Internal electrical fault of converter transformer may generally lead to high-energy arc discharge. Internal arc fault will lead to oil pressure shock and rupture of oil tank. High temperature transformer oil leakage may cause fire. Whether the mechanical strength of converter transformer oil tank can withstand this dynamic oil pressure is the decisive factor to determine whether a fire occurs. In this paper, the mechanical characteristics such as mechanical stress and deformation of oil tank under internal arc fault are simulated and analyzed by FEM method, and technical measures such as flexible oil tank to reduce the probability of rupture are proposed . At the same time, this paper carried out verification test method of mechanical strength of converter transformer oil tank based on arc test in the transformer oil. 
 

Converter transformer; Arc fault; Tank rupture; Finite-element method; Arc experiment;