Effect of Oxygen and Temperature on Thermal Decomposition Characteristics of C4F7N/CO2/O2 Gas Mixture for MV Equipment

Perfluoroisobutyronitrile (C
₄
F
₇
N)/CO
₂
/O
₂
has been considered as a potential eco-friendly gas insulating medium to replace SF
₆
due to its unique dielectric properties. Nowadays, few studies on the thermal stability and decomposition properties of C
₄
F
₇
N/CO
₂
/O
₂
gas mixture were reported, which needs to be evaluated comprehensively. Herein, for the first time, we explored the effect of oxygen and temperature on thermal decomposition characteristics of C
₄
F
₇
N/CO
₂
/O
₂
gas mixture. It was found that CF
₄
, C
₃
F
₈
, C
₃
F
₆
, CO, COF
₂
, CF
₃
CN, C
₂
F
₅
CN and C
₂
N
₂
are the main by-products of C
₄
F
₇
N/CO
₂
/O
₂
gas mixture upon decomposition. The addition of 2%-10% O
₂
in the C
₄
F
₇
N/CO
₂
gas mixture yielded decreased of C
₃
F
₆
and C
₂
N
₂
while the increase of other by-products. The yields and effective formation rates of C
₃
F
₈
and COF
₂
accelerated when the content of O
₂
was higher than 8%. In terms of practical application, adding 4-6% O
₂
to C
₄
F
₇
N/CO
₂
gas mixture is appropriate and COF
₂
, C
₂
N
₂
, C
₂
F
₅
CN can be used as the characteristic products to reflect the severity of partial overheating fault of C
₄
F
₇
N/CO
₂
/O
₂
gas insulated equipment.