Following the recent upgrade of the company to a public service utility with Schedule “A” status, based on the Nathpa Jhakri work, local media report that the 1500MW (6 x 250MW) plant has been closed for some days due to the silt load in the water being temporarily too high.

Local media reported that the silt content in the river Satluj was in excess of 9500ppm, exceeding the permissible threshold of 4000ppm. The surge in silt was due to a rise in inflow from glacial meltwater.

The project infrastructure has major desilting chamber arrangements due to the silt problem in the region. The project operates with a 3500ppm limit for water at the intake, which corresponds to silt loading in the river of 4000ppm. At the intake, a limit of 600ppm is set on coarse particles of 2mm size or greater. The upper limit at the draft tubes is 2000ppm.

Following the floods of 2005, studies looked at coatings for runners, and exploring the possibility of additional desilting measures, such as reservoir operation optimisation in the short term, and the use of welded blank panels and dredging pumps in the medium term. For the long term, the company has been examining upstream storage dams, catchment area treatment to reduce bank erosion, and the possibility of building a new diversion tunnel.

Nathpa Jhakri entered full commercial production in May 2004 and has seen a mostly upward trend in electricity output. In its first year, 2004-5, the plant generated 5147M units and apart from a dip the following year to 4104M units the output has been increasing – reaching 6014M units in 2006-7 and 6432M units last year, respectively.

SJVN said that the upgrade to Schedule “A” status would assist it to further improve operations as well as in developing its expansion plans.

In May, the company also noted that it had received an insurance payout over losses incurred due to flooding at Nathpa Jhakri in September 2005. The payout was just over US$71M, the majority of which related to business interruption losses. In terms of material damages, the insurance payout was approximately US$17M.

The plant was completely shut down due to the flooding, resulting in business losses and material damage, but the SJVN was able to get the first unit operational again by mid-October 2005. Insurance funds were made available on an interim basis, in March 2006, to help the cashflow challenge facing the company when trying to achieve early restoration of the plant.