振荡冲击及交流电压下绝缘子表面金属微粒放电特性研究

近年来由于绝缘子沿面放电引起的绝缘故障较为多见,冲击耐压及冲击下局部放电检测是绝缘考核和诊断的有效手段。文中采用IEC 60060-3推荐的振荡型雷电及操作冲击和工频交流电压,针对110 k V气体绝缘组合开关设备(GIS)真型绝缘子金属微粒缺陷模型进行了局部放电特性研究。在工频交流(AC)电压下,局部放电起始电压和闪络电压的差值小于2种振荡型冲击电压,其随气压增大而增加;在冲击电压下,局部放电大多发生在振荡周期的上升沿处,在电压波谷处会出现相反极性的局部放电脉冲;金属颗粒位置对放电量、放电重复率等影响较大。结论表明,相比于工频交流电压,GIS绝缘子表面金属颗粒缺陷在外施电压为振荡型冲击电压时易产生局部放电,说明了振荡型冲击电压局部放电检测具有较高缺陷检出能力。

Discharge characteristics of metal particles on insulatorsurface under oscillation impulse and AC voltage

In recent years, insulating faults caused by surface discharge of insulators are more common. Impulse withstand voltage detection and partial discharge detection under impulse are effective means for insulation evaluation and diagnosis.In this work, PD diagnosis was performed under standard oscillating lightning impulse (OLI), oscillating switching impulse (OSI) and alternating current (AC) voltages on a 110 kV gas insulated switchgear (GIS) bus model with artificial particles on the insulator surface. The results demonstrated that PDs under OIVs occurred at the rising slopes of the oscillating periods. Most of the reverse polarity pulses were found under OLI voltage, few were found under OSI voltage, and none were found under AC voltage. PD sequences excited from the negative needle point were composed of small and compact pulses. In contrast, positive-point excited PD sequences were composed of larger pulses but fewer of them. These results prove that the defects of particles on the insulator surface are more sensitive to OIVs than to AC voltage.