Research

15 pages, 5848 KiB

Open AccessArticle

The Performance of the High-Current Transformer during Operation in the Wide Frequencies Range

by Michal Kaczmarek, Piotr Kaczmarek and Ernest Stano

Energies 2022, 15(19), 7208; https://0-doi-org.brum.beds.ac.uk/10.3390/en15197208 - 30 Sep 2022

Cited by 5 | Viewed by 1115

This paper presents the performance of the 26 kVA inductive high-current transformer (HCT) during operation in the frequencies range of transformed harmonics from 50 Hz to 5 kHz. Performed research concerns the determination of the possibility of obtaining an order of [...] Read more.

This paper presents the performance of the 26 kVA inductive high-current transformer (HCT) during operation in the frequencies range of transformed harmonics from 50 Hz to 5 kHz. Performed research concerns the determination of the possibility of obtaining an order of the higher harmonic of a given RMS value in its distorted output current for the required RMS value of the main component and the maximum safe instantaneous value of the input voltage equal to 400 V. The results are presented for serial, serial-parallel and parallel configurations of primary and secondary windings (9 cases). Therefore, the most favourable configuration of the primary and secondary windings sections may be chosen. The tests are performed for the transformation of the distorted current containing a fundamental component and one higher harmonic of order from the 5th changed by the 5 up to the 100th. The constant 10% higher harmonic level in relation to the main component of the distorted secondary current is set. The measurements are performed for different resistances and inductances of the secondary winding’s load resulting from the length of the connected current track. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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12 pages, 3243 KiB

Open AccessArticle

Evaluation of the Current Shunt Influence on the Determined Wideband Accuracy of Inductive Current Transformers

by Michal Kaczmarek, Piotr Kaczmarek and Ernest Stano

Energies 2022, 15(18), 6840; https://0-doi-org.brum.beds.ac.uk/10.3390/en15186840 - 19 Sep 2022

Cited by 4 | Viewed by 1141

Abstract

This manuscript presents performed laboratory studies and the analysis of the impact of current shunt values used in the differential connection on the wideband metrological performance of inductive current transformers. Moreover, a comparison of the accuracy of wideband and 50 Hz-type inductive current [...] Read more.

This manuscript presents performed laboratory studies and the analysis of the impact of current shunt values used in the differential connection on the wideband metrological performance of inductive current transformers. Moreover, a comparison of the accuracy of wideband and 50 Hz-type inductive current transformers in the specified frequency range from 50 Hz to 5 kHz is presented. The main factor which may influence the wideband accuracy of inductive current transformers is the phenomenon of self-generation. This causes rapid changes in the accuracy, and simultaneously causes the most positive and the most negative values of current error and phase displacement. To evaluate the metrological performance in the differential measurement setup for higher harmonics of the distorted current, a digital acquisition board was used. Obtained results show that if proper values of current shunt resistance are chosen, such devices may be used to evaluate the wideband accuracy of inductive current transformers. The results indicate that the typical units designed for the transformation of sinusoidal current with a frequency of 50 Hz can achieve a comparable metrological performance to that of the wideband inductive current transformer. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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11 pages, 2934 KiB

Open AccessArticle

The Effect of the Load Power Factor of the Inductive CT’s Secondary Winding on Its Distorted Current’s Harmonics Transformation Accuracy

by Michal Kaczmarek, Piotr Kaczmarek and Ernest Stano

Energies 2022, 15(17), 6258; https://0-doi-org.brum.beds.ac.uk/10.3390/en15176258 - 27 Aug 2022

Cited by 8 | Viewed by 1336

Abstract

In this paper, we present an investigation into the influence of the load power factor of secondary winding on the metrological performance of inductive CTs with frequencies from 50 Hz to 5 kHz of the harmonic of a transformed distorted current. The results [...] Read more.

In this paper, we present an investigation into the influence of the load power factor of secondary winding on the metrological performance of inductive CTs with frequencies from 50 Hz to 5 kHz of the harmonic of a transformed distorted current. The results clearly indicated that the inductive load caused a deterioration in the transformation accuracy of the inductive CT. To ensure the most advantageous conditions of their operation, a resistive load should be used. The inductive CTs for the frequencies of the transformed harmonic of a distorted primary current from 50 Hz to 5 kHz may ensure the accuracy class designated for the transformation of the sinusoidal current of a frequency of 50 Hz with the same limiting values of errors. Moreover, an analysis of the generated low-order harmonics by a 300 A/5 A CT determined for the power factor of 0.8 inductive and 1.0 of the secondary winding was investigated. These results for the transformed distorted currents of 3rd, 5th and 7th higher harmonics were evaluated for a rated load and 25% of this value. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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12 pages, 2481 KiB

Open AccessArticle

Why Should We Test the Wideband Transformation Accuracy of Inductive Current Transformers?

by Ernest Stano, Piotr Kaczmarek and Michal Kaczmarek

Energies 2022, 15(15), 5737; https://0-doi-org.brum.beds.ac.uk/10.3390/en15155737 - 07 Aug 2022

Cited by 12 | Viewed by 1238

Abstract

Inductive current transformers are characterized by different transformation accuracies for higher harmonics of distorted primary currents. Therefore, it is highly required to perform the tests of their metrological properties to choose the best unit that ensures the lowest values of current error and [...] Read more.

Inductive current transformers are characterized by different transformation accuracies for higher harmonics of distorted primary currents. Therefore, it is highly required to perform the tests of their metrological properties to choose the best unit that ensures the lowest values of current error and phase displacement. This study presents a comparison of two manufactured inductive current transformers. The results indicate that some inductive current transformers may be used to accurately transform distorted currents, enabling proper distortion of power metering and quality evaluation. However, to obtain adequate transformation properties in the wide frequency range, the cross-section of the magnetic core of the inductive current transformer should be oversized. Moreover, it is required to use a permalloy magnetic core instead of the typical transformer steel core. In the analyzed case, the metrological performance depends mainly on its accuracy for transforming the main component of the distorted primary current and self-generation of the low-order higher harmonics. This paper constitutes the starting point to define the limiting values of current error and phase displacement for the future wideband accuracy class extension for inductive CTs. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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16 pages, 5063 KiB

Open AccessArticle

Understanding the Frequency Characteristics of Current Error and Phase Displacement of the Corrected Inductive Current Transformer

by Ernest Stano, Piotr Kaczmarek and Michal Kaczmarek

Energies 2022, 15(15), 5436; https://0-doi-org.brum.beds.ac.uk/10.3390/en15155436 - 27 Jul 2022

Cited by 11 | Viewed by 1412

Abstract

The paper presents investigations and analysis of the parameters of the magnetic part of the equivalent circuit of the inductive CT in the frequencies range from 50 Hz to 5 kHz. Therefore, a measuring circuit used to determine the values of the transverse [...] Read more.

The paper presents investigations and analysis of the parameters of the magnetic part of the equivalent circuit of the inductive CT in the frequencies range from 50 Hz to 5 kHz. Therefore, a measuring circuit used to determine the values of the transverse branch elements was developed. The research performed helps to understand the obtained values of the frequency characteristics of the current error and phase displacement of the corrected inductive current transformer. Moreover, the vectorial diagrams for the 1st, 20th and 100th harmonics are provided with consideration of the influence of the applied turns number correction of the secondary winding. The obtained results show that the increase in the frequency of transformed higher harmonics may cause a decrease in the values of the current error and phase displacement for the non-corrected inductive current transformer. However, if the number of turns of the secondary winding is corrected, the behavior is reversed, where the values of the current error are higher with increased frequency. In the paper, the influence of the self-generation phenomenon of the low-order harmonics is also considered. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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10 pages, 3051 KiB

Open AccessArticle

Operation of the Electronic Current Transformer for Transformation of Distorted Current Higher Harmonics

by Michal Kaczmarek, Artur Szczęsny and Ernest Stano

Energies 2022, 15(12), 4368; https://0-doi-org.brum.beds.ac.uk/10.3390/en15124368 - 15 Jun 2022

Cited by 13 | Viewed by 2151

Abstract

This paper evaluates an electronic current transformer’s wideband accuracy in the transformation of distorted current harmonics. The tests were performed in the range of frequencies from 50 Hz to 5 kHz. The utmost importance was dedicated to the transformation of the low-order higher [...] Read more.

This paper evaluates an electronic current transformer’s wideband accuracy in the transformation of distorted current harmonics. The tests were performed in the range of frequencies from 50 Hz to 5 kHz. The utmost importance was dedicated to the transformation of the low-order higher harmonics. The novelty of this paper involves the analysis of the self-generation of the third and fifth higher harmonics caused by the nonlinearity of magnetic core magnetization characteristics. Therefore, what is considered new in this investigation is that this phenomenon has a significant influence on values of current errors and phase displacements despite the presence of the operational amplifiers and the Hall sensors in the output circuits. Another important factor to consider is the influence of the RMS value of the primary current and output load of the ECT on wideband accuracy. To show the backgrounds of the performed laboratory studies, we also discuss the operation principles of the ECTs with closed and open feedback loops. The accuracy of the tested ECT deteriorated—as with the inductive CT—by the self-generation phenomenon. This resulted in rapid changes in the values of current errors and phase displacements determined for the low-order higher harmonics. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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15 pages, 3706 KiB

Open AccessArticle

Two Channels Opto-Isolation Circuit for Measurements of the Differential Voltage of Voltage Transformers and Dividers

by Michal Kaczmarek

Energies 2022, 15(7), 2694; https://0-doi-org.brum.beds.ac.uk/10.3390/en15072694 - 06 Apr 2022

Cited by 3 | Viewed by 1536

Abstract

In this paper the design of the two channel opto-isolation circuit for measurements of the differential voltage is presented. It is used to ensure high impedance of the measuring channel(s) in the differential system to ensure the rated operation of connected voltage divider(s). [...] Read more.

In this paper the design of the two channel opto-isolation circuit for measurements of the differential voltage is presented. It is used to ensure high impedance of the measuring channel(s) in the differential system to ensure the rated operation of connected voltage divider(s). Its conversion accuracy tests are oriented to determine the ratio and phase errors introduced by a tested device under three test conditions. The opto-isolation circuit is tested for the internal noise at various levels of common voltage. In the next step the calibration of the zero output voltage at zero differential voltage is tested. In the last step of the testing procedure, the values of conversion ratio and phase errors are determined. In the first case the analysis is performed during an operation with an additional common voltage divider when both inputs ensure high impedance. In the second case the values of the conversion ratio and phase errors are tested in conditions when only one input ensures high impedance. In this paper the application of the opto-isolation circuit to determine the values of the composite error of the tested voltage divider with the rated voltage ratios equal to 15 kV:100 V, 10 kV:100 V, 5 kV:100 V is presented. Moreover, its usage to determine the values of the composite error of the inductive voltage transformer with voltage ratio (15 kV/√3)/(100 V/√3) is shown. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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16 pages, 4513 KiB

Open AccessArticle

The Method to Determine the Turns Ratio Correction of the Inductive Current Transformer

by Ernest Stano

Energies 2021, 14(24), 8602; https://0-doi-org.brum.beds.ac.uk/10.3390/en14248602 - 20 Dec 2021

Cited by 12 | Viewed by 2549

Abstract

This paper presents the method for evaluation of the turns ratio correction of the inductive current transformer using the magnetization curves determined at the non-load state and in the load conditions. The presented method may be applied to determine even a fractional winding [...] Read more.

This paper presents the method for evaluation of the turns ratio correction of the inductive current transformer using the magnetization curves determined at the non-load state and in the load conditions. The presented method may be applied to determine even a fractional winding correction factor. The standard IEC 61869-2 provides the method to determine the turns ratio correction of the tested CT from the measured rms values of voltages on its primary and secondary winding in the non-load state. However, this approach is limited in determining the significant changes in the number of turns of the secondary winding. Moreover, the paper presents the influence of the applied turns ratio correction on the frequency characteristics of the current error and phase displacement of the inductive current transformers evaluated for the transformation of the distorted current. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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16 pages, 12819 KiB

Open AccessArticle

Application of the Sinusoidal Voltage for Detection of the Resonance in Inductive Voltage Transformers

by Michal Kaczmarek and Ernest Stano

Energies 2021, 14(21), 7047; https://0-doi-org.brum.beds.ac.uk/10.3390/en14217047 - 28 Oct 2021

Cited by 8 | Viewed by 1482

Abstract

In the case of the inductive voltage transformer (VT), the resonance phenomenon may be the main reason for its poor transformation accuracy of the non-sinusoidal voltage. This problem mainly results from the leakage inductance and the parasitic capacitance of its primary winding. The [...] Read more.

In the case of the inductive voltage transformer (VT), the resonance phenomenon may be the main reason for its poor transformation accuracy of the non-sinusoidal voltage. This problem mainly results from the leakage inductance and the parasitic capacitance of its primary winding. The application of the sinusoidal voltage with a frequency from 20 Hz to 20 kHz presented in this study ensures proper identification of the resonance frequencies of the medium-voltage (MV) inductive VTs. The results are consistent with the values obtained in the reference condition at their nominal primary voltage. Therefore, it is proven that the proposed solution is effective in all cases. The influence of the main frequency variation of the non-sinusoidal primary voltage on the resonance properties of the inductive VT is also studied. Moreover, the tests indicate that the capacitance of the load of the secondary winding may cause a decrease in their resonance frequency. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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17 pages, 3489 KiB

Open AccessArticle

Variable DC-Link Voltage Control of Dual Active Bridge Converter in a Standalone Wind Power Generation System for High-Efficiency Battery-Discharging Operation

by Yuto Takayama and Hiroaki Yamada

Energies 2021, 14(20), 6786; https://0-doi-org.brum.beds.ac.uk/10.3390/en14206786 - 18 Oct 2021

Cited by 3 | Viewed by 1823

Abstract

In this study, we deal with a dual active bridge (DAB) converter-based battery charger in a standalone wind power generation system (WPGS) with a small-scale wind turbine. However, the power conversion efficiency under the low power output in the discharging mode is low. [...] Read more.

In this study, we deal with a dual active bridge (DAB) converter-based battery charger in a standalone wind power generation system (WPGS) with a small-scale wind turbine. However, the power conversion efficiency under the low power output in the discharging mode is low. In this paper, we propose variable DC-link voltage control in a standalone WPGS with a DAB converter under a light load. The proposed control can compensate for the shortage of generated power and suppress the peak value of the transformer current. Simulation results demonstrate that the proposed control can decrease the peak value of the transformer current and improve the power conversion efficiency of the DAB converter. An experimental setup was constructed to confirm the basic operation of the variable DC-link voltage control. In addition, a reference DC-link voltage switchover control is proposed to enable a high-efficiency drive under all load ranges. From simulation results, the power loss can be reduced by the switchover control of the reference DC-link voltage. Full article

(This article belongs to the Special Issue Development of Voltage and Current Transformers in Power System)

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