3D Channel tortuosity of long air gap discharge

Abstract

The geometric form of the leader trajectory is an interesting aspect of long air gap discharge research. In this paper, the 3-D discharge channel tortuosity in 3m rodplane gaps is obtained by following steps: Firstly, using two static cameras fixed orthogonally to record the face photo and the side photo of the discharge channel. Secondly, the 3-D discharge channel is reconstructed by employing image recognition technology. Thirdly, the discharge channel tortuosity in two-dimensional space and three-dimensional space are derived respectively, which satisfied the Gaussian distribution law. The statistical results indicate that the channel tortuosity will be conservatively estimated by using a two-dimensional method. Statistical results of the channel tortuosity with three-dimensional method indicate the following conclusions. The angle between the discharge channel segments and the gap axis meets the distribution of rational function and its average value and standard deviation is 23.8°and ±19.0°respectively; the angle between the adjacent channel segments also meets the distribution of rational function, and its average value and standard deviation is 13.3°and ±9.9°.

Experimental study of leader tortuosity and velocity in long rod-plane air discharges

“…Good agreement was obtained with previous laboratory results [28]- [31] in reference to leader parameters like the propagation velocity and the angles describing the path tortuosity. Vernon Cooray received his Ph.D. degree in Electricity with special attention to electrical transients and electrical discharges from Uppsala University, Sweden, in 1982.…”

“…The mentioned restrike events observed in the voltage and current waveforms in Figure 2 are visible at times 114. 28 and 134.28 µs for two different leader branches, an initial one that propagates to the side and extinguishes in the third frame and the main one that finally connects to ground. The final jump condition is achieved at 157.43 µs, when the leader corona region -LCR-in front of the leader tip reaches the grounded plane.…”

“…Spatial coordinates for the leader tip were obtained and whole leader channel was divided into consecutive segments. Following the methodology presented in [28], the leader tortuosity was described using three different angles between adjacent leader segments s i and s j , as it is shown in Figure 5. These angles can be described as:  α -between two consecutive leader segments (0, π)  θ -leader segment inclination with respect to the gap axis; also known as polar angle (0, π)  φ -leader segment projection on a reference plane (e.g.…”

“…The values reported for these angles in [28] were:  α: mean value 13.3°; standard deviation 9.9°  θ: mean value 23.8°; standard deviation 19°…”

“…These latter studies have contributed to the physical understanding of the electrical discharge phenomena and different mathematical ways of representing it. A recent work reporting different aspects of the long air gap discharge based on optical and electrical records [28][29][30][31] was used as reference for the present study.…”