Dynamic behavior of power-frequency arc in transformer oil

In recent years, the phenomenon of pressure rise and tank explosions by internal arcing faults in transformers has been of great concern. Current research on the pressure characteristics of arcing faults mainly focuses on the generation characteristics of arc-induced gas and the dynamic behavior of arc-induced bubbles. In contrast, little research has been performed on the dynamic behavior of arc plasma. This paper established a synchronized observation platform for electrical-optical-mechanical multi-features of power-frequency arcs to analyze the dynamic behavior of the arc formation and evolution process. During an arc formation, a shock wave with high amplitude and narrow pulse width was generated. The reflection of the shock wave and the fluctuation of the arc-induced bubble jointly determined the pressure in transformer oil. During the evolution of the arc, arc-induced gas was heated, which blew the arc and elongated it, thereby increasing the arc voltage. During arc-induced bubble fluctuation, bubble deformation leads to a surge in the internal gas velocity, blowing the arc to be elongated longer, and the arc voltage increased significantly as a result. The elongation of the arc increased the arc voltage and, therefore, the arc energy on the one hand, and the quantity of generated gas per unit of energy on the other. This dual effect led to an increase in the quantity of generated gas, ultimately leading to a significant pressure rise.