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Middle Tamor Hydropower Project (54 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:

  1. 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

3. Hydrology

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

Nos. of chambers                                                               : 2

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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