针板电极下局部放电对油浸绝缘纸板表面的影响

摘要

To study the deterioration of oil immersed pressboard under long-term partial discharge stress,experiments were performed in needle-plane electrode system,and the characteristics of partial discharge and both physical and chemical properties of pressboard surface were measured.Phase-resolved partial discharge (PRPD) patterns in developing process of long-term partial discharge were recorded,and surface morphology and chemical groups of the pressboard in different stages were observed.The influencing mechanism of partial discharge on physical and chemical properties of the pressboard surface was also discussed.The results show that the development of long-term partial discharge (PD) of oil-immersed insulating pressboard undergoes four stages.In different stages,discharge progresses from surface to inside and the damage degree of the paperboard is different.Partial discharge can induce fiber ablation and fracture,resulting in continually expanding holes and bubble layers.Gaseous discharge in the bubble layer generates free radicals,which react with the clusters on the fiber bundle surface and change its microscopic morphology to urge the discharge forward.A bubble column due to accumulation of large number of bubbles inside leads to pressboard breakdown.Damage of the microstructures of the insulation paperboard under long-term partial discharge stress is the main cause of pressboard failure,and the damage is reflected by changing PRPD pattern.%针对油浸绝缘纸板在长期局部放电应力作用下的劣化问题,在针板电极下对油浸绝缘纸板进行了长期局部放电试验,对绝缘纸板的局部放电特性及表面形态的理化特性进行了测量和分析.其中,记录了长期局部放电发展过程中的局部放电相位分布(PRPD)图谱,对处于不同放电阶段的纸板进行了表面形貌、化学基团的观测,研究并给出了放电对纸板表面理化特性的影响机理.结果表明:油浸绝缘纸板的长期局部放电发展经历4个阶段,不同阶段放电由表面向内部发展,对纸板的损伤程度不同;局部放电会造成纸板中纤维的烧蚀及断裂,产生孔洞并不断扩大,形成气泡层;气泡层中不断发生的气体放电生成自由基,这些自由基会与纤维束表面的基团反应并改变其微观形态,促使放电向内不断发展;最终纸板内部堆积大量气泡,形成贯穿的气泡柱并导致纸板击穿.长期局放应力下绝缘纸板的微观结构破坏是导致纸板失效的重要原因,而PRPD图谱的变化是其在局部放电特性上的反映.