Salient Features

ARUN-3 HEP ( 900 MW ) ,NEPAL

SALIENT FEATURES

1.

Location

 

 

River

Arun,a  tributary of Kosi River in Eastern Nepal

District

Sankhuwasabha

Nearest  Railway Head

Jogbani, Bihar ( B. Gauge ) about 300 km from project site

Nearest Airport

Tumlingtar, Nepal  70 km

 

2.

Hydrology

 

 

Catchment Area at Diversion Site

26747 sq.km

Design Flood

PMF-8880 cumec

GLOF-6830 cumec

 

3.

Reservoir

 

 

Submergence area at FRL

66.3 Ha

Reservoir Capacity/ Gross storage at FRL

13.94 MCM

Full Reservoir Level (FRL)

El 845 m

Max. Water  Level (MWL)

El 847.73 m

MDDL

El 835 m

Inactive Storage (below MDDL)

8.29 MCM

Active storage /Peaking volume

5.65 MCM

 

4.

Diversion Tunnel

425 m long, 11 m diameter to divert 1300 cumec

 

5.

Dam

 

 

 

Type of Dam

Concrete Gravity Dam

Dam top Level

El.849 m

River bed Level

El. 790 m

Dam Height above River bed

59 m

Deepest Foundation Level

El.779 m

Height above deepest Foundation Level

70 m

Length of Dam at Top

197.30 m

Top Width of Dam

7 m

 

6.

Upstream Coffer Dam

 

 

Type

Colcrete dam

Top level

El 817.00 m

Height

26 m

Length

120 m

 

7.

Downstream Coffer Dam

 

 

Type

Rock fill dam

Top level

El 797.50 m

Height

8.5 m

Length

92 m

 

8.

Spillway

 

 

Design Flood

PMF-8880 cumec

GLOF -6830 cumec

Energy Dissipation System

Trajectory Bucket type

i)Sluice spillway

   No.

   Size

ii)Overflow spillway

   No.

   Size

 

6

9.0 m (W)X 14.0 m (H)

 

1

5.0 m (W)X 5.0 m (H)

Crest Level

El 808m-Sluice type

El 840m-Overflow spillway

 

9.

Power Intake

 

 

No. & Type

2 Nos., Straight intake with bell mouth

Invert Level

El.819m

Top Level

El.849m

 

10.

Intake Tunnels

 

 

No. & Type

2 Nos., 7 m diameter, horse-shoe shaped

Length

181.50 m & 173.30 m

C.L. of Intake Tunnel

 El  822 m

 

11.

Head Race Tunnel

 

 

Shape & Size

 9.5 m diameter

Length of Tunnel

11769.625 m

Design Discharge

344.68 cum / sec

No. of Adits& size            

4 Nos.,7 m X 7 m D - shaped

ADIT

ADIT  LENGTH

RD OF HRT

DISTANCE BETWEEN ADITS

1

690.82m

1052.51 m

 

2

742.95 m

5148.20 m

4095.69 m

3

379.53 m

8205.02 m

3056.82 m

4

329.55 m

11727.41 m

3522.39 m

 

12.

Surge Shaft

 

 

 

Size & shape

Open to sky,Restricted Orifice

1No.,24.0m diameter, Circular

Height

149.00 m

Top Level

El 940.00 m

Gates,No.& Size

2 Nos.,  5.5m ( W )X 7.5m (H )

 

13.

Butterfly Valve Chamber- Underground

 

Size

 

83.05m (L) X 12 m(W) X 21 m(H)

Butterfly Valve

2 nos, 5.5 m diameter

 

14.

Pressure Shaft

Underground, 2 Nos.

 

Type &Size

Circular,each 5.5 m dia bifurcating into two nos of 4.0 m diameter to feed four units

Length of pressure shafts 1 and 2

 

Pressure shaft-I

432.063m

Pressure shaft-2

391.511 m

Branch 1

82.207 m

Branch 3

82.207 m

Branch 2

58.82 m

Branch 4

58.82m

 

15.

Power House Complex

 

 

Type

Underground on left bank

P/H  Cavern

179.50 m(L)X22.5 m (W)X53.0 m (H)

Design Head ( net )

286.21 m

Gross Head

307.67 m

Turbine

4 Nos., Vertical Francis turbine, 225 MW each

Rated speed  of Turbine

250 rpm

Generation voltage

15.75 kV

Service Bay Floor Level

El. 539.00m

Generator Floor Level

El. 534.00 m

Turbine Floor Level

El. 529.00 m

Distribution Centre Line Level

El. 525.00 m

MIV Floor Level

El.520.50 m

Maximum Tail Water Level

El. 535.00 m

Transformer

Single phase, 12+1 (Spare), 92 MVA 15.75 kV/420/Ö3 kV

 

16.

Transformer Hall

 

 

Size

146.14 m (L)X 16 m (W)x 23 m ( H )

 Transformer Hall Floor Level

El. 552 m

Design Discharge per unit

86.17 Cumec

Design Energy in a 90 % dependable year

3924.03 MU

Annual  Load  Factor

50.98 %

Weighted average efficiency of TG Set

93 %

 

17.

Tail Race Tunnel

 

 

No., Type &  Size

10.00 m dia 108.12 m long

 

18.

Switchyard

 

 

Elevation

El 557 m

Size

207 m (L)X 106 m (W)