Key properties of eco-friendly mixed gases and its ratio distribution with height

To investigate the feasibility of replacing SF
₆
in gas insulated transmission line (GIL) using eco-friendly gas, the physical characteristics and dielectric strength of potential SF
₆
alternative gases are compared in this paper. These gases include c-C
₄
F
₈
-N
₂
mixtures, CF
₃
I-N
₂
mixtures and so on. The by-products and yielding condition of these mixtures are summarized, and the thermal characteristics are compared. As large quantity of N
₂
or CO
₂
is added in the mixture, the heat-conducting property of gas mixture is lower than SF
₆
, which leads to the decreasing of current carrying capacity. Considering the liquidation and dielectric performance, the highest pressure is obtained under certain mixing ratio. In order to know the gas pressure and ratio distribution of mixtures in vertical fall, the spatial distribution of mixing ratio is calculated under the effect of gravity field. The effect of height, mole mass and temperature on the distribution is given out theoretically.