With the proposal of carbon peak and carbon neutrality target

the tank multi-break vacuum circuit breakers technology

which adopts natural gas insulation and vacuum interrupter for breaking technology

is an effective alternative to replace SF6 circuit breakers in the field of high voltage and ultra-high voltage; however

it is not clear to realize the selection of insulating gas and to understand the surface flashover mechanism of the vacuum interrupter ceramic shell. Firstly

the natural eco-friendly insulating gas dry air and CO2 lightning impulse breakdown tests were conducted

an environmentally friendly insulating gas scheme was proposed. On this basis

the surface flashover test of the vacuum interrupter ceramic shell was performed

and the gas-solid surface flashover mechanism was analyzed. The results show that 0.9 MPa dry air and 0.9 MPa CO2 can meet the requirements of the insulation configuration of environment-friendly vacuum circuit breakers. The surface flashover voltage increases with the increase of gas pressure and shows a slightly saturated trend

the surface flashover voltage of the vacuum interrupter by 0.9 MPa dry air reaches 202.98 kV

and the introduction of the center seal ring decreases the surface flashover voltage by 8.47%. When the length of metal particles is 5 mm and the distance from the high-voltage end is 5 mm

the surface flashover voltage amplitude of the ceramic shell is reduced to a relative maximum of 49.67 kV. The introduction of the center seal ring increases the surface charge density herein from 6.62 μC/m2 to 21.54 μC/m2

leading to a decrease in its surface flashover voltage. The above results can provide theoretical basis and experimental supports for the development of environmentally friendly tank vacuum circuit breakers in the ultra-high voltage field.