Simulation and measurement of very fast transient overvoltage up to 2.5mv

Very fast transient overvoltages (VFTOs) generated during circuit breakers or disconnector switches operations in ultra high voltage gas insulated switchgears (GIS) make great threats to the insulation of power equipments. For the purpose of more economical of GIS insulation design and insulation co-ordination, it is necessary to research the insulation characteristics of GIS equipments under VFTOs. In this paper, simulation results of designed high voltage circuit using Electro Magnetic Transients Program, a systemic design method of VFTO generation and measurement were proposed. Besides, the effects of circuit configuration on VFTO parameters were also researched. Finally, VFTO generated by the system was measured. Simulation results revealed that the intermediate storage capacitor had a big effect on output efficiency and frequency of VFTO. The inductance of generation circuit should be as small as possible. While resistance should be chosen properly for higher efficiency and proper oscillation of VFTO. Test results demonstrated the newly developed generation system could generate 2.5MV VFTO, which had a risetime of 49ns and oscillation frequency of 8.1MHz. The VFTO generation system can help to better research insulation characteristics of GIS.