FIELD: measuring equipment.
SUBSTANCE: invention is related to electric measuring equipment and relay protection of power supply systems. Method is based on measurement of leakage current from auxiliary test voltage source in form of periodical sequence of pulses of type
where U1, U2 are voltage constants, U1>U2; τ – time interval, T – period of test voltage pulses repetition, 
Leakage current is measured by measuring voltage drop at measurement resistance connected in series with test voltage source. Signal is formed with delay relative to voltage drop at measuring resistance at interval 
. Delayed signal is subtracted from voltage drop at measurement resistance. Converting the obtained signal um(t) in accordance with the equation
where ε – small time interval, ε<τ, calculating a sliding average value 
, a signal uc(t) at an interval equal to a period of voltage of the controlled network, calculating insulation resistance by formula 
, where rt – source internal resistance; r0 is resistance of measuring resistor. Comparing the obtained value rin with the setpoint R0, and at rin≤R0, electric equipment is disconnected.
EFFECT: invention increases accuracy and speed of measuring insulation resistance and protection reliability of electrical network.
1 cl, 4 dwg
