Mai Hydropower Project

Location:

Danabari and Chisapani VDC, Ilam District, Eastern Development Region of Nepal

Purpose of Project:

To supply hydro-electricity for domestic use by connecting to Integrated Nepal Power System (INPS)

Hydrology:

 

Catchment Area

589.0 km2

Average Flow

32.66 m3/s (minimum monthly flow 7.22 m3/s)

Design Flow

23.43 m3/s (40% exceedence flow)

90% Exceedence flow

7.48 m3/s

Design Flood (Q100)

2070 m3/s

1000 years Flood (Q1000)

3007 m3/s

Diversion Dam:

 

Type

Concrete gravity dam

Shape

Ogee-profile

Crest Elevation

321.1 m above msl

Crest Length

91.12 m

Height

5.1 m (from original river bed level)

Designed flood (Q100) level

325.6 m above msl

River Diversion During Construction:

Alignment

Along the river channel

Diversion flow

250 m3/s

Coffer dams

Two cofferdams facilitating stage1 and stage 2 concreting (Total coffer dam length = 377.5 m)

Intake spillway/ Undersluice:

 

Type

Over-flow weir with under-sluice (3@2x4m width) 

Crest Elevation

321.1 m above msl (undersluice 314.5 m above msl)

Length

111.12 mm

Design Flood (Q100)

2070 m3/s

 

 

Intake:

 

Type

Frontal Intake, submerged, over the undersluice

Number of Orifices

3

Bottom Elevation of Orifice

317.0 m amsl

Top Elevation of Orifice

320.0 m above msl

Length of Orifices

20.0 m (with inner piers, clear opening of each orifice = 2.55 x 6 m width)

Intake canal:

 

Type

RCC open canal

Maximum height

3.0 m

Average Width

6.8 m

Approach Culvert:

 

Type

RCC pressurized conduit

Number

2

Average Height

3.0 m (internal)

Average Width

3.0 m (internal)

Total Length of outer branch

Total length of inner branch

Invert Level

62.69 m

40.98 m

317.10 m

Settling Basin:

 

Type

Conventional flushing

Number of Chamber

4 (four)

Top elevation

322.4  m above msl

Normal Operation elevation

320.50 m above msl

Length of the basin

75 m (settling zone)

Average Height

5.85 m

Bottom width per Chamber

9.5 m c/c

Headrace Culvert:

 

Type

RCC pressurized culvert

Length

1055.69 m

Height

3.3  m

Bottom width

3.5 m

Longitudinal slope

1:1500 (V:H)

Headrace Tunnel:

 

Length

2198.0 m (incl. 66 m after surge-tank)

Dimensions

Inverted D 3.8 x3.96 m, (13.1 m2-finish)

Discharge

23.43 m3/s

Surge Shaft dimensions:

 

Type

Vertical, circular section

Height

35.0 m

Diameter

8.0 m (finish)

Penstock

 

Length

316.38 m (273.6 m up to bifurcation)

Diameter/thickness

2.6 m to 1.5 m internal diameter/10 mm to 25 mm thickness

Power Facilities:

 

Powerhouse Type

Semi-surface

Dimensions

36 m x 22 m

Gross Head

122.1 m (321.1 – 199.0 m above msl)

Net Head

108.93 m

Installed capacity

22.0 MW (3x7.33 MW)

Dry energy

22.11 GWh

Wet energy

103.03 GWh

Annual Net Energy Output

125.14 GWh

Tailrace Culvert:

 

Type

RCC canal

Length

229.5 m

Height

3.3  m

Width

3.5 m

Longitudinal slope

1:450 (V:H)

Power Transformer

 

Type

3-phase, two windings, oil immersed transformer with off load tap-changer;

Installation

Outdoor;

Rated power

10,000 kVA and 20,000 kVA;

Transmission Facilities:

 

Transmission line length

11.6 km

Voltage level

132 kV, single circuit

 

 

Project Cost at completion

3,295 million NPR

 


Recent News

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