SF6混合气体放电的极性反转特性研究OA北大核心CSTPCD

SF6 gas mixture can replace SF6 gas in gas insulated electrical equipment under extremely cold condi-tions.In case of defect in the equipment,it will significantly reduce the breakdown voltage.It is therefore neces-sary to study the discharge characteristics of SF6 gas mixture in extremely uneven electric field induced by the de-fect.The discharge test of SF6/CF4 and SF6/N2 gas mixture under needle plate electrode is performed and,compared with SF6 gas,the variation of hump curve of breakdown voltage with the increase of gas pressure is analyzed.It is found that the hump curve of SF6 gas mixture will shift to the right compared with SF6 gas,and the right shift of SF6/N2 gas mixture is more obvious.The breakdown and partial discharge characteristics of SF6 gas mixtures at different pressures are compared and studied further.It is found that the breakdown voltage of SF6/CF4 and SF6/N2 gas mix-tures has polarity reversal with the increase of gas pressure,that is,from negative polarity breakdown to positive po-larity breakdown,and the gas pressure corresponding to polarity reversal is the gas pressure at the valley of hump curve.At the same time,the characteristics of partial discharge will also change with the increase of gas pressure,namely,from coexistence of both negative and positive partial discharge to only positive partial discharge.It is found through analyzing the variation trend of initial partial discharge voltage of SF6 gas mixture with gas pressure that,in case of exceeding the valley gas pressure,the difference between the initial partial discharge and the break-down voltage is less,showing that SF6 gas mixture equipment is more prone to corona free breakdown at higher gas pressure,which is consistent with the operation and maintenance experience of SF6 gas equipment.The research re-sults have reference significance for the operation and maintenance of SF6 gas mixture equipment.