In case of switching short busbar by GIS disconnector

VFTO will be generated between contacts during the transient breakdown

which poses a serious threat to the insulation of equipment. The breakdown distance between contacts is related to the impedance characteristics of the arc

which affects the time and frequency domain distribution characteristics of VFTO. In order to study the influence of the breakdown arc length between contacts of GIS disconnector on the waveform characteristics of VFTO

in the test duty 1 of switching short short busbar by GIS disconnector

the ultra-widebande voltage measurement system based on the capacitive voltage division is used to accurately measure whole VFTO waveform of DC side during closing operation of disconnector. Then

the VFTO waveforms excited by the first 15 times breakdowns are extracted for time domain

frequency domain and time-frequency distribution analysis. It is found through the analysis that when the length of the breakdown arc between contacts is decreased from 100 mm to 30 mm

the excited duration of time domain waveform of VFTO and the mutation characteristic time of wave-head have no obvious change. The fluctuation range of overshoot coefficient becomes small and has no obvious influence on the maximum overshoot coefficient. In case of reduction of the distance between conatcts

the characteristic frequency point above 50 MHz is gradually reduced with the decrease of arc length

and the maximum instantaneous frequency is decreased from 100 MHz down to 70 MHz. The frequency component above 50 MHz is decreased with the arc length and the duration is shortened. After the distance between conatcts is less than 30 mm

the characteristic frequency above 20 MHz has obvious deviation. The research in this paper provides a strong support for optimizing high frequency model of arc and the structure design of GIS disconnector further.