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Power Transformer Diagnostics, Monitoring and Design Features Power Transformer Diagnostics, Monitoring and Design Features Edited by Issouf Fofana Printed Edition of the Special Issue Published in Energies www.mdpi.com/journal/energies Power Transformer Diagnostics, Monitoring and Design Features Power Transformer Diagnostics, Monitoring and Design Features Special Issue Editor Issouf Fofana MDPI • Basel • Beijing • Wuhan • Barcelona • Belgrade Special Issue Editor Issouf Fofana UniversiteduQu´ ebec´ a` Chicoutimi (UQAC) Canada Editorial Office MDPI St. Alban-Anlage 66 4052 Basel, Switzerland This is a reprint of articles from the Special Issue published online in the open access journal Energies (ISSN 1996-1073) from 2015 to 2018 (available at: https://www.mdpi.com/journal/energies/special issues/power-transformer) For citation purposes, cite each article independently as indicated on the article page online and as indicated below: LastName, A.A.; LastName, B.B.; LastName, C.C. Article Title. Journal Name Year, Article Number, Page Range. ISBN 978-3-03897-441-3 (Pbk) ISBN 978-3-03897-442-0 (PDF) c 2018 by the authors. Articles in this book are Open Access and distributed under the Creative Commons Attribution (CC BY) license, which allows users to download, copy and build upon published articles, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. The book as a whole is distributed by MDPI under the terms and conditions of the Creative Commons license CC BY-NC-ND. Contents About the Special Issue Editor ...................................... vii Issouf Fofana and Yazid Hadjadj Power Transformer Diagnostics, Monitoring and Design Features Reprinted from: Energies 2018, 11, 3248, doi:10.3390/en11123248 ................... 1 Janvier Sylvestre N’cho, Issouf Fofana, Yazid Hadjadj and Abderrahmane Beroual Review of Physicochemical-Based Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers Reprinted from: Energies 2016, 9, 367, doi:10.3390/en9050367 ..................... 6 Issouf Fofana and Yazid Hadjadj Electrical-Based Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers Reprinted from: Energies 2016, 9, 679, doi:10.3390/en9090679 ..................... 35 Chao Tang, Bo Huang, Miao Hao, Zhiqiang Xu, Jian Hao and George Chen Progress of Space Charge Research on Oil-Paper Insulation Using Pulsed Electroacoustic Techniques Reprinted from: Energies 2016, 9, 53, doi:10.3390/en9010053 ...................... 62 Pawel Rozga Streamer Propagation and Breakdown in a Very Small Point-Insulating Plate Gap in Mineral Oil and Ester Liquids at Positive Lightning Impulse Voltage Reprinted from: Energies 2016, 9, 467, doi:10.3390/en9060467 ..................... 97 Wojciech Sikorski, Krzysztof Walczak and Piotr Przybylek Moisture Migration in an Oil-Paper Insulation System in Relation to Online Partial Discharge Monitoring of Power Transformers Reprinted from: Energies 2016, 9, 1082, doi:10.3390/en9121082 ....................109 Jian Li, Xudong Li, Lin Du, Min Cao and Guochao Qian An Intelligent Sensor for the Ultra-High-Frequency Partial Discharge Online Monitoring of Power Transformers Reprinted from: Energies 2016, 9, 383, doi:10.3390/en9050383 .....................125 Jingxin Zou, Weigen Chen, Fu Wan, Zhou Fan and Lingling Du Raman Spectral Characteristics of Oil-Paper Insulation and Its Application to Ageing Stage Assessment of Oil-Immersed Transformers Reprinted from: Energies 2016, 9, 946, doi:10.3390/en9110946 .....................140 Lingjie Sun, Yingyi Liu, Boyang Zhang, Yuwei Shang, Haiwen Yuan and Zhao Ma An Integrated Decision-Making Model for Transformer Condition Assessment Using Game Theory and Modified Evidence Combination Extended by D Numbers Reprinted from: Energies 2016, 9, 697, doi:10.3390/en9090697 .....................154 Chen Wang, Jie Wu, Jianzhou Wang and Weigang Zhao Reliability Analysis and Overload Capability Assessment of Oil-Immersed Power Transformers Reprinted from: Energies 2016, 9, 43, doi:10.3390/en9010043 ......................178 v Youyuan Wang, Kun Xiao, Bijun Chen and Yuanlong Li Study of the Impact of Initial Moisture Content in Oil Impregnated Insulation Paper on Thermal Aging Rate of Condenser Bushing Reprinted from: Energies 2015, 8, 14298–14310, doi:10.3390/en81212429 ...............197 Kapila Bandara, Chandima Ekanayake, Tapan Saha and Hui Ma Performance of Natural Ester as a Transformer Oil in Moisture-Rich Environments Reprinted from: Energies 2016, 9, 258, doi:10.3390/en9040258 .....................210 Chenmeng Xiang, Quan Zhou, Jian Li, Qingdan Huang, Haoyong Song and Zhaotao Zhang Comparison of Dissolved Gases in Mineral and Vegetable Insulating Oils under Typical Electrical and Thermal Faults Reprinted from: Energies 2016, 9, 312, doi:10.3390/en9050312 .....................223 vi About the Special Issue Editor Issouf Fofana, Professor, IET Fellow, held the Canada Research Chair on insulating liquids and mixed dielectrics for electrotechnology (ISOLIME) from 2005 to 2015. At his university, he is the Director of the international research Centre on Atmospheric Icing and Power Network Engineering (CENGIVRE) and holds the research chair on the Ageing of Power Network Infrastructure (ViAHT). Dr. Fofana is/was a member of technical/scientific committees of international conferences (e.g., IEEE ICDL, IEEE CEIDP, IEEE ICHVE, CATCON, ISH, etc.), IEEE DEIS, and CEIDP AdComs. He also serves on the scientific committee as associate editor for IET GTD, IEEE TDEI, a Guest Editor of Energies, and chair of the IEEE DEIS Technical Committee on Dielectric Liquids. He is also a member of several working groups (i.e., CIGRE and ASTM). Dr. Fofana’s research in the area of HV engineering has emphases on insulation systems relevant to power equipment. His lifetime publication record is more than 270 scientific publications and 3 patents. vii energies Editorial Power Transformer Diagnostics, Monitoring and Design Features Issouf Fofana 1,* and Yazid Hadjadj 2 1 Aging of Power Network Infrastructure (ViAHT), Université du Québec à Chicoutimi, Chicoutimi, QC G7H 2B1, Canada 2 Measurement Science and Standards, National Research Council (NRC), Ottawa, ON K1A 0R6, Canada; [email protected] * Correspondence: [email protected]; Tel.: +1-418-545-5011 Received: 12 October 2018; Accepted: 13 November 2018; Published: 22 November 2018 1. Introduction The reliability of the power grid system directly contributes to the economic well-being and the quality of life of citizens in any country. In the electric power distribution and transmission systems, it is essential that key equipment such as transformers function properly for many years. In these important equipment, the Achilles’ heel is the insulation system, i.e., (a) insulation between the high voltage (HV) winding and the tank; (b) insulation between the HV and the low voltage (LV) windings; and (c) inter-phase insulation. Over the past decade, various types of insulating materials have been introduced in these machines. Assessment methods have allowed monitoring their conditions with the aim of providing the basic information required for power grid operators and maintenance planners to understand the issues related to aging. Also, aging indicator indices have been the aim of a large number of investigations. Many transformers around the world are now approaching the end of their theoretical design life. In this context, managing the aging population of power transformers has become one of the most critical issues today’s maintenance planners and engineers have to face. With increasing age, there are potential risks of extremely high monetary losses due to unexpected failures and outages. A simple solution would be to replace all aging and risky transformers at once with new ones. Such an approach is obviously not a fiscally realistic solution. The main objectives are: to extend their service life and optimize their performance through increased availability. For these reasons, transformer life management in the past few decades has gained an ever-increasing interest due to economic and technical reasons. The greatest challenges are related to the need for methods to assess the condition and life expectancy along with the improvement of transformer efficiency by noble designs and/or application of new materials. The special issue was focused on theoretical and practical developments with a special emphasis on new research and development (R&D) trends in transformer designs/diagnostics and maintenance. Additionally, today, “sustainable development” has become a world-wide concept for the scientific community. The focus is now on harvesting renewable resources instead of fossil fuels, and using environmentally friendly materials. In this context, new materials are emerging for the design of electrotechnical insulation systems including biodegradable insulating materials, with properties that are at least equal to conventional materials. Esters with excellent high temperature performance, enhanced fire safety, increased environmental protection and increased moisture tolerance are gaining importance. Some aspects regarding the application of biodegradable fluids in these important machines were therefore also of particular interest. Listed hereafter, among others, were some of the topics of interest considered: • New or emerging diagnostic/monitoring technologies; Energies 2018, 11, 3248; doi:10.3390/en111232481 www.mdpi.com/journal/energies Energies 2018, 11, 3248 • Mineral oils of improved characteristics,
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