Experimental Research on the Characteristics of Very Fast Transient Overvoltage in Ultra High Voltage Gas Insulated Switchgear

Very fast transient overvoltage(VFTO) generated during switching of disconnector in gas insulated switchgear(GIS) may threaten the safety operation of electric equipment,the influence is more serious with the increase of power system voltage and it is preeminent in ultra high voltage(UHV) system.To master the characteristics of VFTO in UHV GIS,lots of experiments by switching of GIS disconnectors were carried out in two VFTO test circuits of UHV GIS and the test results of VFTO were statistically analyzed in this paper.The waveform characters,striking numbers,frequency components and residual voltage distribution of full VFTO waveforms,the waveform characters and oscillation factor distribution of single striking waveform,the characteristics of VFTO magnitudes were proposed.The suppression of VFTO by damping resistor in GIS disconnector was illustrated.The achieved characteristics of VFTO in UHV GIS have been the basis for further VFTO study on simulation and insulation coordination etc.