METHOD OF CONTROLLING THREE-PHASE FEEDER ISOLATION Russian patent published in 2010 - IPC G01R31/02 

FIELD: electrical engineering.

SUBSTANCE: steady-state currents of zero-phase-sequence (for resonance-ground circuits higher-harmonics zero-phase-sequence currents are used), phase voltages and phase shift angle between zero-phase-sequence voltage and current. Current impedance of feeder isolation is calculated by formula , where: R is insulance, MOhm; 3I₀ is zero-phase-sequence current, mA; 3U₀ is zero-phase-sequence voltage, V, φ is phase shift angle between zero-phase-sequence current and voltage, degree. Predicted value is calculated by formula R_n+1=a₀+a₁n+a₂n², where: a₀, a₁, a₂ are factors, n is time intervals, relative units. If said predicted insulance goes to or below preset value, data is originated on necessity in preventive and repair measures to be taken to recover insulance.

EFFECT: possibility to predict insulance of each feeder.

1 tbl, 4 dwg