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Salient Features

Country

 

SALIENT FEATURES

1.

Location

 

 

Nepal

District

Sankhuwasabha

Vicinity

All components of project are on Left bank or River Arun. The Intake Works are at village Pukhwa and Power House at village Beteni about 10 Km upstream of Tumlingtar.

 

2.

Hydrology
Design Flood at Lower Arun PH Site

 

 

10,000 Year

10134 m3/s 

Highest Flood Level

315.10 m

 

Design Discharge

344.68 m3/s
(Only the tail waters of Arun-3 HE Project will be utilized)

 

3.

Tail Race Outfall Pond
(To be constructed as a part of Arun-3 HEP)

 

 

Null Level

537.00 m

Maximum water level

544.00 m

Top elevation of structure 

545.00 m
(Corresponding to Design flood of 15710 m3/s at TRT Outfall in Arun-3 and Maximum water level in pond during Tandem Operation) 

 

4.

Intake Structure

 

 

 

 

No. of Intake

1 No. 

Intake Gates

2 Nos.
6.00 m wide x 7.00 m high 

Length of HRT to be constructed with intake 

100 m 

 

5.

Spill Tunnel cum Construction Adit - 1

 

 

 

Type 

Horse shoe, concrete lined

Taking off at 

STA 300.00 m of HRT

Size 

10.5 m dia 

Length

327.689 m up to centerline of HRT

Spill tunnel invert level at exit

537.00 m 

Spill Tunnel Gate 

1 No
10.5 m wide X10.5 m high 

 

6.

Head Race Tunnel

 

 

Type

Horse Shoe, concrete lined 

Size (finished diameter) 

10.50 m

Length

17.4 km

Velocity 

3.77 m/s

 

3.77 m/s

6 Nos. (Incl. Spill Tunnel Cum Adit-1)

 

Access Gate at the Plug of Adit-3 

1 No
2.50m wide X 2.50 m high 

 

7.

Surge Shaft

 

 

Numbers

One

 

Type

Restricted Orifice, open to sky

Diameter 

33.84 m

Depth

134.75 m from centerline of HRT 

Gate size

5.85m (W)(x5.85 (H) m, 2 nos. 

 

Elevation of center line of head
race tunnel

445.25 m 

 

Elevation of invert of surge shaft

452.5 m

 

Maximum upsurge 

569.95 m 

 

Minimum down surge

502.70 m 

 

8.

Butterfly Valve House

 

 

Type 

Underground 

Size of valve house

91 m long x12m wide x 21 m high 
No. of butterfly valves  2 Nos. 

Size of valves

5.5 m internal dia. 

 

9.

Pressure Shaft/Penstocks

 

 

Numbers

2 number, bifurcating into 4

Size

5.85/4.14 m circular, steel lined

Type

Main Pressure Shaft underground and branch Penstock on surface.

 

Length

 

 

No. Pressure Shaft 5.85 m diameter Penstock 4.14 m diameter Total
Branch 1 Branch 2
P1 627.185 m 58.053 m 58.053 m 685.238 m
P2 635.767 m 58.053 m 58.053 m 693.82 m

 

 

Velocity in 5.85 m dia portion 

6.41 m/sec

 

Velocity in 4.14 m dia portion 

6.40 m/sec 

 

10.

Power House Complex

 

 

Type

Surface

Installed capacity

669 MW

Size

150 m long x 24 m wide x 53 m high 

 

Type of Turbine 

Francis, vertical axis

 

Speed of Turbine

214.3 RPM 

 

Gross head 

229.96 m 

 

Rated Head/Design head

210.46 m/212.68 m 

 

Design Discharge

344.68 cumec 

 

Generators 

4 x 167.25 MW, 0.9 pf, generation voltage 13.8 kV

 

Step up unit Transformers 

13 Nos. 3x71MVA single phase 13.8/420 kV/√ 3 kv ODWF type

 

Special Features 

Lower Arun HEP will operatein Tandem with Arun-3 HEP 

 

11.

Tail Race Channel

 

 

Type 

Rectangular concrete lined and cast in-situ concrete blocks 

Size

50 m wide

Length of tail race channel (including transition)

72.93 m

Crest elevation           

EL 305.355 m

 

 Normal tail water level for power
generation (Q = 344.68 cumec)

EL 307.04 m 

 

 Minimum tail water level
(Q = 8.617cumec 10% of one unit
Discharge) 

EL 305.50 m 

 

 Maximum tail water level (10%
overload)

EL 307.158 m

 

12.

Switchyard

 

 

 

Type

 Surface 400 kV Switch Gear
GIS type with double bus bars arrangement

 

13.

Transmission of Power

 

LILO of both circuits of Arun-3 Dhalkebar 400 kV D/c Quad Moose line at Lower Arun HEP Switchyard (4km)

 

14.

Power Generation

 

 

Annual design energy generation
in 90% Dependable year 

2901.02 GWh 

 

Plant Load Factor 

50.44% 

 

 

Cost Estimate (Price Level Sept 2021)

 

 

Civil works (INR) 

3100.18 Crore

3100.18 Crore

1073.78 Crore 

Sub Total (INR) 

4173.96 Crore 

Total IDC (INR)

789.44 Crore

 

 

Financial Charges (INR)

17.43 Crore

Total Cost 

4980.84 Crore

 

 

Sale Rate / Unit at Bus Bars

 

 

Year

Tariff (INR/KWh)

First Year

4.62

Levelised tariff 

4.30

 

 

Cost Estimate (Cost to Completion Price Level)

 

 

Civil works (INR) 

3634.47 Crore 

 

E.M. Works (INR)

1237.98 Crore 

 

Sub Total (INR) 

4872.45 Crore 

 

Total IDC (INR) 

899.64 Crore 

 

Financial Charges (INR)

20.27 Crore 

 

Total Cost 

5792.37 Crore 

 

 

Sale Rate / Unit at Bus Bars

 

 

Year

Tariff (INR/KWh)

 

First Year 

5.37

Levelised tariff 

4.99