Influence of oxygen on dielectric and decomposition properties of C4F7N-N2-O2 mixture

We investigated the influence of oxygen on insulation and decomposition characteristics of C
₄
F
₇
N-N
₂
-O
₂
gas mixture. The power frequency breakdown voltage, self-recovery characteristics, discharge dispersity as well as the decomposition properties of C
₄
F
₇
N-N
₂
-O
₂
gas mixture under different O
₂
content conditions were tested and analyzed. It is found that the breakdown voltage of C
₄
F
₇
N-N
₂
-O
₂
gas mixture increases with the O
₂
content (0%~8%). The addition of O
₂
could effectively suppress the precipitation of solid by-product on the electrodes surface and reduce the discharge dispersity. The decomposition of C
₄
F
₇
N-N
₂
gas mixture after breakdown mainly produces CF
₄
, C
₂
F
₆
, C
₃
F
₈
, CF
₃
CN, C
₂
F
₄
, C
₂
F
₅
CN, (CN)
₂
and C
₃
F
₆
. Another by-product CF
₂
O is found and amount of CF
₄
is detected after the addition of O
₂
. The self-recovery characteristics of the gas mixture is promoted firstly and then reduced as the oxygen content increases. It is recommended to add 4%-6% O
₂
in the C
₄
F
₇
N-N
₂
gas mixture for engineering application to improve the insulation performance and suppress the precipitation of solid by-products.