Research on insulation design and testing of high-voltage direct current circuit breakers

Multi-terminal flexible direct current transmission technology is one of the effective ways to accommodate a high proportion of new energy. The direct current circuit breaker is a key device to ensure the stable operation of the direct current system. Firstly, the topology and integral structure of the direct current circuit breaker were introduced. Then, the clearance between layers and to ground was calculated. The electric field optimization design of the valve layer equalizing ring and the valve base insulator equalizing ring was carried out. Finally, the non-uniform voltage coefficient of the transfer branch was tested, and the insulation tests between layers and to ground were conducted. The results show that the maximum field strength between terminals and to ground both occur at the interlayer equalizing ring, at 2.66 kV/mm. The non-uniform voltage coefficient of a single-level IGBT is 1.015. Both the interlayer and ground insulation tests were passed, and the direct current circuit breaker meets the requirements for safe operation.