Insulation Characteristics of GIS under Non-Standard Lightning Impulse Oscillations

Insulation Characteristics under Double-Frequency Oscillations with Various Frequencies and Damping Ratios

Abstract

To improve GIS insulation specifications, it is important to recognize the insulation characteristics under oscillatory overvoltage waveforms occurring in the field. This paper describes investigations of insulation characteristics for double-frequency oscillatory waveforms with various frequencies and damping ratios. As a result, it was obtained that minimum breakdown voltages (Vmin) were irrelevant to frequency changes in the range of experimental condition under same damping condition. On the other hand, Vmin rose with damping ratio rising under same frequency condition. The insulation characteristics at valley of oscillation were investigated with actual breakdown voltages. It was found that the insulation characteristics were treated all-inclusively based on the characteristics of Vmin for damping time.