FIELD: electricity.
SUBSTANCE: automatic circuit-breaker (18) includes control unit (26) and circuit-breaker (20) disconnecting the power supply line (14) from power supply source. The control unit (26) detects a fault in the power supply line (14), disconnects circuit-breaker (20) with release time interval commencing with this disconnection, sends a test signal (t(f)) to power supply line, measures a response signal (U(f)), (I(f)), defines impedance of the power supply line (14) against the response signal (U(f)), (I(f)), analyses impedance during release time interval based on comparison with reference threshold value, defines a permanent or intermittent fault based on the analysed impedance, reswitches the circuit-breaker (20) when release time interval is over and the fault is an intermittent one and maintains the disconnected state of the circuit-breaker (20) when release time interval is over and the fault is a permanent one.
EFFECT: improving accuracy and reliability to determine an intermittent fault.
13 cl, 3 dwg
