Effects of DC Bias on Regional Flux and Magnetostriction of a Single-Phase Transformer Core Modeled by 3-D MACC

Pfützner, Helmut; Shilyashki, Georgi; Bengtsson, Claes; Trenner, Gerald; Gerstbauer, Erich

doi:10.1109/tmag.2018.2806346

Cited by 20 publications

(8 citation statements)

References 20 publications

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“…DC bias easily leads to local overheating, the aggravation of noise and vibration of transformers, and mal-operation operation of relay protection. It will seriously threaten the safe operation of power transformers [4]. So, how to identify the DC bias state of transformers is of vital importance.…”

Section: Introductionmentioning

confidence: 99%

State Identification of Transformer Under DC Bias Based on Wavelet Singular Entropy

et al. 2021

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To identify the DC bias state of transformers, a DC bias state identification method of transformer based on wavelet singular entropy is proposed in this paper. The vibration principle of transformers under DC bias has been analyzed. By combining continuous wavelet transform, singular value decomposition, and information entropy, the analysis method of wavelet singular entropy is proposed. The vibration signal of the transformer before and after DC bias is transformed by continuous wavelet transform, and then the wavelet time-frequency diagram is compared and analyzed. Furthermore, the DC bias state of the transformer is identified by wavelet singular entropy of vibration signal. The wavelet singular entropy under different states is in different numerical ranges, and the wavelet singular entropy of vibration signal under DC bias is significantly greater than that under no DC bias. The wavelet singular entropy effectively reflects the DC bias state of transformers. Then the proposed method is applied to a 500 kV transformer and a 220 kV transformer in the China Southern Power Grid. The results show that the proposed method can accurately and effectively identify the DC bias state of transformers.

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Section: Introductionmentioning

confidence: 99%

State Identification of Transformer Under DC Bias Based on Wavelet Singular Entropy

et al. 2021

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“…By analyzing feedback results from the field operation, numerous studies have conducted in-depth researches in dc bias suppression, including impacts of dc blocking capacitors on the power grid protection [15], [16], dc bias tolerance ability of transformers [17]- [19], and resistor-capacitor combined dc bias protection [20]. In terms of optimal placements and combinations of dc bias suppression devices, Ref.…”

Section: Introductionmentioning

confidence: 99%

A System-Level Suppression Method for DC Bias Based on Reverse Unbalanced Currents in the Same Transmission Section

Lin

et al. 2021

IEEE Access

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Conventional dc bias suppression strategies mainly rely on a single type of device, such as blocking capacitor or blocking resistance. However, these methods are passive palliatives and cannot restrain dc bias currents from the sources. In the light of this, a system-level suppression method for dc bias is proposed in this paper. The average value of currents flowing through the earth is offset by actively generating unbalanced current through other dc projects in the same transmission section, which will reduce the currents flowing into the neutral transformers and alleviate the negative impacts of dc bias. First, the feasibility of the same section dc continuous power support is analyzed. Then the dc bias suppression strategy based on reverse unbalanced currents is elaborated. By scanning all the theoretical operable solutions of unbalanced current generation modes and the possible switching combinations of blocking capacitors, the optimal dc bias suppression solution is output considering the number of adjusted dc projects, the overload margin of dc projects and neutral dc currents of transformers. The effectiveness and superiority of the proposed method are verified by comparative case studies of the East China power grid. INDEX TERMS DcBias; System-level Suppression Method; Reverse unbalanced currents.

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“…Due to the geomagnetically induced current (GIC) caused by periodic solar storms, monopole operation of the large-scale construction of high voltage direct current (HVDC) transmission and harmonics caused by the increasing nonlinear loads in the power grid, the direct current (DC) flows through the earthed neutrals of the transformer and cause a DC bias to the magnetizing current of the transformer [1][2][3][4][5]. This results in the asymmetric magnetic core saturation during a sinusoidal half-period, the serious distortion of excitation current, increased reactive power absorption, partial overheating and increase of vibration and noise [6][7][8][9][10][11][12]. Because of depletion of fossil fuel reserves and increasing demand for energy consumption, the ultra-high voltage UHV transmission projects have been put into service for solving the energy crisis.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the DC Bias Effects on the UHV Autotransformer with Rated Load Based on a Reduced-Scale Model Experiment

Wang

et al. 2020

Applied Sciences

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The DC bias of transformers as a result of geomagnetically induced currents (GIC), monopole operation of high voltage direct current (HVDC) transmission and the increasing power electronic devices in the power grid, creates a high magnitude of fundamental and harmonic components in winding currents, reactive power, and vibro-acoustic noise. For transformers with large capacity, it is very expensive and difficult to carry out an in-depth DC bias effects investigation on a practical equipment, especially for the ultra-high voltage (UHV) transformer. In this paper, a reduced-scale model (RSM) based on the principle of identical saturation degree is proposed, and the equivalent relationship of DC bias current is obtained. Furthermore, the DC bias platform with the RSM is established, experiments have been conducted to analyze the characteristics of the transformer under DC bias. It turns out from the experiments that the current of high voltage side and excitation are less tolerated to the DC bias current, the distortion occurs during the first half of the cycle and peaking at the quarter. Besides, the no-load loss and total harmonic distortion (THD) increase significantly with an increasing DC bias. The results of the characteristics of RSM with load under DC bias may provide great services in protecting and reducing the DC bias effects on the UHV transformer in actual operation.

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Effects of DC Bias on Regional Flux and Magnetostriction of a Single-Phase Transformer Core Modeled by 3-D MACC

Cited by 20 publications

References 20 publications

State Identification of Transformer Under DC Bias Based on Wavelet Singular Entropy

State Identification of Transformer Under DC Bias Based on Wavelet Singular Entropy

A System-Level Suppression Method for DC Bias Based on Reverse Unbalanced Currents in the Same Transmission Section

Analysis of the DC Bias Effects on the UHV Autotransformer with Rated Load Based on a Reduced-Scale Model Experiment

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