Lighting impulse voltage breakdown characteristics of vacuum interrupters with 10 to 50mm contact gaps

摘要

The objective of this paper is to understand the standard lighting impulse voltage breakdown characteristics of vacuum interrupters with contact gaps 10 to 50mm and how contact parameters influence the breakdown characteristics. The investigated contact parameters include contact diameter 75mm and 60mm, contact surface roughness 1.6µm and 3.2µm, and contact radius of curvature 6mm and 2mm. Therefore we designed four high-voltage vacuum interrupters in the experiments. The vacuum interrupters were put into a porcelain envelope with SF6 gas as an external insulation of the vacuum interrupters. The contact gaps can be adjusted manually. Negative polarity basic impulse level (BIL) voltage (1.2×50µs) was applied by an up-and-down method. Experimental results revealed the breakdown probability distribution followed a Weibull distribution when the breakdown voltage saturated in the investigated contact gaps 10 to 50mm. And 50% breakdown voltage U50 depends on the contact gap d (10∼50mm), can be expressed by an equation U50=kd^α, where α is a power exponent; k denotes a coefficient which is determined by experiments. Within the contact gaps 10 to 50mm, U50 of vacuum interrupter with contact radius of curvature 2mm was significantly higher than that of vacuum interrupter with contact radius of curvature 6mm. And U50 of contact roughness 1.6µm was close to that of contact roughness 3.2µm. U50 of the contact diameter 60mm was close to that of contact diameter 75mm.