In view of the situation that there are quite a number of accidents of the parallel-connected capacitor banks installed at some substations, the China Shaanxi Province Electric Power Company has organized engineering and technical personnel to carry out investigation and study to dissect products, test power network harmonics, analyze accident causes, and taken corresponding steps with good results achieved. The company holds that the reliability of the capacitor equipment is closely related with factors such as the content of power network harmonics, design field strength of products of manufacturers, and the parameter setting of series-connected reactors. The correct setting of the relay protection of capacitors is an important guarantee measure for protecting against the expansion of accidents.