GIS中SF6绝缘系统缺陷放电的“0-1”现象

“One-Zero” Phenomenon of Discharge Induced by Defects in SF6 Insulation Systems in GIS

气体绝缘金属封闭开关设备(GIS)在电力系统中广泛应用,而SF6绝缘系统缺陷放电是影响GIS安全可靠运行的关键因素之一。文中主要从SF6气体绝缘系统的特点和缺陷放电特征两方面进行综述。首先介绍了SF6气体绝缘的特点,并从电子碰撞截面的角度揭示了'缺陷敏感'的原因。其次,综述了电极凸起、绝缘子附着微粒、绝缘子内部气隙、绝缘子裂纹、自由金属微粒这5类GIS常见缺陷在工频电压下的局部放电特征,发现GIS运行气压下缺陷放电的'0-1'现象,即外施工频电压(Ua)低于击穿电压(Ub)时,缺陷诱发的局部放电量(Q)极小且增长缓慢,呈状态'0';但当Ua逼近Ub时,Q骤增且立即发生贯穿性放电,呈状态'1';状态'0'和'1'之间的转变在很窄的电压区间完成,Q随Ua的变化呈阶跃状。最后,通过'驼峰曲线'、放电形态等揭示了SF6绝缘系统中缺陷放电'0-1'现象的形成机理,即高气压SF6氛围中的缺陷放电的'无晕'击穿机制。

Gas insulated metal-enclosed switchgear(GIS)is widely used in power system,and the discharge induced by defects in SF6 insulation system is a key factor threatening the safety and reliability of GIS.In this paper,both the typical characteristics of SF6 insulation systems and discharge properties induced by insulation defects is reviewed.Firstly,the features of SF6 insulation are briefly introduced,including its extremely high sensitivity of breakdown voltage to the electric field distribution,and the underlying mechanism is also expounded from the view of the electron collision cross section.Secondly,the partial discharge characteristics under power-frequency voltage of five kinds of insulation defects,including electrode protrusion,metal particle attached on insulator,air gap inside insulator,crack in insulator and free metal particle,are reviewed and compared.It is found that,under the operation pressure of GIS,the partial discharge induced by insulation defects shows a'one-zero'phenomenon.When the applied voltage Ua is lower that the breakdown voltage Ub,the magnitude of partial discharge Q is quite low and increases slowly with the increase of Ua,showing a state'Zero',but when Ua approaches Ub,Q increases sharply and the whole gap breaks down suddenly,showing a state'One'.The transition from state'Zero'to state'One'happens in a narrow voltage section,and thus the Q-Ua curve shows a step-like function.Finally,according to the'N-shaped'curve and the morphology of spark path,the inducing mechanism of'one-zero'phenomenon in SF6 insulation system is clarified,and the'non-corona'breakdown pattern in high pressure SF6 atmosphere is thought to be responsible for the'One-Zero'phenomenon.