METHOD OF THE PREVENTIVE MONITORING OF INSULATION IN A THREE-PHASE MAINS WITH AN INSULATED NEUTRAL

The proposed method of the preventive monitoring of insulation in a three-phase mains with an insulated neutral consists in inserting an alternating voltage source and a direct current voltage, that are connected in series, in the circuit between the conducting element of the controlled equipment and the grounding loop, measuring the cycle of the alternating voltage and the instantaneous values of the alternating voltage at arbitrary instants andwithin one forth part of the cycle, measuring the current in the circuit of the said voltage sources at arbitrary instants and within one forth part, one half, and three forth part of the cycle, determining the insulation impedance for steady leakage current, active component of the impedance, and the capacity of the conducting element relative to the grounding loop.