Salient Features of The project

Project Location:

Province

1

District

Taplejung

Municipality / Rural Municipality

Phaktanglung Rural Municipality, ward No. 1, 2, 3, 4, 5, 6 (Former Tapethok, Lelep and Linkhim VDCs.)

Phungling Municipality, ward No. 10 (Former Phurumbu VDC)

Nearest Town

Phungling

Headworks Area

Tapethok Village, Phaktanglung Rural Municipality

Powerhouse Area

Sisne Village, Phaktanglung Rural Municipality

Geographical Co-ordinates:

Latitude

27° 25’ 19” N to 27° 30’ 45” N

Longitude

87° 41’ 40” E to 87° 48’ 03” E

General:

Name of River

Tamor

Type of Scheme

Peaking Run-of-River

Gross Head

450 m

Net Head

433.42 m

Licensed Capacity

285 MW

PPA Capacity

255.281 MW

Hydrology:

Catchment Area at Intake site

1850 km²

Average flow

121.5 m³/s

Minimum mean monthly flow

19.15 m³/s

Design discharge

68.64 m³/s

Design Flood, headworks (200 year return period)

2917 m³/s

Design Flood, tailrace outlet (200 year return period)

3077 m³/s

Diversion Weir/ Barrage:

Type

Floating structure, with overflow and non-overflow sections

Crest Elevation of free overflow section

1360.30 m amsl

Maximum height

36 m (from lowest foundation)

22 m (from lowest river bed)

Length

30 m (overflow section), 91 m (overall length)

Barrage Gates

4 Nos. 12.5 m wide x 9 m high each with bottom sill elevation 1343.00 m

Maximum operation level

1360 m amsl

Minimum operation level

1352 m amsl

Peaking volume

About 0.34 Mm³

Peaking operation time

2 hrs.

Undersluice:

Type

Rectangular Orifice

No. of Bays

2

Invert Elevation

1341.00 m amsl

Size (B X H)

5 m x 5.6 m

Intake:

Type

Side Intake

Number of Orifices

6

Invert Elevation of Orifice

1347.50 m amsl

Size (B X H)

5 m x 3 m

Gravel Trap:

Type

Surface, Hopper Shaped

Particle size to be settled

≥ 5 mm

Number of Chambers

3

Size (L x B)

18.50 m x 11.75 m (2 Nos.)

18.50 m x 11.50 m (1 No.)

Longitudinal bed slope

1 : 40

Approach Culvert

Type

Box Type RCC

Number of Bays

3

Dimension (B x H)

4 m x 2.30 m

Longitudinal bed slope

1:500

Length

84.84 m

Settling Basin:

Type

Surface, Hopper Shaped

Particle size to be settled

≥ 0.2 mm

Number of bays

3 (Two hopper in each bay)

Length

112 m, additional 46.83 m length in inlet   transition and 23.53 m in outlet transition

Dimensions of each bay (B x H)

15.50 m x 18.97 m

Longitudinal bed slope

1: 100

Headpond:

Type

Surface structure bounded by topography and embankments

Effective Storage Capacity

0.8 Mm³

Average Dimensions (L x B)

550 m x 115 m

Peaking operation time

4 hrs.

Embankment Dam:

Dam type

Concrete Face Rockfill Dam

Dam height (D/S toe to top of crest)

Varies from 12.23 m to  28.73 m

Dam top length

593.15 m

Dam crest elevation

1351.23 m amsl

Riverside slope inclination

1V:1.5 H

Headpond side slope inclination

1V: 1.35 H

Crest width

6 m

Concrete face thickness

0.4 m

Maximum operation level

1350 m amsl

Minimum operation level

1339 m amsl

Freeboard (measured from maximum operation level)

3.25 m

Bypass Pipe:

Diameter

5 m

Thickness

14 mm

Length

706.5 m

Concrete Casing

1 m on all sides

Headrace Pipe:

Length

851 m (831 m up to Inlet Portal)

Pipe Diameter

5 m

Pipe Thickness

14 mm

Crossing Structure

1 m thick Concrete Casing

No. of Anchor Block

5

Headrace Tunnel:

Type

Pressure Flow

Shape

Inverted D-shaped

Length

8452.26 m (up to start of surge shaft)

Excavation Diameter

7.2 m

Tunnel inlet invert elevation

1313 m amsl

Support System

Concrete Lining, Rock bolts and Shotcrete

Headrace Adit Tunnel:

No. of Adit Tunnels

3

Shape

Inverted-D

Excavation Diameter

5.5 m (AT-01, AT-02) and 6.5 m (AT-03, AT-03A, AT-03B)

Length

559.2 m (AT-01), 756.5 m (AT-02), 116.2 m (AT-03), 69.3 (AT-03A) and 35.9 m (AT-03B)

Surge Shaft:

No. of surge shaft

1

Type

Simple Cylindrical

Finished Diameter

14 m

Height

93 m

Penstock Shaft:

Type

Concrete encased steel pipe inside tunnel

Layout

Horizontal and Vertical Shafts

Tunnel excavation diameter

5.4 m (horizontal shafts)
5.2 m (vertical shafts)

Pipe Diameter

4 m

Length

630 m (up to Manifold) and 331 m (Manifold)

Pipe thickness

16 mm to 63 mm

No. of Manifold

5

Penstock Adit Tunnels:

Shape

Inverted-D

Excavation Diameter

5.80 m

Lengths

472 m

Underground Powerhouse:

Type

Underground

Dimensions (L x B x H)

104 m x 20 m x 33.53 m

Erection Bay Level

909.27 m amsl

Turbine Axis Level

900 m amsl

Transformer Cavern:

Type

Underground (Linear extension from powerhouse)

Dimension (L x B x H)

102 m x 16 m x 18.38 m

Floor Level

910.27 m amsl

Powerhouse Adit Tunnels:

Shape

Inverted-D

Length and Excavation Diameter

Main Access Tunnel

798 m &7.20 m dia

Access to powerhouse heading

273 m & 5.50 m dia

Access to penstock bottom shaft

250.50 m & 5.50 m dia

Ventilation/ Cable Tunnel

868 m & 5.50 m dia

Drainage Tunnel

702 m & 3.20 m dia

Tailrace Tunnel:

Type

Rectangular Free Flow Tunnel

Excavation Diameter

6.60 m x 7.8 m

Shape

Inverted-D

Size (B x H)

4 m x 5 m

Length

1350 m

Tailrace Culvert

Type

Rectangular Free Flow Culvert

Size (B x H)

6.60 m x 7.80 m

Length

70.25 m

Turbine:

Type

Vertical Axis Pelton Turbine

Number of Unit

5

Turbine Capacity per Unit

53.2 MW

Discharge per Unit

13.73 m³/s

Turbine efficiency

91%

Generator:

Type

Vertical

Number of Unit

5

Rated Output

60 MVA

Generation Voltage

11 kV

Frequency

50 Hz

Power Factor

0.85

Generator efficiency

96%

Transformers:

Type

Single Phase, Oil Immersed, ONWF or OFWF

Number of units

15+1 spare

Frequency

50 Hz

Rating

22 MVA

Voltage Ratio

11kV/ 220 kV

Tap Changer type

On-load, ±10% in step of 1.25%

Transformer Efficiency

99.%

Transmission Line:

Voltage Level

220 kV

Length

15 km (5 km up to Middle Tamor Hydropower Project Switchyard)

Connection Point

Dhungesanghu Substation

Power and Energy:

Licensed Capacity

285 MW

Installed Capacity/PPA capacity

255.28 MW

Dry energy (Peak)

260.57 GWh

Dry energy (Off-Peak)

184.63 GWh

Wet energy

1036.38 GWh

Net Annual Energy

1481.59 GWh