4th International Conference on Electric Power Equipment– Switching Technology (ICEPE-2017)

477 / 2017-05-09 16:03:09

Study on the transient characteristics of 1 100kV VFTO

The very fast transient overvoltage (VFTO) generated by switching disconnector (DS) in gas insulated substation (GIS) with the features of high amplitude, short rise-time and complex frequency components, which may cause damage to the insulation of electrical equipment. Therefore, in order to improve the safety performance of GIS equipment, it is very important to study the transient characteristics of VFTO. Four typical transient parameters: rise-time tr, breakdown steepness k, decay time td, and overvoltage level coefficient H are defined for the purpose of describing the VFTO waveform characteristics accurately. The typical transient statistical law of VFTO waveform is studied. The results reveal that① For UHV voltage level VFTO, the rise time tr is greater than 10ns but no more than 30ns. ②The average decay time td of 1 100kV VFTO is about 30μs and the average overvoltage level coefficient H is less than 1.③The breakdown voltage acts out polarity effect apparently. The forward breakdown voltage is about 1042kV, which is much greater than the reverse breakdown voltage whose value is -607kV. ④With the increasing of breakdown voltage, the maximum value of VFTO peak waveform and the value of H become higher. At the same time, VFTO is oscillating more severely, which results in the decay time td and breakdown steepness k change with the same tendency of H.