基于频域介电响应分频段优化计算的变压器油纸绝缘老化参数定量计算方法

Quantitative Calculation Method of Transformer Oil-Paper Insulation Aging Parameters Based on Frequency Dielectric Spectrum Frequency Range Optimized Calculation

变压器的稳定运行是维护电网安全的重要保证,频域介电谱中各频段可以对变压器内部油纸绝缘老化状态进行更准确的评估,而目前的评估方法多针对于单一油纸绝缘老化状态的评估,对变压器等效模型老化状态评估较少,评估软件在评估老化后变压器内部含水量时也十分不准确。为进一步满足实际工程应用,该文提出一种基于变压器等效模型,通过分频段计算得到变压器内部油纸绝缘老化状态的数值评估方法,并通过加速老化试验进行了相关验证。首先在实验室条件下通过变温介电谱测试,得到不同老化程度油浸纸板的频谱曲线,并根据"频温平移方式"计算不同老化程度油浸纸板的活化能,建立油浸纸板聚合度与活化能的定量表征方程;其次应用"反频温平移方式"得到不同测试温度下,不同老化程度油浸纸板频域介电响应基础数据;最后将绝缘纸板基础数据与变压器介电等效模型相结合并分频段进行数值迭代计算,当测试曲线与计算曲线拟合优度最佳时,可以得到变压器内部油浸纸板的聚合度、含水率、变压器油的电导率,并将其与理化性能分析结果进行对比,可得计算误差较小,因此可以有效地减小现场变压器绝缘老化评估的时间。

Stable operation of transformers is an important guarantee for the safe operation of power grids.The aging of oil-paper insulation in transformer can be evaluated more accurately by frequency-domain dielectric spectroscopy.The current evaluation methods mostly focus on the evaluation of aging status of single oil-paper insulation.The aging state assessment of transformer equivalent model is less,and the evaluation software is extremely inaccurate.In order to further meet the practical engineering application,in this paper,a numerical method for calculating the aging state of transformer oil-paper insulation based on equivalent model of transformer is presented.The relevant validation was carried out by accelerated aging test.Firstly,the variable temperature dielectric spectroscopy curves of oil-immersed pressboard with different ageing were obtained under laboratory conditions.According to frequency-temperature translation,the activation energy of oil-immersed pressboard with different aging degrees was calculated.The quantitative characterization equation of the degree of polymerization and activation energy of oil-immersed pressboard was established.Secondly,the basic data of oil-immersed pressboard at different test temperatures and aging degrees were obtained by inverted frequency temperature translation method.Finally,the influence of the transformer equivalent model structure on the frequency range of the frequency domain dielectric loss factor was analyzed.By using the proposed frequency-range numerical iteration algorithm,when the goodness of fit between test curve and calculation curve is the best,the degree of polymerization,moisture content of oil-immersed pressboard and conductivity of transformer oil in transformer equivalent XY model can be obtained.Compared with the physical and chemical performance analysis results,the error is small.It can effectively reduce the time of insulation aging assessment of transformers in the field.