Breakdown Characteristics of SF6 Gas under Non-Standard Lightning Impulse Voltage

Evaluation of lightning surge waveforms that actually enter into substations is important to rationalization of the test voltage of electric power equipment. The standard lightning impulse voltage (1.2/50μs) is used for factory tests. However, the actual lightning surge waveforms in substations are different from the standard lightning impulse voltage because they are complex and are usually superimposed with various oscillations. Insulation characteristics of SF₆ gas under such complex voltages have not been sufficiently clarified.

This paper deals with gap and spacer surface breakdown characteristics in SF₆ gas under sub-microsecond single pulses. The minimum breakdown voltages (V_min) under experimental waveforms are higher than V_min under the standard lightning impulse voltage. The evaluation method, which deals duration applied over 80% of peak voltage, can also estimate the insulation characteristics under single pulses with various conditions as well as oscillations.