GB901822A - Improvements in systems for high voltage measurement - Google Patents

Abstract

901,822. Voltage measurements. FOSTER TRANSFORMERS Ltd., and JENNINGS, R. E. April 27, 1961 [April 28, 1960], No. 14899/60. Class 37. Apparatus for measuring the alternating voltage output of a step-up transformer comprises an impedance Z in series with the secondary S developing a voltage drop which is vectorially combined with a voltage produced across an auxiliary winding T representing the open circuit secondary voltage, the combined voltage being measured by an instrument V m connected in circuit with the impedance and the auxiliary winding to represent the output voltage compensated for on-load voltage drop (Fig.1). In a modification (Fig. 2), correcting for instrument load the impedance is an air-gapped iron cored reactor X shunted by resistance r and tapped to develop across part b a voltage equal to that across Z (Fig. 1), which is combined in instrument V m with that across T, the part a of the reactor being earthed, while the effect of secondary self capacitance C is compensated by capacitance c across the instrument. In a further modification (Fig. 3), correcting for instrument load, an extension auto transformer connected winding b of reactor X is coupled through resistance R to winding T, and carries a current equal and opposite to that in b to cancel the effect of the ampereturns therein on the voltage drop across the impedance. Design formulµ are given, and by the use of moving iron, rectifier moving coil or peak reading instruments the mean, RMS, or peak values of voltage output are measurable.