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Construction of UHV AC test base of SGCC

Yao Tao*,y, Li Shu-sen and Wu Xiong

State Grid Electric Power Research Institute of SGCC, Wuhan 430074, China

SUMMARY

In order to research ultra high voltage (UHV) transmission technology systematically, State Grid Corpor-ation of China launched the UHV AC test base project to provide strong technical support for UHV gridconstruction. The facilities including UHV power supply, UHV test lines, equipments qualified field,electromagnetic environmental laboratory, climate laboratory, UHV corona cage, impulse test field werebuilt at the test base. Much useful experience had been achieved through the construction and research in thefields of UHVelectromagnetic environment, external insulation characteristic, equipment technical require-

ments, equipments manufactory, electrical design, construction, test, and operation. It accelerated theconstruction of the UHV pilot project of China. Copyright # 2011 John

key words: UHV; AC; test base; test line; construction; achievement

1. INTRODUCTION

Ultra high voltage (UHV) power grid not only realizes the super-capacity and long-distance power

transmission, but also greatly improves security and reliability of the power grid. It can optimize

energy distribution and save the land resources and construction investment. The development of UHV

power grid can improve the utilization efficiency of energy resources and reduce environmental

pollution, which is an important strategic move to build a resource saving and environment-friendly

society.

In the areas of engineering design and construction, UHVAC test base of SGCC played an important

role in the construction process of first 1000 kV UHVAC projects in China. Much experience has been

gained in the filed of UHV electromagnetic environment, equipment technical requirements,

electrical design, engineering construction, test debugging, and operation through construction of the

test base [1].

This paper focuses on the major facilities and achievements of UHV AC test base.

2. OVERVIEW OF UHV TEST BASE

Ultra high voltage AC test base (shown in Figure 1) is located at Jiangxia district, Wuhan city, whichcovers an area of 365 acres. The construction starts from December 2005 to December 2008. The test

base included UHV power supply, UHV test line, equipments qualified field, electromagnetic

environmental laboratory, climate laboratory, corona cage, the impulse test field, and other ancillary

facilities. The electromagnetic environment measurement, corona characteristics detection, live line

work, operation, and maintenance could be carried out at UHV single circuit and double circuit

transmission lines and substations. The test base also provides a best test platform of electromagnetic

environment and external insulation of UHV projects.

EUROPEAN TRANSACTIONS ON ELECTRICAL POWEREuro. Trans. Electr. Power 2012; 22:108118Published online 13 April 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/etep.575

*Correspondence to: Yao Tao, State Grid Electric Power Research Institute of SGCC, Wuhan 430074, China.yE-mail: [email protected]

Copyright # 2011 John

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3. MAJOR TEST FACILITIES

3.1. UHV power supply

Power of the test base is supplied by a three-phase two-winding transformer which is connected to a

220 kV line from Phoenix Hill 500 kV Substation. Thousand kilovolts UHV line voltage is boosted

from 35 kV by three single-phase UHV transformers whose capacity is 3 40MVA [2]. The main

electrical connection is as shown in Figure 2. Figure 3 shows the UHV substation equipments.

Figure 1. UHV AC test base.

Figure 2. The main connection of UHV AC test base.

Figure 3. UHV substation equipments.

Copyright # 2011 John Euro. Trans. Electr. Power 2012; 22:108118

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According to GB311.1-1997 Insulation coordination for high voltage transmission and distribution

equipment, the coordination factor of lighting impulse got 1.4 and the coordination factor of

switching impulse got 1.15.

3.2. UHV test lines

Ultra high voltage test lines at the test base include UHV single-circuit test line and UHV double-

circuit test line in the same tower which is both 1 km long (shown in Figure 4). Each line is composed

with two tension towers and two suspension towers [3]. The single-circuit line uses 8 LGJ-500 wire.

And the double-circuit transmission Lines uses 8LGJ-630 wire. The typical tower structures of

china transmission project are adopted at the test base. Several hanging points are set at the tower cross

arms, which provide the conditions for the adjustment of the phasephase distances. The phase

distance range is up to 4 m, which is satisfied the electromagnetic environment measurement at

different phases. UHV test lines can carry out electromagnetic environment effects test and corona

characteristics experimental research of UHV transmission line. And they are a best platform to study

UHV live line work and line maintenance training.

3.3. Equipments qualified field

Equipments qualified field is below the truss structure of test lines, length 216 m, and width 58 m [4].

Used of truss structure and 1000 kV lead, the power equipments such as power transformers, CVT,

surge arresters, post insulators, bushing, switch, GIS equipments, and so on can be long-term charged

with full voltage.

3.4. Electromagnetic environmental laboratory

The research of electromagnetic environment parameters measurement and simulation of UHV line

has been carried out in electromagnetic environmental laboratory, which is composed of the screening

room, outdoor test site, vehicle-mounted electromagnetic compatibility measurement system, and

Electromagnetic environment simulation platform. Two outdoor test sites are 120m 10m below in

single-circuit and double-circuit test line. Electromagnetic environment measurements are as follows.

Two 9 k30 MHz and two 9 k3 GHz Schwarzbeck radio interference receivers.

Two PMM PMM8053A and two Holday HI3406 frequency electric field measurements.

Four Bruel and Kjr noise meters and 3560B PULSE Multi-analysis system.

Test site layout of the multiple electromagnetic environment testers can carry out multi-parameters

long-term remote automatic measurement under all-weather. Vehicle-mounted measurement system as

shown in Figure 5 consists of transient electromagnetic interference test vehicle and the

Figure 4. UHV test lines.


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electromagnetic environment test vehicle, which can easily carry out the transient electromagnetic

disturbance survey and equipment field immunity test of substation and converter station, the

electromagnetic environmental monitoring of transmission and Distribution Project.

3.5. Artificial climate laboratory

Artificial climate laboratory as shown in Figure 6 mainly composes of the tank testing hall, AC and DC

power supplies, and auxiliary facilities test. The external insulation test of UHV transmission

equipment under the simulated pollution, high-altitude, icing, and other special natural climate could

be carried out in this lab. The clearance diameter of test hall is 20 m and the height is 25 m. The lowest

temperature of the hall is 20 8C. The internal air pressure is as low as 50 kPa (equivalent to simulate

altitude 5500 m).

AC power supply is include of 4800 kVA regulator and 1000 kV/6000 kVA test transformer. The

impedance voltage of regulator is above 5% under (50100)% rated output voltage. The1000 kV/2A

DC power supply took the one double rectifier circuit with the voltage feedback control. AC and DC

power supplies meet IEC60507 and IEC61245 requirements.

3.6. Corona cage

Figure 5. Vehicle-mounted electromagnetic compatibility measurement system.

Figure 6. Artificial climate laboratory.


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Corona cage is the important testing methods to study line corona characteristics and electromagnetic

environment of UHV AC transmission. The audible noise, radio interference, electric field strength,

and corona loss of different section, number, and split conductors could be measured in the corona

cage.

The corona cage structure of UHVAC test base is taken with the rigid double-cage design, as shown

in Figure 7. The cage body section is a 8 m 8 m square, with a total length of 35 m. The protection

sectionof the cage body with the length 5m is used to overcome the end effect caused by the conductors

surface electric field distortion. Corona cage equipped with a rain system can carry out conductor

corona test under different rainfall characteristics. Corona cage can install the 112 split conductors.

The conductors tension can be adjusted by the mechanical power unit. The test power is introduced

with non-corona conductor.

3.7. Impulse test field

The impulse test field covers an area about 21 000 m2, included the control building, the impulse

generator, voltage divider, door-type structure, and supporting tower, as shown in Figure 8. The

Figure 7. UHV corona cage.

Figure 8. 7500 kV impulse generator.


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7500 kV/750 kJ generator can produce switching impulse with 10002500ms front time. Voltage

utilization factor of up to 60%. The clearance space of door-type structure is 70 m 70 m. The research

of the long gap discharge characteristics and the external insulation experimental could be taken in this

field, especially long before time impulse discharge characteristic test.

4. ACHIEVEMENTS

The overall goal of UHV AC test base is to carry out UHV technical studies and meet UHV AC pilot

project which is the first UHV power transmission project of china. Since February 2007, the test bases

work is focused on UHVelectromagnetic environmental impact studies, external insulation, long-term

live assessment of high voltage electrical equipment, operation, maintenance, testing, and training. A

number of major issues related to UHV engineering were completed.

4.1. Obtain the electromagnetic environment measurement of UHV test lines [5,6]

Since February 2007 UHV test lines has been put into operation and immediately launched the

measurement of electric field, radio interference and audible noise. The measurement results on the

given route under fair weather are as follows. The maximum value of power frequency field strength is

6.1 kV/m. The RI level is 53.5 dB(1mV/m is defined as 0 dB). And the AN level is 36.4 dB(A weight).

But the corona in the rainy weather is much serious, which makes RI and AN about 12 or 10 dB higher

than fair weather. The results of electromagnetic environment UHV test lines confirmed that single-

circuit line using 8 500 conductors and double-circuit line using 8 630 conductors of UHV project

is feasible. The important designs of substation buss selection and connections were also confirmed.

All of these verifies the validity of previous research results, which can directly used for UHV pilot

project.

4.2. Optimize substation fittings and reduce noise levels [7]

When the substation and lines were charged for the first time, local large corona noise may exceed therequirements of environmental protection in China. So the related research was carried out. The

structure size of substation fittings took the design optimization. And the corona discharge of the test

base decreased significantly as shown in Figure 9. The ball diameters changed from 400 to 630 mm in

front of the bus with no argument of wiring and jumper. The conducting rod diameter of switch

changed from 100 to 180 mm. It ensured that the electromagnetic environment of UHV AC test

demonstration project was accepted by the State Environmental Protection Agency.

Figure 9. Corona discharge UV imaging map of bus before and after optimization.


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4.3. Live assessment of UHV AC test demonstration project equipments

At the equipments qualified field of test base, the surge arresters, CVT, post insulators, and various

fittings were charged for about 1 year as shown in Figure 10 [4]. Under the 1000 kV assessment, the

long-term reliability of domestic UHV equipments were scientifically verified in order to achieve a

successful UHV project.

Figure 10. Live assessments of UHV AC test demonstration project equipments.

Figure 11. Corona loss measurement of UHV line.


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4.4. Corona performance test of UHV test line

The first set corona loss measurement unit based on optical fiber insulator sensing technology was hung

in UHV test line as shown in Figure 11 [8]. The results are useful for the corona loss assessment of

UHV lines. While the simulation tests were carried on the corona cage. Those data can be used to

modify the prediction formula and method for Transmission Conductor Selection.

4.5. Anti-ice test

After power grid suffered icing disasters in 2008, a large number of icing tests were carried out in the

artificial climate laboratory [9]. The 500 kV long insulator strings icing flashover test as shown in

Figure 12 was taken for the first time in the world, which can support the external insulation design.Various anti-icing and de-icing methods were verified in the artificial climate laboratory, such as robot,

coating, shooting gun, and hot air.

Figure 12. 500 kV long insulator strings icing flashover test.

Figure 13. Impact test between UHV transmission and radio station.


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4.6. Influence of UHV transmission on radio station

Using UHV test base, the test and flight inspection were carried on with short-wave radio direction

finding station, short-wave radio receiving station, air intelligence radar station, aviation radio

navigation station, sea range radio navigation station, AM broadcasting station, and televisionbroadcasting station, which accesses the worlds first test data as shown in Figure 13 [10].

4.7. UHV live working

Based on the research of minimum safe distance, the smallest combination space and the insulation

tools minimum effective insulation length of UHVAC Transmission 1000 kV live work, the real live

working was carried out in the UHV lines and live working operations safety rules and operating

guidelines of 1000 kV UHVAC Transmission Line was established. Many UHV live working workers

were trained at the test base as shown in Figure 14.

Figure 14. UHV live work.

Figure 15. 1000 kV GIS test platform.


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4.8. Study of VFTO

Thousand kiloVolts GIS test platform of UHV AC test base was established as shown in Figure 15. And

the typically VFTO waveform was measured by real-type GIS devices. The data confirmed the

problems during UHV GIS disconnector operating process and the effect of related restrictions. While

the measured data and simulation results were compared to modify the simulation model. It is very

valuable for the GIS line design [11].

5. LONG-TERM RESEARCH GOALS

The research framework base on UHV test base has been drawn up. And it includes the following six

aspects:

(1) Optimization of UHV construction and design.

(2) UHV corona and environmental problems.

(3) UHV power network security.

(4) The operation characteristics of UHV equipment.

(5) External insulation characteristics under special climate conditions.

(6) UHV training system.

Based on the test facilities of UHV test base, the research for UHV project design, environment,

operation, construction, and equipment manufacture are carried on to guide and promote the UHV

construction.

6. CONCLUSION

It has been proved that related UHV key designs are reasonable by the successful operation of UHVAC

test base. The key technical achievements are obtained at the test base, including insulation gap

selection of UHV tower, conductor selection, optimization of substation fittings, and construction

technology, which can be directly applied to the design and construction of UHVAC pilot project and

strongly supported its construction.The research results of the test base show that its integrated test ability has reached international

advanced level, at the aspect of the electromagnetic environment, external insulation, UHV equipment

live assessment, and UHV live working.

7. LIST OF ABBREVIATIONS

AC Alternating Current

CVT Capacitor Voltage Transformer

GIS Gas Insulated Switchgear

SGCC State Grid Corporation of China

UHV Ultra High VoltageVFTO Very Fast Transient Overvoltage

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