Effects of the GIS parameters on very fast transient overvoltages

Although it has been observed that gas insulated substations (GIS) are more reliable than open air substations, there is concern that switching operations performed within GIS at voltage levels higher than 300 kV may result in anomalous failure within GIS and of connected plant. This is attributed to the generation of very fast transient overvoltages (VFTO) during switching operations of load break switches, circuit breakers and especially disconnecters in GIS. The studies which are reported in the paper describe the effects of following GIS parameters on the first peak and maximum values (magnitude and time of its occurrence) of the voltages, at certain points within the GIS, and on the rate of rise of the voltages: (1) effects of variation of spacer simulation on the VFTO; (2) effects of inclusion and variation of arc resistance on the VFTO; and (3) effects of inclusion and variation of spark collapse time on the VFTO.<
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