热老化交联聚乙烯绝缘状态评估和介电参数计算的新型电荷表征和分析方法*

Study on Dynamic Charge Characteristics of Thermal Aging XLPE Based on Direct Current Integral Charge Technique

  • 摘要: 基于电流积分电荷量(DCIC-Q(t))技术研究了不同热老化时间下交联聚乙烯(XLPE)的动态电荷特性。对XLPE薄片试样施加电场,观察其电荷量随电场强度的变化规律,提出电荷量之比k作为判定空间电荷积累的依据;通过瞬时充电电荷Q0与电压的线性关系拟合得到XLPE电容,进一步计算获得介电常数;提出松弛时间τ与介电常数、电导率之间的关系,获得不同电场下电导率变化曲线。随着热老化时间的增加,XLPE绝缘动态电荷比值、介电常数以及电导率先略有增加,然后迅速上升。这说明短时间的热老化对XLPE的电性能影响不明显,但热老化时间的增加会导致电缆绝缘电气性能发生明显劣化。XLPE片状试样的研究为整体电缆老化评估提供试验依据。

     

    Abstract: The dynamic charge characteristics of XLPE under different thermal aging times are studied using DCIC-Q(t) technique. The curves of dynamic charge under different applied voltage is obtained, and the concept of charge ratiok is put forward to judge the injection and accumulation of space charge. XLPE capacitance is obtained by fitting the linear relation between instantaneous chargeQ0 and voltage, and the variation rule between dielectric constant and thermal aging is further calculated and analyzed. The relationship between relaxation time and dielectric constant and conductivity is determined, and the variation curve of the conductance under different electric fields is obtained. The change of dynamic charge ratio, dielectric constant and conductivity of XLPE samples are analyzed, and it is found that with the thermal aging process, the three unchange at first and then increase quickly, indicating that the thermal aging of a short time has a little effect on the electrical performance of XLPE insulation, but the increase of aging time would degrade it. The XLPE lamellar experiment provides a theoretical basis for the whole cable aging evaluation model.

     

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