Identification of Dielectric Response Equivalent Circuit of Transformer's Oil-Paper Insulation Based on Quadratic Differential Decomposition Spectroscopy of Frequency Domain Spectroscopy
Lin Zhiyong1,2, Li Ronghua1,2, Huang Guotai3, Deng Dongping4, Zhang Damin1,2
1. School of Electrical Engineering and Automation Xiamen University of Technology Xiamen 361024 China; 2. Xiamen Key Laboratory of Frontier Electric Power Equipment and Intelligent Control Xiamen 361024 China; 3. Fujian Electric Power Supplies Limited Fuzhou 350003 China; 4. State Grid Zhangping Electric Power Supply Company Longyan 364400 China
Abstract：This paper presents a novel approach in addressing the challenges where the number of polarization branches in equivalent circuits is often assumed, and parameter identification requires complex iterative optimization algorithms. By analyzing the relationship between the extended Debye model equivalent circuit and frequency domain spectroscopy characteristics, this paper researches the real part of the polarized complex capacitance. This study transforms and reconstructs it to create the quadratic differential spectral lines of the real part of the polarized complex capacitance. The characteristics of these sub-spectral lines are analyzed as follows: (1)Each sub-spectral line exhibits a unique peak point, gradually decaying to zero on both sides of the peak. The sub-spectral lines shift to the right as the time constant decreases. (2)The spectral line comprises several sub-spectral lines with different time constants. The number of peak points corresponds to the number of polarization branches in the extended Debye equivalent model. (3)Sub-Spectral Lines: The previous sub-spectral line significantly influences the subsequent one, while the latter has minimal impact on the peak of the former. (4)By performing spectral decomposition starting from the first peak point, the characteristics of each sub-spectral line can be obtained. Based on the characteristics of these sub-spectral lines, this paper proposes a method to determine the number of polarization branches of the equivalent circuit by using the number of peak points of the quadratic differential spectral line of the real part of the polarization complex capacitance, and a method of using the coordinates of the peak points of the sub-spectral lines to determine the equivalent circuit parameters. Due to the significance and uniqueness of each peak point, this method can avoid the problems of presetting the number of polarization branches and the non-uniqueness of the identification results in the existing parameter identification methods, thus improving the accuracy of parameter identification. this paper proposes the parameter identification steps based on the frequency domain dielectric spectrum quadratic differential decomposition spectroscopy method. To verify the reliability of the proposed method, the real part of the polarized complex capacitance of a transformer is first identified by the proposed method for the quadratic differential decomposition spectroscopy and equivalent circuit parameters. Then, to verify the applicability of this method to transformers with different aging states, the polarization complex capacitance real part method is studied for multiple transformers with varying states of aging. To evaluate the effectiveness of this method for transformers in various aging states, the quadratic differential decomposition spectroscopy technique was applied to multiple transformers with differing conditions. The findings are as follows: This method achieves an impeccable 100% accuracy in identifying the number of polarization branches within the equivalent circuit. The technique surpasses 98% accuracy in identifying equivalent circuit parameters. The correlation between the spectrum obtained through spectral decomposition and the actual measured values exceeds 97%, the quadratic differential spectral line of the real part of the polarized complex capacitance can accurately and uniquely identify the equivalent circuit parameters. This approach effectively enhances the reliability and efficiency of identifying these parameters by utilizing the characteristics of the frequency domain spectroscopy. Additionally, it offers a novel method for accurately diagnosing the aging state of transformer oil-paper insulation.
林智勇, 李荣华, 黄国泰, 邓东平, 张达敏. 基于频域二次微分解谱法的油纸绝缘等效电路参数辨识[J]. 电工技术学报, 2025, 40(15): 4966-4975.
Lin Zhiyong, Li Ronghua, Huang Guotai, Deng Dongping, Zhang Damin. Identification of Dielectric Response Equivalent Circuit of Transformer's Oil-Paper Insulation Based on Quadratic Differential Decomposition Spectroscopy of Frequency Domain Spectroscopy. Transactions of China Electrotechnical Society, 2025, 40(15): 4966-4975.
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