Discussion on the Voltage Waveform of Switching Impulse Test on Transformers and Reactors

In the switching impulse test of the transformers, magnetic saturation of core is produced when full test voltage is applied to the winding. The waveform then appearing is different from the waveform of the switching impulse test voltage which has been discussed in the standard waveform 250/2500 microseconds.On the reactor testing, damped oscillation discharge is generated when voltage of an impulse generator is applied to the winding since the inductance of the reactor is far below the exciting impedance of the transformer. In some cases, therefore, it is not possible to obtain the specified waveform in a large shunt reactor.This paper shows for determining a method the waveform of the switching impulse voltage and recommends the obtainable values of waveform parameters on reactors that wider tolerances may have to be accepted.