Experimental Investigation of the Prestrike Characteristics of a Double-Break Vacuum Circuit Breaker under DC Voltages

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.

Capacitive making of double‐break vacuum circuit breaker: Transverse magnetic field contacts are superior to axial magnetic field contacts

“…The prebreakdown probability of each VI under the same applied voltage and closing speed appears to be equal. When the vacuum gap between two contacts is less than 5 mm, the breakdown voltage of the VI and the vacuum gap length follow a linear equation [19], as shown in Equation (6), $$\begin{equation}{U_B} = k \times {d_V}\end{equation}$$where $${U_B}$$ is the breakdown voltage of the VI, k is the breakdown factor, and $${d_V}$$ is the vacuum gap length between two contacts in the VI. The prestrike gaps are all below 5 mm, so Equation (6) is suitable for the prestrike process in double‐break VCBs.…”

“…The high‐precision linear displacement transducers are used to measure the travel curve ( L disp ) of the moving contact in each VI. The measurement method of the prestrike gap d pre is described in detail in [19].…”

“…The prebreakdown probability of each VI under the same applied voltage and closing speed appears to be equal. When the vacuum gap between two contacts is less than 5 mm, the breakdown voltage of the VI and the vacuum gap length follow a linear equation [19], as shown in Equation (6),…”

“…Besides, in [19], double-break VCBs can reduce the prestrike gaps and the scatters in prestrike gaps compared with single-break VCBs under direct current (DC) voltages. The new discovery in [19] can give a new idea in capacitive switching. In summary, previous studies mainly focused on the prestrike process of single-break VCBs during capacitive making operations.…”

“…Another way was focused on the switching strategies, such as controlled switching [10]. Besides, in [19], double‐break VCBs can reduce the prestrike gaps and the scatters in prestrike gaps compared with single‐break VCBs under direct current (DC) voltages. The new discovery in [19] can give a new idea in capacitive switching.…”