Middle Tamor Hydropower Project (73 MW)
Technical Summary
The catchment area of Middle Tamor Hyropower Project is 2007 km2. The design discharge of the Project is 73.71 m3/s, which corresponds to 41.78% exceedance flow (design discharge corresponds to NEA requirements to meet the dry and wet season energy ratio of 15:85 while based at 40% exceedance flow). With a gross head of 94 m, the resulting installed capacity of the Project is 54 MW. The 72.5m long weir has its crest level at 860 m above mean sea level (amsl). The maximum height of weir crest from its original ground level is 11m which diverts the required flow to the Intake. Two undersluice gates maintain the design water level for intake and flush excessive deposits deposited in front of the intake area. Intake comprises of 4 openings, which guides the flow towards gravel trap and successively towards the settling basin. The 140 m long settling basin designed with 90% trap efficiency passes the clean water into the tunnel. About 1780m long tunnel (concrete lining and shotcrete) with finished diameter of 5.4m passes the design discharge to the penstock. Proposed penstock is of 4.5m internal diameter till the branching length of 215m after which three penstock pipes each of 2.6m internal diameter supplies the water to the powerhouse. Powerhouse is 47 m long and 26 m wide with the normal level at 766 m amsl. The tail water is channelized back to the Tamor River via 420 m long tailrace culvert. Three units each of 18 MW capacity is proposed to generate the designed output of 54 MW. Power evacuation from powerhouse is planned through 12km long 132 kV single circuit transmission line to Dungesanghu (Hangpang) Substation proposed by NEA.
Gross head : 94 m
Design Discharge (at 41.7% PoE) : 73.71 m3/s
Catchment area : 2007 km2
Headrace Tunnel : 1783 m
Turbine : Three Francis units each of 18 MW rated output capacity
Total energy output (PPA) : 309.56 GWh
Transmission line : 132 kV single circuit, 12 km in length to Hangpang substation
Salient Features of the Project:
- Project Location
Development Region : Eastern Development Region
Zone : Mechi
District : Taplejung
VDCs : Khoklin/Hangdewa/Sawadin and
Phurumbu
Headworks :Phurumbu, Sawadin
Powerhouse :Khoklin
Geographical Co-ordinates
Latitude : 27° 23’ 57” N to 27° 27’ 09” N
Longitude : 87° 40’ 18” E to 87° 42’ 40” E
2. General
Name of River : Tamor
Nearest Town : Phungling
Type of Scheme : Run-of-River
Gross Head : 94 m
Installed Capacity : 54 MW
Catchment Area : 2007 km2
Mean Annual Discharge : 125.89 m3/s
Design Discharge (at 41.7% PoE) : 73.71 m3/s
Riparian Release : 1.93 m3/sec
100 Yrs Flood Discharge : 2798 m3/s
Average Annual Precipitation : 1,637 mm
4.Diversion Weir
Type : Concrete weir
Weir length (main body) : 72.50 m
Weir height (Max from original ground level) : 11.00 m
Weir crest level : 860 m amsl
5. Undersluice
Size (B x H) : 5.0 m x 4.0 m (each)
Number : 2
6. Intake Structure
Type of Intake : Side Intake
Nos of Opening : 4
Intake size (BxH) : 6.0 m x 4.0 m (each)
7. Gravel Trap
Type : Rectangular, RCC
Particle size to be settled : 5mm – 100 mm
No. of bay : 4
Size of gravel trap : 16 m x 6.75 m x 21 m (average)
Gravel flushing culvert
Number : 4
Size (B x H) : 1.5 m x 1.5 m (each)
Length : 47 m (average)
8. Settling Basin
Dimension (L x B) : 140 m x 62.05 m
Particle trapping efficiency : 90 %
Longitudinal slope : 1:100
9. Sediment flushing culvert
Number : 4
Total length : 40m (average)
Size (B x H) : 1.5 m x 2.0 m
10. Headrace Tunnel
Type : Inverted U shaped
Length : 1783 m (approx.)
Finished Diameter : 5.4 m
Support System : Concrete lining and shotcrete
11. Surge shaft
Shape : Vertical, circular section
Height : 40 m
Finished diameter : 25 m
12. Steel Penstock Pipe
Material : Mild steel
Total length : 227 m up to branching
Internal diameter : 4.5 m / 2.6 m
Pipe thickness : 12 mm ~ 32 mm
13. Powerhouse
Type : Semi-surface
Size : 47 m x 26 m (L x B)
Turbine axis level : 764 m amsl
14. Tailrace Culvert
Type : RCC, Rectangular
Length : 420 m
Size (B x H) :3 m x 4.5 m (separated into 2 chambers)
Normal Operating Level : 766m amsl
15. Turbine
Type : Francis
Number : 3
Rated Output Capacity per unit : 18 MW
Efficiency : 91 %
Synchronous speed : 600 rpm
Net head : 83.10 m
Discharge per unit : 24.57 m3/s
16. Generator
Type :Synchronous, Single Phase, Vertical axis
Rated Output Capacity per Unit : 20.43MVA
Power Factor : 0.85
Voltage : 11kV
Frequency : 50 Hz.
No of Units : 3 (Three)
Excitation System : Brushless
Efficiency : 97 %
17. Transformer
Type : Outdoor, oil immersed, single phase
Nos of Unit : 4 (3+1 spare)
Rated Capacity : 22.5 MVA
Vector Group : Ynd11
Voltage Ratio : 132 kV/ 11kV
Efficiency : 99 %
18. Transmission Line
Voltage level : 132 kV single circuit
Length : 12 km
Conductor : ACSR “BEAR”
To : NEA Proposed Hangpang Substation
(Koshi corridor)
19. Energy
Total energy at delivery point : 312.60GWh
Dry energy : 47.94GWh
Wet energy : 264.72GWh
20. Construction Period : 4 years
RCOD : September 2021
Project Cost Estimate
Total Cost of the Project (before financing) : MNPR 7429
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