METHOD FOR INCREASING ACTIVE CURRENT OF SINGLE PHASE-TO-GROUND FAULT IN RESONANT GROUNDED SYSTEMS WITH NEUTRAL GROUNDED VIA ARC-SUPPRESSION COIL AND DEVICE FOR SUCH METHOD IMPLEMENTATION Russian patent published in 2012 - IPC H02H9/00 

FIELD: electricity.

SUBSTANCE: in case a single phase-to-ground fault has been revealed (the average effective value of neutral offset voltage equal to or in excess of 30% of the rated value), after a time delay allowed for the single phase-to-ground fault self-extinguishing (the fault having not been extinguished). One carried out short-term connection of the first resistor with the largest resistance value parallel to the arc-suppression coil control winding. One measures the neutral offset voltage and calculates its average effective value. If the value is less than 30% of the rated one the phase-to-ground fault is deemed eliminated. At a value in excess of 50% the condition of the commutator commutating groups remains unchanged. At a value from 33 to 50% of the rated one the second commutating group is triggered and the second resistor is connected the voltage whereof is equal to half that of the first resistor. At a voltage value less than 33% but equal to or in excess of 30% the paralleled resistors are connected (in parallel) to the arc-suppression coil control winding. If the single phase-to-ground fault has failed to disappear upon expiry of time sufficient for the protection triggering the above operations are repeated.

EFFECT: enhancement of protection promptness, selectivity and reliability.

5 cl, 1 dwg