Calculation of Electric Field Distribution of 220 kV SF6 Current Transformer and Simulation Analysis of Bubble Defect Inside Basin-type Insulator

In recent years, the accidents of SF
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current transformer occur frequently, which seriously threaten the safe and reliable operation of the power system. In order to study the electric field distribution of SF
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current transformer and find out the weak point of insulation, this paper takes 220 kV SF
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current transformer as the research object, using finite element simulation software, establishing a model according to the actual structure and size of the current transformer, then calculating and analyzing the electric field distribution, and finally making a simulation analysis of the situation when there is a micro-bubble defect inside the basin-type insulator. The results show that the electric field strength is larger on the surface of the primary winding, the arc surface at both ends of the secondary shielding cover and the arc surface inside the bottom end of the high-voltage shielding cylinder. The maximum electric field strength is 4.68 kV/mm, 4.09 kV/mm and 4.73 kV/mm, respectively. The electric field strength of the tri-dielectric junction, which consists of the baseplate, insulator and SF
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gas, as well as the countersink nut head and the neck of the basin-type insulator, is larger. The maximum electric field strength is 3.12 kV/mm. According to the above results, the local electric field strength of the current transformer is larger, which will increase the risk of partial discharge. When there are defects in the insulation, partial discharge is more likely to occur, which affects the safety and stability of the device. Therefore, it is not only necessary to optimize the insulation structure, but also to continuously improve the production process to eliminate insulation defects at the source.