Abstract
The prestrike phenomenon in vacuum circuit breakers (VCBs) is interesting but complicated. Previous studies mainly focus on the prestrike phenomenon in single-break VCBs. However, experimental work on prestrike characteristics of double-break VCBs cannot be found in literature. This paper aims to experimentally determine the probabilistic characteristics of prestrike gaps in a double-break VCB consisting of two commercial vacuum interrupters (VIs) in series under direct current (DC) voltages. As a benchmark, single-break prestrike gaps were measured by short-circuiting one of the VIs in a double break. The experimental results show that the 50% prestrike gap d50 of each VI in a double break, which is calculated with the complementary Weibull distribution, was significantly reduced by 25% to 72.7% compared with that in a single break. Due to the voltage-sharing effect in the double-break VCB, scatters in prestrike gaps of each VI in a double break was smaller than that in a single break. However, without the sharing-voltage effect, d50 of the low-voltage side in the double break was 65% higher than that of the same VI in the single break, which could be caused by the asynchronous property of mechanical actuators, the difference of the inherent prestrike characteristics of each VI and the unequal voltage-sharing ratio of VIs.
Highlights
Vacuum circuit breakers (VCBs) are widely used in medium voltage power systems while SF6 gas circuit breakers are still the prevailing technology in high- and extra high-voltage networks
The results showed that the pre-breakdown conduction was dominated by high field-electron emission and could be valuable for the design of vacuum gaps in field emission displays
Gap circuit breakers can be characterized by prestrike gap
Summary
Vacuum circuit breakers (VCBs) are widely used in medium voltage power systems while SF6 gas circuit breakers are still the prevailing technology in high- and extra high-voltage networks. It has been of increasing interest to develop VCBs to higher voltage levels due to their advantages such as being maintenance free, having a long mechanical life, excellent dielectric strength, high interruption capability, and environment-friendly characteristics [1]. The major difficulty of extending the application of VCBs to higher voltage levels arises from the physical disadvantage of a vacuum in terms of the dielectric characteristics, i.e., the non-linear relationship between the dielectric strength and contact gap length [2]. The breakdown voltage is nearly linear to the vacuum gap length within about 5 mm [3]. For a larger gap, the dielectric strength shows a strong full voltage effect. An appropriate way to develop high voltage
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