绝缘纸板表面微纳Al2O3/PTFE复合功能层制备及其对空间电荷注入的影响

Fabrication of the Micro/Nano-Structure Al2O3/PTFE Composite Functional Film on the Surface of Insulation Pressboard and Its Effect on Space Charge Injection

抑制油浸绝缘纸空间电荷注入和积聚对提升换流变压器油纸绝缘系统稳定性有重要意义。传统抑制油浸绝缘纸空间电荷注入的方法是对绝缘纸进行体掺杂纳米材料改性,但其改性效果受限于纳米颗粒分散程度。与此相比,材料表面改性方法的工艺简单、重复性好,在赋予材料新颖特性的同时也能基本保持材料本体的性能。鉴于此,该文首先以射频磁控溅射为技术手段,在绝缘纸板表面构筑Al2O3/PTFE复合功能层,对Al2O3/PTFE复合功能层的组成成分和微观形貌进行表征分析;然后以空白绝缘纸板为参照,测试分析Al2O3/PTFE复合功能层油浸绝缘纸板的空间电荷、直流击穿和陷阱分布特性。结果表明,Al2O3/PTFE复合功能层以微纳结构形式存在于绝缘纸表面;微纳Al2O3/PTFE复合功能层能显著抑制油浸绝缘纸板空间电荷的注入并提升其直流击穿电压;与空白油浸绝缘纸板相比,直流15kV/mm下微纳Al2O3/PTFE复合功能层油浸绝缘纸板内部积聚的电荷总量减少了40%,且由空间电荷积聚引起的电场强度畸变率由33.33%降至6.7%;微纳Al2O3/PTFE复合功能层油浸绝缘纸板的无预压直流击穿电压和预压直流击穿电压分别比空白油浸绝缘纸板提升5.3%和15%;热刺激去极化电流测试结果表明,微纳Al2O3/PTFE复合功能层引入大量深陷阱,这是Al2O3/PTFE复合功能层对绝缘纸板产生空间电荷注入抑制和直流击穿电压提升作用的主要原因。

The suppression of space charge injection and accumulation is of great significance for improving the stability of the oil-paper insulation system in converter transformer.The conventional method of decreasing the space charge amount is to modify the materials by nano doping.However,its modification effect is limited by the degree of nano particles.Surface modification has the advantages of simple craft and good reproducibility,and it can add some new property to the material without affecting other bulk properties.This paper successfully fabricated a micro/nano-structure Al2O3/PTFE composite functional film on the surface of the insulation pressboard using ratio frequency magnetron sputtering.The chemical composition and micro morphology were detected.Then the characteristic of space charge,DC breakdown and trap level distribution were analyzed by a comparative method.The results show that,the prepared functional film exists on the surface of the insulation pressboard in a form of micro/nano structure.The functional film can effectively suppress the space charge injection,thereby promoting the DC breakdown voltage.Compared to the untreated pressboard,the total charge amount decreases by 40%under the electric field strength of 15kV/mm,and the distortion of the electric field drops from 33.33%to 6.7%.The DC breakdown promotion of the pressboard increases by 5.3%for the direct breakdown test and 15%for the pre-stress test.The results of the thermal stimulated depolarization current(TSDC)test indicate that the introduction of numerous deep traps is the key factor to explain the space charge mitigation and the increase of DC breakdown voltage.