基于放电特性的动车组乙丙橡胶电缆绝缘老化表征参量及灵敏性研究

搭建动车组乙丙橡胶(EPR)电缆绝缘放电检测系统,制备4组分别近似等效EPR电缆绝缘在90℃下运行960,1 920,7 680和15 360 h的绝缘样品,在柱板电极系统下对其进行局部放电测试,将放电过程分为放电起始、放电发展、放电平稳和放电激发(S1-S4) 4个阶段;计算正负半周放电总能量差ΔW,分析放电量q-相位φ归一化谱图的偏斜度Sk和正负偏斜最大相似度|ΔSk|min;对最大放电量qmax作改进型Z-score规范化,计算规范化正值z+的频数比例P (z+)和最大正值zmax。结果表明:老化程度较深的EPR电缆绝缘,ΔW在S3阶段之前波动更明显,且在S3阶段ΔW<0;表征参量Sk随放电发展呈现递减速度逐渐变缓的单调性,能明显区分放电阶段,但对EPR电缆绝缘老化程度反应不够灵敏;表征参量|ΔSk|min用于表征EPR电缆绝缘老化程度反应较灵敏,当S2和S3阶段的P (z+)及zmax表征参量辅助使用时,|ΔSk|min的灵敏性显著提高。

Research on Characteristic Parameters and Sensitivity of Insulation Aging of Ethylene-Propylene Rubber Cable for EMU Based on Discharge Characteristics

The insulation and discharge detection system of Ethylene-Propylene Rubber(EPR) cable for EMU was set up. 4 sets of insulation samples of approximately equivalent EPR cable insulation operated at 90 °C for 960, 1 920, 7 680 and 15 360 h respectively were prepared. The partial discharge test was carried out under the column plate electrode system. The discharge process was divided into 4 stages: discharge initiation, discharge development, discharge stabilization and discharge excitation(S1-S4). The total energy difference ΔW of the positive and negative half-cycle discharge was calculated. The skew Sk and the maximum similarity of the positive and negative skew |ΔSk|min in the normalized spectrum of discharge amount q and phase φ were analyzed.The Z-score normalization of the maximum discharge qmaxwas improved. The frequency ratio P(z+) of the normalized positive value z+ and the maximum positive value zmax were calculated. Results show that, for the EPR cable insulation with deeper aging, ΔW fluctuates more significantly before S3 and ΔW < 0 at S3. The characteristic parameter Skshows a monotonicity of decreasing speed and decreasing gradually with the development of discharge, which can clearly distinguish the discharge stage, but it is not sensitive enough to the aging degree of EPR cable insulation. The characteristic parameter |ΔSk|min is more sensitive to characterize the insulation aging degree of EPR cable. When the P(z+) and zmax characteristic parameters in S2 and S3 stages are used in conjunction, the sensitivity of |ΔSk|min is significantly improved.