电缆接头绝缘用硅橡胶热老化及超声特性

Thermal Aging and Ultrasonic Characteristics of Silicone Rubber for Cable Joint Insulation

硅橡胶凭借其高弹性与优良的电气性能,广泛应用于预制式交联聚乙烯高压电缆接头的主绝缘中。但长时间的异常温升会加速材料的老化,导致其相关性能的下降,从而引发事故。为此设计并开展了预制式高压电缆接头绝缘用硅橡胶的加速热老化试验,对比分析了其热老化前后的微观结构、力学性能、电学性能与声学性能。结果表明:热老化后电缆接头硅橡胶绝缘残余的交联副产物挥发,侧链有机含量降低,主链间发生交联;随着老化温度与时间的增大,试样的断裂伸长率与拉伸强度逐渐下降,杨氏模量逐渐上升,导致柔顺性变差,材料逐渐硬化,弹性丧失;体积电阻率与相对介电常数略有上升,变化不明显,介电损耗因数随热老化的进行而降低;热老化后电缆接头绝缘用硅橡胶的超声声速显著增大,测试结果符合相关理论公式,与杨氏弹性模量的变化趋势良好对应,在评估电缆接头硅橡胶绝缘的热老化状态有广阔的应用前景。

With its high elasticity and excellent electrical properties, silicone rubber is widely used in the main insulation of prefabricated cross-linked polyethylene high-voltage cable joints. However, the abnormal temperature rise for a long time will accelerate the aging of the material, resulting in the decline of its related properties, thereby causing accidents.In this paper, an accelerated thermal aging test of silicone rubber for insulation of prefabricated high-voltage cable joints was designed and carried out. The microstructure, mechanical properties, electrical properties and acoustic properties of silicone rubber after thermal aging were compared and analyzed. The results show that the residual crosslinking by-products of silicone rubber insulation of cable joints volatilize after thermal aging, the organic content of side chain decreases, and the crosslinking occurs between main chains. With the increase of aging temperature and time, the elongation at break and tensile strength of the samples will decrease, and the Young’s modulus will increase gradually, resulting in poor compliance, hardening and loss of elasticity. The volume resistivity and relative permittivity will increase slightly,and the dielectric loss factor will decrease with the progress of thermal aging. The ultrasonic velocity will increase significantly after thermal aging, and the test results are in accordance with the relevant theoretical formula, which corresponds well with the change trend of Young’s elastic modulus. It has a broad application prospect in evaluating the thermal aging state of silicone rubber insulation of cable joints.