The gas-insulated high-speed mechanical switchgear（HSMS）for high-voltage DC circuit breaker has the shortcomings of short stroke

high separating speed and big mechanical shock.In this study

a gas damper system is proposed to reduce the speed of contact movement and improve mechanical and electrical performances of switchgear.The motion of the HSMS with gas damper involves multiple physical fields such as transient electromagnetic field

airflow field and mechanical field.The multi-physics coupling method is adopted

and a dynamic model of HSMS with gas damper is established by using a finite element software.The motion characteristics of the HSMS with gas damper are simulated

and the influences of the parameters of the gas damper system on the dynamic performance of the swithgear are analyzed.Simulation results show that the high-speed movement of the metal plate in the electromagnetic repulsive mechanism results in the change of internal airflow field

and the hence produced air resistance can realize damping of HSMS effectively.At the last stage of the movement

the gas pressure gradually returns to the initial atmospheric pressure to prepare next high-speed reclosing operation of high-speed disconnect switch.