FIELD: electrical engineering. SUBSTANCE: method involves analysis of leakage current passed through specially set up circuits connecting supply mains under protection to ground. Phases placed at highest and lowest voltages to ground are chosen by means of switch and connected to ground through separate resistors. Ground-fault current and phase voltages are measured, insulation resistance to ground is determined and compared with permissible value; if it is below specified limits, signal is shaped to disconnect faulty member of supply mains. At the same time, first harmonic component of leakage current is separated, its parameters are measured to locate ground fault, and appropriate information signal is shaped. Insulation resistance of supply mains is continuously monitored under normal conditions, ground faults are detected at any point without dead zones, type and point of ground fault can be easily determined in emergency situations. EFFECT: reduced outage period for repairs and reduced maintenance charges, improved reliability, reduced probability of accidents. 3 cl, 9 dwg
