In order to study the decomposition characteristics of SF

6

under partial discharges in SF

6

gas insulation transformers

an experimental platform which consists of a transformer winding and the reduced-scale model of floating potential defects was constructed.Partial discharge tests were carried out under different test voltages and moisture levels.The results show that in the low-intensity partial discharge tests of 340～1 500 pC

the typical decomposition products are SO

2

F

2

SOF

2

CO and CF

4

among which the formation rate is in

the order SOF

2

>SO

2

F

2

>CO>CF

4

.The ratio of the volume fraction of SOF

2

to that of SO

2

F

2

tends to be stable with time

and the stronger is the discharge intensity

the smaller the stability will be.In the environment of excessive moisture(volume fraction is 2 143×10

-6

and 4 000×10

-6

)

the development of partial discharge is faster which promotes the generation of SO

2

.Therefore

the type of typical decomposition products and the variation law of volume fraction can be used to assess the strength of partial discharge.