CHARACTERISTICS OF GIS DISCONNECTOR-INDUCED SHORT RISETIME TRANSIENTS INCIDENT ON EXTERNALLY CONNECTED POWER-SYSTEM COMPONENTS

The authors provide an indication of the waveshape and magnitude of transients which emerge from the GIS and propagate to externally connected apparatus. Capacitively graded bushings, overhead line connections, etc. tend to reduce the magnitude and cause a slight degradation in the risetime. Computer simulations and measurements have shown that external apparatus connected to GIS can be subjected to waveforms with risetimes in the range of 10-20 ns and voltage rate-of-rise as high as 40 MV/μs. This is comparable to or in excess of the rate of rise during a chopped wave test.