In this paper

first

the insulation performance of SF

6

/N

2

mixed gas in GIL is calculated

focusing on the effect of SF

6

ratio and gas pressure on the insulating ability and the influence of high drop on the insulation of mixed gas is studied. Second

the lightning impulse breakdown voltage of SF

6

/N

2

mixed gas under different mixing ratios and pressures are measured by means of test equipment

and the difference between the test results and the calculated results is analyzed. The results show that the SF

6

/N

2

mixed gas insulation strength increases with the increase of SF

6

percentage content

but while the content of SF

6

reached 10%

the breakdown voltage of gas mixture show saturation trend. In high drop conditions

the mixture ratios of SF

6

and N

2

changes very little with height. The lightning impulse test results of the prototype verify the correctness of the breakdown voltage calculation results.