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Issue 4

Issn No ISSUE2021

Issued On 2021

Author

Lhendup Namgyal and Tandin


Abstract

The sediments transport in the rivers of the Himalayan region is significantly high due to the fragile geology and rugged terrain of the
landscape. This poses a serious challenge to sediment management and increases reservoir capacity loss in the hydropower plants and sediment induced wear on underwater components of hydropower plants. Sediment induced wear requires repairing, replacement, and causes loss of revenue due to reduced turbine efficiency or downtime during replacement/repairing works. It is, therefore, economical to close the water intake and stop the turbine operation when Suspended Sediment Concentration (SSC) and particle sizes exceed limit values.

In view of optimizing power plant operation during high sediment periods and to improve the life and efficiency of the turbines, sediment impact assessments were carried out for the four high head power plants under the Druk Green Power Corporation (DGPC) in Bhutan, namely Basochhu Hydropower Plant – Upper Stage (BHP – US), Basochhu Hydropower Plant – Lower Stage (BHP – LS), Chhukha Hydropower Plant (CHP), and Tala Hydropower Plant (THP). Based on the erosion rate and the economic analysis for the uncoated runners, the optimal SSC was estimated for each power plant for the switch–off decision: 1,445 ppm for BHP – US, 1,690 ppm for BHP – LS, 6,546 ppm for CHP and 5,540 ppm for THP.

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