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Advances in Electric Insulating Materials and Applications

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Electronic Materials".

Deadline for manuscript submissions: closed (20 May 2023) | Viewed by 6325

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Special Issue Editors

Prof. Dr. Robert Hebner

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Guest Editor

Center for Eletromechanics, The University of Texas at Austin, Austin, TX, USA
Interests: resilience; insulation life; transportation electrification; microgrids

Prof. Dr. Gian Carlo Montanari

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Guest Editor

Center for Advanced Power Systems, Florida State University, Tallahassee, FL 32310, USA
Interests: insulation; diagnostics; partial discharges; materials; techniologies; space charge; insulation system design; condition monitoring; failure statistics; life and resilience; reliability

Special Issue Information

Dear Colleagues,

Innovative electrical assets are being developed in electrified transportation, from three-wheelers, to ships to aerospace. In general, power electronics have to master the whole power supply to achieve the high specific power, low weight and volume components, and to enable the flexible and highly variable power flow required for these applications. In these conditions, electrical and electronic insulation systems and materials have to withstand new types and levels of electric stresses, while still having to be reliable for the design life of the apparatus. Voltage waveforms far from the ubiquitous ac sinusoids can also be encountered in renewable generation.

This Special Issue advances transportation electrification and renewable generation technology by highlighting the challenges and advances in relevant materials, design criteria, diagnostic and monitoring tools and algorithms.

Contributions highlighting the feasibility of robust, reliable and optimized insulation systems for any electrical apparatus involved in electrified transportation and renewable generation assets are particularly relevant. We also encourage contributions dealing with ac and dc supply, including voltage transients, which could feed the same insulator depending on operation, according to a hybrid asset paradigm.

Prof. Dr. Robert Hebner
Prof. Dr. Giancarlo Montanari
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. Materials 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

electrified transportation
electrical assets
renewable generation
advanced materials
insulation system design
diagnostics
hybrid supply
AC modulated volatge
AC sinusiodal voltage
DC voltage
voltage and field transients
partial discharges
space charge
diagnostics
condition monitoring

Published Papers (5 papers)

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Research

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13 pages, 2875 KiB

Open AccessEditor’s ChoiceArticle

Modeling and Characterization of Surface Discharges in Insulating Material for Spacers: Electrode Shape, Discharge Mode, and Revision of the Creepage Concept

by Debasish Nath, Qichen Yang, Giancarlo Montanari, Weijun Yin, Han Xiong and Karim Younsi

Materials 2023, 16(3), 989; https://doi.org/10.3390/ma16030989 - 20 Jan 2023

Cited by 2 | Viewed by 1699

Abstract

In the design of MV AC and DC spacers, the predominant factors are surface and interface conditions. Design is generally carried out on specifications and standards which are based on long-term experience and lab testing. However, the diffusion of power electronics with a trend to increase electric field, switching frequency, and rise time to achieve higher power density calls for an innovative, global approach to optimized insulation system design. A new methodology, based on field simulation, discharge modeling, and partial discharge inception measurements, called the three-leg approach, can form the basis to optimize insulation design for any type of supply voltage waveform. This paper focuses on the influence of the type of electrode on the inception and phenomenology of surface discharges and, as a consequence, on the interpretation of the results used for application of the three-leg approach. It is demonstrated that a typical electrode system used for insulating material testing can generate both gas and surface discharges at the triple point, when the electrodes have a smooth profile that is used to avoid corona or flashover. Hence, testing partial discharge may not provide a straightforward indication of the surface discharge inception and, thus, be partially misleading for insulation design. Another takeover is that such analysis must benefit from PD testing tools endowed with analytics able to provide automatic identification of the type of defect generating PD, i.e., internal, surface, and corona, since design and remedy actions can be taken, and adequate insulating materials developed, only knowing the type of source generating PD. Hence, testing partial discharge may not provide a straightforward indication of surface discharge inception and, thus, be partially misleading for insulation design. In addition to the importance of the three-leg approach to favor reliable and optimized design of insulation systems, there is a clear need to have a PD testing tool endowed with analytics. It should preferably be able to provide automatic identification of the type of defect generating PD, i.e., internal, surface, and corona. Full article

(This article belongs to the Special Issue Advances in Electric Insulating Materials and Applications)

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18 pages, 2284 KiB

Open AccessArticle

On Molecular Dynamics and Charge Transport in a Flexible Epoxy Resin Network

by Orestis Vryonis, Alun S. Vaughan, Thomas Andritsch, Peter H. F. Morshuis and Aurore Claverie

Materials 2022, 15(18), 6413; https://doi.org/10.3390/ma15186413 - 15 Sep 2022

Viewed by 1175

Abstract

An epoxy based on diglycidyl ether of bisphenol A was reacted with a long-chain poly(oxypropylene diamine) hardener in the presence of an accelerator, resulting in a flexible epoxy network. Tensile properties were tested as a function of accelerator concentration. All systems exhibited high levels of extensibility, with strain at failure values in excess of 65%. Molecular dynamics in a formulation containing 10 phr of accelerator were then examined using dielectric spectroscopy over the temperature range of 103–433 K. At low temperatures, a molecular relaxation process (γ relaxation) was observed and shown to conform well to both the Arrhenius equation and activated tunnelling. A stronger relaxation appeared (203–303 K) just before the onset of charge transport, which dominated the behaviour at higher temperatures. The former takes an unusual bimodal form, which we consider a result of overlapping β and α relaxations, consequently termed αβ mode. Analysis of this mechanism revealed a Vogel–Fulcher–Tammann (VFT) behaviour. The temperature-dependent DC conductivity, σ_DC (deduced from the low-frequency charge transport contribution to ε_r″), also revealed VFT behaviour with an onset statistically equivalent to that of the αβ mode, therefore suggesting that charge transport, at this temperature regime, is strongly affiliated with cooperative molecular motion. Full article

(This article belongs to the Special Issue Advances in Electric Insulating Materials and Applications)

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14 pages, 6582 KiB

Open AccessArticle

Surface Modification-Dominated Space-Charge Behaviors of LDPE Films: A Role of Charge Injection Barriers

by Yuanwei Zhu, Haopeng Chen, Yu Chen, Guanghao Qu, Guanghao Lu, Daomin Min, Yongjie Nie and Shengtao Li

Materials 2022, 15(17), 6095; https://doi.org/10.3390/ma15176095 - 02 Sep 2022

Viewed by 1264

Abstract

Gradually increasing power transmission voltage requires an improved high-voltage capability of polymeric insulating materials. Surface modification emerges as an easily accessible approach in enhancing breakdown and flashover performances due to the widely acknowledged modification of space-charge behaviors. However, as oxidation and fluorination essentially react within a limited depth of 2 μm underneath polymer surfaces, the nature of such bulk space-charge modulation remains a controversial issue, and further investigation is needed to realize enhancement of insulating performance. In this work, the surface oxidation-dependent space-charge accumulation in LDPE film was found to be dominated by an electrode/polymer interfacial barrier, but not by the generation of bulk charge traps. Through quantitative investigation of space-charge distributions along with induced electric field distortion, the functions of surface oxidation on the interfacial barrier of a typical dielectric polymer, LDPE, is discussed and linked to space-charge behaviors. As the mechanism of surface modification on space-charge behaviors is herein proposed, space-charge accumulation can be effectively modified by selecting an appropriate surface modification method, which consequentially benefits breakdown and flashover performances of polymeric insulating films for high-voltage applications. Full article

(This article belongs to the Special Issue Advances in Electric Insulating Materials and Applications)

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15 pages, 4621 KiB

Open AccessArticle

Insulating Material Development for the Design of Standoff Insulators Fed by Hybrid Voltage

by Gian Carlo Montanari, Riddhi Ghosh, Robin Ramin and Debasish Nath

Materials 2022, 15(15), 5307; https://doi.org/10.3390/ma15155307 - 02 Aug 2022

Viewed by 1068

Abstract

Innovative electrical assets are being developed in transmission and distribution, as well as in electrified transportation, from ships to aerospace. In general, power electronics have to master the whole power supply, being the driver of high specific power, low weight and volume components, in addition to enabling flexible and highly variable power flow. In these conditions, electrical and electronic insulation systems will have to withstand new types and levels of electric stresses, while still maintaining its reliability throughout its whole design life. This paper presents a study on the interrelation between insulating material properties and surface field of standoff insulators. The aim is mainly to provide indications on material properties which can be tailored to provide a robust, reliable and optimised insulator design that will hold for any type of electrical stress the insulation will have to withstand during operation. Specifically, we focus on ac and dc supply, including voltage transients, which could feed the same insulator depending on operation, according to a hybrid asset paradigm. The challenge is, indeed, to establish a pattern to material and insulation system design which takes into account the differences between the types of electrical stress profile and magnitude when insulators are supplied either in a dc or in ac, in order to infer which type of material characteristics would be more appropriate for the sake of life and reliability. The main contribution of this paper is to show that engineering the values of bulk and surface conductivity (which can be done selecting appropriate materials or modifying them, e.g., by nano-structuration) and modelling surface discharge inception would allow the electric field profile to be stabilised whatever the shape of the applied waveform. This will enable us to reach a reliability target that not only accounts for macroscopic phenomena, but also for the likelihood of extrinsic accelerated aging mechanism occurrence as partial discharges. In such a way, optimization of conditions to improve life, reliability, design and creepage and clearance characteristics can be achieved. Full article

(This article belongs to the Special Issue Advances in Electric Insulating Materials and Applications)

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Review

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17 pages, 3659 KiB

Open AccessEditor’s ChoiceReview

Aerospace Environmental Challenges for Electrical Insulation and Recent Developments for Electrified Aircraft

by Maricela Lizcano, Tiffany S. Williams, Euy-Sik E. Shin, Diana Santiago and Baochau Nguyen

Materials 2022, 15(22), 8121; https://doi.org/10.3390/ma15228121 - 16 Nov 2022

Cited by 8 | Viewed by 2302

Abstract

The growing trend towards high voltage electrical assets and propulsion in the aeronautics and space industry pose new challenges in electrical insulation materials that cannot be overlooked. Transition to new high voltage electrified systems with unprecedented high levels of voltage, power, and efficiency must be safe and reliable. Improvements in both performance and safety of megawatt power systems is complicated because of the need for additional power transmission wiring and cabling and new safety requirements that have the potential of making the resulting systems heavier. To mitigate this issue, novel lightweight materials and system solutions are required that would result in lower specific weights in the insulator and conductor. Although reduced size and weight of system components can be achieved with new concepts, designs, and technologies, the high voltage (≥300 V) operation presents a significant challenge. This challenge is further complicated when considering the extreme operating environment that is experienced in aircraft, spacecraft, and targeted human exploration destinations. This paper reviews the extreme environmental challenges for aerospace electrical insulation and the needs associated with operating under high voltage and extreme environments. It also examines several recently developed robust lightweight electrical insulation materials that could enhance insulation performance and life. In aerospace, research must consider mass when developing new technologies. The impact of these recent developments provides a pathway which could enable next generation high altitude all electric aircraft, lightweight power transmission cables for a future sustained presence on the Moon and missions to Mars using HV propulsion, such as spacecraft with Nuclear Electric Propulsion systems. Full article

(This article belongs to the Special Issue Advances in Electric Insulating Materials and Applications)

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