Pelton Runner Erosion Due To Cavitation : A Case Study Of Storage Hydropower Plant, Kulekhani First Hydropower Station.

Abstract

Storage Hydropower Plants with reservoir are more flexible and reliable than the Run-off River Plants. It actually acts as battery bank or power bank for desire power generation for uncertain demand. Kulekhani First Hydropower Station is only one storage type hydropower station in Nepal. It is 60 MW plant and is very reliable power plant of Nepal. Electricity produced from each m3 of reservoir water is calculated as 1.27 kWh. Measurements & sedimentation data from the primary and secondary sources were taken for analysis. Trend lines and bar charts were used for analysis purpose. This study is an attempt to find out that Pelton runner erosion due to cavitation phenomena along with efficiency deterioration, though it operates under atmospheric pressure, where sediment concentration is quite low. This was found from the case study of storage hydropower plant, Kulekhani First Hydropower Station. Sediment analysis were carried out on laboratory as per the guidelines of International Electro-Technical Commission (IEC) 62364. The laboratory Test report informs that the sediment concentration of reservoir water feeding to turbine is quite low i.e. 70 ppm. Also the major mineral contents are Quartz, Feldspar, Mica and Other (Tourmaline, Homblende, Calcite, Clay, Hard rock fragments, clay lumps etc.). Sizes of mineral content ranges from 0.001 to 1mm. The result of the study clearly shows that cavitation do occur, though it operates under atmospheric condition. The Pelton runner erosion due to cavitation occurs mainly at the splitter tip back side zone and gradually increasing on operation basis. Erosion contribution due to cavitation is about 0.5045 mm/yearwhereas erosion contribution due to sand particle is about 0.0046 mm/year. Also the study reveals that the plant efficiency has a degrading trend line along with fluctuations. The efficiency calculation are done on the basis of daily water consumption and fluctuating effective head where water volume is determined with polynomial based reservoir capacity equation.