憎水性涂层导致盘形绝缘子陡波击穿性能下降的机理研究

In recent years, China has applied more than 900,000 cap and pin suspension ceramic and glass insulators with RTV coating in the strain insulator-strings of AC and DC UHV transmission lines, in order to optimize the anti-pollution flashover performance and mechanical strength of insulator strings. However, the unexpected sharp decline of breakdown performance of RTV coated insulator was discovered in the steep-front impulse voltage test, which is obviously deviated the original design of combination of two advantages such as large-tonnage insulator and RTV coating. For instance, the steep-front impulse voltage test pass rate of 550kN insulator is only about 50%. This unexpected phenomenon has put forward serious challenges for the breakdown mechanism of insulator and lots of industrial applications.. Steep-front impulse voltage test together with ultra-high-speed ICCD will be used as experimental tools, and electric field analysis will be adopted as simulation methods. The transient electric field changes and the development of surface discharge of disc insulator with RTV coatings and without RTV coatings under steep-front impulse voltage will be studied. Special detachable electrode will be used to study the position of puncture point. The impacts of RTV coating parameters and insulator parameters on the discharge and breakdown process will be analyzed. And then the changes in the breakdown performance of cap-and-pin insulator brought by RTV coating under steep-front impulse voltage will be determined, and the influence mechanism of hydrophobic coating on cap-and-pin insulator under steep-front impulse voltage will be revealed. Theoretical basis for the selection of cap-and-pin insulator with RTV coating, steep-front impulse voltage test and the study on its lone-term operational reliability will be provided.

为使绝缘子串同时具备优异的防污闪性能和机械强度，近年来我国使用了超过90万片带RTV涂层的大吨位盘形悬式瓷、玻璃绝缘子，用于交、直流特高压线路的耐张串。但在陡波试验中，却意外发现这种将大吨位绝缘子与防污闪涂层相结合的初衷，导致绝缘子陡波击穿性能的大幅下降。比如550kN绝缘子的陡波通过率仅有约50%。这一意外现象对绝缘子的击穿机理和大量工程应用都提出了紧迫挑战。.本课题采用陡波试验加超高速ICCD照相的试验研究和电场分析的仿真研究相结合的手段，针对陡波前冲击电压下有、无RTV涂层的盘形绝缘子头部区域瞬态电场变化和沿面放电发展开展研究，利用特制的可拆卸电极研究击穿点位置，分析RTV涂层参数和绝缘子参数对放电和击穿过程的影响，进而明确RTV涂层带来的盘形绝缘子陡波击穿性能的变化，揭示憎水性涂层对绝缘子陡波击穿的影响机理，为涂RTV盘形绝缘子的选用、陡波检验和研究其长期运行可靠性提供理论依据。

为使绝缘子串同时具备优异的防污闪性能和机械强度，近年来我国使用了超过600万片带RTV涂层的大吨位盘形悬式瓷绝缘子和玻璃绝缘子，用于交、直流特高压线路的耐张串。但是在陡波试验中，却意外地发现这种将大吨位绝缘子与防污闪涂层相结合的初衷，导致绝缘子陡波击穿性能的大幅度下降，比如涂覆RTV的550kN玻璃绝缘子的陡波通过率不足50%。这一意外现象对绝缘子的击穿机理和大量的工程应用都提出了紧迫的挑战。.本项目采用陡波试验加超高速ICCD照相的试验研究和电场分析的仿真研究相结合的手段，针对陡波前冲击电压下有、无RTV涂层的盘形绝缘子表面沿面放电过程及绝缘子瞬态电场变化两类物理过程开展研究，定量获得了大吨位盘形玻璃绝缘子和瓷绝缘子涂RTV前后陡波击穿性能下降的幅度，探寻了击穿点的位置，获得了涂层参数和绝缘子参数对两类过程的影响规律，建立了陡波击穿机理模型，揭示了憎水性涂层导致盘形绝缘子陡波击穿性能下降的机理。陡波下涂覆RTV的绝缘子的击穿本质上属于绝缘件内绝缘的电击穿，RTV涂层诱导绝缘子表面电弧更紧贴绝缘子表面，电弧通道的变化和涂层参数的双重影响使得绝缘件在陡波下的瞬态电场强度增大，促使绝缘子易在其绝缘件的电气强度薄弱部位击穿，导致涂覆RTV的盘形绝缘子陡波击穿性能下降。.项目成果明确了现行陡波试验方法中规定的试验电压幅值对涂覆RTV的盘形绝缘子不适用，为陡波试验标准的修订提供了重要理论依据，也为涂RTV盘形绝缘子的选用和其长期运行可靠性提供了重要理论依据。