Upper Kotmale

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Upper Kotmale Hydro Power ProjectField Visit Report

Name : S.P.M Sudasinghe

Index No. : 100523G

Field : EE

Date of submission : 2013/11/10


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INTRODUCTION

Upper Kotmale hydropower project is a large hydroelectric dam under construction in

Talawakele, in Nuwara Eliya in the central province of Sri Lanka. It is planned to be completed in

late 2011, the facility will be the third largest hydroelectric dam in the country. Achieving

another milestone in the countrys development drive, the longest tunnel which would carry

water from the Kotmale reservoir to the underground power station under the Upper Kotmale

Hydro Power project which adds 150 MW of power to the national grid.

This project, estimated to cost Rs. 44 billion financed by the Government of Japan and Ceylon

Electricity. The construction began in 2006. But this concept is discussed for the first time of the

project by the Sri Lankan authorities in 1968 under the Mahaweli scheme. But this project was

not implemented in the framework of the accelerated Mahaweli Development Plan. As per the

provision in the National Environment Act of 1998, the Environment clearance was granted to

the Upper Kotmale Power Project. There were several objections to the project initially and theywere settled by the courts of law. The project was implemented under five phases.

The Japanese Government provided a loan of 33,265 million yen, while the CEB making

investment 5931 million rupees for this project. Upper Kotmale Power Plant expected to

generate 409 GWh of electricity annually from this project and the installed capacity 150MW.

The dam will be constructed across the stream Kotmale and the length of the dam is 180 meters

and the height is 35.5 meters.

Figure 1: Upper Kotmale Hydro Power Proposal


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Basic Project Cost : 40,000 Million Rs.

Regulating Pond : 0.8 MCM, 0.25 Sq.km

Plant Capacity : 2 x 75 MW

Annual Energy : 409 GWh

Full Supply Level : 1,194 masl

Min Operating Level : 1,190 masl

Tail Water Level : 703 masl

Net head at FSL : 473m

Max Plant discharge : 35.6 Cub. m/s

Plant factor : 31%

Main Intake Dam

Catchment Area = 310 km2

Length of Dam = 180 m

Height of Dam = 33.5 m

Elevation of Dam top level = 1196.00

Swept Area of Reservoir = 0.25 km2

Effective Storage = 0.8 MCM

Spillway Gates Capacity = 3300 m3/s

Average annual rain fall 2300 mm per year

Average annual inflow 17.8 m3/s

Run off type concrete gravity dam

Dam mainly consists of Spillways Gate, Main Out let Gates, Intake Gate, Sand Flush Gate, Flap

gate, Raking Equipment and Inspection Gallery. Spill way gate is Steel Radial type Gate which can

be used to release required flow rate by opening required height. Flap gate is used to control the

water level. Sand flush gate is used to flush out the sand after filling the sedimentation.


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Tunnel

The 4.55.2 m (14.817.1 ft) diameter, 12.89 km (8.0 mi) long Upper Kotmale Tunnel, the

longest excavated tunnel in Sri Lanka, will be used to deliver the water to the powerhouse. The

tunnel begins at the dam site, and stretches north at a distance of approximately 7.4 km (4.6 mi)

towards Pundaluoya, before stretching a further 5.5 km (3.4 mi) north-west towardsKumbaloluwa and ending up at its powerhouse at the Kotmale River near Niyamgamdora, at

approximately 070233N 803923E, 2 km (1.2 mi) downstream of the confluence of Pundal

River and the Kotmale River.

Surge tank is an opening of the tunnel used to reduce the damage from surges.

When there is weak rock, concrete layer is applied around the tunnel to increase the strength of

the tunnel

Turbine

Francis type turbine has been selected for Upper Kotmale power plant to accommodate futureKotmale dam lifting for high loads and due its high efficiency. Spherical type valve, which is

suitable for high head has been selected as main inlet valve. Two Sealing rings, Upstream and

Downstream available to completely shut the water flow. Servomotor (Piston) operate the Main

Inlet Valve.

Figure 2: Intake Dam

Figure 3: Cross section view of tunnel, surge tank & penstock

Figure 4: Tunnel cross sectional view


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Generator

Two 88,000 kVA alternating current generators of standard type are coupled to turbines to

generate power. (75 MW each)

Special Features in Generator at UKPS

Electrical Brake (first time in Sri Lanka)

PEEK Thrust Bearing

Carbon Duct Collector

Oil Mist Eliminator

PSS (Power System Stabilizer)

Figure 5: Standard type generator

Figure 6: Cross section of power cavern


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Power Transformer

Power Transformer in Upper Kotmale is special three phase transformer (not 3 single phase or

single three phase transformer). Two power transformers are used for two generators.

Type : core type oil immersed

Capacity : 88 MVA

Vector group : Ynd11

HV side : 220 Kv

LV side : 13.8 Kv

Tap range : HV side +10% to -5% in 2.5 steps

Buchholz relay is used to protect the transformer from insulation failure faults.

Switchyard

SF6 is used as insulating medium for this indoor switchyard. It saves 5% floor space and 1%

volume than air insulated system. Protection devices such as CTs, Vts and Circuit breakers are

installed here.

To connect the separate units to transmission system two bus bars with bus coupler is used.

Figure 7: Buchholz relay

Figure 8: GIS Bay at UKHP


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Transmission System

220 kV transmission line of Length -15.5 km is used to connect Upper Kotmale plant at

Niyamgamdora to substation of existing Kotmale power plant. Then power is transmitted from

there to Biyagama through existing transmission system. TDL, TD1, TD2, TD3 and TDT types of

towers are used. ACSR ZEBRA conductors are used and aluminum cladded steel wire is for earth

wire. Optical fiber cable is going through one conductor of this transmission system for

communication purposes. OPGW cable is used for that.

Communication System

Microwave Communication, Optical Fiber Communication and Flood Forecasting System (VHF)

are three communication systems used here.

Frequency Bands of 8363 MHz and 8482 MHz with 7 MHz bandwidth is used for micro wave

communication.it is a 2 Hops Link. Communication between Dam and power station is

accomplished with the help of intermediate hop located in Gongalla mountain and use line of

site communication.

Single mode optical fiber running middle of transmission conductor is used for optical fiber

communication between UKHP control room and Kotmale power plant. Early flood warning

system use VHF communication. Rain fall and water flow data are the inputs and 2D model of the

river and Forecasted Inflow is the output of the flood forecasting system.

Figure 9: Single line of UKHP


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Energy generation Data

Figure 10 (a): Month vice average generation 2012

Figure 10 (b): Month vice average generation 2013


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Social Environmental Impact

The construction of the dam, tunnel, and powerhouse, required the relocation of families from

495 houses. New homes were built away from the site with access to vital facilities such as water

and power. The relocated families are provided with concessionary loans to start new self-

employment ventures, while additional facilities such as the Talawakele Central College, places

of worship, a cinema hall, a library, and a community centre, are being established.

Similar most other dam's impacts on rivers around the world, the Upper Kotmale Dam will

periodically stop the St. Clair's Falls, located 2.2 km downstream of the dam, and a further 2.9 km

of the Kotmale River downstream of St. Clairs Falls, before the river is restored by water from

the Devon River, the river forming the picturesque Devon Falls. As ordered by the Government

Extraordinary, the St. Clair's waterfall will maintain a continuous flow of 47,250 m 3of water for

10 hours and 30 minutes daily, between sunrise and sunset. Upper Kotmale project has positive

impact on St, Claire waterfall because now the waterfall is available for dry season as well due torelease of water from reservoir.

References

Ceylon Electricity Board (2013) Upper Kotmale Hydropower Project Retrieved from

http://www.ukhp.lk/

Ministry of Power & energy, (2013) Second phase of Upper Kotmale Hydro Power

Generation, Retrieved November 05, 2013 fromhttp://powermin.gov.lk/english/?p=565

Wikipedia (2013) Upper Kotmale Dam, Retrieved November 05, 2013 from

http://en.wikipedia.org/wiki/Upper_Kotmale_Dam

Figure 11: Relocation of families
http://www.ukhp.lk/http://www.ukhp.lk/http://powermin.gov.lk/english/?p=565http://powermin.gov.lk/english/?p=565http://powermin.gov.lk/english/?p=565http://en.wikipedia.org/wiki/Upper_Kotmale_Damhttp://en.wikipedia.org/wiki/Upper_Kotmale_Damhttp://en.wikipedia.org/wiki/Upper_Kotmale_Damhttp://powermin.gov.lk/english/?p=565http://www.ukhp.lk/

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