Electric Field Joint Checking Method for Isolated Power Supply Transformer of 535kV DC Circuit Breaker Considering Air Conductivity

As an important part of DC circuit breaker, isolated power supply transformer belongs to AC/DC hybrid equipment. It is necessary to adopt appropriate field types in the electric field check of isolated power supply transformer to ensure the accuracy of the results. In this paper, the difference between electrostatic field and constant electric field is analyzed from the basic electromagnetic field theory. The electric field joint checking method for this kind of AC/DC hybrid equipment is put forward. The finite element model of 535kV isolated power supply transformer is constructed, and the method of outsourcing entity is used to partition. The solution is completed in electrostatic field and constant electric field. The influence of air conductivity on electric field calculation results is also considered in constant electric field. The results show that the surface electric field strength of fittings in electrostatic field is greater than that in constant electric field. And in constant electric field, surface electric field strength of metal fittings and other conductors almost does not change with the change of air conductivity, but the surface electric field strength of external insulating materials such as post insulator will decrease first and then increase with the increase of air conductivity. It is suggested that the electrostatic field calculation results should be used in the electric field check of fittings, and the constant electric field calculation results considering the change of air conductivity should be used in the external insulation electric field check according to the actual environment.