A Coupled Simulation Model of the Anode Erosion Process under Vacuum High-Frequency Inrush Current

The process of anode erosion exerts a profound effect on the cessation of high-current vacuum arcs. The objective of this paper is to conceptually explore the process of anode surface erosion caused by the combined influence of high-frequency inrush current energy flow density and arc pressure. Using a pure copper anode with a radius of 20mm, a model was established to study the erosion of the anode area due to the impact of high-frequency inrush currents in a vacuum interrupter, using the equivalent arc energy of a typical high-frequency inrush current with a peak of 20 kA and a frequency of 4250 Hz within 2 ms as conditional input. Using the moment when the current crosses zero as the reference point. The results indicate that significant erosion occurs on the anode surface due to the combined effects of inrush energy flow density and the arc pressure generated by the high-frequency inrush current. After 0.3 ms of arc discharge, the temperature reaches the fusion temperature of the anode and forms a molten pool, and the liquid metal begins to flow. Consequently, the maximum temperature of the anode surface did not stay centered on the anode surface.

I. Introduction

Anodic activity is pivotal in intense-current vacuum arcs within vacuum circuit breakers (VCBs) [1]–[3]. When vacuum switches are used for capacitive reactive compensation, high-frequency and high-amplitude inrush currents may occur, leading to localized temperature rise on the anode surface due to the plasma of the arcing [4]. According to the IEC back-to-back capacitor switching standard, the high-frequency inrush current has an amplitude of 20 kA and frequency of 4250 Hz [5]. In our previous high-frequency inrush current observation experiment, all the exposure time of the arc is within 2 ms [6]. Therefore, this paper sets the ignition time of the high-frequency inrush current pre-strike arc as 2 ms. The high-temperature action of the arc can lead to the formation of a metal pool on the anode surface. Due to arc pressure, the metal in the pool undergoes deformation and splattering, causing mass loss [7], [8]. Intense anode melting can produce an excessive amount of metal vapor in the VCB at current zero, leading to interruption failures. After arc extinction, the anode surface is left with eroded craters, which intensify the local electric field on the anode surface, making the breaker more susceptible to faults during switching operations [2].