Insulation Characteristics of GIS under Non-standard Lightning Impulse Oscillations
Shigemitsu Okabe, Masanori Koto, Takeshi Kawashima, Keiichi Kato, Sadayuki Yuasa · IEEJ Transactions on Power and Energy · 2001
When GIS insulation specifications are improved, it is necessary to recognize the insulation characteristics under oscillatory overvoltage waveforms occurring in the field. Actual overvoltage waveforms, which have oscillation and steep rising, are different from standard lightning impulse waveform. We call these actual waveforms “non-standard lightning impulse waveforms”. In this paper, insulation characteristics under non-standard lightning impulse waveforms which are simulated the actual overvoltage waveforms on GIS were investigated. As the first step, we picked up the important actual overvoltage waveforms for insulation design which are double-frequency oscillatory waveform and single-frequency oscillatory waveform. The experimental circuit was designed for generating simulated waveforms by EMTP analyses. Insulation characteristics under single-frequency oscillatory waveforms and double-frequency oscillatory waveforms, which were generated on the experimental circuit, were investigated. As a result, it was obtained that the insulation characteristics under single-frequency oscillatory waveforms are about 15_??_24% higher than that of standard lightning impulse waveform and insulation characteristics under double-frequency oscillatory waveforms are about 6_??_13% higher than that of standard lightning impulse waveform.