基于极化电流的挤压力和热应力作用下电缆用乙丙橡胶绝缘性能的研究

Research on Insulation Performance of EPDM for Cables Under Extrusion Pressure and Thermal Stress Based on Polarization Current

为了明确电应力、热应力和机械应力共同作用对乙丙橡胶绝缘性能的影响,本研究制备了乙丙橡胶(EPDM)绝缘试样,分别测试了温度为30~120℃、挤压力为0~1.0 MPa和场强为1~25 kV/mm时乙丙橡胶的极化电流。为了评估乙丙橡胶的绝缘性能,引入吸收比K。通过极化电流中的稳态电导电流,计算得到试样的准稳态电导电流密度和电导率。结果表明:乙丙橡胶的绝缘性能与温度和电场强度呈负相关,其中在低场强区,试样的电导特性符合欧姆电导特性,在高场强区符合空间电荷限制电流机制。通过计算得出乙丙橡胶的载流子迁移率,分析发现载流子迁移率随着挤压力的升高先减小后增大,最终导致乙丙橡胶的绝缘性能发生变化。

In order to clarify the interaction of electrical stress, thermal stress and mechanical stress on the insulating properties of ethylene propylene diene monomer(EPDM), we prepared EPDM samples and measured the polarization current of the sample at temperatures of 30-120℃, pressures of 0-1.0 MPa, and electric field strengths of 1-25 kV/mm, respectively. For further evaluating the insulation performance of EPDM, the absorption ratio(K) was introduced. Based on the steady-state electrical conduction currents in the polarization currents, the quasi-steady-state electrical conduction current densities and conductivities of the sample were calculated. The results show that the insulation performance of EPDM is negatively correlated with temperature and electric field strength. In the low-field-strength area, the electrical conductivity of the sample conforms to the ohmic conductivity characteristics;in the high-field-strength area, conductivity conforms to the space charge limited current mechanism. By calculating the carrier mobility of EPDM, it is found that the carrier mobility decreases at first and then increases with the increase of pressure, which leads to the change of the insulation performance of EPDM.