Time–frequency characteristics and influencing factors of the pressure wave caused by power–frequency arc inside a closed oil tank

The arc faults inside oil-immersed power equipment can produce high-amplitude pressure waves inside tanks, which might cause ignition and explosion accidents. This kind of failure is one of the most severe faults for power equipment and has attracted considerable attention in recent years. However, due to the high risk of the experiments and the complex development of arc in oil, the characteristics of the pressure wave formed by the arc are still confusing. In this paper, the time–frequency characteristics of pressure waves are analysed using several experiments of 1–8 kA power–frequency arc inside a closed oil tank. The experimental results show that the pressure wave produced by the arc in oil contains three frequency bands, 0–500 Hz, 500 Hz–40 kHz, and above 40 kHz, which are related to the arc energy, the average current around arc ignition and the metal wire explosion respectively. This helps further understand the formation mechanism of the pressure wave caused by the arc in oil. This paper discusses the influences of ignition wire on arc-formed pressure waves. A wire diameter selection method for arc experiments is established to reduce the pressure differences between wire-ignited arcs and actual arc faults.