GB338533A - Improvements in apparatus for testing compensation for earth leakage currents produced by means of earth leakage coils - Google Patents

Abstract

338,533. Allgemeine Elektricitõts- Ges. Aug. 1, 1929, [Convention date]. Locating faults; phase differences and power factors, measuring. - Apparatus for testing the compensation for earth leakage currents produced by means of earth leakage coils comprises an earth leakage coil b connected to the winding a of a transformer and arranged in series with an alternating generator c and the current coil of a power factor indicator e, the voltage coil of which is excited by the generator. A frequency meter or a speedof-rotation meter f measures the frequency of the current produced by the generator. The speed of the generator is adjusted until the instrument e indicates a power factor of unity, at which point resonance is set up in the oscillatory circuit consisting of the inductance of the coil b and the capacity of the means, and the frequency produced in the generator is equal to the resonance frequency of the oscillatory circuit. The resonance frequency is inversely proportional to the square root of the degree of compensation, so that the meter f indicates on a suitable scale the degree of compensation directly. In another form the generator is of constant frequency and is in parallel with the coil b and the capacity of the mains with a transformer between. The current and voltage of the generator are supplied to the current and voltage coils of a measuring instrument. In another form, the source of current is a transformer, the secondary of which is in series with the coil b and in parallel with a reactance meter.