Idukki Hydroelectric Project
reservoir
The Idukki Hydroelectric Project is the biggest hydrolectric Project in Kerala (India). It comprises of three dams at Idukki, Cheruthony and Kulamavu and related systems. The power house at Moolamattom  is the longest underground power station in India and the pressure shaft is the largest in the country. The Idukki dam is one of the highest dams in the world and the first arch dam in India. Cheruthony is the largest and highest gravity dam in Kerala.

SALIENT FEATURES

Total drainage area 250.7 square. miles (649.3 square kilometres)
Full Reservoir Level (FRL) +2403 feet (732.62 m)
Maximum Water Level (MWL) +2408.5 feet (734.3 m)
Gross Storage of FRL 70500 million cubic feet (1996.3 million cubic metres)
Dead storage
below Minimum Draw Down Level (MDDL) of +2280 ft.
 18957 million cubic feet (536.79 million cubic metres)
Live storage 51543 million cubic feet (1459.5 million cubic metres)
Water Spread area
23.1 sqare miles (59.83 sq. km)
Installed Capacity
 780 Mega Watt (MW)
Firm Power Potential
210 MW (at 100% load factor)

DAMS

Idukki Dam
Type
 Concrete double, curvature parabolic, thin arc
Height above deepest foundation 555 feet (168.91 m)
Length at top
 1200 feet (365.85 m)

Idukki
Cheruthony Dam
Type Straight gravity concrete
Height above deepest foundation
453.4 feet (138.2 m)
Length at top 2135 feet (650.9 m)
Spillway length 240 feet (73.2 m)
No. of gates (radial) 5 nos. 40 feet x 34 feet (12.19 m x 10.36 m)
Cheruthony

Kulamavu Dam
Type Gravity masonry
Intake sill level 2245 feet (684.45 m)

WATER CONDUCTOR SYSTEM
Type Masonry, straight gravity
Height above deepest foundation 328 feet (99.97 m)
Length at top 1263 feet (384.96 m)

POWER TUNNEL
Section
 23 inch dia (7.01 m) finished horse shoe concrete lined (18 inches ie. 45.7 cm minimum 22 inches average i.e. 55.9 cm)
Length
 6652 feet (2027.53 m)


SURGE SHAFT
Type
Restricted orifice type with inclined shaft completely underground.
Size
 28 feet 6 inches (8.69 m) dia. finished 250 feet (76.25 m) long and inclined at 53°.

PRESSURE SHAFT
No.of pressure shafts (under ground) 2 nos. (steel lined)
Length 3259 feet (993.34 m), 3136 feet (955.85 m)
Butterfly valves One in each pressure shaft located 300 feet away from surge shaft

UNDERGROUND POWER HOUSE
No. of machines 6
Capacity of each 130 MW, 144 MVA
Power Factor
 0.9
Size of power house 463 feet (141.1 m) length.
65 feet (19.8 m) width
113.5 feet (34.6 m) height
Turbines 6 nos. Vertical Pelton wheel type
Normal Speed
375 rpm
Runaway Speed
 625 rpm


TAIL RACE TUNNEL
Length of tunnel 4000 feet (1220 m)
Tunnel section 26 feet x 23 feet (7.29 m x 7m)
'D' shaped, finished with full section lining.
26 feet x 24 feet (7.92 m x 7.32 m) in weak zones
'D' shaped, finished with lining only for floor and sides.
Length of open channel 852 feet (259.7 m)

SWITCH YARD
Switch yard area 821 feet x 282 feet (250.24 m x 85.95 m)
Transmission lines One double circuit line to Kalamassery one single circuit line to Tamil Nadu One single circuit line to Pallom and three feeder bays forfuture.


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