Wen Hao, Zhang Xiaoxing, Xia Rong, Yang Zilai, Wu Yunjian
School of Electrical Engineering, Wuhan University, Wuhan 430072, China.
Wuhan Branch, China Electric Power Research Institute Co., Ltd., Wuhan 430074, China.
Materials (Basel). 2018 Dec 26;12(1):75. doi: 10.3390/ma12010075.
As a promising alternative for pure SF₆, the mixture of SF₆/N₂ appears to be more economic and environment-friendly on the premise of maintaining similar dielectric properties with pure SF₆. But less attention has been paid to the thermal properties of an SF₆/N₂ mixture, especially with insulation materials overheating happening simultaneously. In this paper, thermal decomposition properties of epoxy resin in SF₆/N₂ mixture with different SF₆ volume rates were studied, and the concentrations of characteristic decomposition components were detected based on concentrations change of some characteristic gas components such as CO₂, SO₂, H₂S, SOF₂, and CF₄. The results showed that thermal properties of 20% SF₆/N₂ (volume fraction of SF₆ is 20%) mixture has faster degradation than 40% SF₆/N₂ mixture. As ratio of SF₆ content decreases, thermal stability of the system decreases, and the decomposition process of SF₆ is exacerbated. Moreover, a mathematical model was established to determine happening of partial overheating faults on the epoxy resin surface in SF₆/N₂ mixture. Also thermal decomposition process of epoxy resin was simulated by the ReaxFF force field to reveal basic chemical reactions in terms of bond-breaking order, which further verified that CO₂ and H₂O produced during thermal decomposition of epoxy resin can intensify degradation of SF₆ dielectric property.
作为纯六氟化硫（SF₆）的一种有前景的替代物，SF₆/氮气（N₂）混合物在与纯SF₆保持相似介电性能的前提下，似乎更经济且环保。但人们对SF₆/N₂混合物的热性能关注较少，尤其是在绝缘材料同时发生过热的情况下。本文研究了不同SF₆体积比的SF₆/N₂混合物中环氧树脂的热分解特性，并基于二氧化碳（CO₂）、二氧化硫（SO₂）、硫化氢（H₂S）、二氟化亚砜（SOF₂）和四氟化碳（CF₄）等一些特征气体成分的浓度变化，检测了特征分解成分的浓度。结果表明，20% SF₆/N₂（SF₆的体积分数为20%）混合物的热性能比40% SF₆/N₂混合物降解得更快。随着SF₆含量比例降低，系统的热稳定性下降，SF₆的分解过程加剧。此外，建立了一个数学模型来确定SF₆/N₂混合物中环氧树脂表面局部过热故障的发生情况。还用ReaxFF力场模拟了环氧树脂的热分解过程，以从键断裂顺序方面揭示基本化学反应，这进一步证实了环氧树脂热分解过程中产生的CO₂和水会加剧SF₆介电性能的降解。
