A Numerical Study on Oil Pressure Rise Caused by Arcing Faults Inside a Converter Transformer

Oil pressure rise caused by internal faults in converter transformers and the possible resulting tank rupture have long been a serious concern for the power industry. This paper presents a numerical method to study overpressures inside a converter transformer tank during an arcing fault. Specifically, an arc-driven bubble dynamics model is established to quantitatively describe the gas bubble behavior with the release of arc energy and the overall variations in oil pressure. Meanwhile, a fluid model and the bubble-fluid interaction model are utilized to simulate the complex fault effects within the converter transformer. In addition, a simulation model of a full-scale 415 MVA/500 kV converter transformer is established, and representative results of the dynamic evolution of the gas bubble and oil pressure fluctuations under internal faults with arc energy of 1.2 MJ are obtained and analyzed. The simulation results show that the oil pressure rise inside the faulty converter transformer tank depends on the gas bubble, and exhibits an obvious uneven spatial distribution.