油纸绝缘中非活性硫的活化机理及影响因素研究

Strong corrosive active sulfur in the mineral insulating oil has been considered to be the main culprit to induce the insulation failures of oil-immersed power equipment. In order to protect the oil-paper insulation from sulfur corrosion, active sulfur is cleared in the refining process of crude oil. Some inactive sulfur with high antioxidant is still retained in the mineral oil to improve the oxidation stability of oil. However, the activation of inactive sulfur under the operating condition of oil-immersed power equipment and its effect on the insulation properties of oil-paper insulation are not gained attention. This project is aimed to study the activation mechanism and influential factors of inactive sulfur in oil-paper insulation. At first, Material analysis and detection methods and quantum chemical analysis are used to investigate the activation product, activation pathway and activation mechanism of inactive sulfur from the microscopic molecular level. Secondly, combined with the operation and fault conditions of oil-immersed power equipment, the activation conditions and influential factors of inactive sulfur in oil-paper insulation were further analyzed in theory, then the experimental research is conducted to verify the theoretical analysis. Finally, the inhibitory methods for the activation of inactive sulfur are explored by blocking the activation pathway and absorbing the energy required for activation. The above work will contribute to illuminate the activation mechanism of inactive sulfur under the operating condition of oil-paper insulation and provide theoretical and experimental basis to further inhibit the sulfur corrosion, which is of great value in theory and engineering.

矿物绝缘油中腐蚀活性较强的硫化物已被证实会诱发油浸式电力设备绝缘故障，在绝缘油精炼过程中会被去除。部分非活性硫因其高效抗氧化性保留于矿物绝缘油中以提高油品的氧化安定性。然而，非活性硫在油浸式电力设备运行条件下的活化问题及其对绝缘性能造成的影响并未得到关注。因此，本项目首次聚焦油纸绝缘中非活性硫的活化机理及影响因素。首先，采用材料物相检测手段及量子化学分析等，从微观分子层面探究非活性硫的活化产物、活化路径及反应机理；其次，结合油浸式电力设备的运行及故障条件，进一步从理论上分析油纸绝缘中非活性硫的活化条件，并对理论分析进行试验验证；最后，考虑从阻断非活性硫活化反应路径与吸收活化所需能量两个方面入手，探索阻断或抑制非活性硫活化的方法。项目研究成果将有助于认识非活性硫在油纸绝缘运行环境下的活化机制，为进一步抑制硫腐蚀的方法选择提供理论及实验依据，具有重要的理论和工程价值。

近年来，因油硫腐蚀问题导致油浸式电力设备绝缘劣化，进一步引发绝缘故障的问题受到了国内外学者的广泛关注。现有研究主要集中在矿物绝缘油中腐蚀活性较强的硫化物导致设备绝缘性能下降方面，并未涉及占矿物绝缘油中硫含量绝大部分的非活性硫在设备运行过程中的活化问题及其对绝缘性能造成的影响。基于此，本课题首次聚焦油纸绝缘中非活性硫的活化机理及影响因素。首先，利用分布式活化能模型，构建各类非活性硫化物的热解活化能和转化率之间的函数关系，分析其在不同升温速率下的活化能变化规律，通过热重试验析出的气体产物进入傅里叶变换红外光谱仪，获得热解过中气体产物的红外吸收峰随波数的变化规律，分析反应过程中产物官能团成分变化信息，并采用气相色谱质谱联用对非活性硫在活化过程中的气体产物成分进行分析，揭示了矿物绝缘油中的典型非活性硫噻吩类硫化物（噻吩、苯并噻吩、二苯并噻吩）在活化过程中的活化产物。其次，通过分子动力学模拟揭示了噻吩类硫化物分子中的C-S、C-H单键在热场作用下易断裂生成游离的硫离子（S2-）与氢离子（H+）等，并进一步发生聚合反应，诱发硫稳定形态的活性化，最终生成多类含硫低分子碳链产物与无机产物，包括硫化氢（H2S）与单质硫（S）等强腐蚀性低分子硫、氢气（H2）与氢离子（H）等无机产物。接着，开展了非活性硫在油纸绝缘的热、电场下的试验研究，评估非活性硫噻吩类硫化物在油纸绝缘热、电场作用下的腐蚀活性，从宏观层面揭示了油纸绝缘中的典型非活性硫的活化影响因素，获得了油纸绝缘中的典型非活性硫的活化条件。最后，研究了物理吸附和化学反应两种绝缘油处理方法对绝缘油中噻吩类硫化物的吸附效果，提出了能有效消除油中噻吩类硫化物的物理吸附剂及吸附条件，以及化学反应试剂和反应条件，为对具有油硫腐蚀风险的绝缘油再生处理实施方案提供了理论及实验依据。