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Reference: ISH2015_393

Type:
ISH Collection
Title:

INFLUENCE OF VERY FAST TRANSIENT OVERVOLTAGE WAVEFORM PARAMETERS ON THE BREAKDOWN VOLTAGE IN SF6 GAS GAPS

 

Abstracts

Gas insulation switchgear (GIS) has been widely used in electrical power systems for decades due to its good compactness and tightness, slight impact on the environment, and long maintenance cycle. However, it has been noticed that the failures of GIS insulation due to very fast transient overvoltages (VFTOs) increases with the increase of voltage levels. In this paper, a generating system of VFTO with different oscillating coefficients and double-exponential impulses with different front times was established. Using the system, the discharge characteristics of SF6 gas gaps under VFTO with different front times simulated by double-exponential impulses and different oscillating coefficients were studied. Experimental results show that the 50% breakdown voltage under different impulses increases linearly with the increasing of gas pressure and the waveform front time has an insignificant effect on the 50% breakdown voltage in quasi-uniform field. When the pressure of SF6 is lower, the 50% breakdown voltage under negative impulse is higher than that under positive impulse. By contrast, the 50% breakdown voltage under impulse with positive polarity is higher than that under impulse with the negative polarity when the pressure of SF6 exceeds a critical value. Besides, the 50% breakdown voltage of SF6 gas gap increases with the increasing of oscillating coefficient, which can be explained by the equal-area criterion. Through this research, it can find that the oscillating coefficient of VFTO, compared with the front time, has greater influence on the discharge characteristics of SF6 gas gaps.
 

File Size: 656,6 KB

Year: 2015

 
 
 
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