Breakdown Characteristics of Gas-Insulated Switchgear for Nonstandard Lightning Impulse Waveforms Under Nonuniform Electric Field

摘要

To improve the insulation specification of gas-insulated switchgear (GIS), it is necessary to recognize the insulation characteristics of SF_6 gas during actual surges (called nonstandard lightning impulse waveforms) occurring at field substations. The authors observed the insulation characteristics of SF_6 gas gap under various types of nonstandard lightning impulse waveforms and compared them quantitatively with those obtained with standard lightning impulse waveforms. The experimental results were used to derive an evaluation method for real surges, which was applied to typical surges for various UHV and 500-kV systems. In the preceding study, therefore, only the case of a quasi-uniform electric field (with a typical range of field utilization factors in the bus of a GIS) was investigated. In the present investigation, the insulation characteristics of an SF_6 gas gap for a nonuniform electric field were observed experimentally and an evaluation method for converting nonstandard lightning impulse waveforms equivalently to the standard lightning impulse waveform was investigated.