Statistical characteristics of breakdowns in long air gaps at negative switching impulses

Abstract

Discharge characteristics in long air gaps follow certain statistical regularities. Statistical methods and finite element simulation were both employed to deeply study discharge characteristics. The statistical results indicate that the height of grounding rod has a slight influence on the 50% breakdown voltage of rod-rod air gaps and that the breakdown time is longer than the wave front time when 20/2,500 μs switching impulse is applied and shorter than the wave front time when 80/2,500 μs switching impulse is applied. Furthermore it can be shown that the distribution of the breakdown voltages in 10 m rod-plane gap follow the normal distribution and that the V-t characteristics of rod-rod gaps is lower than that of rod-plane gaps. Calculation results indicate that the non-uniform coefficient of the electric field increases with increasing gap distance and that the ratio of gap distance to the non-uniform coefficient also increases with the gap distance. The work described in this paper can be used for the insulation coordination of UHV transmission lines.

Multiple discharges before leader inception in long air gaps under positive switching impulses

“…In related studies, the experimental investigation is one of the most important tools. Many long air gap discharges have been observed under different conditions, for example, with the length ranging from tens of centimetres to more than 10 m [4][5][6][7][8], under the lightning impulse [9][10][11][12] or the switching impulse [5,[13][14][15][16], with the rod-plate [13,17,18], the rod-rod [19][20][21] or the plate-rod [22].…”

Evaluation of statistical methods used in the estimation of breakdown voltage distribution

“…The methods have been used for years for determining the breakdown voltage of gaseous [24][25][26][27] and liquid insulation [28][29][30][31], and are considered consolidated techniques without questions as to their reliability. However, there are very few studies that analyse the methods themselves [32][33][34], and even in these works their reliability was not analysed as a function of their parameters.…”

Reconsidering insulation coordination and simulation under the effect of pollution due to climate change

“…Insulators of transmission lines crossing specific areas can be subject to pollution. The type of pollution and duration of exposure to it are among other factors affecting the system insulation . Pollution of the external surface of insulators including industrial and coastal insulators is the major cause of electrical discharge of insulators in common power systems.…”