Internal Pressure Characteristics of Oil-immersed Power Transformer Under Internal Arc Fault

In recent years, there have been many accidents of oil-immersed power transformer explosion caused by internal arc fault worldwide, which seriously endanger the security of power system. As the most direct cause of deformation and rupture of transformer oil tanks, the pressure distribution changes caused by the internal arc fault in oil-immersed power transformers is worth to be studied, but the current research is not yet complete. And protection schemes based on pressure characteristics also mostly remain in the stage of pressure relief devices that act on pressure amplitude reaching threshold. In this paper, a real scale 25MVA/110kV oil-immersed power transformer is reformed, several groups of arc breakdown experiments in transformer oil are carried out. And multipoint pressure signals on the oil tank wall under the internal arc fault are simultaneously recorded and analyzed. The experiment results and analysis show that the amplitude of pressure signal is negatively correlated with the distance between the fault point and the pressure measurement point, and the time delay of pressure signal is positively correlated with the distance between the fault point and the pressure measurement point. The pressure signal measured at the pressure measurement points that are relatively close to the fault point have an obvious dominant frequency. The research results lay a foundation for the further development of new non-electric protection based on the pressure characteristics.