Improved DC flashover performance of epoxy insulators in SF6 gas by direct fluorination
Improved DC flashover performance of epoxy insulators in SF6 gas by direct fluorination
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DOI：
10.1109/tdei.2017.006112
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发表时间：
2017-04
影响因子：
3.1
通讯作者：
L. Que;Z. An;Yong Ma;Danli Xie;F. Zheng;Yewen Zhang
中科院分区：
文献类型：
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作者：
L. Que;Z. An;Yong Ma;Danli Xie;F. Zheng;Yewen Zhang
为了证明直接放电对改善环氧绝缘子在SF6气体中直流闪络性能的有效性，同时也为固体绝缘子表面电导率的重要性提供证据，制备片状和截头圆锥形环氧树脂样品，并在实验室不锈钢容器中使用具有12.5%（重量）的F2/N2混合物氟化通过ATR-FTIR和SEM技术对氟化表面层的物理化学特性进行了评估，结果表明表面层发生了实质性的化学改性，其厚度为0.89 μm，表面粗糙。此外，正如预期的基础上，以前的研究，表面氟化样品的表面电性能的测量，相比于未氟化的，揭示了四个数量级更高的表面电导率和更快的衰减后电晕充电的表面电位。在0.1MPa的SF6气体中，对截锥试样进行了直流闪络试验，试验前后电压逐步升高。闪络试验结果表明，直流闪络电压有一定的改善。例如，在63.2%概率下的闪络电压或电压阶跃持续2 min的平均闪络电压，在电压阶跃之后增加了13.8%或13.6%。性能的改善主要归因于由于氟化层的高导电性，沉积在表面氟化样品上的电荷容易从气相中泄漏和分散。闪络试验结果还显示了电压阶跃持续时间对闪络电压和闪络电压增长率的影响。这意味着即使快速气相充电的时间常数也应该大于2 min，并且在原始样品和氟化样品之间应该存在不同的不均匀表面传导的影响。
In order to prove the effectiveness of direct fluorination in improving dc flashover performance of epoxy insulators in SF6 gas and also to provide evidence for the importance of surface conductivity of solid insulators, sheet-shaped and truncated cone epoxy samples were prepared and were fluorinated in a laboratory stainless vessel using a F2/N2 mixture with 12.5% F2 by volume at 0.1 MPa and 85 °C for 30 min. Physicochemical characteristics of the fluorinated surface layer were evaluated by ATR-FTIR and SEM techniques, and the results showed substantial chemical modification of the surface layer, which has a thickness of 0.89 μm and a roughened surface. Further, as expected on the basis of previous studies, measurements of surface electrical properties of the surface fluorinated sample, compared to the unfluorinated one, revealed a four orders of magnitude higher surface conductivity and a much more rapid decay of surface potential after corona charging. Dc flashover tests were performed on the truncated cone samples in SF6 gas at 0.1 MPa with a stepwise increasing voltage before and after the fluorination. The flashover test results showed a definite improvement in dc flashover voltage. For example, the flashover voltage at 63.2% probability or the mean flashover voltage for 2 min duration of the voltage step increased by 13.8% or 13.6% after the fluorination. The performance improvement is mainly attributed to easy leakage and dispersion of the charge deposited on the surface fluorinated sample from the gas phase, due to high conductivity of the fluorinated layer. The flashover test results also showed the influences of the duration of the voltage step on the flashover voltage and on the increase rate of flashover voltage. This means that even the time constant of the fast gas phase charging should be larger than 2 min, and that there should be different influences of the inhomogeneous surface conduction between the virgin sample and the fluorinated sample.