Interruption Characteristics Of Serial Vacuum And SF₆ Gaps In The Novel Hybrid HVDC Circuit Breakers

HVDC flexible system has gradually became the direction of the smart grid in the future with its unique advantages.The HVDC circuit breaker is the key protection device of the HVDC flexible system.The dielectric recovery speed of vacuum gap is fast,but there is a saturation effect of vacuum gap and the number of series fractures for the ultra-high voltage DC breaking is large.The dielectric recovery speed of SF₆gap is slow but the insulation characteristics are excellent.The serial vacuum and SF₆gaps are adopted,with the dielectric recovery speed of short vacuum gap and the insulation characteristics of SF₆ gap.Through the reasonable regulation method,it is expected to realize UHVDC interruption by series with fewer breakers.The novel hybrid HVDC circuit breaker based on serial vacuum and SF₆ gaps has been set up and the working principle and process have been analyzed theoretically.The voltage distribution regulation and“voltage-zero”have been obtained.The simulation model and circuit have been set up by ATP-EMTP.And the influence parameters of“voltage-zero”have been obtained according to the ATP-EMTP.The simulation results indicate that changing the capacitance and inductance synchronously can increase the“voltage-zero”and dielectric recovery stength.The“voltage-zero”can reach 338.62?s.The platform of the inherent dielectric recovery characteristics has been set up.The inherent dielectric recovery characteristics of vacuum and gas gaps are tested with different gap and di/dt.The inherent dielectric recovery strength and the time of inherent dielectric recovery strength of vacuum gap in 5-7mm gap is 40kV and 20?s.The SF₆ gas in 25-45mm gap is 60kV and 200?s.And the best dielectric recovery strength is 80kV based on100?s“voltage-zero”.Then the prototype of the novel hybrid HVDC circuit breaker has been set up.The interruption characteristics of the novel hybrid HVDC circuit breaker have been researched with“voltage-zero”and voltage distribution.The actual interruption indicate that“voltage-zero”and the voltage distribution can realize synergistic breaking of vacuum and SF₆ gaps.This paper verifies the feasibility and effectiveness of the novel hybrid HVDC circuit breaker by theory and experiment.It supplies the reference for the novel HVDC circuit breaker based on serial vacuum and SF₆ gaps.