Dynamic pressure analysis and protection of transformer in internal arcing fault by FEM

In view of the transformer internal fault would lead to the tank cracking, fire, explosion and other serious accidents, power transformers are usually equipped with pressure relief valve and gas relay. However, due to the lack of theoretical innovation and reliability remain in the existing protections. This paper proposes a numerical method to research the pressure behaviors of transformer tank under internal overpressure caused by the high-energy arcing faults and develops protection principles based on pressure characteristics. According to the real full-scale 100MVA/110kV oil-immersed transformer parameters, a transformer model has been set up. Then, the 4.4MJ and 3.1MJ arcing faults have been provoked as the simulation examples by employing 3D FEM. The transient pressure characteristics such as pressure rise curves and effective pressure indexes at different positions have been studied. Moreover, this paper develops new protection principles for heavy gas protection and light gas protection based on pressure characteristics. In addition, both the theoretical model and the simulation method proposed in this paper can be extended to study tank structure and overpressure in other types of transformers instead of dangerous and costly tests.