Research on the Extinguishing Peak Characteristics of Air Arc in the Model Extinguishing Chamber

In order to investigate the waveform changes of arc voltage before zero crossing in the arc extinguishing chamber, this paper constructed a model of the arc extinguishing chamber for arc ignition experiments. The experiment collects and records the arc voltage waveforms using an oscilloscope and captures the dynamic characteristics of the arc during the experiment with a high-speed camera. The experiment is conducted under two conditions: free arcing and applying an external magnetic field. In the case of free arcing, by varying the input current levels, it is found that the appearance of the extinguishing peak is not simply proportional to the current level; if an extinguishing peak occurs, the arc shape extends towards the outlet in a “ $\Lambda$ “pattern. Under the condition of an external magnetic field, changing the input current level results in the constant existence of arc extinguishing peak; and the lower the current level, the higher the extinguishing peak. In addition, under the condition of an external magnetic field, the influence of different outlet sizes on the waveform of arc voltage was investigated. Additionally, under the external magnetic field condition, the study explores the effect of different exhaust port sizes on the arc voltage waveform. Experimental results indicate that with larger exhaust ports, the stable arcing voltage and extinction voltage values are slightly higher than those with smaller exhaust ports. Through analysis, it is concluded that the observed variations in arc voltage waveforms are collectively influenced by factors such as temperature, airflow field, and magnetic field.

I. Introduction

During the interruption of short-circuit currents by low-voltage circuit breakers, the movement characteristics of the arc significantly impact the arc voltage and the overall interruption performance of the circuit breaker. During the disconnection process, the arc gradually elongates under the action of the moving contact, enters the arc extinguishing grid under the contraction force of the magnetic field lines, and is cut into several short arcs by the grid. During the cutting process, the arc plasma strongly interacts with the metal grid, forming a cathode anode arc root on the surface of the grid, resulting in a near pole voltage drop. Under the effect of near pole voltage drop, the arc voltage will significantly increase. Under the action of de ionization and cooling of the arc extinguishing grid, the arc is extinguished when the current crosses zero. However, when the arc extinguishing performance of the circuit breaker is weak, the phenomenon of arc reignition may occur, resulting in the failure of the circuit breaker to open. Research has shown that there is a certain relationship between the voltage before the arc extinguishes and whether the arc reignites [2]–[4]. Through statistical analysis of successful and failed disconnection cases, it was found that there was no significant difference in arc energy between successful and failed disconnection cases, and the only relevant measurement parameter was the “outlet voltage”, which is the voltage within about 20 microseconds before the arc current crosses zero [5]–[6]. Therefore, it is very important to analyze the waveform and dynamic of the arc voltage during the short period before zero crossing in the low voltage circuit breaker extinguishing chamber.