Electric field analysis for hybrid high voltage DC circuit breaker

The structure and potential distribution of the 535kV HVDC circuit breaker are complex. In order to improve the reliability of insulation design in valve tower, this paper takes the forced commutation hybrid HVDC circuit breaker as the research object. Firstly, its topology and working principle are explained. Then, based on the insulation performance requirements of a flexible DC power grid demonstration project, and the electrostatic field analysis method, the electric field distribution and electrical shielding design of the HVDC circuit breaker are carried out. The results show that the reasonable electrical shielding design and application can effectively improve the electric field distribution of the DC circuit breaker. The maximum field intensity of the valve tower is 1.74kV/mm, located at the arc part of the U-shaped tubular shielding, and is lower than the corona inception gradient 3kV/mm. The field intensity of the valve unit in transfer branch generally shows a law of decreasing first and then increasing with the increase of the valve layer. Finally, the reliability of the insulation design is verified by experiments, which provides a reference for the insulation design of HVDC circuit breakers.