Lighting Impulse Voltage Breakdown Characteristics of Vacuum Interrupters with 10 to 50mm Contact Gaps

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 1.6 mu m and 3.2 mu m, 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 (1.2x50 mu s) 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 U-50 depends on the contact gap d (10 similar to 50mm), can be expressed by an equation U-50=kd(alpha), where ex is a power exponent; k denotes a coefficient which is determined by experiments. Within the contact gaps 10 to 50mm, U-50 of vacuum interrupter with contact radius of curvature 2mm was significantly higher than that of vacuum interrupter with contact radius of curvature 6mm. And U-50 of contact roughness 1.6 mu m was close to that of contact roughness 3.2 mu m. U-50 of the contact diameter 60mm was close to that of contact diameter 75mm.