变压器油纸绝缘老化介电谱特性及特征量研究

Dielectric spectroscopy and characteristic parameters of transformer oil-paper insulation aging

为了研究系统的老化状态和水分含量对油纸绝缘介电响应特性的影响,测量了在相同试验条件下,经过相同处理油浸纸板试样的去极化电流、频域介电谱以及含水率,获得时频域的介电响应特性曲线,利用最小二乘法、扩展Debye模型对去极化电流曲线进行拟合,分析拟合结果,得到热老化对松弛时间较长的扩展Debye支路影响较为明显;利用Davidson-Cole模型对不同老化程度及不同含水率试样的频域介电谱实测曲线进行拟合,并提取介电特性相关参数,得到松弛时间随老化程度加深和含水率的增大均呈减小趋势,此变化规律可用于对变压器油纸绝缘老化状态和含水率的评估。

In order to research the influence of aging and moisture content on dielectric response characteristics of oil-paper insulation,the depolarization current,frequency domain dielectric spectroscopy and moisture content of the test sample of oil immersed pressboard were measured under the same conditions.The dielectric response characteristic curves in time and frequency domain were obtained.The least square method and the extended Debye model was used to fit the depolarization current.It is obvious from the results that the thermal aging has an important effect on the Debye RC branch with longer relaxation time.The Davidson-Cole model was used to fit the measured curves in frequency domain dielectric spectroscopy with different aging state and different moisture content,and used to extract characteristic parameters.It is shown that the relaxation time decreases with the increasing of aging and moisture content,which can be used to assess the aging and moisture content of oil-paper insulation in power transformer.