充油电缆终端用PIB与SR/EP的相容性研究

Research on Compatibility Between PIB and SR/EP for Oil-filled Cable Terminals

高压充油电缆终端中既有硅橡胶(SR)、三元乙丙橡胶(EP)和绝缘自粘带等固体介质,也有二甲基硅油或聚异丁烯(PIB)等液体介质,液固介质的相容性直接关系到高压充油电缆终端的绝缘性能的稳定性以及工作的可靠性。文中首先在120℃下开展了168 h的PIB与SR和EP的相容性试验,接着测量了液固介质的理化性能与电气性能指标,根据不同老化时间下液固介质,以及相同老化时间下不同液固介质组合之间理化和电气性能的变化特征,并结合电介质性能指标的物理含义,综合比较后得到PIB和SR的相容性优于PIB与EP的相容性。为明确PIB与SR和EP的相容性机理,文中进一步采用Materials Studio软件,构建了液固介质的分子模型及界面结构,利用分子动力学获得了不同温度下PIB-SR界面和PIB-EP界面的焓值;计算表明,在温度由363 K升高到393 K时,PIB-EP界面的焓变小于0,有溶解趋势,而PIB-SR界面的焓变值大于0,因此,PIB-SR界面较PIB-EP界面更具稳定性。文中结论可为高压充油电缆中液固介质的选择提供理论依据。

There are not only such solid medium as silicone rubber(SR),EPDM rubber(EP)and insulating self-adhesive tape,but also such liquid medium as dimethyl silicone oil or polyisobutene(PIB)in high voltage oil-filled cable terminals.The compatibility of liquid and solid mediums is directly related to the stability of insulation performance and reliability of high voltage oil-filled cable terminals.In this paper,the compatibility test among PIB,SR and EP at 120℃is performed for 168 h firstly,then the physical and chemical properties and electrical properties of liquid solid medium index is measured.It is concluded that the compatibility of PIB and SR is superior to that of PIB and EP in accordance with the physical and chemical performance variation characteristics of the liquid and solid medium at different aging time and the that of different liquid and solid medium combination at the same aging time,as well as in combination with the physical meaning of the dielectric performance and comprehension comparison.For defining the compatibility mechanism among PIB,SR and EP,the Materials Studio software is used further in this paper to construct the molecular model and interface structure of liquid and solid medium.The enthalpy values of PIB-SR interface and PIB-EP interface at different temperatures are obtained by molecular dynamics technology.The calculation result shows that when the temperature is increased from 363 K to 393 K,the enthalpy variation of PIB-EP interface is less than 0 and tends to dissolve,while the enthalpy variation of PIB-SR interface is more than than 0.Therefore,the PIB-SR interface is more stable than the PIB-EP interface.The conclusion in this paper can provide a theoretical basis for the selection of liquid and solid medium in high voltage oil-filled cable.