Submit to Energies Review for Energies Propose a Special Issue

Journal Menu

Journal Browser

► Journal Browser

Design and Optimization of Power Transformer Diagnostics II

Print Special Issue Flyer
Special Issue Editors
Special Issue Information
Keywords
Benefits of Publishing in a Special Issue
Related Special Issues
Published Papers

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

Deadline for manuscript submissions: closed (19 June 2024) | Viewed by 11789

Share This Special Issue

Special Issue Editor

Prof. Dr. Zbigniew Nadolny

E-Mail Website
Guest Editor

Department of High Voltage and Electrotechnical Materials, Faculty of Environmental Engineering and Energy, Institute of Electrical Power Engineering, Poznan University of Technology, 60-965 Poznan, Poland
Interests: high voltage; insulation materials; transformer; electric and magnetic fields; insulation oil; heat transfer; thermal properties; thermal conductivity
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Power transformers play a significant role in the electric power system. All over the world, there is a tendency for transformers to work as long as possible, far beyond their technical lifetime. This is certainly due to the high price of the new units. It is not surprising, therefore, that many offline diagnostic methods have developed in recent decades. The use of these methods is associated with the frequent shutdown of transformers from the system. This is an undesirable situation by system operators because it causes a decrease in system stability. For this reason, an important aspect is skillful design and optimization of diagnostic methods of transformers in offline mode and the development of diagnostic methods that can be used online, which is what this Special Issue is devoted to.

Prof. Dr. Zbigniew Nadolny
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

power transformers
diagnostic methods
offline, online methods
transformer insulation system
transformer tap changer

Benefits of Publishing in a Special Issue

Ease of navigation: Grouping papers by topic helps scholars navigate broad scope journals more efficiently.
Greater discoverability: Special Issues support the reach and impact of scientific research. Articles in Special Issues are more discoverable and cited more frequently.
Expansion of research network: Special Issues facilitate connections among authors, fostering scientific collaborations.
External promotion: Articles in Special Issues are often promoted through the journal's social media, increasing their visibility.
e-Book format: Special Issues with more than 10 articles can be published as dedicated e-books, ensuring wide and rapid dissemination.

Further information on MDPI's Special Issue polices can be found here.

Related Special Issues

Design and Optimization of Power Transformer Diagnostics in Energies (18 articles)
Design and Optimization of Power Transformer Diagnostics: 3rd Edition in Energies (1 article)

Published Papers (10 papers)

Download All Papers

Order results

Result details

Show export options Show export options

Select all

Export citation of selected articles as:

Research

16 pages, 18233 KiB

Open AccessArticle

Electromagnetic–Structural Finite Element Analysis of Copper and Aluminum Windings in Power Transformers under Short-Circuit Conditions

by Richard Gonçalves Cornelius, Betina Luísa Lenhard, Leonardo Hautrive Medeiros, Herber Cuadro Fontoura, Cristian Hans Correa, Rodinei Carraro, Rafael Concatto Beltrame, Tiago dos Santos, Tiago Bandeira Marchesan and Vitor Cristiano Bender

Energies 2024, 17(16), 3994; https://doi.org/10.3390/en17163994 - 12 Aug 2024

Viewed by 889

Abstract

Electromagnetic forces can lead to the structural failure of power transformers due to extreme loading conditions, vibration, and/or fatigue. Therefore, studying the nature and the magnitude of these forces is a key task in the design and failure analysis of such important equipment. Keeping this issue in mind, this work aims at conducting a numerical analysis in order to evaluate the mechanical stresses and displacements of windings in power transformers due to the action of electromagnetic forces. With this purpose, a finite element model is developed considering electromagnetic and mechanical effects assuming short-circuit conditions. The study compares the cases employing copper and aluminum windings with header tap, in different temperatures. The model developed in this work is verified against analytical solutions. The numerical calculations allow for performing a detailed analysis in terms of the distribution of both displacements and stresses along the windings, which is of great relevance for identifying critical structural points and avoiding structural failure. Overall, the obtained results demonstrate that the finite element model is a useful tool for the structural design of power transformers that allow for investigating and optimizing key aspects before manufacturing. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Figure 1

13 pages, 2404 KiB

Open AccessArticle

Evaluation of Thermal Properties of Various Insulating Liquids Used in Power Transformers

by Zbigniew Nadolny

Energies 2024, 17(12), 3037; https://doi.org/10.3390/en17123037 - 20 Jun 2024

Viewed by 814

Abstract

This article is a summary of many years of work by the author, in which the thermal properties of various types of insulating liquids, used in power transformers, were evaluated. Recently, esters have been displacing mineral oil. There is a common view that mineral oil has better thermal properties than esters. This claim is supported by comparative results of tests of both materials as a liquid only filling the remaining volume of the transformer. The effect of the type of liquid on the thermal properties of the paper–oil insulation has not been analyzed so far. On this basis, the conclusions formulated may be incomplete. For this reason, the author has analyzed the influence of the type of liquid on both the thermal properties of the liquid filling the remaining volume of the transformer and the paper–oil insulation. It was proved that the more effective liquid filling the remaining volume of the transformer was indeed mineral oil. On the other hand, a more effective electrical insulating liquid, which is an element of paper–oil insulation, is a natural ester. A comprehensive assessment that takes into account both the paper–oil insulation and the remaining transformer volume showed that the natural ester proved to be a slightly more effective electrical insulating liquid than the other analyzed liquids. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Figure 1

17 pages, 4394 KiB

Open AccessArticle

Buildup of Fault Protection for High-Current Single-Phase Transformers in Ore Furnaces

by Dilara Rakhimberdinova, Aleksandr Novozhilov, Evgeniy Kolesnikov, Vladimir Goryunov and Timofey Novozhilov

Energies 2024, 17(11), 2630; https://doi.org/10.3390/en17112630 - 29 May 2024

Viewed by 604

Abstract

High-power ore furnaces mainly use single-phase transformers supplied by phase-to-phase voltage with the secondary winding made in the form of four to eight isolated splits and a high-voltage busbar assembly made of the same number of pairs of tube buses. Due to these design features, turn-to-turn faults are the main faults in the primary winding of the transformer, and flexible coupling breaks and arc faults in splitting circuits prevail in the high-voltage system. This is why current and gas protections are currently used to protect transformers against short circuits. However, current protections are insensitive to turn faults, and the gas protection response time can be long since it strongly depends on the oil temperature. High-current systems are protected from arc faults only by insulating tube buses. However, this insulation is gradually destroyed under the impact of abrasive dust in the air, and the presence of coal dust in the air creates conditions for arc faults. There is no protection against breaks in the circuits of pairs of tube buses. The extent of damage in a transformer and its high-current system due to the faults can be significantly reduced by using new protection devices based on the measurements of the longitudinal and transverse asymmetry of the stray magnetic fields of the protected transformer. To implement these protections, this article suggests a method for protecting a transformer and a high-current system using magnetic current transformers (MCTs). The number and points for MCT winding coils are determined through the analysis of their EMF values versus their positions relative to the windings of the transformer operating under different modes. The results serve as the basis for the protection circuit design; the protection response threshold is calculated, the protection operation is described, and the results of the experiment are given. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Figure 1

17 pages, 4651 KiB

Open AccessArticle

Thermal Ageing of Dry Cellulose Paper Impregnated with Different Insulating Liquids—Comparative Studies of Materials Properties

by Piotr Przybylek

Energies 2024, 17(4), 784; https://doi.org/10.3390/en17040784 - 6 Feb 2024

Cited by 2 | Viewed by 1151

Abstract

Natural and synthetic esters are increasingly being chosen instead of mineral oil for environmental and fire safety reasons. However, their use in power transformers is limited due to insufficiently well-understood ageing processes affecting their properties and the properties of cellulosic materials impregnated with them. The research results presented in many scientific papers prove that the use of esters slows the ageing process of cellulosic materials. This article presents the results of research aimed at answering the question of whether the effect of slowing the ageing process will also occur in the case of insulation with very low initial moisture. The answer to this question will allow us to better understand the role of water in the ageing process of the transformer’s insulation system. The thermal ageing process was carried out at a temperature of 150 °C in closed systems. The degree of cellulose polymerisation was taken as a measure of the degree of paper ageing. Great attention was paid to measuring the water content in both paper and electro-insulating liquids at various stages of their ageing. Furthermore, measurements of the properties of electro-insulating liquids were made, which are considered markers of ageing. The test results obtained indicate that in the case of a dry insulation system, corresponding to the initial moisture of the new units, the type of liquid used to impregnate the cellulosic material does not significantly affect its depolymerisation process. However, in the case of paper impregnated with natural esters, a lower dynamic of moisture increase in insulation was observed. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Figure 1

18 pages, 7069 KiB

Open AccessArticle

Impact of Electrode Distance in a Quasi-Uniform Model Electrode System on Lightning Impulse Breakdown Voltage in Various Insulating Liquids

by Wiktor Kunikowski, Pawel Rozga, Bartlomiej Pasternak, Jakub Staniewski, Filip Stuchala and Konrad Strzelecki

Energies 2024, 17(4), 782; https://doi.org/10.3390/en17040782 - 6 Feb 2024

Cited by 1 | Viewed by 1021

Abstract

This study presents findings on the influence of gap length distance on the lightning impulse breakdown voltage of three dielectric liquids of different chemical origins. The liquids were tested in a model electrode system with a quasi-uniform electric field distribution and a pressboard plate placed on the grounded electrode. The experimental studies were supported using calculations and simulations to show the individual relationships between the lightning impulse breakdown voltage and gap distance, which represent the so-called volume effect of the most stressed liquid. The results of the experiment, which involved four considered gap distances of 2, 4, 6, and 8 mm, show that a dynamic increase in lightning impulse breakdown voltage with an increase in gap distance is associated with mineral oil and bio-based hydrocarbons. However, similar trends were not observed for synthetic ester. Calculations that allowed us to assess the impact of gap length distance on lightning impulse breakdown voltage support the observations from the experimental studies. The curves obtained in this field can be considered in the process of designing insulating systems for transformers. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Figure 1

21 pages, 2266 KiB

Open AccessArticle

Application of Under-Impedance Criterion to Protect against Effects of Phase-to-Phase Short Circuits in Medium-Voltage Networks

by Beata Zięba, Bartosz Olejnik and Iwona Grobelna

Energies 2024, 17(2), 505; https://doi.org/10.3390/en17020505 - 20 Jan 2024

Viewed by 926

Abstract

Common overcurrent criteria used to detect phase-to-phase short circuits in medium-voltage (MV) networks in some cases do not bring the expected results. In particular, this applies to instantaneous overcurrent protections in lines with variable ranges and lines leading to local power plants (LPP), which generate a short-circuit current slightly greater than the rated current. When using overcurrent protections, there are some problems with ensuring the appropriate sensitivity and selectivity. This article proposes a protection based on impedance measurement against the effects of phase-to-phase short circuits in MV lines. The protection can be used at switchgears and also at protection points (PP) located deep in the network. The under-impedance criterion has a range independent of the value of the short-circuit current, and it can be alternative or complement to classic overcurrent protection. The introduction of these criteria allows the protection range to be independent of the type of short circuit and the short-circuit power on the busbar, and to determine this range more precisely. The under-impedance protection is particularly useful in conditions of a growing number of energy sources deep inside the networks and its automation. The main idea was to develop a uncomplicated characteristic that would ensure the possibility of setting the under-impedance protection by people who are not specialists in the field of distance protections. The characteristics have been optimally developed both in terms of the area of detected impedances and easy implementation, operation, and configuration. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Figure 1

14 pages, 6572 KiB

Open AccessArticle

Method of Reducing the Effects of Repeated Ignition during Earth Faults in Compensated Medium Voltage Networks

by Jerzy Andruszkiewicz, Józef Lorenc, Bartosz Olejnik, Agnieszka Weychan and Bogdan Staszak

Energies 2024, 17(1), 93; https://doi.org/10.3390/en17010093 - 23 Dec 2023

Viewed by 1005

Abstract

The article presents the results of research in the field of limiting the effects of overvoltages and improving the conditions for the self-extinguishing of transient faults in medium voltage networks with earth fault current compensation. The aim of the research was to estimate the level of overvoltages generated by an earth fault during re-ignition of the electric arc and to assess the possibility of reducing them by increasing the attenuation of the earth fault circuit. The results of the conducted tests show that to increase the attenuation, which ensures a significant effect of limiting such overvoltages, it is enough to change the way of operation of the devices forcing an additional active component of the earth fault current (AWSCz/ACFA). In Poland, such devices are commonly used to improve the effectiveness of earth fault protection. It was also found that the proposed solution enables accurate tuning of the Petersen coil in networks with natural asymmetry of earth capacitances. Therefore, changes in the operation of AWSCz/ACFA devices may have a beneficial effect on the limiting the effects of repeated ignitions during earth faults and, at the same time, enable the accurate tuning of the Petersen coil and increase its ability to extinguish arc-fed faults. Research and theoretical analysis of the issue were carried out on the basis of data characterizing the parameters of the earth fault circuits of the real 15 kV network. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Figure 1

17 pages, 3231 KiB

Open AccessArticle

The Tools and Parameters to Consider in the Design of Power Transformer Cooling Systems

by Przemyslaw Goscinski, Zbigniew Nadolny, Ryszard Nawrowski and Tomasz Boczar

Energies 2023, 16(24), 8000; https://doi.org/10.3390/en16248000 - 10 Dec 2023

Cited by 2 | Viewed by 1521

Abstract

Transformers are the most important elements of electric power systems. Many conditions must be met for power transformers to work properly. One of them is a low operating temperature. This condition will be met if the transformer cooling system is properly designed. One of the components of a cooling system is insulating liquid. The heat transfer coefficient α of liquid determines its ability to cool the transformer. The higher its value, the more effectively the liquid transfers heat to the environment. This article describes the influence of the position of the heat source, which is usually in the windings of the transformer, on the coefficient α value of the insulating liquid. The vertical and horizontal positions of the heat source were analyzed. The coefficient α was analyzed at different points of the heat source. The tests were carried out for mineral oil and various esters. Heat transfer coefficient measurements were carried out for various surface heat loads of the heat source. It has been proven that, in the case of a horizontal heat source, the coefficient α has a value several dozen percent higher than in the case of a vertical source. It has been proven that the coefficient α has different values in different places of the heat source. Regardless of the location, the highest value of the coefficient α occurred in the lower part of the heat source. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Figure 1

12 pages, 4427 KiB

Open AccessArticle

Determination of Mineral Oil Concentration in the Mixture with Synthetic Ester Using Near-Infrared Spectroscopy

by Piotr Przybylek

Energies 2023, 16(17), 6381; https://doi.org/10.3390/en16176381 - 3 Sep 2023

Cited by 1 | Viewed by 1511

Abstract

Currently, synthetic ester is gaining a bigger share in the market. This type of insulating liquid is used both in new and operated transformers filled with mineral oil. In the case of transformers in operation, the synthetic ester is used in the retrofilling procedure, drying the cellulose insulation, or as a blend with oil, the properties of which are better than those of base liquids. In all these three cases, we are dealing with a mixture of synthetic ester and mineral oil. The concentration of both of these liquids in the mixture has a significant impact on its properties; therefore, methods are necessary to determine the content of individual mixture components. The article presents a method for determining the concentration of mineral oil in a mixture with synthetic ester using near-infrared spectroscopy. Based on the conducted tests, an absorption band was determined that can be used for this purpose. This band is centered at 2126 nm. The determined dependence of the absorbance on mineral oil concentration in the mixture with synthetic ester confirmed the linear nature of this relationship. The conducted research confirmed the possibility of using the method based on near-infrared spectroscopy to determine the concentration of individual components of a mixture of mineral oil and synthetic ester. The proposed method can be used both for a mixture of new liquids and mixtures of new synthetic ester with mineral oils of different degrees of aging. The method of determining the concentration of mineral oil in a mixture with synthetic ester based on near-infrared spectroscopy is new and is characterized by a higher accuracy in relation to the methods previously described in the literature. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Figure 1

11 pages, 1730 KiB

Open AccessArticle

The Use of Methanol Vapour for Effective Drying of Cellulose Insulation

by Piotr Przybylek and Jaroslaw Gielniak

Energies 2023, 16(11), 4465; https://doi.org/10.3390/en16114465 - 31 May 2023

Cited by 3 | Viewed by 1471

Abstract

The paper deals with a new method of drying cellulose insulation, which uses methanol vapour present in nitrogen as a drying medium. Compared to the insulation drying methods currently used in the industry, the method presented in the article has the following advantages: there is no cellulose depolymerization because there is no need to heat the insulation, there is no need to use large-size and energy-intensive dryers because the whole process takes place in the tank of the transformer. Important parameters of the drying process, such as methanol concentration in the nitrogen, flow rate, and process duration, were determined in four separate experiments. For the purposes of these experiments, a special system was constructed to control and measure the flow of drying medium. Controlling the flow rate of the carrier gas (nitrogen) made it possible to obtain different concentrations of methanol in nitrogen. Such values of concentration and flow rate were determined that allow drying of pressboard and paper in less than 144 h to a level lower than 1%. Full article

(This article belongs to the Special Issue Design and Optimization of Power Transformer Diagnostics II)

► Show Figures

Journal Menu

Journal Browser

Design and Optimization of Power Transformer Diagnostics II

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Related Special Issues

Published Papers (10 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI