Prediction of impulse voltage-time characteristics of air and oil insulation for different wavefronts

The insulation of all the power apparatus in the power system are tested with 1.2/50 ¿s standard lightning impulse voltage and this waveshape plays an important role in the insulation coordination of the power system. But in practice all the equipment in the power system are exposed to impulses of varying front times from nano seconds to micro seconds. Hence, it is essential to obtain the voltage-time characteristics of impulses of varying front times. But it is impractical to estimate the insulation strength for all possible impulses. To overcome this difficulty a few impulses of different front times from nano seconds to microseconds are generated and their voltage-time characteristics are obtained for air and oil. From these voltage-time characteristics a generalized mathematical model is obtained by regression analysis to predict the impulse voltage-time characteristics of any wavefront and this mathematical model is experimentally validated.