GB199068A - Protective systems for alternating current circuits - Google Patents

Abstract

199,068. McColl, A. E., Garrard, C. C., Wilson, W., and Railing, A. H. Feb. 13, 1922. Protective arrangements for alternating-current circuits employing split conductors, of which one portion forming the main conductor surrounds another smaller portion in parallel therewith and constituting a subsidiary conductor, as described for example in Specification 29984/13, provide for balancing the conductors against one another, for protection on the percentage biassed principle for faults on either conductor. Fig. 1 shows the adaptation to the present invention of the arrangement described with reference to Fig. 3 of Specification 119,937. Current transformers C, D arer inserted with main and subsidiary conductors A, B at each end and their outputs are arranged to be equal with normal current flow. Their secondaries are so connected that their output is circulated from each through one another and through the coils E, F of a dynamometer or induction relay and through a shunting resistance R. On the occurrence of a fault on either conductor the current in one or other of the coils E, F is reversed and the point at which the reversal takes place in relation to the excess current in the faulty conductor is determined by the value of the resistance R, as described in Specification 119,937. A relay of the mechanicallybalanced type may be used instead of a dynamometer or induction type relay.