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INTRODUCTION

 The Government of Sikkim as a part of national drive for the development of Hydro Potential of the country has awarded Rangit Stage-IV Hydro Electric Project to Jal Power Corporation Limited on 1st Nov. 2004. An agreement for setting up of Rangit Stage-IV Hydro Electric Project was signed with the Govt. of Sikkim on 9th December, 2005 on Build, Own, Operate and Transfer (BOOT) basis under joint sector with the State Government through Sikkim Power Development Corporation (SPDC). The project, a Run of the River (ROR) scheme, envisages installation of 3 nos. Francis Turbine driven Generating Units of 40 MW each at a rated head of 103.67m in a surface Power House.

LOCATION MAP & GENERAL LAYOUT PLAN

 The project is located in West Sikkim district of Sikkim. Location map and general layout of the project are given at Exhibit-I & Exhibit-II respectively.

 POWER STATION

 RANGIT STAGE-IV HYDRO ELECTRIC PROJECT

 Rangit Stage-IV Hydro Electric Project was identified as a part of the master plan evolved in 1974 for the development of hydro power potential of Teesta and Rangit rivers of Sikkim. Detailed field investigations and office studies were taken up on this project by the Central Water Commission (CWC) in 2003. A Detailed Project Report (DPR) has been brought out by CWC in August, 2006. The project is a run-of the river (ROR) scheme, envisaging construction of a 44m high Concrete Gravity Dam near Reshi, a 6.5km long water conductor system comprising of intake, desilting basin, head race tunnel, surge shaft, penstock and a surface power house having an installation of 3 Francis Turbine driven Generating units of 40MW each at a rated head of 103.67m. Rangit Stage-IV Hydro Electric Project has been accorded Techno-Economic Clearance (TEC) by Central Electricity Authority (CEA) on 6th July, 2007.

BPTA for Long Term Open Access has been signed with PGCIL on 29.04.2013.

Long Term and Short Term PPAs have been signed with M/s. Tata Power Trading Company Ltd. (TPTCL) in Feb., 2010.

Back to Back PPA for Long Term Sale of Power to WBSEDCL has been signed with TPTCL in Jan., 2011. Long Term PPA has been approved by WBERC on 8th April, 2011. 1st Stage Investment approval for PPA has been already accorded by WBREC on 16th Dec., 2013.

It is proposed to avail CDM benefits for the project and case is already registered with UNFCC. WCD validation is also done.

PRESENT STATUS OF PROJECT (AS ON 30.10.2013)

Components where work completed.

1 Road Diversion Tunnel completed. (Total Length 310 m)
2 Approach Road to Steel Bridge for approaching left Bank of Dam completed.
3 Approach Road to Left Bank of River completed.
4 River Diversion work completed.
5 Approach Road to Surge Shaft completed. (Total Length 705 m).
6 Adit -1 has been completed. (Total Length 200 m)
7 Adit -2 has been completed. (Total Length 151.5 m)
8 Surge Shaft (18m dia) excavation completed.
9 Adit to Intake Chamber completed. (Total Length 196 m)
10 Letter of Award for Generating Units including cooling water system, drainage& dewatering system, compressed air system and SCADA has been issued to M/s ANDRITZ Hydro on 28.08.09.
11 Approach Road to Power House completed. (Total Length 410m).
12 Adit-4 has been completed. (Total Length 102m).
13 Excavation of Ventilation Shaft has been completed. (Total Height is 73.5m).
14 Slope stabilization of P.H. has been completed. Excavation of Power House has been completed.
15 Excavation of Unit Pressure Shaft has been completed. (Total Length in Unit#1- 63.85m, Unit#2- 77.63m & Unit#3- 91.41m).
16 Construction power work completed and Grid supply is being used to meet construction power requirements at Power House, H.R.T., Road Diversion Tunnel & Dam etc. DG sets are also being used to meet construction power requirements.
17 Contract Agreement for Balance of Plant signed with M/s. Siemens Ltd. on 14.04.2011.
18 Letter of Award for HM package issued to M/s. Texmaco Rail & Engineering Limited on 5th Mar, 2012.
19 Letter of Award for 220kV D/C dedicated Transmission line from Rangit-IV Power House to New Melli sub-station has been placed to M/.s Ashish Infratech (P) Ltd. on 16th Nov.,2012.
20 Contract Agreement for 220kV GIS Bay at Pooling Station of PGCIL at New Melli has been signed with M/s. PGCIL on 29.04.2013.

Components where work in progress.
1 In Dam & Intake area 2,90,732.5cum excavation has been done (total quantity Dam & Spillways – 3,83,542 m³, Intake structure –1,36,345 m³).Concreting of Dam is in progress and Block No.8 has been raised upto EL.449m, Block No.7 from El.443.5m to EL.445m, Block No.6 from El.437m to EL.445m, Block No.5 upto EL.445m, Block No.4 upto 445m and Block No.3 upto 436 and total 36,348.5cum concreting has been done out of 1,25,816cum.
2 Widening of pilot in Desilting Chamber-1,2 & 3 at crown is in progress. Excavation of HRT in about 3757m has been completed. (Total Length 6478 m) – Face1- 131m, Face 2- 1950m, Face 3- 1574m and Face 4- 102m.
3

Excavation of Horizontal Pressure shaft has been completed.Excavation of Vertical pressure Shaft is in progress and 60.5m out of 84.75m has been completed. (Total length of pressure shaft is 151.85m).
4

Earth mat of PH is in progress and concreting work has been started on 01.04.12. (Total concreting completed till date is 8006.062cum out of total quantity of 19,900cum). P.H. concreting has been completed upto El.340.15m in Unit#1&Unit#2 between B&D line, upto El.342.99m for Unit#1 between A&B line. Erection of Draft Tubes for Unit-1&2 has been completed. PCC in Unit-3 has been completed and consolidation grouting is in progress. Raft concreting in Service bay has been done upto El.354.95m. Eight nos. of Columns raised upto El.360.75, two nos. of columns raised upto El.358.25mand two nos. of columns raised upto El.356.55m. Beams have also been casted between D3 & D4 at El.357.50m to El.358.25m.


 SALIENT FEATURES
 

I.

 

LOCATION

 

 

 

1

Country

:

India

 

2

State

:

Sikkim

 

3

District

:

West Sikkim

 

4

Tehsil

:

Soreng

 

5

River

:

Rangit

 

6

Name of river basin

:

The Brahmaputra

 

7

Longitude

:

88° 18' 10" E

 

 

 

 

 

II.

 

TYPE OF PROJECT

 

 

 

1

Type

:

Hydro Electric Project (ROR)

 

2

Installed capacity

:

120 (3x40) MW

 

3

Firm Power

:

15.72 MW

 

4

Annual energy generated during 90% dependable year

:

513 MUs. (Corresponding to 95% availability of the Machine)

 

 

 

 

 

III.

 

HYDROLOGY & CLIMATE

 

 

 

1

Catchment area upto head works

:

1232.00 Sq Km

 

2

Snow catchment area

:

267.00 Sq Km

 

3

Average yield

:

3473.00 M Cum

 

4

Average annual rainfall

:

1551.394 mm

 

5

Maximum daily rainfall

:

236.90

 

6

Minimum daily rainfall

:

9.80 mm

 

7

90% available discharge

:

16.33 Cumecs

 

8

Maximum Temperature

:

29.2°C

 

9

Minimum Temperature

:

4.9°C

 

 

 

 

 

IV.

 

DAM

 

 

 

1

Type of Dam

:

Concrete gravity dam

 

2

Height of Dam

:

44.00 m

 

3

Top of Dam

:

El. 471.00 m

 

4

F.R.L.

:

El. 468.00 m

 

5

M.D.D.L.

:

El. 458.00 m

 

6

Dead storage level

:

El. 445.00 m

 

7

Gross storage capacity

:

1.81 M Cum

 

8

Pond age between F.R.L. and M.D.D.L. (Live storage capacity)

:

1.22 M Cum

 

9

Dead storage capacity

:

0.59 M Cum

 

10

Dimension of Spillway gate

:

10.5 m ( W ) x 14 m ( H )

 

11

Crest elevation (Sluice)

:

El. 445.00 m

 

12

Type of gate (Sluice)

:

Radial

 

13

Crest elevation (Ogee)

:

El. 465.00 m

 

14

Type of gate (Ogee)

:

Vertical lift

 

15

Length of Dam at top

:

135.3 m

 

 

 

 

 

V.

 

SUBMERGENCE AT F.R.L.

 

 

 

1

Area under submergence

:

13.25 Ha

 

2

Number of villages affected

 

 

 

 

i) Full

:

Nil

 

 

ii) Partial

:

Nil

 

3

Number of persons/families to be rehabilitated

 

 

 

 

i) Urban

:

Nil

 

 

ii) Rural

:

42 families

 

 

 

 

 

VI.

 

DESILTING CHAMBER

 

 

 

1

Type of Desilting chamber

:

Underground

 

2

Number of Desilting chambers

:

3

 

3

Dimension of single Desilting chamber

:

120 m (L) x 13 m (W) x 15 m (H)

 

4

Size of silt particle to be removed

:

0.25 mm and above

 

5

Average flow velocity

:

25.30 cm/sec

 

 

 

 

 

VII.

 

HEAD RACE TUNNEL

 

 

 

1

Type of Head race tunnel

:

Modified horse shoe

 

2

Dia of Head race tunnel

:

6.40 m

 

3

Length

:

6488.00 m

 

4

Slope

:

1 in 478

 

5

Design Discharge

:

128.00 Cumecs

 

6

Number of Adits

:

2 Nos.

 

 

 

 

 

VIII.

 

VETILATION SHAFT

 

 

 

1

Dia of Vertical shaft from El. 523m to 493.7m

:

7m

 

2

Dia of Vertical shaft from El. 493.7m to Overt of HRT

:

4m

 

3

Height upto overt of HRT

:

73.5m

 

 

 

 

 

IX.

 

SURGE SHAFT

 

 

 

1

Type of Surge shaft

:

Restricted orifice, Semi-underground

 

2

Dia of Surge shaft

:

18.00m

 

3

Dia of orifice

:

2m

 

5

Maximum downsurge level

:

El.445.7 m

 

6

Top elevation of Surge shaft

:

El. 492.00m

 

7

Bottom elevation of Surge shaft

:

El. 427.0 m

 

8

Height of Surge Shaft

:

59 m

 

 

 

 

 

X.

 

PRESSURE SHAFT

 

 

 

1

Type of Pressure shaft

:

Underground

 

2

Dia of Pressure shaft

:

5.50 m

 

3

Length of Pressure shaft

:

247 m

 

4

Thickness of Steel liner

:

20 mm to 36 mm

 

 

 

 

 

XI.

 

POWER HOUSE

 

 

 

1

Type of Power house

:

Surface

 

2

Length of Power house

:

75.30 m

 

3

Width of Power house

:

20.20 m

 

4

Height of PH from lowest excavated level

:

41.385m

 

5

Centre to centre spacing of units

:

16.50 m

 

6

Length of service bay

:

18.60 m

 

7

Distance between A line to B line

:

9.60 m

 

8

Distance between B line to C line

:

9.00 m

 

9

Distance between C line to D line

:

11.20 m

 

10

Centre line of Turbine

:

El. 344.0 m

 

11

Turbine floor level

:

El. 344.835 m

 

12

Upper generator floor level

:

El. 352.835 m

 

13

Lower generator floor level

:

El. 348.835 m

 

14

Service bay level

:

El. 355.00 m

 

15

Top elevation of Roof truss

:

El. 374.00 m

 

16

Number of Machine

:

3

 

17

Type of Turbine

:

Vertical Francis

 

18

Rated unit capacity

:

40 MW

 

19

Specific speed

:

178.38 rpm

 

20

Synchronous speed & frequency

:

250 rpm, 50 Hz ± 5%

 

21

Generator rated capacity

:

44.45 MVA with 10% continuous overload

 

22

Power factor

:

0.9

 

23

Generator voltage

:

11 KV ± 5%

 

24

Excitation system

:

Static

 

25

Heaviest component to be transported

:

25 T

 

26

Power House crane

:

1 No., 150/30T

 

27

Max. Gross Head

:

123.50m

 

28

Max. net head with one M/c. running at rated head

:

118 m

 

29

Minimum net Head

:

97.0 m

 

30

Rated net Head

:

103.67 m

 

31

Minimum tail water level

:

El. 344.50 m

 

32

Max. tail water level under PLF

:

El. 354.0 m

 

33

Max. tail water level with three M/c. in operation

:

El. 347.1 m

 

34

Design Discharge

:

128.0 Cumecs

 

35

Unit Penstock diameter

:

3.2 m (after trification)

 

 

 

 

 

XII.

 

TAIL RACE CHANNEL

 

 

 

1

Tail Race Channel Size

:

Rectangular, Length about 42.00m

 

 

 

 

 

XIII.

 

GENERATOR TRANSFORMERS

:

16.50 MVA, 11/220/√3 KV Single phase- 10 nos.

XIV.

 

SWITCHYARD

 

 

 

1

Type of Switchyard

:

220kV GIS Indoor

 

2

Number of bays in the switchyard

:

6 nos.

 

 

 

 

 

XV.

 

EVACUATION OF POWER

:

Double Circuit 220kV line from Power House to New Melli Pooling station (About 3.2Km.)