Rampur hydroelectric project feeds on upstream unit's discharge

S Shanker/ Business Newsline

Mumbai, April 6

The Rampur hydroelectric project, downstream of Nathpa Jhakri hydro electric project (NJHEP) in Himachal Pradesh, is the second unit in the country that will use the water discharge of an upstream power station.

The 120-MW Kodri power project in Uttaranchal, downstream of the 240-MW Chibro power station, is the first that functions by drawing water from the collection gallery of the Chibro project through a six-km tunnel.

An advantage of such projects is that it does not involve construction of a dam or de-silting chambers and hence will not impact the environment.

The under-development 412-MW (6 x 68.67) Rampur project is downstream of the 1,500-MW Jhakri project (6 x 250 MW). It is designed to use the water discharged by the upstream project. The outfall from the upstream NJHEP is to be diverted through a 10.5-m-diameter head race tunnel (almost the height of a three-storeyed building).

The tunnel will be 15 km long of which about nine km is near completion. The cost of the project is Rs 2,047 crore and Rs 782 crore has been spent so far. It is slated for completion in 2013.

De-silted water

A major advantage of such downstream projects is that they get de-silted water. Accumulation of silt is a major issue in hydro projects due to the gradient they operate in which, besides dampening water flow, also damages the runners (wheels spinning the turbine).

The runners suffer substantial damage, including erosion and deformation. The NJHEP plant has set up a Rs 5-crore hard coating robotic facility to coat (tungsten carbide) the runners to withstand the damage, which officials claim is the only one at a hydro station. This apart, the NJHEP has six spare runners to ensure that maintenance downtime is as low as 10 days. Each of the runners cost about Rs 20 crore.

The Nathpa Jhakri project is the largest underground hydro-electric power project and the first undertaken by the Sutluj Jal Vidyut Nigam (SJVN). The plant generates about 661 crore units.

The SJVN (formerly the Nathpa Jhakri Power Corporation) was incorporated in 1988 as a joint venture between the Centre (75 per cent holding) and Himachal Pradesh (25 per cent) to plan, investigate, organise, execute, operate and maintain hydro-electric power projects.

According to the terms of the joint venture, Himachal gets 12 per cent free power and 25 per cent of the balance of 88 per cent as well.

The SJVN is not permitted to sell merchant power and the entire generation is fed to the northern grid.