Numerical Investigation of Magnetic Field in AMF Vacuum Arc Switch With Transverse Magnetic Field From Three-Phase Structure

When short current is interrupted in three-phase vacuum interrupter in switchgear, the “U”-type loop composed of external busbar, conductive rod, and vacuum interrupter, and its adjacent phases will generate external actual transverse magnetic field (EATMF) in the interrupter. The existence of EATMF will deflect the vacuum arc, which will affect the breaking performance of vacuum switch. In view of this situation, this article establishes two kinds of electrode system simulation models considering and not considering EATMF. The simulation results show that EATMF is not uniformly distributed in the interelectrode region, but is stronger in the contact cup edge area outside the “U”-type loop, weaker in the “U”-type loop, and mainly affects ${B} _{x}$ . In different short-circuit cases, EATMF is also different due to the difference of phase distance and short current. In the case of three-phase short circuit, the magnetic field in the interelectrode region of the middle phase is most significantly affected by EATMF. EATMF is closely related to the structure size of vacuum switch. By changing the structure size of vacuum switch (e.g., phase spacing ${d}$ , conductive rod length ${h} _{1}$ , ${h} _{2}$ ), EATMF can be weakened to some extent.

I. Introduction

Plasma [1] widely exists in our production and daily life. A vacuum arc plasma is an arc that forms in metal vapor that is evaporated from contacts that operate in a vacuum. Vacuum switches are widely used in the medium voltage field of power systems, and play a dual role of control and protection. Their performance and reliability are directly related to the safe and stable operation of power systems [2], [3]. To improve the breaking performance of the vacuum switch, magnetic field control technology is often introduced in the vacuum arc. There are also researches on the influence of axial magnetic field (AMF) contact on the breaking capacity of arc extinguishing chamber with the change of contact diameter before and after the critical radius [4]. At present, the experimental research or modeling and simulation of vacuum arc is generally carried out, but the latter is more economical and efficient. It is possible to systematically and comprehensively study the variation of the vacuum arc magnetic field distribution and typical parameters, so as to deepen the understanding of the internal physical processes of the vacuum arc magnetic field.