Dielectric Strength on Repetitive Impulse Voltages for Inter-Coil and Turn Insulation models of Transformer Winding

Abstract

A relationship between the repetitive impulse voltage and the number to breakdown becomes matter of great concern since the lightning impulse withstand voltage of UHV transformers will be remarkably reduced owing to the low protective level by high performance surge arresters. It is shown that the inclination of V-N characteristics is rather flat up to 1000 shots of lightning impulse and switching impulse for inter-coil and turn insulation models by experimental results. Finally, it is concluded that the modification of lightning impulse withstand test voltage based on V-N characteristics is not necessary.