FIELD: electrical measuring equipment; relay protection.
SUBSTANCE: invention is intended to improve safety in electrical networks of alternating, direct and double current with an isolated neutral. Essence: the method is based on measuring leakage current from an auxiliary test voltage source in the form of a periodic sequence of pulses. The repetition period of test voltage pulses is set equal to an even number of measured voltage periods of the controlled network T=kTc, where k=2.4,…. The test voltage is synchronized with the voltage of one of the phases of the controlled network. The test voltage is connected through additional resistors to the DC buses of the controlled network, the leakage current is measured by measuring the voltage drop across the measuring resistance connected in series with the test voltage source. A signal is generated that is delayed with respect to the voltage drop across the measuring resistance by an interval 
. The delayed signal is subtracted from the voltage drop across the measuring resistance, and the resulting signal is converted by correction. The moving average value of the signal is calculated over an interval equal to the period of the voltage of the controlled network, and the insulation resistance is calculated. The obtained value is compared with the setting. When the calculated insulation resistance is less than the setting, the electrical equipment is turned off. Additionally, the output of the test voltage source is connected through resistors to the poles of the DC circuit. The test voltage is synchronized with the voltage of one of the phases of the controlled network. The moving average of the signal value over the test voltage period is measured and the area of insulation failure is identified.
EFFECT: increasing the accuracy of continuous monitoring of electrical insulation resistance and reliability of protection of an electrical network of double current with an isolated neutral when the frequency of the controlled network changes and expanding functionality by determining the section of the electrical network in which an insulation failure occurred.
1 cl, 5 dwg
