A Note on the Impulse Testing of Power Transformers

Difficulties are sometimes encountered in generating the standard 1/50-microsec impulse-voltage wave, free from excessive oscillations, when testing low-voltage windings of large transformers. The paper shows that a circuit using inductance and resistance to control the wavefront can be made to give a better waveshape than a circuit in which the shape of the front is controlled by resistance and capacitance. The improvement is illustrated by waveforms taken during tests on a 33-kV 30-MVA transformer winding. Given suitable circumstances, the suggested method of wave control should overcome some of the difficulties previously encountered.