PROJECT DESCRIPTION

Sanjen (Upper) Hydroelectric Project (SUHEP):

The source river is known as Sanjen River which is a snow fed river. The catchment area at the SUHEP weir site at Tiloche is about 180 km2 out of which only 4 km2 lies below El. 3000 m. The catchment area at the SUHEP powerhouse site, Simbu, is about 190 km2. Annual precipitation is 1143 mm and monsoon precipitation is 958.7 mm. The long term mean monthly flows in the project area at SUHEP weir site reveals a maximum of 42.49 m3/s in August and minimum 2.33 m3/s in February. 100 years design flood is 194 m3/s. The design flow is 11.07 m3/s.

The tail water of the upper scheme of cascade development named Sanjen (Upper) Hydroelectric Project SUHEP feeds in to the intake arrangement of lower scheme of cascade development, the Sanjen Hydroelectric Project (SHEP). In addition, SHEP utilizes 0.5 m3/s flow from Chhupchhung Khola. The catchment area of Chhupchhung Khola at the weir site is 24 km2. Annual precipitation is 1200 mm and monsoon precipitation is 1000 mm. The long term mean monthly flows at Chhupchhung weir site reveals a maximum of 3.58 m3/s in August and minimum 0.28 m3/s in April. 100 years design flood is 71 m3/s.

Diversion weir lies on the stable and relatively flat channel of the Sanjen River. It is characterized by about 3-4 m thick alluvial deposits consisting of predominately coarse gravel to boulder derived from gneiss, schist and quartzite in sand matrix with large boulders of augen gneiss. Desanding basin, peaking reservoir and forebay lie on a flat alluvial terrace.

Common rock types along the tunnel alignment, surge tank and penstock tunnel are fair to good and are therefore, suitable for the underground works. Penstock is partly underground and partly surface. Powerhouse will be founded on the bed rock.

SUHEP is a run-of-river scheme with daily peaking facility for 1 hour 10 minutes. The whole scheme is divided into three work sites, viz.Headworks Site that covers diversion weir, undersluice, intake, gravel trap, spillway, desanding basin, peaking pond, forabay and pressure conduit, Underground Works that covers headrace tunnel, rocktrap, surge tank, penstock tunnel and construction adits, and Powerhouse Site that covers surface penstock, powerhouse structure, tailrace and switchyard.

The headworks site is located at Tiloche of Chilime VDC. The headworks consist of overflow diversion weir of height 3.3m and one number of undersluice of size 3m wide and 3m high, side intake structure of 12m long, gravel trap of size 25 m long and 4.2 m wide, dufour type double chamber surface desander basin of size 60m long, 8.5 m wide and 6 m deep, peaking pond of size 138 m long and 65 m wide, forebay and 30m long low pressure conduit connecting to the headrace tunnel portal.

Headrace tunnel is 1378m long, inverted D shape of excavated section 3.5m x 3.75m. Surge tank is simple cylindrical type of height 40m and diameter 6m. Surface powerhouse is located at Simbu Village of Chilime VDC. Powerhouse accommodates three units of horizontal axis Francis turbines of capacity 5.1 MW each and three units of 3-phase synchronous AC generators of capacity 5.85 MVA each. Three numbers of tailrace canals each of 5 m long discharges the tail water to the Forebay/Intake of Sanjen Hydroelectric Project (SHEP). Surface switchyard is located adjacent to the powerhouse complex.

Generated power from Sanjen (Upper) Hydroelectric Project is being evacuated through a 5km long 132 kV single circuit transmission line to connect from SUHEP powerhouse to 11kV transmission line (Transmission line under contingency plan) which is further connected to 66kV transmission line of Chilime Hydropower Company Limited. The Chilime Hub of NEA is still in under construction stage, which after being completed will be used to transmit the power generated from SHEP and SUHEP, and the hub is connected to the national grid via 220 kV double circuit line up to Trishuli 3B hub of NEA.