变压器油纸绝缘的介电响应特性研究——加速热老化的介电谱

为了研究变压器油纸绝缘老化的介电响应特征量,本文对油纸绝缘试品进行了加速热老化,并在老化的不同阶段开展了相同试验温度下的极化、去极化电流(PDC)和频域谱(FDS)试验。在PDC试验数据的基础上,引入时域介电谱理论,提取其峰值和峰值时间常数作为老化特征量,研究了该特征量与绝缘老化的关系。结果表明,绝缘老化使PDC试验的极化及去极化电流曲线均明显上移,FDS试验的复电容实部和虚部曲线在低频段均向右上平移,时域介电谱曲线则向左上方平移,这是由于老化引起水分、有机酸等含量的增加以及对纤维素结构的破坏,提高了油纸绝缘间夹层介质界面极化的强度和响应速度而造成的。在本文的试验条件下,油纸绝缘的时域介电谱对其老化反应灵敏,可定量反映油纸绝缘老化程度的变化情况,其峰值和峰值时间常数可考虑用作表征油纸绝缘老化程度的特征量。

Investigation of Dielectric Response Characteristics of Transformer Oil-Paper Insulation—Dielectric Spectroscopy of Acceleratedly Thermal Aging

For achieving the characteristic parameters of dielectric response phenomena of transformer oil-paper insulation aging,the oil-impregnated pressboard samples were acceleratedly thermally aged.The dielectric response tests,including polarization and depolarization current(PDC) and frequency domain spectroscopy(FDS),were performed on the samples with different aging degree at the same temperature.The time-domain dielectric spectroscopy theory was introduced to investigate the aging characteristic parameters of dielectric response based on the PDC data.The results reveal that,with sample aging,its polarization and depolarization currents shift upwards to higher value,the real and imaginary capacitance and dissipation factor shift upwards and rightwards at lower frequencies,and the time-domain dielectric spectroscopy shifts upwards and leftwards.It is considered that aging process induces the increment of water and organic acids content and the rapid degradation in amorphous regions of cellulose paper,which greatly impacts the oil-paper interfacial polarization and enhances its intensity and response speed.It is confirmed that time-domain spectroscopy is sensitive to the aging condition of oil-paper insulation,and can quantitatively distinguish the change of aging condition to some degree.The peak value and peak time constant of time-domain spectroscopy can be considered as the characteristic parameters to evaluate the aging condition of oil-paper insulation.