油纸绝缘老化评估的Davidson-Cole模型参数提取方法

针对目前变压器油纸绝缘老化状态评估中的纸板聚合度测定破坏性取样、介电响应法测量没有定量判据等问题,提出一种基于Davidson-Cole模型的现场绝缘老化状态定量评估方法。首先仿真研究Davidson-Cole模型参数提取方法,借助现场测量的去极化电流数据,计算出油纸绝缘等值电路参数与频域复介电常数,并利用所得数据绘制Davidson-Cole图,采用多变量最小二乘拟合方法得出松弛时间、介电常数变化量等Davidson-Cole模型参量。实验研究了油纸绝缘不同老化程度的Davidson-Cole模型,采用非线性拟合方法对其老化状态进行Davidson-Cole模型参量提取并分析参数变化,研究结果表明,模型参数与老化程度有直接关系,仿真结果与实验结果一致,对变压器油纸绝缘老化状态评估有参考价值。

Parameters extraction of Davidson-Cole model on aging assessment of oil-paper insulation

Aiming at problems of destructive sampling for measuring polymerization degree of insulating board,non-quantitative criterion for dielectric response measurement in present aging assessment of transformer oil-paper insulation,a quantitative on-site insulation assessment method was proposed on the basis of Davidson-Cole model.The extraction method of Davidson-Cole model parameters was studied.Using the on-site testing data of depolarization current,equivalent circuit parameters and frequency domain complex permittivity of oil-paper insulation were calculated,and Davidson-Cole graphs was plotted.The Davidson-Cole model parameters,such as relaxation time,permittivity change,were fitted by using multivariable least squares method.The Davidson-Cole model parameters with difference aging degree in oil-paper insulation were investigated,meanwhile,the extraction method of nonlinear fitting was adopted,and changing rules of Davidson-Cole model parameters were analyzed in detail.It is shown that Davidson-Cole model parameters have some relationship with the degree of aging,and the simulation results are consistent with experimental results.The study is helpful to aging assessment of oil-paper insulation in power transformers.