基于累积损伤曲线的电寿命模型步进应力试验方法及在XLPE电缆中的应用

交联聚乙烯（XLPE）的反幂函数电寿命模型（IPM）表征了XLPE电缆绝缘的长期耐压特性，包括电压耐受指数（VEC）在内的IPM模型参数是电缆绝缘设计和预鉴定试验电压选取的重要依据。步进应力试验具有耗时短、效率高的优点，适用于求取电缆样品的电寿命模型参数。然而，步进应力试验参数的选择尚无规程可参考，目前主要依靠经验和主观确定，严重影响了试验结果的有效性和可比性。将固体绝缘材料累积损伤“D-t曲线”作为判断绝缘失效机理的主要依据，分析不同试验参数下步进应力与恒定应力试验的等效性，提出适合工程应用的步进应力试验参数选取及现场试验方案。通过该方法设计绝缘厚度分别为2.8 mm和3.5 mm的2种模型电缆的步进应力试验，并获取2种模型电缆的IPM电寿命模型参数，验证该方法的可行性。

Step-Stress Test Method for Electrical Life Model Based on Cumulative Damage Curve and Its Application in XLPE Cable

The inverse power function electrical life model (IPM) of XLPE represents the long-term voltage endurance characteristics of XLPE cable insulation. The parameters of IPM model including voltage endurance coefficient (VEC) are the important basis for cable insulation design and pre-qualification test voltage selection. The step-stress test has the advantages of short time and high efficiency, and is more suitable for obtaining the electrical life model parameters of cable samples. However, there are no standards for selection of step stress test parameters. At present, it mainly depends on experience and subjective determination, which seriously affects the validity and comparability of test results. In this paper, the “D-t curve” of accumulated damage of solid insulating materials is taken as the main basis to judge the failure mechanism of insulation. The equivalence of step-stress test and constant-stress test under different test parameters is analyzed, and the step-stress test parameters and field test scheme suitable for engineering application are proposed. With this method, a step-stress test is designed for two types of model cables with insulation thickness of 2.8 mm and 3.5 mm respectively, and the parameters of IPM electrical life model for the two types of model cables are obtained, which validates the feasibility of the proposed method.