GB333516A - Improvements relating to measuring and like apparatus for use with electric circuits - Google Patents

Abstract

333,516. British Thomson-Houston, Co., Ltd., Clinker, R. C., Mayo, C. G., and Wellings, J. G. May 8, 1929. Current and pressure meters.-In measuring systems for high tension circuits wherein the instruments are connected on the low tension side and wherein the power transformers are starconnected on the high tension side, the measuring apparatus is fully compensated for phase reactance drops occuring on the star side of the power transformer. Further compensation is also provided for the effects of residual meter &c. currents. I non e arrargement, Fig. 1, the meters which are connected to voltage and current transformers 7, 11 and reactor 10 on the low tension side are compensated for earther unbalance currents on the star power winding 4 by a current transformer 13 connected to an impedance 12 in the neutral of the measuring apparatus. In a modification, the impedance 12 may be omitted and the current transformer 13 designed with an air-gap core. In another arrangement, Fig. 3, to compensate for residual current in the metering apparatus an auxiliary transformer 15 has a delta-connected primary winding 16 to the current transformer 13 and a star-connected primary winding 14 to the current transformer 11, the star-connected reactor 10 being in shunt to the measuring apparatus. In a modification, the reactor 10, auxiliary trans. former 15 and current transformer 11 are combined into a single interconnected-star transformer energized from the delta-connected low tension lines and from the star-connected side through the current transformer 13. Specification 224,873 is referred to.