An Experimental Study of the Dynamic Characteristics of the Short-gap and Low-energy Arcs in Insulating Oil

Arc faults pose a considerable threat to oil-immersed power equipment and power systems. Arc faults typically stem from short-gap low-energy arcs, which are attributed to local defects. Consequently, it is imperative to comprehend the dynamic characteristics of these arcs and elucidate their sustentation and development mechanisms. In this paper, experimental simulations of short-gap arcs in oil under AC voltage were conducted, and the arc voltage and current were measured and recorded. The formation and sustentation of arcs in oil, along with the volt-ampere characteristics, were investigated by combining with the arc image analysis. The experimental results demonstrate that the zero-crossing modes of short-gap AC arcs in oil encompass electric breakdown and thermal breakdown, and are influenced by the motion of the main bubble of the arc. The volt-ampere characteristics of the arc manifest as a hysteresis curve through the second and fourth quadrants, and the arc current crosses zero before the arc voltage, indicating the existence of a periodic and short-lived negative power phase, referred to as the electro-sustaining effect. High-time resolution spectral analysis further reveals part of the physical mechanism of the electro-sustaining effect after crosses-zero points.