Infrastructure development (bridges,
roads)
Before
construction work on the Rajwakti power
plant could commence, it was required
that infrastructure be developed for
the accommodation of site staff. Roads
and bridges had to be constructed to
provide access to the excavation and
construction sites and for the transportation
of materials and labour and manpower
to the sites. |
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Diversion Dam/Weir
The diversion dam on the river
Nandakini, a 68 metre long, 6.5
metre high reinforced cement concrete
structure, is an ogee shaped dam
provided with a raised overflow
type, under-sluice with side-intake
that diverts water into the feeder
channel. |
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Silting Basin
and Water conduit system Silting
basin
With
dimensions of 60m x 25m x 4m,
the reinforced cement concrete
silting basin reduces the speed
of the flow of water resulting
in the settlement of sediment
and sand from river water. This
process of removal greatly reduces
the wear on the turbine blades
with consequent reduction in operational
and maintenance costs. |
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Water
conduit system |
| i. Channel
The
1.2 km channel is a reinforced
cement concrete open box structure
with dimensions of 3.1m x 2.2
m and wall thickness of 0.25 m,
resting on a prepared bed with
additional stone masonry walls
to support it and provide strength
in areas that are prone to land
slides or falling rock. |
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| ii. Fore-bay
This refers to the 50m x 8m x 7m reinforced
concrete water storage structure in
the shape of a box at the end of the
RCC water channel and the start of the
mild steel water pipe. |
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| iii. Pipe
The pipe section of the water conduit
system consists of a 0.9 km long mild
steel pipe with an internal diameter
of 2.2 metres and wall thickness of
eight millimetres. This pipe was fabricated
in-house using a plate bending machine
to bend mild steel plates which were
then welded to form the shape. Finally,
the exterior was painted for corrosion
protection. |
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| iv. Penstock
Consisting of a pipe length of 30m with
an internal diameter 2.2m and further
bifurcating into two pipes of length
20m and internal diameter of 1.2m each
the penstock carries the water under
pressure to the turbines in the powerhouse.
The discharge flow through the pipes
is 10 cumec.
Also incorporated
is the system of a surge tank, which
acts as a valve to release the pressure
when the turbines are turned off. It
is served by a pipe of length 80m, internal
diameter 1.8m heading towards the surge
tank, wall thickness 12mm. |
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Turbines and Powerhouse
The powerhouse
houses two horizontal Francis water
turbines rated at 1,800 kW, and a switchgear
panel for synchronising the power generated
with the local grid and feeding it into
the switchyard and transformer. |
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Switchyard and Transmission
The step
up of the generated power from 3.3kV
to 66kV at 50Hz through a 5mVA transformer
is accomplished at the switchyard: works
include the excavation of the foundation
and the erection of the transformer
and 12 transmission towers, stringing
of 5 kilometres of double circuit “dog”
conductor transmission line and finally
site development.
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Substation (for Rajwakti and Vanala)
Construction
of complete 66kV substation including
meter room: the works include excavation
of foundation and installation of isolators,
lightning arrestors, circuit breakers,
steel structures for installation of
current transformers (CT) and potential
transformers (PT), site development
and stringing of double circuit, loop-in
loop-out (LILO) with “dog” and “panther”
conductors.
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20.47
Crores (US$ 5m).
