Flashover phenomena in positive rod‐to‐plane air gaps under impulse and DC voltages

Abstract

Discharge phenomena in positive rod‐to‐plane air gaps under lightning impulse and dc voltages were investigated. Under impulse voltages, the 50 percent flashover voltages agree with the 50 percent corona inception voltages only in a gap shorter than a certain value dc which increases with the rod diameter φ. The 50 percent flashover voltage at dc rises at a rate of about 14 kV/cm with dc in the range of dc < 2.8 cm (φ ⩽ 1.5 cm), and then it rises at a rate of about 5 kV/cm. Experimental results show that the flashover process in the former region (termed the Gp process) is different from that in the latter region (the Lp process). Under dc voltages, the critical gap length, at which the first corona may lead to flashover without any succeeding streamer corona, corresponds to dc under impulse voltage. In a gap shorter than dc flashover occurs through the Gp process (φ ⩽ 1 cm) or Lp process (φ ≥ 2 cm), but in gap longer than dc flashover may occur through another process which cannot be seen under impulse voltages. In this paper, those flashover characteristics and processes are described on the basis of experimental results and photographic observations with an image converter camera.

A prediction method for breakdown voltage of typical air gaps based on electric field features and support vector machine

“…According to the optical observation and electrical measurement in [33], the curve in Figure 9 can be divided into three regions, in region A, U b ≈U c ; in region B, U b >U c ; and in region C, U b > U g >U c . Here, U b is the breakdown voltage, U c is the corona onset voltage, and U g is the inception voltage for stable glow discharge.…”