特快速瞬态过电压和雷电冲击作用下特高压GIS绝缘特性

随着电压等级的提高,气体绝缘开关设备(GIS)的额定雷电冲击(LI)耐受电压和特快速瞬态过电压(VF-TO)水平的差异越来越小,由VFTO引起的绝缘事故也日益严重。为研究特高压GIS在VFTO下的绝缘耐受水平,设计了VFTO模拟产生装置,研究了不同气压下SF6棒-板和球-板间隙在VFTO和雷电冲击下的绝缘特性。实验结果表明:稍不均匀电场间隙在VFTO下的击穿电压高于雷电波;对于高气压下棒-板间隙,负极性VFTO下的击穿电压和伏-秒特性曲线位于雷电波之下;雷电冲击下棒-板间隙极性效应在一定的气压下会出现反转现象。分析表明:在不同冲击波前和振荡波尾的VFTO和雷电波作用下SF6气体间隙击穿特性的差异与放电过程中空间电荷行为的差异有关。

Insulation Characteristics of UHV GIS Under VFTO and Lightning Impulse

With increase of voltage level,difference between the rated lightning impulse(LI) and the very fast transient overvoltage(VFTO) level of gas insulated switchgear(GIS) decreases.Insulation failures caused by VFTO become severer.To clarify VFTO withstand level of 1 100 kV GIS,we designed a simulation system for generation of VFTO,and investigated the breakdown characteristics of sphere-plane and rod-plane gaps in SF6 under VFTO and LI for different gas pressures.Experimental results show that the breakdown voltages in slightly inhomogeneous field gaps under VFTO were higher than those under LI.However,for the rod-plane gaps,the breakdown voltages and voltage-time curves under VFTO were lower than those of LI at higher pressure in the case of negative polarity.The polarity effect of rod-plane gaps under LI was reversed at a certain pressure.Based on the analysis,it is concluded that the different breakdown characteristics of SF6 gaps may be attributed to the differences between space charge behaviors during discharge development under the impulse with different wave front and oscillation tail of VFTO and LI.