UA69915C2 - Method of centralized directed protection of alternating-current mains with a possibility to determine faulty connections and phase circuits with faulty connections - Google Patents

Abstract

The proposed method of centralized directed protection of alternating-current mains with a possibility to determine faulty connections and phase circuits with faulty connections, which are induced by insulation defects or ground short circuits, consists in applying, via a switching device, current of defined frequency to the auxiliary windings of zero-phase-sequence current transformers that are installed at the points of connecting power consumers to the mains, comparing the output current of each transformer with a specified value, and measuring the phase shift angle between the current and phase-to-phase voltage. If the output current of the zero-phase-sequence current transformer that is installed at the corresponding point of connecting power consumers to the mains exceeds the specified value while the phase shift angle between the current and phase-to-phase voltage is within a specified range, this suggests ground short circuit orinsulation fault in the phase circuit that corresponds to the connection point. The range of the phase shift angle used for determining ground short circuits differs from that used for determining insulation faults. The proposed method provides a possibility to increase sensitivity of devices for protecting mains against ground short circuits and insulation faults, which is provided due to the directivity of protection, and use a protective device that is common to all the points of connecting the power consumers to the mains.