基于等温松弛电流法和活化能法的110kV XLPE电缆老化状态评估

Aging State Assessment of 110 kV XLPE Cable Based on Isothermal Relaxation Current Method and Activation Energy Method

为准确判断110 k V交联聚乙烯(XLPE)电缆的老化状况,引入了等温松弛电流(isothermal relaxation current,IRC)法和活化能(activation energy,AE)法,讨论了老化因子、活化能与电缆老化状态之间的关系。结果表明:老化后电缆老化因子比未老化电缆大0.348,活化能整体降低;运行25 a电缆的老化因子比运行14 a电缆的老化因子大0.327,活化能小15.05 k J/mol,剩余寿命小30.6 a;内部陷阱增多、加深和化学键的解裂是电缆老化的主要微观表现;不同厂家生产电缆的配料体系和生产工艺存在一定的差异,致使交联聚乙烯分子间的化学结构改变而改变电缆的活化能,但不影响电缆老化的评估方式。采用等温松弛电流法和活化能法从微观方面评估电缆老化状态具有准确性和有效性,评估结果与预期符合,从电气性能和化学性能为XLPE电缆老化状态评估提供了一种有效的方法,可指导电缆和电网的维修、规划工作。

In order to accurately evaluate the aging condition of 110 kV XLPE cables, we introduced the isothermal relaxation current （IRC） method and the activation energy （AE） method to discuss the relationship about the aging factor, the activation energy, and the insulation aging state of cables. The results show that, compared with the unaged cable, the aging factor of artificially aged cable is 0.348 bigger than that of unaged cable, and its activation energy is basically lower. Compared with the cables running for 14 years, the aging factor of cables running for 25 years is 0.327 bigger, its activation energy is 15.05 kJ/mol less than that of cables running for 14 years, and its remaining life is 30.6 years less. All these show that, increasing of the internal trap＇s number and deepening of the internal trap＇s depth and the disintegration of chemical bonds are the major micro-economic performance in cable aging. There are some differences in batching system and production technology system from different manufacturers of cables, which leads to the changing of the chemical structure between XLPE molecule, and will change the cable＇s activation energy. However, the cable aging assessment methods do not vary with these changes, and assessment results is in line with expectations. From the microscopic aspects, it is accurate and valid to adopt the isothermal relaxation current method and the activation energy method to evaluate the cable aging state, which provide an effective method for the evaluation of XLPE cable＇ aging state from electrical and chemical aspect, and the guidance to repair or make a plan for the cable and the grid.