Parameters Identification and Application of Equivalent Circuit at Low Frequency of Oil-Paper Insulation in Transformer

Xie, Yiming; Ruan, Jiangjun

doi:10.1109/access.2020.2992681

Cited by 8 publications

(7 citation statements)

References 21 publications

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“…To assess the state of insulation in power transformers, the dielectric loss factor or resistance measurements determined using the absorption coefficient R60/R15 [1,2] are mostly used. New methods consisting of the measurement and analysis of relaxation phenomena in the insulation of transformers over a wide range of time or frequency are also applied.…”

Section: Introductionmentioning

confidence: 99%

Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

et al. 2020

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This article presents direct σDC and alternating σ(f) current conductivity measurements obtained by the frequency domain spectroscopy (FDS) method on cellulose-transformer oil–water nanoparticle composite with a moisture content of (5.0 ± 0.2)% by weight in a temperature range from 293.15 to 333.15 K with step of 8 K. The uncertainty of temperature maintenance during measurements was below ±0.01 K. The sample was prepared for testing in a manner as close as possible to the cellulose insulation moisturizing process in power transformers. For the analysis of the results obtained, a model of alternating and direct current hopping conductivity was used, based on the quantum phenomenon of electron tunneling between the potential wells and nanodrops of water. It was observed that on the d(logσ)/d(logf)-derived waveforms there was a clear low-frequency maximum, and a tendency to reach the next maximum in the high-frequency area was visible. On this basis it was established that the increase in conductivity takes place in two stages. It was found that the position of σ(f) waveforms in the double logarithmic coordinates is influenced by the temperature dependence both of the conductivity and of the relaxation time of the conductivity. These relationships are described with the appropriate activation energies of the conductivity and relaxation time of conductivity. Based on the analysis of experimental data using Arrhenius diagrams, average values of the activation energy of conductivity ΔWσ ≈ (0.894 ± 0.0134) eV and the relaxation time of conductivity ΔWτσ ≈ (0.869 ± 0.0107) eV were determined. The values were equal within the limits of uncertainty and their mean value was ΔW ≈ (0.881 ± 0.0140) eV. Using the mean value of the activation energy, the frequency dependence of conductivity, obtained at different temperatures, was shifted to 293.15 K. For this purpose, first the waveforms were shifted along the horizontal and then the vertical axis. It was found that after the shift the σ(f) waveforms for the different temperatures overlap perfectly. This means that the shape of the frequency dependence of the conductivity is determined by the moisture content of the pressboard. The position of the waveforms in relation to the coordinates is determined by the temperature relationships of the conductivity and the relaxation time of the conductivity.

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Section: Introductionmentioning

confidence: 99%

Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

et al. 2020

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“…Fig. 5 shows the measured value of ε′(ω) and the corresponding simulating curves with different model orders (i.e., n=2, 3,4). The goodness of fitting for various model orders is illustrated in Table 3.…”

Section: A Analysis and Simulation Of Fds Curves Based On The Exponementioning

confidence: 99%

“…The deterioration of insulation oil can be solved by replacing oil and filtering oil, but no effective measures have been put forward to solve the deterioration of insulation paper (cellulose insulation). In this case, the service life of the transformer is mainly affected by the performance of oil-immersed cellulose insulation [2], [3].…”

Section: Introductionmentioning

confidence: 99%

A Novel Curve Database for Moisture Evaluation of Transformer Oil-Immersed Cellulose Insulation Using FDS and Exponential Decay Model

et al. 2020

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In recent decades, mo isture evaluation of transformer oil-immersed cellulose insulation has been widely studied by using the frequency domain spectroscopy (FDS) technique. Ho wever, due to the difficult ies in sample preparation, most of the existing evaluation methods are based on a small number of samples, which greatly limits the evaluation accuracy of these methods. To accurately evaluate moisture inside transformer oil-immersed cellulose insulation, a novel method co mbin ing the FDS technique and the exponential decay model is proposed. In current work, the exponential decay model is introduced to analyze the FDS data, which can be used to assess the quantitative relationship between moisture and extracte d parameters. Then, the FDS curves with different moisture can be predicted by using these parameters to form a curve database. Findings reveal the relat ive error of evaluation results in lab condition is less than 10.57% when using the proposed curve database. In that respect, the feasibility of the proposed database is proved for moisture evaluation of transformer oil-immersed cellulose insulation.

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“…E-mail: xqc.hust@qq.com insulation status of electrical equipment. Notably, FDS allows the quantification of moisture levels and the aging status of transformer insulation paper, facilitating the quantitative evaluation of moisture and aging of the transformers [4][5][6][7][8]. However, using the FDS method, only the frequency spectrum of the major insulation of the transformer can be measured, not the insulation paper.…”

Section: Introductionmentioning

confidence: 99%

Error Analysis of XY Model Equivalent Circuit Based on Finite Element Simulation

Tu,

Xu,

Jiang

et al. 2024

IEEJ Transactions Elec Engng

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The XY model is a simplified insulation model for transformers that aims to connect the frequency spectrum of major insulation, insulation paper, and oil. It enables the calculation of the paper's frequency spectrum, facilitating a quantitative evaluation of the transformer's insulation status. Given the scarcity of research addressing the accuracy of the XY model and its corresponding equivalent circuit, this paper investigates the accuracy of the XY model and conducts an in‐depth analysis of the error associated with its equivalent circuit. Firstly, the frequency spectrum of oil‐paper insulations based on the XY model with varying moisture content and structure configurations were measured, followed by the simulation of both the corresponding 2D‐coaxial and XY models. By comparing the results obtained from these simulations with experimental data on oil‐paper insulation, the accuracy of XY model is verified. Subsequently, two variants of the equivalent circuit of the XY model are derived by combining the oil, spacer, and paper differently, which denoted as Type I and II circuits. Finally, we analyzed and explained the errors present in these equivalent circuits compared with the XY model. Our findings show that the width‐thickness ratio of oil‐paper insulation is the most critical influencing factor, while moisture content and insulation structure have a less decisive impact. Notably, for general transformers, as the width‐thickness ratio is between 30 and 70, the relative error of the Type I circuit remains consistently below 0.3% across different frequencies. Consequently, the Type I circuit proves to be a more suitable representation of the equivalent circuit for the XY model in the context of general transformers. © 2024 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

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Parameters Identification and Application of Equivalent Circuit at Low Frequency of Oil-Paper Insulation in Transformer

Cited by 8 publications

References 21 publications

Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

Precise Measurements of the Temperature-Frequency Dependence of the Conductivity of Cellulose—Insulating Oil—Water Nanoparticles Composite

A Novel Curve Database for Moisture Evaluation of Transformer Oil-Immersed Cellulose Insulation Using FDS and Exponential Decay Model

Error Analysis of XY Model Equivalent Circuit Based on Finite Element Simulation

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