GB559654A - Arrangements for indicating a characteristic of an alternating current electric supply system - Google Patents

Abstract

559,654. Current, frequency and phase-difference measurements; detecting faults. STANDARD TELEPHONES & CABLES, Ltd., McWHIRTER, E. M. S., DUNN, R. H., and CHAMBERS, C. H. Aug. 25, 1942, No. 11933. Addition to 547,665. [Class 37] In an arrangement for indicating a characteristic of an alternating current supply system, as claimed in the parent Specification, the inductive impedance of one of the coils at the limiting unbalanced condition is neutralized, at least in part, by a capacity in shunt with the coil, which capacity may roughly tune the coil to supply frequency. As described in the parent Specification the winding P in series with the load and the winding S in shunt are arranged to produce opposing magnetomotive forces in the iron of the transformer, so that it is operated at or near a neutral or zero condition of flux. A winding T, together with its indicating relay RL which can be either an A.C. or D.C. relay depending on whether or not the rectifier RB is included, is used to detect small current changes in either of the windings P, S by the creation of a flux in the common core. In order to prevent excessive rise of voltage across the winding T, a condenser C and resistance R are connected in parallel therewith, the condenser roughly tuning the coil to supply frequency. The condenser may alternatively be connected across either of the windings P, S.