiles of the ground, and white aluminium alloy light-steel keel for the

suspended ceiling is adopted for the above rooms.

The 600×600 antistatic floors are adopted for the central control room,

communication power supply room, and communication facility room. White wall paint

is adopted as finish and white aluminium alloy light-steel keel is adopted for the

suspended ceiling.

White wall paint is adopted for the exhaust fan room, cable floor, and pump room as

finish. Cement mortar with skirting which is 150 mm high is adopted and cement mortar

is adopted for the ground.

Acid-proof floor tiles are adopted for the battery room. Acid-proof tile with

wainscot which is 1.5 m high is adopted and other wall surfaces should be of cement

mortar top with white paint. Enamel paint is adopted for the ceiling as finish after it is whitened.

6.6.4.4 Other Rooms

White wall paint is adopted for other rooms. Cement mortar with skirting which is

150 mm high is adopted and cement mortar is adopted for the ground.

6.6.5 Summary Sheet of Fire protection Apparatus

Refer to Table 6.6-2 for main fire protection apparatuses of the HPP.

Table 6.6-2 Summary Sheet of Fire protection Apparatus


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S/N Description Specification Unit Qty.

1 Fire pump Q=360m3/h H=50m Set 2

2 Pump control valve DN250, PN1.6MPa Nr. 2

3 Fire fighting device of generator Set 14

4 Y-type filter DN200 PN1.6MPa Nr. 39

5 Automatic water filter Q=360m3/h P=1.0MPa Nr. 2

6 Ball valve DN250 PN1.6MPa Nr. 4

7 Ball valve DN65 PN1.6MPa Nr. 33

8 Butterfly valve DN150 PN1.6MPa Nr. 11

9 Butterfly valve DN100 PN1.6MPa Nr. 6

10 Water spray nozzle ZSTWB-40-90 Nr. 2140

11 Water spray nozzle ZSTWB-160-120 Nr. 240

12 Deluge valve DN200 Nr. 39

13 Indoor fire hydrant SN65 Nr. 58

14 Signal butterfly valve DN200 PN1.6MPa Nr. 78

15 Check valve DN200 PN1.6MPa Nr. 4

16 Check valve DN150 PN1.6MPa Nr. 4

17 Pump adapter DN200 PN1.6MPa Nr. 4

18 Pump adapter DN150 PN1.6MPa Nr. 4

22 Start cylinder V=70L PN=15MPa Nr. 2

23 Portable dry powder fire extinguisher

MFA6 Nos. 92

24 Wheeled dry powder fire extinguisher

MFAT35 Nos. 4

25 Gas mask Set 20

26 Anti-fire plug (fast solidification)

SFD-II type t 4.5

27 Anti-fire plug (fast solidification)

XFD type t 1.5

28 Anti-fire plug (soft) DFD-III(A) type t 12

29 Fireproof coating G60-3D type t 4.5

30 Fireproof bag of expansible PFB-720 type m3 30


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S/N Description Specification Unit Qty.

cable

31 Fireproof bulkhead EFW-A type m2 150

32 Fireproof bulkhead EFF-C type m2 200

33 Fireproof tray ESW-Z type m2 450

34 Power distribution panel for fire protection

400 V Nos. 2

35 Emergency lighting 25 W Pcs. 180

36 Exit indicator light 13 W Pcs. 110

37 Emergency light 2×32 W Pcs. 100

38 Fire alarm and control system

39 Monitoring computer and software for fire protection

Set 1

40 Fire alarm and joint controller Set 1

41 Point-type smoke and temperature sensing detectors

Nr. 300

42 Infrared beam smoke sensing detector

Pair 20

43 Cable type temperature sensing detector

km 5

44 Manual alarm button Nr. 40

45 Isolator and connector modules Nr. 100

46 Audible and visual alarm Nr. 40

47 Alarm and control signal line and power line

km 10

48 Protection casing of flame-retardant flexible metal cable

km 8

49 Sand box 2m3 Pcs. 6

50 Explosionproof axial flow fan Set 3

51 Fire damper Nr. 20

6 M&E Equipment and Hydraulic Steel Structures

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