PD Inception and Breakdown Voltage Characteristics in PFC and SF6 gas mixtures

Since SF₆ gas has excellent properties like a high dielectric strength, and is chemically inert, nontoxic, and so on, it has been widely used as an insulation material for gas insulated switchgears (GIS) and insulated transmission lines (GIL)(1,2). However, SF₆ gas is a potent green house gas and its global warming potential (GWP) is estimated as a very large at 23,900. Accordingly, SF₆ gas was designated as one of the emission gases to regulate at COP3. It is necessary to decrease the use of SF₆ gas, design techniques to retrieve SF₆ gas and reduce its emission into the atmosphere and develop alternative gases having much lower GWP values. SF₆/N₂ gas mixtures have been proposed as a promising alternative to SF₆. To date, the authors have shown that adding a small amount of CO₂ to an SF₆/N₂ gas mixture results in a prominent increase in the insulation performance under both uniform and nonuniform electric fields(2,3).