Salient Features of the Project:
Super Mai Hydropower Project 7.8MW, Ilam
- Project Location
Development Region : Eastern Development Region
Zone : Mechi
District : Ilam
VDCs : Sumbek, Barbote & Soyang
Geographical Co-ordinates
Latitude : 260 56′ 27″ N to 260 58′ 00″ N
Longitude : 870 56′ 30″ E to 870 57′ 47″ E
- Hydrology
River Name : Mai Khola
Catchment Area (At Intake) : 163 km2
River Type : Rain fed, Perennial River
Design Discharge : 7.35 m3/s (Q40)
Riparian Release : 0.235 m3/sec
Design Flood Discharge at Intake : 608 m3/s (100Yr. flood)
- Headworks and Intake Structure
Crest Elevation of Weir : 825 amsl
Length of Weir : 25 m
Type of Weir : Free overflow, concrete weir
Type of Intake : Side Intake
Height of Weir : 3.8 m from river bed
- Intake
Type : Side Intake with Orifice
Size : 2.6 m (W) x 1.6 m (H)
Nos : 3 (Three)
- Trash Rack
Type : Coarse Trash Rack
Rack Dimension : 20 mm thick, 50 mm wide flat bar 100 mm c/c
- Gravel Trap
No of Gravel Trap : 1
Size : 9m (L) x 7.6m (B) x 3.8m (H)
Bed load size to be trapped : 2-100 mm
Flushing system : Continuous during monsoon
- Spillway
Type : Sharp Crested
Crest Elevation : 825 amsl
Width : 9 m
- Settling Basin
Type : Intermittent Gravity Flushing
No of Bays : 2 (Two)
Inlet Transition Length : 13 m
Main Settling Zone Length : 50.0 m
Width : 5.6 m each
Depth : 6.25 m – 7.5 m
Flushing system : Hydraulic flushing
Flushing Opening Size : 1 m x 1 m, RCC Canal
Outlet : Trash rack and connected to low pressure penstock pipe inlet
- Surge Tank
Type : Circular, RCC Tank
Diameter : 7.0 m (Internal)
Height : 24 m
- Steel Penstock Pipe
Material : Mild Steel
Length : 3500 m (upto bifurcation)
Internal Diameter : Varies from 2m – 1.8m
Shell Thickness : 8mm-20mm
No. of Anchor Blocks : 46
- Powerhouse
Type : Surface with 2 units of turbine
Size : 24.6 m x 16.6 m
Turbine Type : Francis
Tail Water Level : EL. 690.5 amsl
No of Units : 2
Type of Switchyard : Outdoor
- Tailrace canal
Shape : Rectangular
Size of Tailrace canal : 2.6 m x 2 m
Length of tailrace canal : 245 m
Tailrace outlet : Mai Khola
Tail Water Level : EL. 690.5 amsl
- Turbine
Type : Francis
Number : 2
Rated Output Capacity per unit : 4.4 MW
Turbine Axis Level : 693.0 m
Net Head : 124.617 m
Discharge per Unit : 3.675 m3/sec
Efficiency : 91.1%
- Governor
Type : Digital Electronic with PID type
Adjustment for Speed Drop : Adjustable to any degree between zero and 10%
- Generator
Type : Salient pole, synchronous
Rated Output Capacity per Unit : 4.75 Mva
Power Factor : 0.85
Voltage : 6.6kV
Frequency : 50 Hz
No of Units : 2
Excitation System : Self-excited
Efficiency : 96.3%
- Transformer
Type : Three phase, two
Rated Capacity : 4.75 Mva
Voltage Ratio : 11/√3/33/√3
No of Units : 2
Vector Group : YNd11
Efficiency : 99%
- Power and Energy
Gross Head : 134.5 m
Net Head : 124.617 m
Installed Capacity : 7800 kW
Dry Season Energy : 8.334 GWh
Wet Season energy : 39.063 GWh
Total Energy : 47.398 GWh
- Transmission Line & Substation
Length : 12 km (Approx.)
From : Powerhouse
To : Godak Substation
Type : 33 kV Single Circuit
- Financial Indicators
Project Cost with IDC : Rs. 150.484 crore
Interest Rate : 11 %
NPV NRs (0000) : 868852
BC Ratio : 1.66
IRR : 14.28 %
Payback Period : 10 year with respect to total investment