【作者】 赵林杰；

【导师】 李成榕；

【作者基本信息】 华北电力大学（北京） ， 高电压与绝缘技术， 2008， 博士

【摘要】 由于硅橡胶材料独特的憎水性能,复合绝缘子在电力系统防污闪方面获得了广泛的应用。然而,人们对其憎水性、污闪特性及相关机理的认识却远没有达到全面透彻的程度。本文在充分考虑复合绝缘子的运行环境特征和表面状态的基础上,对复合绝缘子的憎水性和污闪特性进行了四方面的试验研究并揭示了相关机理。本文首先针对复合绝缘子憎水性检测技术的薄弱环节,基于喷水分级法和数字图像分析技术,研制了便携式复合绝缘子憎水性带电检测装置,并提出了基于K (最大水珠或水迹与整幅图像的面积比)和fc(最大水珠或水迹的形状因子)联合计算的憎水性等级判断新方法。基于所开发的憎水性带电检测技术,首次在我国北方重污秽地区开展了长达一年半的复合绝缘子憎水性在线检测试验,发现了运行复合绝缘子憎水性的季节变化特性,提出了基于带电检测的运行复合绝缘子憎水性动态评估新方法,该方法充分考虑了冬季憎水性下降特性和夏季憎水性恢复特性的评估。针对运行复合绝缘子在冬季污闪高发期容易出现弱憎水性状态的情况,采用升降法研究了高岭土染污弱憎水性复合绝缘子的污闪特性,发现了完全湿润的污层表面依然可以存在分离水珠的现象,分离水珠的存在使得试样的耐污闪能力比亲水性试样提高了40%。基于Obennaus模型,揭示了这种弱憎水性试样的污闪机理,即:湿润条件下污层中可溶盐分的外迁会导致污层表面电导率的不均匀分布,从而进一步降低试样污层的平均表面电导率并提高试样的耐污闪能力。针对运行复合绝缘子经常遭遇的两种典型的长时间高湿气象条件,在不考虑电应力同时作用的前提下,首次研究了长时间(长达200小时)高湿微雾环境中高岭土染污弱憎水性复合绝缘子和硅藻土染污强憎水性试样的憎水性变化特性和污闪特性,发现了两种试样均表现出了优异的抵抗憎水性丧失的能力,但是硅藻土染污强憎水性试样的耐污闪能力发生了严重下降,普遍接近于高岭土染污弱憎水性试样的情况。基于Obennaus模型和不均匀电场中的放电理论,揭示了长时间高湿作用后强憎水性试样的低污闪电压主要是由于污层表面电阻的显著下降、水珠间的局部电场的严重畸变以及合模缝附近区域的局部电场的严重畸变的联合作用所导致的。针对绝缘子污闪发生时的典型环境温度特征,首次研究了环境温度在-2°C~2°C范围内周期变化时硅藻土染污强憎水性复合绝缘子的污闪特性,揭示了:低温冷雾中试样表面薄冰的存在会强制融化后的冰水向污层体内扩散并沿污层表面扩展,从而会导致试样表面的憎水性能发生显著下降,并进一步造成闪络电压的显著下降。根据试验结果,本文给出了在进行复合绝缘子外绝缘配置工作时应重点参考弱憎水性试样的污闪试验结果的建议。更多还原

【Abstract】 Silicone rubber (SIR) composite insulators have been widely used in electric power systems to combat pollution flashover problems of transmission lines due to the unique hydrophobic properties of SIR materials. However, the hydrophobic and pollution flashover properties of SIR insulators and the relevant mechanisms have not been thoroughly understood by people. In this dissertation, four aspects of research work on the hydrophobic and pollution flashover properties of SIR insulators were carried out with the consideration of the typical operation environments and the surface status of the operated SIR insulators. The relevant mechanisms were also explained in detail.In order to better master the hydrophobic properties of polluted SIR insulators under actual operating environmental conditions, an on-line hydrophobicity inspection technology was developed. Firstly, based on the spray method and the digital image process technique, a new hydrohobicity class evaluation method was brought forward, in which two parameters K (the ratio of the area of the maximal water droplet or trace in a image of a water sprayed insulator surface to the gross area of the analyzed region in the image) and fc (the shape factor of the maximal water droplet or trace) are calculated. Also, a new on-line hydrophobicity inspection device was designed, which consists of an automatically electric sprayer, a mini digital video camera and a hydrophobcity analyzing software. Then, on-line hydrophobicity inspection was conducted for the polluted SIR insulators on four AC transmission lines in the north of China for more than one year by using the device. It is found from the inspection results that the surface hydrophobcity of the SIR insulators varies remarkably with seasons. On the Basis of the inspection results, an on-line dynamic inspection method on the surface hydrophobicity of SIR insulators is proposed, in which the surface hydrophobicity decrease in winter and its recovery in summer are considered.Considering the fact that the surface of the operated SIR insulators often appear the weak hydrophobic status from November a year to April of the coming year during which period more than 90% pollution flashover accidents happened in China, the pollution flashover properties of kaolin-polluted SIR insulators with weak surface hydrophobicity were studied by using the up and down method. It is found that although the pollution layer of the samples can be completed wetted by fog, the discrete water droplets still can be formed on the sample surfaces, resulting in their 50% withstand voltage higher about 40% than that of the hydrophobic samples. Based on the Obennaus theory, it is believed that the uneven distribution of the surface conductivity, caused by the diffusion of soluble salt from the pollution layer to the discrete water droplets, decreases the effective surface conductivity of the samples, and increases the pollution flashover voltage.Because the long-time wetting stresses, i.e., high relative humidity and fog, are considered as the important factors heavily influencing the outdoor insulation properties of the operated SIR insulators, the hydrophobic change properties and pollution flashover properties of kaolin-polluted SIR insulators with weak surface hydrophobicity and kieselguhr-polluted SIR insulators with high surface hydrophobcity were studies under the long-time light-fog conditions. The test results show that both two kinds of samples exhibit the good anti-hydrophobicity-lose capability. However, after subjected to the long-time wetting stress, the pollution flashover voltage of most kieselguhr-polluted SIR insulators heavily decrease to the case of the kaolin-polluted SIR insulators with weak surface hydrophobicity. According to the Obennaus theory and the discharge theory under uneven electric field, it is believed that the phenomena of the low flashover voltage on the high hydrophobic samples is caused by the combination of the decrease of the surface resistance and the intensification of the partial electric field between the water droplets and along the mold junction areas on the samples.According to the typical ambient temperature characteristics of the pollution flashover accidences of insulators, the pollution flashover properties of kieselguhr-polluted SIR insulators with high surface hydrophobcity were studied by using a cold fog test method we developed, in which the ambient temperature is controlled to cycle in the range of -2°C~2°C during testing. The test results show that under the cold fog conditions, the existence of a thin ice layer on the sample surface forces the melting ice water to diffuse into the pollution layer and to spread along the pollution layer surface, causing the distinct decrease of the surface hydrophobicity on the samples, and further resulting in the decrease of the flashover voltage of the samples.Finally, on the basis of the whole experimental results mentioned above, it is suggested that the outdoor insulation parameters of SIR insulators intended for use in pollution areas should be designed by using the artificial pollution test results of the weak hydrophobic SIR insulator samples.更多还原