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Advances in Transformer Technology: Intelligent Condition Monitoring and New Materials

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "F3: Power Electronics".

Deadline for manuscript submissions: closed (10 October 2023) | Viewed by 7366

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Special Issue Editors

Dr. Patrick Picher

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Guest Editor

Institut de Recherche d’Hydro-Québec (IREQ), Varennes, QC, Canada
Interests: power transformer insulation; power transformers; monitoring and diagnostics

Prof. Dr. Issouf Fofana

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Guest Editor

Aging of Power Network Infrastructure (ViAHT), Université du Québec à Chicoutimi (UQAC), Chicoutimi, QC G7H 2B1, Canada
Interests: dielectrics and electrical insulating materials; insulating fluids; diagnostic and monitoring; atmospheric icing of power network equipment; electric discharge and lightning-related phenomena; HV testing techniques and computer modeling
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Special Issue Information

Dear Colleagues,

Transformers constitute the heart of the power system. High attention and due emphasis are being laid by transformer owners and utility engineers to optimize the technical and financial aspects of the energy transition. In view of the diversity in the use of condition monitoring technologies, and progress in the use of alternative insulating materials, a careful understanding of the evolving technologies is essential to adapt transformer utilization to the context of the network of the future. Therefore, this Special Issue aims to combine new trends in transformer digitalization and new materials for improved insulation system performance. Such a combined lecture will be helpful for researchers and engineers to better understand the rapid advancements in technologies that will improve asset management, operational reliability, and safety.

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

Transformer modelling, digital twins
Intelligent condition assessment and monitoring
Diagnosis and prognosis of power transformers
New materials to improve transformer performance
Low pour-point liquids for transformers

Dr. Patrick Picher
Prof. Dr. Issouf Fofana
Guest Editors

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

ageing and performance models
digital twins, digitalization, and data analytics
diagnostics and prognostics
condition assessment and monitoring
new materials
low pour-point liquids

Published Papers (4 papers)

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Research

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17 pages, 2968 KiB

Open AccessArticle

Modeling and Predicting the Mechanical Behavior of Standard Insulating Kraft Paper Used in Power Transformers under Thermal Aging

by Ahmed Sayadi, Djillali Mahi, Issouf Fofana, Lakhdar Bessissa, Sid Ahmed Bessedik, Oscar Henry Arroyo-Fernandez and Jocelyn Jalbert

Energies 2023, 16(18), 6455; https://doi.org/10.3390/en16186455 - 06 Sep 2023

Cited by 2 | Viewed by 797

Abstract

The aim of this research is to predict the mechanical properties along with the behaviors of standard insulating paper used in power transformers under thermal aging. This is conducted by applying an artificial neural network (ANN) trained with a multiple regression model and a particle swarm optimization (MR-PSO) model. The aging of the paper insulation is monitored directly by the tensile strength and the degree of polymerization of the solid insulation and indirectly by chemical markers using 2-furfuraldehyde compound content in oil (2-FAL). A mathematical model is then developed to simulate the mechanical properties (degree of polymerization (DP_V) and tensile index (Tidx)) of the aged insulation paper. First, the datasets obtained from experimental results are used to create the MR model, and then the optimizer method PSO is used to optimize its coefficients in order to improve the MR model. Then, an ANN method is trained using the MR-PSO to create a nonlinear correlation between the DP_V and the time, temperature, and 2-FAL values. The acquired results are assessed and compared with the experimental data. The model presents almost the same behavior. In particular, it has the capability to accurately simulate the nonlinear property behavior of insulation under thermal aging with an acceptable margin of error. Since the life expectancy of power transformers is directly related to that of the insulating paper, the proposed model can be useful to maintenance planners. Full article

(This article belongs to the Special Issue Advances in Transformer Technology: Intelligent Condition Monitoring and New Materials)

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26 pages, 6827 KiB

Open AccessFeature PaperArticle

Proof of the Concept of Detailed Dynamic Thermal-Hydraulic Network Model of Liquid Immersed Power Transformers

by Marko Novkovic, Zoran Radakovic, Federico Torriano and Patrick Picher

Energies 2023, 16(9), 3808; https://doi.org/10.3390/en16093808 - 28 Apr 2023

Cited by 3 | Viewed by 1318

Abstract

The paper presents a physics-based method to calculate in real time the distribution of temperature in the active part of liquid immersed power transformers (LIPT) in a transient thermal processes during grid operation. The method is based on the detailed dynamic thermal-hydraulic network model (THNM). Commonly, up to now, lumped models have been used, whereby the temperatures are calculated at a few points (top-oil and hot-spot), and the parameters are determined from basic or extended temperature-rise tests and/or field operation. Numerous simplifications are made in such models and the accuracy of calculation decreases when the transformer operates outside the range of tested values (cooling stage, loading). The dynamic THNM reaches the optimum of accuracy and simplicity, being feasible for on-line application. The paper presents fundamental equations of dynamic THNM, which are structurally different from static THNM equations. The paper offers the numerical solver for the case of a closed-loop thermosyphon. To apply the method for real transformer grid operation, there is a need to develop details as in static THNM, which has been used to calculate the distribution of the temperatures in LIPT thermal design. The paper proves the concept of dynamic THNM using the experimental results of a closed-loop thermosyphon small-scale model, previously published by authors from McGill University in 2017. The comparison of dynamic THNM with measurements on that model are presented in the paper. Full article

(This article belongs to the Special Issue Advances in Transformer Technology: Intelligent Condition Monitoring and New Materials)

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Review

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23 pages, 2765 KiB

Open AccessReview

Bubbling Phenomena in Liquid-Filled Transformers: Background and Assessment

by Ghada Gmati, Ungarala Mohan Rao, Issouf Fofana, Patrick Picher, Oscar Arroyo-Fernàndez and Djamal Rebaine

Energies 2023, 16(9), 3829; https://doi.org/10.3390/en16093829 - 29 Apr 2023

Cited by 1 | Viewed by 1507

Abstract

The degradation of the insulation system in liquid-filled power transformers is a serious concern for electric power utilities. The insulation system’s ageing is accelerated by moisture, acids, oxidation products, and other decay particles (soluble and colloidal). The presence of these ageing by-products is detrimental to the insulation system and may further lead to premature ageing and serious consequences. The ageing mechanisms of oil-paper insulation are complex, highly interrelated, and strongly temperature-dependent. The operating temperature of the transformer insulating system has a direct relationship with the loading profile. The major aspect that is witnessed with the fluctuating temperatures is moisture migration and subsequent bubble evolution. In other words, gas bubbles evolve from the release of water vapor from the cellulosic insulation wrapped around the transformer windings. The models presented in the existing standards, such as the IEC Std. 60076-7:2018 and the IEEE Std. C57.91:2011, are mainly based on the insulation temperature, which acts as a key parameter. Several studies have investigated the moisture dynamics and bubbling phenomenon as a function of the water content in the paper and the state of the insulation system. Some studies have reported different prototypes for the estimation of the bubble inception temperatures under selected conditions. However, there are various attributes of the insulation system that are to be considered, especially when expanding the models for the alternative liquids. This paper reviews various evaluation models reported in the literature that help understand the bubbling phenomenon in transformer insulation. The discussions also keep us in the loop on the estimation of bubbling behavior in alternative dielectric liquids and key attributable factors for use in transformers. In addition, useful tutorial elements focusing on the bubbling issue in transformers as well as some critical analyses are addressed for future research on this topic. Full article

(This article belongs to the Special Issue Advances in Transformer Technology: Intelligent Condition Monitoring and New Materials)

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32 pages, 2063 KiB

Open AccessReview

Performance Assessment of Cellulose Paper Impregnated in Nanofluid for Power Transformer Insulation Application: A Review

by Andrew Adewunmi Adekunle, Samson Okikiola Oparanti and Issouf Fofana

Energies 2023, 16(4), 2002; https://doi.org/10.3390/en16042002 - 17 Feb 2023

Cited by 7 | Viewed by 2790

Abstract

Insulation cellulose paper is a basic measure for a power transformer’s remaining useful life, and its advantageous low cost, electrical, and mechanical properties have made it an extensive insulation system when impregnated in a dielectric liquid. Cellulose paper deteriorates as a result of ageing due to some chemical reactions like pyrolysis (heat), hydrolysis (moisture), and oxidation (oxygen) that affects its degree of polymerization. The condition analysis of cellulose paper has been a major concern since the collection of paper samples from an operational power transformer is almost impossible. However, some chemicals generated during cellulose paper deterioration, which were dissolved in dielectric liquid, have been used alternatively for this purpose as they show a direct correlation with the paper’s degree of polymerization. Furthermore, online and non-destructive measurement of the degree of polymerization by optical sensors has been proposed recently but is yet to be available in the market and is yet generally acceptable. In mitigating the magnitude of paper deterioration, some ageing assessments have been proposed. Furthermore, researchers have successfully enhanced the insulating performance of oil-impregnated insulation paper by the addition of various types of nanoparticles. This study reviews the ageing assessment of oil-paper composite insulation and the effect of nanoparticles on tensile strength and electrical properties of oil-impregnated paper insulation. It includes not only significant tutorial elements but also some analyses, which open the door for further research on the topic. Full article

(This article belongs to the Special Issue Advances in Transformer Technology: Intelligent Condition Monitoring and New Materials)

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