Remanent Flux Negative Effects on Transformer Diagnostic Test Results and a Novel Approach for Its Elimination

Gerdroodbari, Yasin Zabihinia; Davarpanah, Mahdi; Farhangi, Shahrokh

doi:10.1109/tpwrd.2018.2827179

Cited by 16 publications

(4 citation statements)

References 14 publications

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“…S7(d). The elimination of FC's remanence can be realized by applying an ac magnetic field to the FC [44].…”

Section: Improvement Of the Measurement Contrast (C)mentioning

confidence: 99%

$T_2$-limited dc Quantum Magnetometry via Flux Modulation

Xie¹,

Xie²,

Zhu³

et al. 2022

Preprint

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High-sensitivity magnetometry is of critical importance to the fields of biomagnetism and geomagnetism. However, the magnetometry for the low-frequency signal detection meets the challenge of sensitivity improvement, due to multiple types of low-frequency noise sources. In particular, for the solid-state spin quantum magnetometry, the sensitivity of low frequency magnetic field has been limited by short T * 2 . Here, we demonstrate a T2-limited dc quantum magnetometry based on the nitrogen-vacancy centers in diamond. The magnetometry, combining the flux modulation and the spin-echo protocol, promotes the sensitivity from being limited by T * 2 to T2 of orders of magnitude longer. The sensitivity of the dc magnetometry of 32 pT/Hz 1/2 has been achieved, overwhelmingly improved by 100 folds over the Ramsey-type method result of 4.6 nT/Hz 1/2 . Further enhancement of the sensitivity have been systematically analyzed, although challenging but plenty of room is achievable. Our result sheds light on realization of room temperature dc quantum magnetomerty with femtotesla-sensitivity in the future.

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“…S7(d). The elimination of FC's remanence can be realized by applying an ac magnetic field to the FC [44].…”

Section: Improvement Of the Measurement Contrast (C)mentioning

confidence: 99%

$T_2$-limited dc Quantum Magnetometry via Flux Modulation

Xie¹,

Xie²,

Zhu³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…where R expresses the total resistance in the circuit. According to (5) and (6), the relationship between τ and μrd at Br is expressed as…”

Section: Rfementioning

confidence: 99%

“…When the power transformer is cut-out operation and in various test operations [1]- [3], the internal magnetic flux density in the iron core does not fall to zero and thus an unknown residual flux density (Br) is produced, which is resulted by the hysteresis characteristics of iron core materials [4]- [6]. When the transformer is switched to connect with power grid again, a magnetizing inrush current will be produced as the existence of Br [7], [8].…”

Section: Introductionmentioning

confidence: 99%

Residual Flux Density Measurement Method of Single-Phase Transformer Core Based on Time Constant

Huo

Yang

et al. 2020

IEEE Access

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Residual flux density in the single-phase transformer core can dramatically increase inrush current when the transformer is energized. To reduce inrush current, it is necessary to study residual flux density measurement. This paper proposes a new residual flux density measurement method based on time constant. Firstly, the generation principle of residual flux density is analyzed under different magnetization states, and it is found that the positive relative differential permeability is smaller than the negative at different residual flux density. To obtain the relative differential permeability, when an appropriate DC excitation is applied, the measurement circuit is equivalent to a first-order RL circuit. Then, combining magnetic circuit and transient circuit analysis, the relationship between time constant and relative differential permeability is obtained. It is conclusion that the positive time constant is less than the negative. Residual flux density direction is determined by comparing the positive and negative time constant, and the magnitude of residual flux density is calculated by the relationship between residual flux density and the difference of the positive and negative time constant. Finally, the empirical formula between residual flux density and time constant difference of the square core is obtained in finite element method, and then verified on the experimental platform. Compared with other measurement methods, the relative error of proposed empirical formula is within 4.58 %, and it has higher accuracy in this paper. The proposed method in this paper can provide a reference for selecting the demagnetization voltage, which improves the effectiveness of demagnetization. INDEX TERMS Residual flux density, relative differential permeability, time constant difference, empirical formula.

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“…Compared with the two methods, the direct current method is simpler and more efficient [3,4]. The main demagnetization method of current transformer core is DC method, which can reduce the magnetic flux of core by controlling the polarity of dc voltage source [5,6]. The residual flux suppression time of DC method is shortened obviously, but the excitation current increases too fast and the accuracy is not enough when the core is saturated.…”

Section: Introductionmentioning

confidence: 99%

Study on Two Residual Flux Suppression Strategies of Current Transformer During Automatic Reclosing

Deng

Wang

et al. 2022

J. Phys.: Conf. Ser.

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After power system short-circuit fault occurs, there is a large amount of residual magnetism in current transformer core, which will lead to wrong operation of connected relay protection and affect its reliability. Based on the direct current method, this paper puts forward two kinds of current transformer residual flux suppression strategies, which are constant voltage variable frequency (CVVF) and variable voltage constant frequency (VVCF), the magnetic flux of the core is gradually reduced by controlling the polarity of the output voltage of the switch module. The principle of residual flux suppression is introduced, and the method of parameter selection is given. The suppression effect of two residual flux suppression strategy is simulated and analyzed by experiment simulation. The results show that the two residual flux suppression strategies can demagnetize the current transformer core during automatic reclosing, but the constant voltage CVVF residual flux suppression strategy is simpler and more efficient.

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Remanent Flux Negative Effects on Transformer Diagnostic Test Results and a Novel Approach for Its Elimination

Cited by 16 publications

References 14 publications

$T_2$-limited dc Quantum Magnetometry via Flux Modulation

$T_2$-limited dc Quantum Magnetometry via Flux Modulation

Residual Flux Density Measurement Method of Single-Phase Transformer Core Based on Time Constant

Study on Two Residual Flux Suppression Strategies of Current Transformer During Automatic Reclosing

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