Research on optimization of valve hall grounding switches configuration in ±1100KV UHVDC converter station

According to the design scheme of the Zhundong-Wannan ±1100kV power transmission project built this year, there are 24 grounding switches (GS) configured in the valve hall to ensure safety when maintenance. A huge investment is required due to the expensive GS and their huge volume causing a huge valve hall area. Therefore, it is necessary to optimize the grounding switches configuration (GSC) to decrease the valve hall building area and reduce the investment. In this paper, a high accurate model for GSC is established with the parameters from the design. Based on the model, valve hall residual energy distribution and release characteristics under different GSC after converter station block are investigated. The influence factors on the residual energy release characteristics are also studied. Then an optimum GSC is selected considering its comprehensive investment and its performance of discharging residual energy. The optimum GSC is Y1D1 strategy, in which two GS are installed on any phase of Y/Y and Y/D side of the converter transformer respectively.