Insulation characteristics of GIS under oscillatory waveforms of non-standard lightning impulse

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

“…In this study we use single-frequency oscillatory waveforms with relatively high peak values obtained by GIS surge analysis [9] in a 500-kV cable-based substation [1]. An example of an analyzed waveform is shown in Fig.…”

“…In disconnector surge analysis, the oscillatory component damps and converges to 1 pu. In terms of insulation, the voltage-to-earth must be considered; previous experiments [9] suggest that breakdown seldom occurs below 70% of peak voltage. Thus, the damping time (τ) was calculated; for analyzed waveforms, it was 1.2 µs to 9.1 µs.…”

“…This study deals with simulated field overvoltage waveforms referred to as nonstandard lightning impulse waveforms. Using these waveforms, insulation characteristics are investigated in order to relax the insulation requirements for electric devices [9]. With cable-based substations, lightning surges penetrating from outside are small, and overvoltages related to disconnector surges and other internal reignition surges gain importance.…”

Review of accumulative failure of winding insulation subjected to repetitive impulse voltages

“…For example, Okabe et al presented four typical nonstandard impulse waveforms that were recorded at a power substation. They maintained that most impulse voltages recorded at this substation differed from the standard forms [96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112][113][114]. Even impulse voltages measured on transmission lines may also differ from the standard impulse voltage [113][114][115][116][117].…”