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Problems during the Design and Testing of Instrument, Special and Power Transformers

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "F1: Electrical Power System".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 12814

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Special Issue Editors

Prof. Dr. Elzbieta Lesniewska

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Guest Editor

Institute of Mechatronics and Information Systems, Lodz University of Technology, 90-924 Łódź, Poland
Interests: instruments; special and power transformers; accuracy of operation; transient analysis of current and voltage; designing and laboratory tests; electromagnetic field theory; insulation of electrical HV and MV devices

Prof. Dr. Xose Lopez-Fernandez

E-Mail Website
Guest Editor

E.E.Industriales, Universidad de Vigo, 36310 Vigo, Spain
Interests: power transformers; losses and heating in power transformer; assessing the dielectric stress on insulation; overvoltages in dielectric testing; short-circuit transient currents; harmonics measurement

Prof. Dr. Pawel Witczak

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Guest Editor

Institute of Mechatronics and Information Systems, Lodz University of Technology, 90-924 Łódź, Poland
Interests: power transformers; electrical machines; magnetic vibrations; acoustic emission; numerical modeling; designing and laboratory tests

Special Issue Information

Dear Colleagues,

It is hard to imagine modern society without the use of electrical devices. Power transformers as well as current and voltage transformers are essential elements of both the power system and renewable energy conversion systems. The operating principle of all types of transformers is the same, but their tasks are different. Power transformers transfer power, and therefore power losses in the core that cause heating as well as forces that cause noise and vibration of the core are important. The purpose of instrument transformers is to accurately transform the currents or voltages during the operation of the system, which are then used to measure the transmitted power and protect the power grid, making them very precise devices. Power transformers and instrument transformers are located at all transformer stations, specialized high-voltage and high-power laboratories, as well as research and teaching laboratories. Special transformers work in other conditions, e.g., at high frequencies, and are necessary in some specialized research laboratories. Therefore, the design requirements for different transformers are very different depending on their type, function and operating voltage. Design requirements concern not only the operation, but also the strength of the insulation system at high and medium voltages, and sometimes mechanical strength.

This Special Issue aims to present and disseminate the latest developments in the theory, design, modelling, and laboratory testing of all types of transformers.

Topics of interest for publication include, but are not limited to:

All kinds of instrument transformers: their measurement and protection; current; voltage; combined high, medium and low voltage; inductive and capacitive and other structures
Various types, constructions and applications of special transformers
Different types, constructions and applications of power transformers, 1- and 3-phase, for different voltages
Designing and assessing the dielectric stress on insulation in high- and medium-voltage transformers
Thermal and vibroacoustic analyses of transformers
Optimal design methodologies
Advanced modeling methods
Innovative methods of technical research
Diagnostics of insulation of medium- and high-voltage transformers and testing of partial discharges

Prof. Dr. Elzbieta Lesniewska
Prof. Dr. Xose M. Lopez-Fernandez
Prof. Dr. Pawel Witczak
Guest Editors

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Keywords

instrument transformer
special transformer
power transformer
designing
FEM simulation
laboratory testing
insulation diagnostics
thermal analyses
vibroacoustic analyses

Published Papers (12 papers)

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Editorial

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5 pages, 178 KiB

Open AccessEditorial

Problems during the Design and Testing of Instrument, Special and Power Transformers: The Outlook

by Elzbieta Lesniewska and Pawel Witczak

Energies 2024, 17(2), 363; https://doi.org/10.3390/en17020363 - 11 Jan 2024

Viewed by 488

Abstract

In 1831, Michael Faraday discovered the phenomenon of electromagnetic induction, which allowed for the construction of previously unknown electrical devices and significantly impacted economic and social development [...] Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

Research

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21 pages, 9171 KiB

Open AccessArticle

A New Wall Current Transformer for Accurate Beam Intensity Measurements in the Large Hadron Collider

by Michal Krupa and Marek Gasior

Energies 2023, 16(21), 7442; https://doi.org/10.3390/en16217442 - 4 Nov 2023

Viewed by 895

Abstract

The Large Hadron Collider (LHC) stores two high-energy counter-rotating particle beams consisting of multiple bunches of a nanosecond length. Precise knowledge of the number of particles within each bunch, known as the bunch intensity, is crucial for physicists and accelerator operators. From the very beginning of the LHC operation, bunch intensity was measured by four commercial fast beam current transformers (FBCTs) coupling to the beam current. However, the FBCTs exhibited several shortcomings which degraded the measurement accuracy below the required level. A new sensor, the wall current transformer (WCT), has been developed to overcome the FBCT limitations. The WCT consists of eight small radio frequency (RF) current transformers distributed radially around the accelerator’s vacuum chamber. Each transformer couples to a fraction of the image current induced on the vacuum chamber by the passing particle beam. A network of RF combiners sums the outputs of all transformers to produce a single signal which, after integration, is proportional to the bunch intensity. In laboratory tests and during beam measurements, the WCT performance was demonstrated to convincingly exceed that of the FBCT. All originally installed FBCTs were replaced by four WCTs, which have been serving as the LHC reference bunch intensity sensors since 2016. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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18 pages, 12750 KiB

Open AccessArticle

Effect of Magnetic Shunts on Shell-Type Transformers Characteristics

by Bronisław Tomczuk and Dawid Weber

Energies 2023, 16(19), 6814; https://doi.org/10.3390/en16196814 - 26 Sep 2023

Cited by 1 | Viewed by 999

Abstract

A three-dimensional analysis of the leakage magnetic field in a transformer with beveled edges in a magnetic shunt is described. This paper contains a mathematical description of the finite element method used in performing numerical calculations. Formulas allowing to determine the differential and integral parameters of the magnetic field were presented. Magnetic flux density distributions and the points with high values were determined in the shell-type core and movable shunt sub-areas. For different positions of the magnetic shunt, the short-circuit transformer reactance was calculated as the integral parameter of the above-mentioned magnetic field analysis. Their amounts for the extreme positions of the shunt were given, as well. The movable magnetic shunt geometry impact on the short-circuit current value is given. In order to validate the calculation results, the research included some point measurements of magnetic flux density vectors and the winding reactances as well, and good compliance with the simulation data has been obtained. Thus, this analysis can also be applied to other objects with movable shunts in their magnetic systems. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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15 pages, 5310 KiB

Open AccessArticle

Selection of the Winding Type of Solid-State Transformers in Terms of Transmitting the Greatest Possible Power in the Frequency Range from 500 Hz to 6000 Hz

by Elzbieta Lesniewska and Daniel Roger

Energies 2023, 16(18), 6528; https://doi.org/10.3390/en16186528 - 11 Sep 2023

Cited by 1 | Viewed by 748

Abstract

Solid-state transformer (SST) is an emerging technology that integrates with transformer power electronics converters and control. The most noticeable advantages of SST are the size and weight reduction compared with low-frequency transformers. Since this device is used in many devices such as smart grids, traction systems, systems with renewable energy sources (RESs) and electric vehicle charging devices, it is important to build a high-efficiency device at a low cost. The article evaluates a medium frequency transformer (SST) operating at a frequency of 500 Hz to 6000 Hz with coils wound with aluminum foil or Litz windings and of a grain-oriented electrical steel (GOES) core. The calculations were made using the 3D field method using the numerical finite element method, and the results were compared with the tests of the real model. The measurement method based on the Fourier analysis of real signals was used for the research. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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10 pages, 3414 KiB

Open AccessArticle

Field Test Method and Equivalence Analysis of Delay Characteristics of DC Electronic Current Transformer

by Mengmeng Zhu, Hongda Tang, Zhaolei He, Yaohua Liao, Biao Tang, Qunqun Zhang, Hongchun Shu, Yaqi Deng, Fang Zeng and Pulin Cao

Energies 2023, 16(15), 5727; https://doi.org/10.3390/en16155727 - 31 Jul 2023

Viewed by 642

Abstract

DC electronic current transformer is the data source of the system control and protection device, so its measurement delay has always been concerned. In this paper, the DC current transformer is modelled equivalently and the key factors affecting the delay of shunt and the remote module are analyzed. A field test method for the delay characteristics of the DC electronic current transformer is proposed. Moreover, a complex multi-state large current generator and integrated test system are developed. On the basis of the IEC 60044-8 standard transmission protocol, the accuracy of standard signal acquisition with the shunt is better than 0.2%. The maximum output current of the established testing system is 600 A. Based on the field test in an actual HVDC project, transient step and various frequency signal components are applied for analyzing. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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21 pages, 4659 KiB

Open AccessArticle

Inrush Current Reduction Strategy for a Three-Phase Dy Transformer Based on Pre-Magnetization of the Columns and Controlled Switching

by Marian Łukaniszyn, Bernard Baron, Joanna Kolańska-Płuska and Łukasz Majka

Energies 2023, 16(13), 5238; https://doi.org/10.3390/en16135238 - 7 Jul 2023

Cited by 2 | Viewed by 1355

Abstract

The methodology and test results of a three-phase three-column transformer with a Dy connection group are presented in this paper. This study covers the dynamics of events that took place in the first period of the transient state caused by the energizing of the transformer under no-load conditions. The origin of inrush currents was analyzed. The influence of factors accompanying the switch-on and the impact of the model parameters on the distribution and maximum values of these currents was studied. In particular, the computational methods of taking into account the influence of residual magnetism in different columns of the transformer core, as well as the impact of the time instant determined in the voltage waveform at which the indicated voltage is supplied to a given transformer winding, were examined. The study was carried out using a nonlinear model constructed on the basis of classical modeling, in which hysteresis is not taken into account. Such a formulated model requires simplification, which is discussed in this paper. The model is described using a system of stiff nonlinear ordinary differential equations. In order to solve the stiff differential state equations set for the transient states of a three-phase transformer in a no-load condition, a Runge–Kutta method, namely the Radau IIA method, with ninth-order quadrature formulas was applied. All calculations were carried out using the authors’ own software, written in C#. A ready-made strategy for energizing a three-column three-phase transformer with a suitable pre-magnetization of its columns is given. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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11 pages, 7085 KiB

Open AccessArticle

Analysis of Core Losses in Transformer Working at Static Var Compensator

by Piotr Osinski and Pawel Witczak

Energies 2023, 16(12), 4584; https://doi.org/10.3390/en16124584 - 8 Jun 2023

Cited by 1 | Viewed by 1157

Abstract

This article presents the comparison of 3D and 2D finite element models of a power transformer designed for reactive power compensation stations. There is a lack of studies in the literature on internal electromagnetic phenomena in the active part of a transformer operated in these conditions. The results of numerical 2D and 3D calculations of no-load current and losses in the transformer core were obtained by using various methods and models. The impact of considering the hysteresis loop phenomenon on the calculation of core losses was investigated by using the Jiles–Atherton core losses model. The results obtained in the paper show that the model of the core must contain the areas representing the influence of overlappings on the no-load current and also on the flux density field in the core. The capacitive load of the transformer increases the flux density in the core limbs by several percent, so the power losses there must also increase accordingly. As a summary of the research, differences in the values of losses in each core element between the capacitive load and no-load conditions are presented. The results presented in this paper indicate that considering nonlinearity related to the magnetic hysteresis loop has a significant impact on the calculation of the core losses of power transformers. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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13 pages, 2466 KiB

Open AccessArticle

Numerical and Analytical Determination of Steady-State Forces Acting on Cleats and Leads Conductor of the Power Transformer

by Michał Smoliński and Paweł Witczak

Energies 2023, 16(8), 3600; https://doi.org/10.3390/en16083600 - 21 Apr 2023

Viewed by 1170

Abstract

Electromagnetic forces acting on conductors of the cleats and lead of a power transformer can cause permanent damage to the insulation of conductors. Determining the force acting on the conductor of cleats and leads cannot be performed using the standard analytical formula because those conductors are in close proximity to the construction part of the active part made of ferromagnetic material. To calculate those forces in a steady state of a three-phase AC current, a parametric numerical simulation was conducted. Based on the simulation, a new analytical formula for forces acting on cables near the ferromagnetic plate was proposed by the authors. It was also noted that the presence of the ferromagnetic plate can increase the forces up to 60% compared to the same geometry without the plate. This publication also discusses how eddy currents and the proximity effect influence forces acting on conductors. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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15 pages, 3803 KiB

Open AccessArticle

New Approach to Evaluate the Transformation Accuracy of Inductive CTs for Distorted Current

by Michal Kaczmarek and Ernest Stano

Energies 2023, 16(7), 3026; https://doi.org/10.3390/en16073026 - 26 Mar 2023

Cited by 3 | Viewed by 1034

Abstract

This paper presents a newly developed method to determine the values of current error and phase displacement for the transformation of distorted current harmonics by the inductive current transformers. This approach eliminates the necessity for the utilization of an expensive, high-current supply system for the measuring setup. In this method, the secondary winding is fed by the distorted voltage with RMS values of harmonics calculated in order to reproduce the operation point of the inductive current transformer on the magnetization characteristic of its magnetic core, as in primary winding excitation conditions. This proposed approach is successfully verified with the typically used primary current excitation method, where the secondary currents of the reference and tested current transformers are compared in the differential measuring setup. It was confirmed that the inductive CT with current error and phase displacement for transformation of distorted current harmonics determined in the rated ampere-turns conditions may be effectively used in the measuring setup as the reference source of the primary current. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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12 pages, 7140 KiB

Open AccessArticle

Transmission of Vibrations from Windings to Tank in High Power Transformers

by Pawel Witczak and Michal Swiatkowski

Energies 2023, 16(6), 2886; https://doi.org/10.3390/en16062886 - 21 Mar 2023

Cited by 1 | Viewed by 1285

Abstract

This article presents a step-by-step methodology for calculating transformer tank vibrations caused by electromagnetic forces. This approach uses 3D finite element models for both magnetic and structural calculations. Particular attention was paid to the description of momentum transfer between structural and fluid areas of the transformer. The actual geometry of the coils in the phase windings was taken into account. The dominant role of the axial component of the Lorentz force is the main conclusion of the article. The results are given in the form of three-dimensional displacement fields of the transformer tank presented together with the acoustic pressure field in the oil. The theoretical analysis is verified by laser-scanned vibration patterns on the tank wall. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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Review

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27 pages, 4468 KiB

Open AccessFeature PaperReview

SPICE-Aided Models of Magnetic Elements—A Critical Review

by Krzysztof Górecki and Kalina Detka

Energies 2023, 16(18), 6568; https://doi.org/10.3390/en16186568 - 12 Sep 2023

Cited by 2 | Viewed by 840

Abstract

This article analyzes the problem of modeling the properties of such magnetic elements as inductors, coupled inductors, and transformers using the SPICE software (version 17.2). Both the classical models of magnetic elements, built in this software, and the models implemented in the form of subcircuits are described. In particular, attention was paid to the possibility of taking into account the non-linearity of the characteristics of the considered elements and mutual couplings between electrical, magnetic, and thermal quantities. Using the results of thermographic measurements, the need to take into account the differences in temperature values between the individual windings and the core of inductors and transformers was justified. Selected models of the considered elements given in the literature are briefly characterized. The network structures of the electrothermal models of the considered elements elaborated at Gdynia Maritime University are presented. The results of calculations and measurements illustrating the correctness of the described models and their prac-tical usefulness for the elements of different structures are presented and discussed. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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17 pages, 5066 KiB

Open AccessReview

Challenges of Accurate Measurement of Distorted Current and Voltage in the Power Grid by Conventional Instrument Transformers

by Michal Kaczmarek and Ernest Stano

Energies 2023, 16(6), 2648; https://doi.org/10.3390/en16062648 - 11 Mar 2023

Cited by 6 | Viewed by 1227

Abstract

Power grids are a combined system where the electrical energy produced by the power plants is transmitted to consumers. This forms a specific interdependence where the recipients have a significant impact on the power quality. Therefore, the nonlinear loads connected by households and industrial customers cause current and voltage distortion in the power networks. This creates the need for accurate measurement of nonsinusoidal voltage and current composed not only from the fundamental component but also containing higher harmonics, interharmonics, and subharmonics. In order to ensure high transformation accuracy of distorted current and voltage, the inductive instrument transformers have to be tested in these conditions. Many papers describe their behavior during the transformation of sinusoidal current or voltage. Nowadays, the scientific field in this scope is focused on the evaluation of their exploitation properties for distorted signals. The common problem of inductive instrument transformers is the self-generation of low-order higher harmonics to the secondary current or voltage. In the case of the inductive VTs, an additional problem results from the resonance caused by the parasitic capacitance of the primary winding. The proposed solutions to compensate for the values of current or voltage errors and phase displacement of inductive instrument transformers are also analyzed. Full article

(This article belongs to the Special Issue Problems during the Design and Testing of Instrument, Special and Power Transformers)

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