FIELD: transport engineering, vehicles with traction current converters. SUBSTANCE: method includes measuring of leakage current of converter input circuits to frame by means of voltage variable in value and frequency, compensation for voltage from load current in pickups at contact system poles, subtracting the difference in readings of metering elements and control of protection means. Prior to setting the drive into operation, express testing of input power circuits under no-load is carried out. Measuring voltage source is switched on only during express testing and monitoring in motion. In system implementing this method, such source is electric arc as spectral phantom source. EFFECT: reduced cost of protection equipment. 5 cl, 1 dwg
