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INTRODUCTION
Achieving another milestone in the country’s 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 has
been started its rising and will provide the full power by the time of next March.
This project which is estimated to cost Rs. 44 billion is funded by the Government of Japan
and Ceylon Electricity Board. The construction of the project commenced in 2006.
This concept of the project was first mooted by the Sri Lankan authorities in 1968 under the
Mahaweli scheme. But this project was not implemented under the accelerated Mahaweli
Development Scheme of the UNP Government.
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 they were settled by the courts of law. The project was implemented
under five phases.
The Japanese Government provided a loan of Japanese Yen 33,265 million while the CEB
makes an investment of Rs 5,931 million for the project.
It is targeted to generate 409 GWH of electricity annually by this project and the installed
capacity is 150MW. The dam will be constructed across the Kotmale stream. The length of
the dam is 180 meters and the height 35.5 meters.
SPECIALITY ABOUT THIS POWER PLANT
This is the 2nd underground power house and the 2nd run of the river hydro electricity
system in Sri Lanka. Also this is counted as the longest headrace tunnel in the country and
the last large scale hydro project happening in the country.
The type of the dam is gravity Dam and it has five spillways and also has a Hydraulic head
of 473 m (1,552 ft).
GENERAL SPECIFICATIONS
1. Turbine : Two 77,000 kW vertical shaft Francis type turbines
2. Generator : Two 88,000 kVA alternating current generators
3. Overhead Traveling Crane : Double trolley, Two 75 T main Hoists and two
(2) Mono rail hoists
4. Power Transformer : Two 88,000 kVA Indoor, Special three-phase,
oil immersed transformers
5. Switchyard Equipment : Outdoor Type 245 kV SF6 gas insulated metal
enclosed switchgear
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6. Power Plant Equipment : Protection Relays , Unit Local Controllers, 110 V
Dc supply system, 400/230 V AC Power supply, 33kV and 13.8 kV Metal Enclosed
circuit breakers, 33kV Power Cables and Control Cables
PROJECT HISTORY
The project was initially planned in 1968 by
the local authorities, before
the Government of Japan funded a study
between 1985 and 1987 to further examine
the hydroelectric potential in the upper
reaches of Kotmale River. The feasibility
study included five sites and eight
alternative development schemes, and concluded with two sites which were more
technically and economically feasible.
The two sites were a conventional type at Caledonia, and a run-of-the-river type
atTalawakele. The project at Caledonia involved the displacement of over 2,700 families
and inundation of large areas of land used for tea plantations, and thus the Caledonia site
was dropped. Further funding was then provided by Japan for the engineering study,
which included a review of the feasibility study, selection of an optimal development plan,
development of the detailed design, and the preparation of tender documents and anenvironmental impact assessment report.
The environmental impact assessment report was completed in September 1994, with the
final design report completed in March 1995. The environmental assessment identified key
issues associated with the project, which includes impact on St. Clair's Falls aesthetics due
to stream flow reductions, social impacts due to resettlement of affected people, possible
effects on ground water due to tunneling, impacts on downstream water uses due to de-
watering of streams, and impacts on biodiversity. These impacts led large delays in project
development.As per the National Environment act, the environmental clearance was then granted to the
project. The project initially faced several objections, before being officially permitted by
courts of law. In further the Government agreed to the people to give them new houses,
schools, temples, churches, hospitals, basically almost all re-civilization agreement. After
that they had begun the constructions of the major Hydro project.
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SPECIFICATIONS OF WATERWAYS
Water Source : Kotmale reservoir 800,000 m3 (28,000,000 cu ft) (Making a
reservoir across the Kotmale river by using a dam)
Main Intake Dam : Gravity Dam (With a Height of 35 m(115 ft) , Length of 180
m(591 ft) and Crest Width of 7 m(23 ft))
Headrace tunnel : This is the main tunnel which supplies water to turbines. This
is almost circular shape with 4.5m-5.2m of diameter and 12890m long. The tunnel
goes through a rocky mountain which does not need additional supporting concrete.
Therefore concrete lining requirement is less. Upstream surge tank: This is for protection of the headrace tunnel from high water
pressure caused by sudden shutdown of the power plant. This is 12m of diameter
and 98m of high.
Underground inclined shaft for penstock: The penstock is underground due to
reduce losses and the cost of construction. The penstock having 4.5m-1.45m of
diameter and 791m long.
Draft tunnel : This is 78m long tunnel with 3m of diameter and circular
shape
Downstream Surge Chamber: 58m high and 8m of diameter.
And also there is a tunnel for maintaining a periodic continuous flow of water for
St.Clair waterfall and downstream uses.
SCOPE OF WORKS
Site preparations, construction of employers and workers living quarters,
construction of access roads, and relocation of affected people.
In this session Building access roads with drains, culverts and bridges to the respective
construction site. In here the improvement of existing road was also done.
All key civil engineering works, such as construction of tunnel, dam, underground
power house etc. This takes about 50% of the project cost.
In this section Constructing and providing the Employer and the Engineer with adequate
facilities such as Residential Houses, Office Complexes, and Recreation Facilities etc was
also included.
Providing permanent Facilities for the Re-settlers
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This consists of constructing and providing permanent facilities for the persons affected
by the project. The re-settlers are mainly estate workers but include a good number of
varied occupants, shop owners, workshops, garages etc. Their new houses was planned to
construct in an area which is close to their residential places .And also For a village a new
school, a new hospital, a new cinema hall were to be constructed. The resettles have now
being offered modern new homes with most of the common facilities (electricity, Water
supply) and some of them have great sceneries and views to their homes.
Hydro-mechanical works such as construction of spillways, penstocks, intake
gates, etc.
Main intake dam consists of construction of River Diversion Works, Intake Dam, Control
Building, Land Reclamation Works and Road and Bridge Works and Water ways consists
of construction of Headrace Tunnel, Upstream Surge Tank, Shaft for Penstock, Draft
Tunnel, Downstream Surge Chamber, Tailrace Tunnel and Outlet.
Building 33 kV Construction Supply line and concrete Pole lines of capacity 20 MW and
10 MW respectively for each circuit including 21 km 33kV Lynx conductor double circuit
tower line from Nuwara Eliya Grid Substation to the Niyangamdora power house and
11.5 km 33kV Lynx conductor double circuit tower line from Henfold to Talawakele intake
dam via Lidula Gantry to supply the Talawakele Intake dam.
POWER TRANSFORMER
Three single phase transformers instead of three phase transformer because for
installing a three phase transformer requires lot of area.
Those are oil immersed transformers.
There is a spare oil tank and oil treatment system.
In case of a fault, the oil composition would be changed and according to the
composition we can find the internal fault.
SWITCHYARD EQUIPMENT AND TRANSMISSION LINE
There is an outdoor type gas insulated metal enclosed switchgear and also there is
a conventional switch gear at switch yard.
The transmission line is designed to construct 220kv XLPE power cable. But it is notfinished yet
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Facilitators : Mr.Shavindranath Fernando
: Mr.R.S.W.Wagarachchi
References : wikipedia.org/wiki/Upper_Kotmale_Dam
: dailynews.lk/2010/11/05/news02.asp
: development.lk/news.php?news=828
Spillway and Intake gates
Access Tunnel Turbine
Rotor
Transmission Tower
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UPPER KOTMALE HYDROPOWER PROJECT
FIELD VISIT REPORT
NAME : Isuru Kasthurirathne
INDEX NO : 090253H
DATE : 23,09,2011
Department of Electrical Engineering