摘要
复合绝缘子在运行过程中受到电场、紫外线、污秽等条件综合作用下而发生老化。这种老化导致复合绝缘子憎水性下降甚至丧失,降低了复合绝缘子污闪电压,增加了污闪发生的机率,影响了电力系统的可靠运行。为及时发现复合绝缘子的事故隐患、避免突发事故、提高输电线路运行的安全可靠性,亟需开展科学有效的复合绝缘子运行状态检测与性能评估方法研究。国内外现有复合绝缘子运行检测与性能评估方法还不够成熟,且目前尚未获得定量的复合绝缘子憎水性与绝缘性能之间的规律,这也是国内外亟需解决的难题。针对此,本论文围绕复合绝缘子憎水性评估方法与憎水性相关的绝缘状态评估开展了以下研究:
①对液体在固体表面动态接触角进行理论分析,提出采用动态接触角测试复合绝缘子憎水性的方法,利用该方法测量不同憎水性复合绝缘子样片,对比研究了静态接触角、动态接触角与喷水分级法之间的关系,结合不同憎水性复合绝缘子表面的微观形貌分析,分析了微米级突起对复合绝缘子表面水珠浸润和铺张等特性的影响,研究了动态接触角评估复合绝缘子憎水性的合理性和有效性。
②利用动态接触角对复合绝缘子憎水性进行评估,测试了不同环境温度、不同浸泡时间和不同pH值下复合绝缘子表面的动态接触角,研究了环境温度、浸泡时间、酸碱度对复合绝缘子表面憎水性的影响,讨论了复合绝缘子“不明闪络”发生的特点和原因,研究和分析了浸泡时间对复合绝缘子表面憎水性的影响,实验分析了浸泡溶液酸碱性对憎水性的影响,探索了酸碱性对复合绝缘子运行的影响。
③以硅橡胶复合绝缘子片为研究对象,采用浸污法对硅橡胶复合绝缘子片表面进行染污,利用升压降压法对硅橡胶复合绝缘子片进行了大量交流污秽闪络试验,根据卡方检验对交流污闪电压分布规律进行检验,采用数据拟合方法分析了污秽程度与憎水性程度对硅橡胶复合绝缘子片闪络电压与闪络概率的影响,依据国内关于污秽等级的标准中对单位爬电比距的要求,对运行于线路复合绝缘子的安全区域和危险区域进行了划分。
上述研究结果表明,利用动态接触角方法能实现复合绝缘子憎水性的有效评判,利用该方法对复合绝缘子憎水性影响因素进行研究,并利用均匀升压降压法研究了染污后硅橡胶复合绝缘子片闪络特性,评估了硅橡胶复合绝缘子片的可靠性。
Composite insulators in power network operation were aged because of the combined effects of the electric field,ultraviolet,the contamination and so on. The aging of composite insulators led to decline of the hydrophobicity, which lowered the flashover voltages of the silicone rubber composite insulator, increased the flashover probability of the silicone rubber composite insulator and reduced the reliability of power system operation. To detect potential accident of the composite insulators in time, avoid incidents of emergency and improve the safety and reliability of transmission line, it is necessary to carry out scientific and effective studies on the detection and performance evaluation with the composite insulators in the power network operation. The methods of the detection and performance evaluation with the composite insulators in the power network operation are immature, and the quantitative relationships between the hydrophobicity and the insulation characteristics haven’t known for us. This paper carries out some studies on the new methods of hydrophobicity evaluation of composite insulators and the flashover characteristics of the composite insulators. The work focuses mainly on the following contents:
①Theory of dynamic contact angle was analyzed,combining with theoretical analysis of the different hydrophobicity classes of composite insulators, different hydrophobicity composite insulators using the method of dynamic contact angle were measured,and the scanning electron microscope analysis (SEM) of the surface morphology on different hydrophobic compsite insulators, by which the feasibility of hydrophobicity evaluation of composite insulators using the dynamic contact angle was verified, were carried out.
②Based on the methods of hydrophobicity evaluation using the dynamic contact angle, this paper studied the factors affected hydrophobicity of the composite insulators, measured the dynamic contact angle in different climate temperature, in different immersion times and in different pH values, analyzed the influences of climate temperature and humidity on levels hydrophobicity of composite insulators, discussed the characteristics and the reasons of“unidentified flashover”, which usally occurred on the composite insulators, studied the influences of the immersion times on the hydrophobicity, analyzed the effects of pH values on the hydrophobicity classes and explored the effects of pH values on the operation of the composite insulators.
③The simplified model of composite insulators in operation was proposed,and up-down method was employed in a large number of contamination flashover tests when the composite insulators had different hydrophobicity levels and contamination levels. Then theories of mathematical statistics were adopted to study the flashover probability on the silicone rubber composite insulators sheet the influences of the receding angle and the salt deposit density on the flashover voltages and the flashover probabilities. Based on the regulations of the specific creepage distances in the standards of different contamination classifaction, divisions of the safe area of the composite insulators on power plants and the substations were accomplished.
The above results revealed that the method of dynamic contact angle could objectively evaluate the hydrophobicity. By this method this paper studied the factors affected hydrophobicity of the composite insulators, employed up-down methods to study the flashover charactirasitc on the composite insulator chip, evaluated the reliability of the composite insulators.
引文
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