Rehabilitation of Katse dam mini-hydropower plant

Abstract

The Katse Dam Mini-Hydropower station was designed to generate and supply electricity to auxiliary systems without connecting to the grid. This would increase the dam power supply and reliability thereby reducing the electricity bill incurred on the Lesotho Highland Water Project (LHWP) for operations. However, to date, the Mini-Hydropower station is not fully operational. In this study, the decommissioned Katse Dam Mini-Hydropower plant’s rehabilitation is evaluated. Three significant activities characterized this rehabilitation process. The upgrading of electro-mechanical equipment or damaged parts, using condition assessment filters. Uprating is explored by flow duration plots for the possibility of increasing plant capacity. Lastly, the capacity dispatch (Integration) is studied intensively with computer software package (DigSilent Power Factory), for grid integration alternatives. In general, electrical equipment is the plant's most vulnerable to fatigue. Mechanical equipment is moderately damaged, with governor and guide bearing systems standing out. Assessment of the potential of the plant’s capacity increase revealed that the reservoir compensation flow regime resulted in minimum design values of head and discharge being fulfilled 96% of the time. The Katse Dam load capacity is met 90% of the time, while the maximum single machine power is exceeded 84% of the time. The Mini-Hydropower stable response to dam load growth and decline without a grid was shown in the grid integration option. However, there was a substantial deviation to a sudden loss of grid without load shedding, and the local bus voltage dropped below 6% tolerance. The findings of this investigation demonstrated the need for this plant to be rehabilitated. All the necessary tests on relevant components point to the goals of the plant and the necessity for restoration. According to the economic study, implementing this project will result in a 9- year return on investment and a 2.02 MWh annual energy guarantee, which is 54% of the yearly energy consumption of the auxiliary systems