Research on the performance of insulation detection system and improvement of the calibration method in Hebei south power system

Through analyzing the work principle of AC-injection insulation monitoring and bridge insulation monitoring, the paper expounds the merits and demerits of several monitoring methods. The performance index and functions of the main insulation monitoring device of Hebei south power system are analyzed and the influence scope of balance bridge resistance and switch bridge resistance on the fluctuation and excursion of DC earth ground voltage is calculated. The calibration method for off-line DC system insulation monitoring device is analyzed. It uses different operation conditions of DC grounding calibrator to simulate different grounding faults of DC system and calibrate operation conditions of multi-point grounding, bipolar equilibrium grounding, AC grounding and voltage excursion. The proposed calibration method can regulate the function of insulation monitoring device, and effectively avoid the malfunction of protection device when one-point grounding occurs.