基于电应力损伤特征值的XLPE绝缘电压耐受指数评估方法研究

Study on evaluation method of XLPE insulation voltage endurancecoefficient based on electrical stress damage characteristic value

XLPE绝缘的电压耐受指数n表征绝缘电寿命特性,对加速寿命试验中获取的失效数据进行分析可以获取n值,然而,加速寿命试验中的外施场强与试验所获失效数据的分析方法影响n值的准确性。本文研究电压耐受指数n的评估方法,对XLPE绝缘试样分别进行恒定应力试验与步进应力试验,提出基于损伤特征值的试验数据分析方法,该方法通过损伤矩阵建立试验中累积损伤阈值(Dc)与n的映射关系,以矩阵秩的变化作为n值的选取依据。结果表明:本文所提方法在恒定应力试验中获取的XLPE绝缘电压耐受指数n2=12.43,在步进应力试验中获取的XLPE绝缘电压耐受指数n3=12.04,较线性拟合获取的XLPE绝缘电压耐受指数n1=12.83仅相差3%与6%,且本文所提方法能够节省75%以上的试验时间,验证了该方法的有效性。

The voltage endurance coefficient n of XLPE insulation can characterize the electrical life characteristics of the insulation,and the n value can be obtained by analyzing the failure data obtained from the accelerated life test.However,the accuracy of the n value is affected by the applied field strength in the accelerated life test and the analysis method of the failure data obtained in the test.In this paper,the evaluation method of voltage endurance coefficient n was studied.The constant stress test and the step stress test were conducted on XLPE insulation samples,respectively,and a test data analysis method based on damage eigenvalues was proposed.This method established the mapping relationship between accumulated damage threshold(Dc)and n in the test through the damage matrix,and used the change of matrix rank as the selection criteria of n value.The results show that according to the proposed method,the XLPE insulation voltage endurance coefficient n2 obtained in constant stress test is 12.43 and n3 obtained in step stress test is 12.04,which compare with the XLPE insulation voltage endurance coefficient n1 of 12.83 obtained by linear fitting,the difference is only 3%and 6%.Moreover,the proposed method can save more than 75%of the test time,which verifies the effectiveness of the method.