for INMR WEEKLY TECHNICAL REVIEW
近十五年来,随着空心复合绝缘子技术的应用开始 飞速扩大,硅橡胶伞盘上生长霉菌和其它生物的 报道不断出现。如果复合空心绝缘子发生了此类事件, 有理由对此担忧吗?如果答案是肯定的,处理该问题的 正确方式是什么?
在此顺便提一下,绝缘子上的霉菌和其它生物污秽物并 不仅限于硅橡胶材料,也可以滋生在瓷材料上。在硅橡 胶上看到霉菌之所以更加忧心的唯一原因是,用户在认 知上感觉到霉菌对材料的关键性能造成了威胁,即憎水 性迁移和恢复。
硅橡胶空心绝缘子上滋生霉菌最严重的文献报道,或许 是二十世纪九十年代中期发生在美国佛罗里达西海岸的 电力公司。这里的运行环境以其高温和高湿度为特点, 为微生物的繁殖创造了理想的环境。通过空气传播的花 粉清晰可见地沉积在230kV线路上外壳接地断路器的 硅橡胶套管表面。这些花粉随后成为了霉菌群体的食物 来源,并最终不仅影响到某些套管,而且影响到断路器 本身的钢外壳。照片上看到的多数受污染的套管伞盘令 人十分触目惊心,很多地方长着厚厚的霉菌。
裂纹或其它表面损坏的痕迹。目测检查结果没有发现这 方面的证据,下一步是在干燥和潮湿的条件下进行电气 试验(在套管上施加200kV的直流电压),找出霉菌的生 长是如何影响泄漏电流的。
解决的方法是使用高压水枪和工业酒精清洗套管,再喷 上去离子水。然后进行试验查看清洗对硅橡胶憎水性的 影响。结果证实,伞 盘上面的水呈水滴状,足以证明硅 橡胶的憎水性又恢复正常。然后对清洁后的套管重新进 行电气试验,发现泄漏电流明显下降了。
按照电力部门工程师的看法,对霉菌的生长不是置之不 理而是清除它们证实是明智之举。问题首次出现的几年 后,据报道,受感染的套管运行正常,没有再发生霉菌问 题,也没有发现退化的证据和固有憎水性的明显损失。
根据这个事件和其它地方的类似经验,可以得出结论:硅 橡胶表面像霉菌这样的生物组织的存在不会对空心绝缘 子构成严重威胁,不会造成永久性的损坏或过早的老化。 但是,依据严重性的不同,建议通过清洗彻底清除霉菌。
Mold growth before removal. Hydrophobicity of cleaned surface restored.
Over the past fifteen years, as the application of hollow core composite insulator technology has begun to skyrocket, there have been periodic reports of mold and other biological growths appearing on their silicone rubber weathersheds. Is there cause for concern if this occurs on a composite hollow core insulator and, if so, what is the proper way to deal with the problem?
Minor biological contamination shows no impact on hydrophobicity and probably does not need to be removed.
Incidentally, the presence of mold and other biological contaminants on insulators is not necessarily limited to silicone rubber types. It can develop on porcelain as well. The only reason users would be more concerned to see it in the case of silicone is because of a perceived threat to the material’s key properties of hydrophobicity transfer and recovery.
Perhaps the most extreme documented case of mold growth on silicone hollow core insulators took place in the mid 1990s at a U.S. utility operating on the western coast of Florida. The service environment here was characterized by high temperatures and humidity, providing an ideal environment for microorganisms to thrive. Air-borne pollen had apparently become deposited on the surface of silicone-housed bushings of a 230 kV dead tank breaker. This pollen then served as a food source for a colony of mold that ultimately affected not only some of the bushings but also the steel tank of the breaker itself. Photos of the affected sheds on the most contaminated of these bushings looked quite striking, with areas of thick mold growth.
Not knowing what impact this might have, engineers at the utility inspected the bushing visually for signs of cracking or other surface damage that might have resulted from the presence of the mold. Seeing no evidence of this, the next step involved electrical tests under both dry and wet conditions (at up to 200 kV DC across the bushing), to find out how the mold growth had affected leakage current.
Indeed, the results showed a dramatic increase in leakage current under wet conditions. This suggested that leaving the mold problem unresolved would not be prudent.
The bushing was therefore cleaned using high-pressure water and de-natured alcohol, following which it was sprayed again with de-ionized water. Tests were then conducted to see the impact of cleaning on the silicone rubber’s hydrophobicity. Results confirmed that hydrophobicity levels returned to normal, with ample evidence of water beading. The clean bushing was then re-tested electrically and it was found that leakage current dropped significantly.
According to engineers at the utility, this confirmed the wisdom of not leaving the mold growth unattended but instead removing it. Several years after the problem first appeared, the affected bushings were reported to be operating without any further mold problem, no evidence of degradation and no apparent loss of intrinsic hydrophobicity.
Based on this and similar experiences elsewhere, it can be concluded that the presence of biological organisms such as mold on the surface of silicone rubber does not pose a serious threat to a hollow core insulator in terms of permanent damage or premature ageing. However, depending on its severity, it would seem advisable to remove the mold through cleaning.
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