基于修正Debye模型的油浸绝缘纸不均匀老化时域介电特性

Time Domain Dielectric Properties of Oil-impregnated Paper with Non-uniform Aging Based on Modified Debye Model

变压器内部存在的温度梯度导致油浸绝缘纸不均匀老化,为研究油浸绝缘纸在温度梯度下的时域介电特性,在实验室搭建油浸绝缘纸不均匀老化试验平台,测定试样老化过程中聚合度变化规律和极化/去极化电流曲线,并对其进行等效模型参数辨识,得到如下结论：发热端附近油浸绝缘纸极化/去极化电流均向左上方平移,纸内电导率提高,极化的响应速率加快;发热端附近等温区极化电阻和时间常数最小,修正Debye模型和扩展Debye模型参数存在关联关系;扩展Debye模型只能评估油纸绝缘平均老化程度,用其进行绝缘状态评估时会出现＂老化被高估区＂和＂老化被低估区＂,发热端附近绝缘实际状况比评估结果恶劣将近50%。研究结果为将极化/去极化电流法更精确地应用于实际变压器油纸绝缘状态评估提供了参考。

Temperature gradient inside oil-immersed transformers will cause non-uniform aging of a paper.In order to study the time domain dielectric property of oil-paper insulation under temperature gradient,we established a test platform in laboratory.We measured the polymerization degree and polarization/depolarization currents of test samples.Finally we identified its equivalent model parameters.The results indicate that polarization/depolarization currents of insulation paper near heat source move to the top left with higher conductivity and higher polarization response speed.The polarization resistance and time constant in isothermal zone near heat source have minimum values,and there exists a relation between parameters from the extended Debye model and modified Debye model.The extended Debye model can only assess average aging condition of the insulation paper,and there exist an aging overvalued area and aging undervalued area when using the extended Debye model for paper condition assessment with up nearly 50% deviation.The results provide a reference for the polarization/depolarization current method to more accurately be applied to condition assessment of transformer oil-paper insulation.