Vanala 15 MW
The second of the power projects constructed by the
company, with a project cost at  120.7 Crores (US$ 27m),
six times that of Rajwakti, and an installed capacity of
15MW, almost four times that of Rajwakti, Vanala pushed
the company to scale up its experience, operations, and
manpower, and finally achieve the status and recognition
as an infrastructure company of note within its field.
Construction work on Vanala started in January 2007 with
the project commissioned and operational by September
2009. Vanala has the operational capacity to generate
81.1 Million kWh of electricity per annum.
Infrastructure development (bridges,
roads)
Infrastructure
development work for Vanala Hydro-electric
power project has now been completed.
This includes bridges, roads and buildings
for staff and construction material
and various other structures, such as
the foundations for the batching plant
and the crushing plant. |
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Diversion Dam/Weir
including feeder channel
The diversion dam on the river
Nandakini is Barrage type and
made of reinforced cement concrete
with an under-sluice gate and
side intake diverting water into
a feeder channel of length 140
metres. The width of the structure
is 38m, length 40 metres( five
metres of which is below river
water level)l with a height of
15 metres including foundation. |
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Silting
Basin and Water conduit system |
| Silting basin
Measuring 115 m x 85m x 25 metres, 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 channel is a reinforced concrete
box structure with dimensions of 1.9km
length and internal dimensions of 3.2m
x 2.2m with a wall thickness of 0.2
metre resting on a 0.4m thick bed. The
discharge flow is 12.5 cumec.
ii. Fore-bay
The fore-bay is a 10m x w5.5m x h2.5m
reinforced cement 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.
iii. Pipe
The 2.6 kilometre long mild steel pipe
with an internal diameter of 2.6 m and
a wall thickness of eight millimetres
is made up of individual 1.5 metre long
hoop sections that are welded along
the circumference to form one continuous
pipe. The complete works were done in-house
using a plate bending machine to bend
mild steel plates which were then welded.
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Penstock
A mild steel pipe of length 1.2 km with
internal diameter 2.2m and wall thickness
varying between 12-16 mm, further bifurcating
into two 16 m long pipes of diameter,
the penstock carries water under pressure
to the turbines in the powerhouse. |
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Turbines and Powerhouse
The 42
m x 12 m x 11 m surface powerhouse houses
two vertical Francis turbines of rated
power of 7,500 kW each, set 10m below
surface level, 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 generated
power is stepped from 11kV to 66kV at
50 Hz through 20mVA transformer at the
switchyard: works include the excavation
of the foundation and the erection of
the transformer and 25 transmission
towers, stringing of 8 kilometres of
double circuit “dog” conductor transmission
line and finally site development.
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