GB269983A - Improvements in or relating to protective arrangements for duplicate feeder electricsystems - Google Patents

Abstract

269,983. Reyrolle & Co., Ltd.. A., Biles, R. W., and Piquet, J. Jan. 28, 1926. Cut-out arrangements. - In the protection of parallel feeders whereby a sensitive setting of the protective relays dealing with earth faults is afforded and a heavy setting for the relays dealing with interphase faults, a directional earth-leakage relay N, L has its current coils L connected in the circulating current circuit of two core-balance transformers in the parallel feeders and its potential coils N variably connected automatically on fault across the voltage of different phases depending upon which phase develops the earth fault. Interconnected current transformers B, B<1> in the parallel feeders supply the current coils F, F<1> of two three-pole reverse-power relays D, D<1> through the actuating coils P of auxiliary contactors O. The potential coils of these relays are supplied from potential transformers C, C<1>. For earth leakage protection the core-balance transformers M, M<1> are connected through a diverter relay R (to reduce the sensitiveness of the earth leakage relay during heavy straightthrough earth-fault currents) to the current coils L of the earth-fault relay, and its potential coils are energized from the potential transformers C<1> through that one of the contactors which has been closed corresponding to the earthed phase. In this way a potential of the correct phase to ensure sensitive action of the relay is chosen. The main circuit-breakers are associated with switches T, T<1> which, when the current-breaker is tripped, short-circuit the current coils of the relays and isolate the secondary side of the potential transformer.