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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.

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Authors proposed a simple electric model to simulate the windings used in gas-insulated shunt reactors up to a high frequency range. Its applicability was evaluated by comparison with measurements of the full-scale apparatus model. The impedance of the high frequency electric model is well simulated over a frequency range of several kHz to I O MHz.In this paper, the proposed high frequency electric model was used for analysis of the re-ignition surges at interruptions of the reactor of a model substation. The analysis waveform gave a faster rise and lower peak value than those of the low frequency electric model, and the cause was clarified.

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