基于脱陷电流时域谱的变压器油纸绝缘老化特性研究

Evaluation Method of Aging State of Oil-Paper Insulation Based on Isothermal Decay Current

变压器的稳定运行是维护电网安全的重要保证,准确评估变压器油纸绝缘的绝缘状态至关重要。本文制备了变压器油纸绝缘等效模型,并在不同温度下对老化变压器油纸绝缘等效模型的极化去极化电流进行测试,同时计算得到相应测试温度下油纸绝缘脱陷电流曲线。根据计算结果发现,测试温度越高,脱陷电流的松弛时间越小;随着测试温度升高、油纸绝缘老化程度增加,脱陷电流的时域介电谱曲线峰值出现的时间变大,其主松弛峰值、松弛时间常数也逐渐增大。为合理计算变压器油纸绝缘老化程度,本文建立了脱陷电流时域介电谱主峰值松弛时间与油纸绝缘聚合度的定量表征关系,可准确评估变压器油纸绝缘内绝缘的老化程度。

The stable operation of the transformer is an important guarantee for maintaining the safety of the power grid.It is very important to accurately assess the insulation state of oil-paper insulation of transformer.In this paper,the equivalent model of transformer oil-paper insulation was prepared,and the polarization depolarization current of the equivalent model of aging transformer oil-paper insulation was tested at different temperatures.Meanwhile,the current curves of oil-paper insulation at the corresponding test temperature was calculated.According to the calculation results,it is found that the higher the test temperature,the smaller the relaxation time of the isothermal relaxation current is.With the increase of test temperature and oil-paper insulation aging,the time for the peak value of time domain dielectric spectrum curve of the trap current to appear becomes longer,and its main relaxation peak value and relaxation time constant also gradually increase.To reasonably calculate the aging for oil-paper insulation of transformers,this paper establishes the calculation equation of main peak relaxation time and cellulose oil-impregnated pressboard cellulose,which can reasonably assess the aging of oil-paper insulation in transformer.