Insulation characteristics of GIS under nonstandard lightning impulse oscillations: Insulation characteristics under double‐frequency oscillations with various frequencies and damping ratios

Abstract

SUMMARYTo 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. It was found that minimum breakdown voltages (V min ) were irrelevant to frequency changes in the range of experimental conditions under the same damping conditions. On the other hand, V min rose with the damping ratio rising under the same frequency conditions. The insulation characteristics at a valley of oscillation were investigated using actual breakdown voltages. It was found that the insulation characteristics were treated all-inclusively based on the characteristics of V min for damping time.

Quantitative evaluation of lightning surge range voltage–time characteristics in high‐pressure SF6 gas

“…However, one must pay due regard to the waveform effect of standard lightning impulses and to lightning surges (or disconnector surges) with respect to the V-t characteristics. As regards the GIS V-t characteristics, there are sufficient data on standard lightning impulses [3], while some reports deal with lightning surges and disconnector surges [4][5][6][7][8][9]. However, the basic V-t curves for GIS have not been examined clearly in the short-time range below 1 µs; instead, extrapolation has been employed [10].…”