Research on static pressure caused by arc discharge in transformer oil within a sealed tank

In recent years, short-circuit explosion accidents in ultra-high voltage oil-filled equipment have occurred frequently, causing significant economic losses. Internal short-circuit faults in oil-filled equipment can trigger arc discharge, leading to the vaporization and decomposition of oil, which generates significant relative pressure and may cause explosion and fire accidents. The typical waveform of relative pressure includes four stages: shock wave, fluctuating pressure, quasi-static pressure, and steady-state pressure. Among the components of relative pressure, static pressure is the dominant factor. However, existing methods for calculating static pressure have ignored two main factors: the influence of free gas on static pressure and the time-varying temperature of discharge-induced gas, causing deviations in the calculation results. This paper addresses the two aspects through theoretical analysis and experimental research. A time-varying static pressure calculation method is proposed, which significantly improves the accuracy of calculations when considering the free gas within the tank. Additionally, the relative significance of each factor influencing the static pressure is analyzed. This research provides a reference for calculating the static pressure generated by arc discharge inside transformer tanks.