【作者】 翟鹏飞；

【导师】 彭玉峰；

【作者基本信息】 河南师范大学 ， 工程硕士（专业学位）， 2021， 硕士

【摘要】 复合硅橡胶作为绝缘子的重要组成材料,在输电线路上有着举足轻重的地位。复合硅橡胶又名甲基乙烯基硅橡胶,分子结构呈螺旋状,结构比较稳定。然而复合硅橡胶长期在外界环境的影响下,绝缘老化是无法避免的。从而导致复合硅橡胶会出现裂纹、憎水性以及耐污闪电压大幅度降低,致使复合硅橡胶内部被击穿、污闪等现象发生,严重影响了电网线路运行和维护。本文主要研究不同温度下、高电压对复合硅橡胶的绝缘性能影响,主要研究如下:(1)分析了复合硅橡胶分子体积电阻率受温度的变化,发现复合硅橡胶的体积电阻率随着温度的升高而逐渐降低且下降的趋势逐渐减缓,从微观上揭示了复合硅橡胶分子键长的变化。(2)分析了复合硅橡胶分子微观结构原子之间键长、键角随电场强度的变化,发现了复合硅橡胶分子内部温度先增大再减小,分子能量朝着最小化的方向减小,分子的化学键缩短,分子中的原子间相互靠近,分子运动非常剧烈并慢慢达到稳定,揭示了电场对复合硅橡胶的内部温度的影响。(3)分析了复合硅橡胶分子弹性性能受温度、压强的变化,发现了在同温度体系下,随着压强的增大,弹性模量越小,材料表现的柔性就越强;泊松比值随着压强的增大而逐渐增大,当压强相同时,在500K时,泊松比反而随着温度的升高而降低,原因在于此时复合硅橡胶分子状态处于橡胶态,在0.01GPa时,受压强影响较大,使泊松比值增大,揭示了温度及压强对复合硅橡胶分子弹性性能、泊松比值的变化。(4)分析了复合硅橡胶分子分子链运动受温度、压强的变化,发现了随着时间步数的增加,MSD值一直逐渐增大,分子链的运动呈现非线性的变化趋势,在同等温度下,压强越大,分子链的运动能力减弱。在同等压强条件下,温度越高,分子的运动能力越剧烈,同时由于膨胀,分子间距增加,高分子内部自有体积增加,而分子链运动能力越强力学性能越低,从微观上揭示了不同温度、压强对分子链运动的影响。通过研究外电场、温度及压强对复合硅橡胶的绝缘老化影响,掌握其分子结构、化学键长、弹性模量等参数变化规律,揭示了高电压对复合硅橡胶的绝缘击穿机理。研究结论对掌握不同温度、高压环境下复合硅橡胶的绝缘性能变化规律提供一定的理论依据,对诊断复合硅橡胶的绝缘性能具有潜在的应用价值。更多还原

【Abstract】 As an important component of insulators,composite silicone rubber plays an important role in a transmission line.Composite silicone rubber,also known as methyl vinyl silicone rubber,which has a helical molecular structure and relatively stable structure.However,under the influence of external environment for a long time,insulation aging of composite silicone rubber cannot be avoided.As a result,the cracks,hydrophobicity,and anti pollution flashover voltage of it will be greatly reduced,resulting in the internal breakdown and pollution flashover of the composite silicone rubber,which seriously affects the operation and maintenance of power grid lines.In this paper,the effects of temperature and high voltage on the insulation properties of composite silicone rubber were studied:(1)The change of molecular volume resistivity of composite silicone rubber affected by temperature was analyzed.it was found that the volume resistivity of composite silicone rubber decreased gradually with the increase of temperature,and the decreasing trend slowed down gradually,the change of molecular bond length of composite silicone rubber was revealed microscopically.(2)The change of bond length and bond angle with electric field strength of the microstructure atoms of the compound silicone rubber was analyzed,it is found that the internal temperature of composite silicone rubber increases first and then decreases,the molecular energy decreases towards the minimum,the chemical bond of the molecule shortens,the atoms in the molecule are close to each other,and the molecular motion is very violent and gradually reaches stability,the effect of electric field on the internal temperature of the composite silicone rubber was revealed.(3)The changes of molecular elastic properties of composite silicone rubber under temperature and pressure were analyzed,it was found that with the increase of pressure at the same temperature,the smaller the elastic modulus,the stronger the flexibility of the material;The Poisson’s ratio increases with the increase of pressure,when the pressure is the same,at 500 K,the Poisson’s ratio decreases with the increase of temperature,the reason is that the molecular state of the composite silicone rubber is in the rubber state,at 0.01 GPa,the pressure has a greater influence on the Poisson’s ratio,which reveals the changes of temperature and pressure on the molecular elastic properties and Poisson’s ratio of the composite silicone rubber.(4)The changes of the bond length and angle between the atoms of the molecular structure of the composite silicone rubber with the electric field strength were analyzed,it was found that with the increase of time steps,the MSD value increased gradually,and the movement of molecular chain showed a nonlinear trend.At the same temperature,the higher the pressure,the weaker the movement ability of molecular chain,under the same pressure,the higher the temperature is,the stronger the molecular motion ability is,at the same time,due to the expansion,the increase of molecular spacing,the internal volume of polymer increases,and the stronger the molecular chain motion ability is,the lower the mechanical properties are.By studying the effects of external electric field,temperature,and pressure on the insulation aging of composite silicone rubber,the variation rules of its molecular structure,chemical bond length,elastic modulus and other parameters were mastered,and the insulation breakdown mechanism of composite silicone rubber under high voltage was revealed.The research results provide a theoretical basis for understanding the change of insulation properties of composite silicone rubber under different temperature and high voltage environment,and have potential application value for diagnosing the insulation properties of composite silicone rubber.更多还原