Analysis of AC Filter Tripping Accident based on UHV Converter Station

An AC filter tripping accident occurred in a converter station of the North China Power Grid in 2019, which seriously affected the safe and stable operation of the power grid. In this paper, combined with the configuration of the AC filter in the converter station and the principle of capacitor unbalance protection, the tripping mechanism of the AC filter is explained. It is considered that the direct cause of the tripping of the AC filter is the short-circuit discharge phenomenon between the layers caused by the dead trees (grass) branches on the capacitor tower, which causes the instantaneous fault between the layers of the low-voltage capacitor, and finally leads to the action of the capacitor unbalance protection. From the perspective of operation and maintenance, some practical preventive measures are put forward, which will help to improve the safety of AC filter operation in the future, and then improve the reliability of DC transmission system, especially during the peak summer, peak winter and special power protection period, to ensure that there will be no fluctuation in DC load transmission and protect the safe and stable operation of power grid.