Electric Field Evaluation and Optimization of the Shielding Electrodes for ±535 kV DC Circuit Breaker

The ±535 kV DC circuit breaker is adopted by Zhangbei HVDC grid project. The rational design of insulation structure for the ± 535 kV DC circuit breaker is the key to system security. In this paper, the insulation design requirements of one ± 535 kV hybrid DC circuit breaker and the preliminary designs of insulation structure were described. The 1:1 3-D simplified FEM model of the whole DC circuit breaker was built, and then the fine model of the main power supply transformer was established with the sub-model method. The surface electric field evaluation and optimization was proposed, which was verified through the tests. The results show that after optimization, the maximum electric field strength on surface of the shielding electrodes for the DC circuit breaker decreased from 20.8 kV/cm to 17.8 kV/cm, lower than the critical value. The research result was used in the design of the DC circuit breaker for Zhangbei HVDC grid project.