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Detection and Diagnosis of Polymer Composites for Electrical and Electronic...
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Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Applications".

Deadline for manuscript submissions: closed (10 September 2023) | Viewed by 28954

Special Issue Editors

Dr. Hongwei Mei

E-Mail Website
Guest Editor
Tsinghua Shenzhen International Graduate School, Shenzhen, China
Interests: composite insulator; nondestructive testing; terahertz wave technology; thermal wave technology
Dr. Li Cheng

E-Mail Website
Co-Guest Editor
School of Electrical Engineering, Chongqing University, Chongqing, China
Interests: composite insulating oil; composite insulator; nondestructive testing; terahertz wave technology; thermal wave technology; microwave technology
Prof. Dr. Xiaobo Meng

E-Mail Website
Co-Guest Editor
School of Mechanical and Electrical Engineering, Guangzhou University, Guangzhou 510006, China
Interests: composite insulator; streamer discharge; electrical engineering polymeric materials; surface flashover
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We cordially invite you to submit your research papers, communications or review articles to the Special Issue entitled “Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application”.

Polymer composites have been widely applied in electrical power systems, electrical insulation equipment, electrical and electronic devices, etc. Their operation performances directly affect the safety of equipment and power grid. Because the deterioration of polymer composite is affected by its own performance, operation and maintenance conditions, atmospheric environment and other factors, only relying on advanced detection and diagnosis methods, technologies and devices can we grasp its service status in time.

This Special Issue focuses on the detection and diagnosis of polymer composites applied in the field of electrical and electronic equipment, including but not limited to methods, technologies and devices such as the detection and diagnosis of the operating states of polymer composites, the detection and characterization of ex-factory performances of polymer composites, and the application evaluation of polymer composites.

We are looking forward to receiving your outstanding work for this Special Issue.

Dr. Hongwei Mei
Dr. Li Cheng
Prof. Dr. Xiaobo Meng
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. Polymers 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 2700 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

  • polymer
  • composite material
  • detection
  • diagnosis
  • operating states
  • factory performances
  • application evaluation

Published Papers (16 papers)

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Research

15 pages, 5827 KiB  
Article
Quantitative Measurements of DP in Cellulose Paper Based on Terahertz Spectroscopy
by Qiyu Chen, Lijun Yang, Hua Yu, Yuxin He, Hong Liu and Xuan Wang
Polymers 2023, 15(1), 247; https://doi.org/10.3390/polym15010247 - 03 Jan 2023
Cited by 4 | Viewed by 1880
Abstract
The power transformer is vital to the reliability of the power grid which is most commonly insulated with Kraft paper and immersed in mineral oil, among which the aged state of the paper is mainly correlated to the operating life of the transformer. [...] Read more.
The power transformer is vital to the reliability of the power grid which is most commonly insulated with Kraft paper and immersed in mineral oil, among which the aged state of the paper is mainly correlated to the operating life of the transformer. Degree of polymerization (DP) is a direct parameter to assess the aged condition of insulating paper, but existing DP measurement by viscosity methods are destructive and complicated. In this paper, terahertz time-domain spectroscopy (THz-TDS) was introduced to reach rapid, non-destructive detection of the DP of insulating paper. The absorption spectra of insulating paper show that characteristic peak regions at 1.8 and 2.23 THz both exhibit a log-linear quantitative relationship with DP, and their universalities are confirmed by conducting the above relationship on different types of insulating paper. Fourier transform infrared spectroscopy (FTIR) analysis and molecular dynamics modeling further revealed that 1.8 and 2.23 THz were favorably associated with the growth of water–cellulose hydrogen bond strength and amorphous cellulose, respectively. This paper demonstrates the viability of applying THz-TDS to the non-destructive detection of DP in insulating paper and assigned the vibration modes of the characteristic absorption peaks. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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16 pages, 6432 KiB  
Article
Effect of Ultraviolet—A Radiation on Alicyclic Epoxy Resin and Silicone Rubber Used for Insulators
by Xiaoqing Wang, Haonan Fan, Wenrong Li, Yuyang Zhang, Ruiqi Shang, Fanghui Yin and Liming Wang
Polymers 2022, 14(22), 4889; https://doi.org/10.3390/polym14224889 - 12 Nov 2022
Cited by 3 | Viewed by 1646
Abstract
Compared with the high-temperature vulcanized silicone rubber (HTVSR) insulator, the alicyclic epoxy resin insulator has higher hardness and better bonding between the core and the sheath. This makes the latter very promising in the coastal area of Southern China. Outdoor insulators are often [...] Read more.
Compared with the high-temperature vulcanized silicone rubber (HTVSR) insulator, the alicyclic epoxy resin insulator has higher hardness and better bonding between the core and the sheath. This makes the latter very promising in the coastal area of Southern China. Outdoor insulators are often subjected to high intensity of ultraviolet (UV)-A radiation. The influence of UV-A radiation is significant for alicyclic epoxy resin insulators. To help address the concern, the surface of two kinds of samples, namely the alicyclic epoxy resin insulator and HTVSR insulator, with UV-A aging time was characterized by tests of scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The operation properties (mechanical properties, hydrophobicity) for outdoor insulators were also analyzed. It was found that the appearance color of the alicyclic epoxy resin has changed greatly, and there is a certain degree of fading. The mechanical properties of the alicyclic epoxy resin are maintained well and, the hydrophobicity decreases gradually. For silicone rubber, the appearance color change of silicone rubber is smaller, and the mechanical properties of silicone rubber decreased greatly. In addition, although the hydrophobicity of silicone rubber decreased gradually, it is still better than that of alicyclic epoxy resin. Both materials have broken chemical bonds, but the degree is relatively light, which meets the requirements of insulators for outdoor operation. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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16 pages, 3767 KiB  
Article
Mechanical Properties of High Temperature Vulcanized Silicone Rubber Aged in the Natural Environment
by Zhijin Zhang, Jianjie Zhao, Xiaodong Wan, Xingliang Jiang and Jianlin Hu
Polymers 2022, 14(20), 4439; https://doi.org/10.3390/polym14204439 - 20 Oct 2022
Cited by 7 | Viewed by 2183
Abstract
Composite insulators operate in harsh field environments all year round. Their various properties and states of aging require attention. It is important to study the performance changes of composite insulator sheds after aging to evaluate the life of insulators operating on grids. For [...] Read more.
Composite insulators operate in harsh field environments all year round. Their various properties and states of aging require attention. It is important to study the performance changes of composite insulator sheds after aging to evaluate the life of insulators operating on grids. For this reason, 22 composite insulator sheds from different factories, with different voltage levels and different ages years were selected to conduct mechanical properties testing. The mechanical properties include hardness, tensile strength, and elongation at break, and were investigated by thermogravimetric (TGA) testing, surface morphology, and nuclear magnetic resonance (NMR) characterization. The changes in mechanical properties of high temperature vulcanization (HTV) composite insulator silicone rubber aged in the natural environment were analyzed, including the reasons for these changes. The results showed that the transverse relaxation time T2 of the sample was closely related to its aging state. The more serious the silicone rubber’s aging, the smaller was the T2. The state of the composite insulator can be evaluated by using T2 and aging years simultaneously. With the actual degree of aging in the silicone rubber intensified, its tensile strength and elongation at break generally showed a downward trend. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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12 pages, 2068 KiB  
Article
A Service Life Prediction Method of Stranded Carbon Fiber Composite Core Conductor for Overhead Transmission Lines
by Yongli Liao, Ruihai Li, Chuying Shen, Bo Gong, Fanghui Yin and Liming Wang
Polymers 2022, 14(20), 4431; https://doi.org/10.3390/polym14204431 - 20 Oct 2022
Cited by 2 | Viewed by 1190
Abstract
The effect of temperature on the service life of stranded carbon fiber composite core conductors was studied based on the kinetic theory of material pyrolysis. The thermal decomposition activation energy calculation for stranded carbon fiber composite cores was carried out by thermogravimetric analysis [...] Read more.
The effect of temperature on the service life of stranded carbon fiber composite core conductors was studied based on the kinetic theory of material pyrolysis. The thermal decomposition activation energy calculation for stranded carbon fiber composite cores was carried out by thermogravimetric analysis (TGA). The activation energy E of stranded carbon fiber composites was calculated according to the Flynn–Wall–Ozawa, Kissinger, and Coast–Redfern methods, which were 168.76 kJ/mol, 166.79 kJ/mol, and 160.35 kJ/mol, respectively. The results from these different treatments were within 10% or less, and thus the thermochemical reactions of stranded carbon fiber composite cores were considered to be effective. The life prediction model of the carbon fiber composite core was developed based on the kinetic equation of thermal decomposition. The service life is related to the reaction mechanism function G(α) and the reaction rate parameter k(t). The reaction mechanism function G(α) = ((1 − α)−3.3 − 1)/3.3 and the reaction rate parameter k(t) = 2.14 × 1012exp(E/RT) were obtained by fitting the thermal weight loss data of stranded carbon fiber composite cores. Based on the 5% mass loss criterion for the end of life of stranded carbon fiber composites, the service life of the carbon fiber composite core is given at various operating temperatures. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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16 pages, 14907 KiB  
Article
Locating Method for Electrical Tree Degradation in XLPE Cable Insulation Based on Broadband Impedance Spectrum
by Tao Han, Yufei Yao, Qiang Li, Youcong Huang, Zhongnan Zheng and Yu Gao
Polymers 2022, 14(18), 3785; https://doi.org/10.3390/polym14183785 - 09 Sep 2022
Cited by 1 | Viewed by 2077
Abstract
Electrical treeing is one of the main causes of crosslinked polyethylene (XLPE) cable failure. The current methods for locating electrical trees are mainly based on the partial discharge (PD) signal. However, PD signals are easily attenuated in the long cable and the PD [...] Read more.
Electrical treeing is one of the main causes of crosslinked polyethylene (XLPE) cable failure. The current methods for locating electrical trees are mainly based on the partial discharge (PD) signal. However, PD signals are easily attenuated in the long cable and the PD test voltage may cause damage to the insulation. This work proposes an improved broadband impedance spectrum (BIS) method to locate electrical trees in XLPE cable. A mathematical model of a long cable containing local electrical tree degradation is established. The Gaussian signal is chosen as the simulated incident signal to reduce the spectral leakage. The location spectrum is obtained by multiplying the frequency domain function of the single-ended reflection coefficient and the Gaussian pulse. It has been found that the location spectrum of the local capacitance change can be characterized as a typical double-peak waveform and the spectrum of the local conductance change can be regarded as a typical single-peak waveform. Electrical tree experiments at different temperatures were carried out to initiate different types of electrical trees. A vector network analyzer (VNA) was used to test the high frequency capacitance characteristics in the treeing process. The location spectra of the 20 m long cable containing different types of electrical trees was calculated by the improved location algorithm. The results show that the location error of local electrical tree degradation is less than 3%. The capacitance of the sliced sample decreases with treeing time. The effect of the bush-pine tree on capacitance parameters is greater than that of the branch-pine tree. A typical double-peak is found in the bush-pine tree location spectrum and a single-peak is found in the branch-pine tree spectrum. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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17 pages, 8385 KiB  
Article
Effect of Trap Regulation on Vacuum DC Surface Flashover Characteristics of Nano-ZnO/PI Film
by Jiang Wu, Bo Zhang, Tianjiao Li, Yan Du, Wen Cao and Hao Yang
Polymers 2022, 14(17), 3605; https://doi.org/10.3390/polym14173605 - 01 Sep 2022
Cited by 1 | Viewed by 1197
Abstract
The operating safety of spacecraft in space environments is closely related to the surface discharging phenomenon of dielectrics such as polyimide (PI) film in solar arrays; moreover, carrier traps in the dielectric can affect its insulation performance. Therefore, to improve the vacuum surface [...] Read more.
The operating safety of spacecraft in space environments is closely related to the surface discharging phenomenon of dielectrics such as polyimide (PI) film in solar arrays; moreover, carrier traps in the dielectric can affect its insulation performance. Therefore, to improve the vacuum surface flashover characteristics of PI film by nano modification and reveal the effect of trap distribution on the flashover of PI composite film, first, the original PI and nano-ZnO/PI composite films with different additive amounts (0.5, 1, 2, and 3 wt.%) were prepared by in situ polymerization and their performance was evaluated by the physicochemical properties characterized by methods such as thermogravimetric analysis; second, the surface traps of the original and nanocomposite films were measured and calculated by surface potential decay method, and the carrier mobility was also obtained; finally, the vacuum direct current (DC) surface flashover characteristics and bulk resistivity of all the film samples were measured and analyzed. The experiment results showed that with the increase in the amount of nano-ZnO, both the shallow and deep trap density increased significantly, while the trap energy varied slightly, and the surface flashover voltage also increased obviously. Based on the multi-core model, the increases in the shallow and deep trap density after the introduction of nano-ZnO into the PI matrix was analyzed from the microscopic perspective of the interface. Based on the comparative analysis of the trap distribution and surface flashover voltage characteristics, a bilayer model of vacuum DC surface flashover development was proposed. In the bilayer model, deep traps and shallow traps play a dominant role in the vacuum–solid interface and the inner surface of the dielectric, respectively, and increasing the trap density could effectively inhibit secondary electron multiplication on the surface and accelerate charge dissipation inside the film. Consequently, nano-ZnO can purposefully control the trap distribution, and then improve the flashover characteristics of nano-ZnO/PI composite films, which provides a new approach for improving the spacecraft material safety. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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15 pages, 4189 KiB  
Article
Research on Silicone Rubber Sheds of Decay-Like Fractured Composite Insulators Based on Hardness, Hydrophobicity, NMR, and FTIR
by Zhijin Zhang, Guohui Pang, Ming Lu, Chao Gao and Xingliang Jiang
Polymers 2022, 14(16), 3424; https://doi.org/10.3390/polym14163424 - 22 Aug 2022
Cited by 12 | Viewed by 1987
Abstract
The safety and stability of power systems are seriously threatened by the decay-like fracture of composite insulators. This paper analyzes the aging characteristics (physical properties, NMR, and FTIR) of the silicone rubber sheds of the decay-like fractured insulator. The same V-string insulator and [...] Read more.
The safety and stability of power systems are seriously threatened by the decay-like fracture of composite insulators. This paper analyzes the aging characteristics (physical properties, NMR, and FTIR) of the silicone rubber sheds of the decay-like fractured insulator. The same V-string insulator and a new insulator are used for comparison. The study shows that the sheds’ degradation is concentrated on the side with heavy pollution. The physical properties (appearance, pollution, hardness, and hydrophobicity) of the high voltage end decrease significantly compared to other positions, but there is no direct connection between the physical properties of sheds and the decay-like fracture of the core rod. The severity of aging increases with a decrease in the equivalent transverse relaxation time T2. The main chain of the PDMS material was severely damaged at the location of the insulator fracture. NMR and FTIR can well judge the aging degree of silicone rubber housings. However, no definite characteristic quantity can characterize the decay-like fracture. It is challenging to evaluate the decay-like fracture of the silicone rubber shed only by its aging degree. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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16 pages, 7392 KiB  
Article
Nondestructive Evaluation of Composite Bonding Structure Used in Electrical Insulation Based on Active Infrared Thermography
by Chenjun Guo, Lishuai Liu, Hongwei Mei, Yanxin Tu and Liming Wang
Polymers 2022, 14(16), 3373; https://doi.org/10.3390/polym14163373 - 18 Aug 2022
Cited by 1 | Viewed by 1321
Abstract
Nondestructive testing and evaluation of composite insulating components of electrical equipment is extremely necessary for assuring the safety of a power system. However, most existing nondestructive testing methods are not applicable for fast and effective live detection due to their time-consuming operation, high [...] Read more.
Nondestructive testing and evaluation of composite insulating components of electrical equipment is extremely necessary for assuring the safety of a power system. However, most existing nondestructive testing methods are not applicable for fast and effective live detection due to their time-consuming operation, high cost, and contact or near-field measurement. In this work, the effectiveness of active infrared thermography was investigated for detecting defects in silicone rubber (SIR)–fiber-reinforced plastic (FRP) bonding structures, which have been commonly used in insulating components of power equipment. The effectiveness of differential thermal image for enhancing the contrast of defective and sound areas and eliminating additive noise was demonstrated. Particularly, frame difference thermal image obtained by subtracting two differential thermal images extracting from respectively before and after the contrast inversion was proposed to enhance defect identification. The results revealed that defects of various sizes and depths such as voids, cracks, and interface disbonding of the SIR–FRP bonding structure were accurately detected by thermographic data. With the advantages of a quick and simple process, safety, universal applicability, visual results, far-field measurement, and quantitative defect estimation capabilities, active infrared thermography would be quite promising for live detection of electrical equipment. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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16 pages, 9655 KiB  
Article
Thermal Aging Evaluation of XLPE Power Cable by Using Multidimensional Characteristic Analysis of Leakage Current
by Yong Liu, Hao Wang, Han Zhang and Boxue Du
Polymers 2022, 14(15), 3147; https://doi.org/10.3390/polym14153147 - 02 Aug 2022
Cited by 4 | Viewed by 2437
Abstract
Thermal aging is a common form of cable deterioration. In this paper, the effect of thermal aging on cables is evaluated by analyzing the harmonic characteristics in cable leakage currents. Cable samples were first fabricated and subjected to accelerated thermal aging tests at [...] Read more.
Thermal aging is a common form of cable deterioration. In this paper, the effect of thermal aging on cables is evaluated by analyzing the harmonic characteristics in cable leakage currents. Cable samples were first fabricated and subjected to accelerated thermal aging tests at 120 °C. The experimental circuits were built to test the dielectric loss factor and the AC leakage current of the cable at different aging times. Then, the improved variational modal decomposition (VMD) algorithm was used for the time–frequency analysis of the leakage current, and the relationship between thermal aging and leakage current harmonics was investigated. Thermal aging was discovered to increase the capacitance and dielectric loss factor of the cable as well as generate harmonics in the leakage current, with harmonics at 150, 450, and 650 Hz being particularly sensitive to thermal aging. The multidimensional characteristic parameters such as the time-domain, frequency-domain, and relative energy and the sample entropy of the leakage current harmonics were calculated. The results demonstrated thermal aging increased the relative energy and power spectrum energy of the harmonics and increased the disorder of the harmonic sequence. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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15 pages, 9201 KiB  
Article
An Environmentally-Friendly Three-Dimensional Computer-Aided Verification Technique for Plastic Parts
by Chil-Chyuan Kuo, Zong-Yan He and Chil-Xian Lee
Polymers 2022, 14(15), 2996; https://doi.org/10.3390/polym14152996 - 24 Jul 2022
Viewed by 1251
Abstract
Plastic components play a significant role in conserving and saving energy. Plastic products provide some advantages over metal, including reducing part weight, manufacturing costs, and waste, and increasing corrosion resistance. Environmental sustainability is one of the sustainable development goals (SDGs). Currently, the non-contact [...] Read more.
Plastic components play a significant role in conserving and saving energy. Plastic products provide some advantages over metal, including reducing part weight, manufacturing costs, and waste, and increasing corrosion resistance. Environmental sustainability is one of the sustainable development goals (SDGs). Currently, the non-contact computer-aided verification method is frequently employed in the plastic industry due to its high measurement efficiency compared with the conventional contact measuring method. In this study, we proposed an innovative, green three-dimensional (3D) optical inspection technology, which can perform precise 3D optical inspection without spraying anything on the component surface. We carried out the feasibility experiments using two plastic parts with complex geometric shapes under eight different proposed measurement strategies that can be adjusted according to the software interface. We studied and analyzed the differences in 3D optical inspection for building an empirical technical database. Our aim in this study is to propose a technical database for 3D optical measurements of an object without spraying anything to the component’s surface. We found that the research results fulfilled the requirements of the SDGs. Our research results have industrial applicability and practical value because the dimensional average error of the two plastic parts has been controlled at approximately 3 µm and 4.7 µm. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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10 pages, 4628 KiB  
Article
A Modified Langmuir Model for Moisture Diffusion in UGFRE of Composite Insulator Considering the Composite Degradation
by Zhikang Yuan, Cheng Wang, Lijun Jin, Youping Tu, Yingyao Zhang, Zhenlian An and Yongfei Zhao
Polymers 2022, 14(14), 2922; https://doi.org/10.3390/polym14142922 - 19 Jul 2022
Cited by 2 | Viewed by 1655
Abstract
Water invasion induced aging and degradation of the unidirectional glass fiber reinforced epoxy resin (UGFRE) rod is inferred as the primary reason for the decay-like fracture of the composite insulator. In this paper, the moisture diffusion processes in the UGFRE from different directions [...] Read more.
Water invasion induced aging and degradation of the unidirectional glass fiber reinforced epoxy resin (UGFRE) rod is inferred as the primary reason for the decay-like fracture of the composite insulator. In this paper, the moisture diffusion processes in the UGFRE from different directions at various test humidities and temperatures are studied. The moisture diffusion of the UGFRE sample obeys the Langmuir diffusion law under the humidity conditions of 53%, 82% and 100% at 40 °C. In deionized water, the moisture diffusion of the UGFRE sample also obeys the Langmuir diffusion law when the invading direction is vertical to the glass fiber. However, when the water invades the UGFRE sample, parallel with the glass fiber, the weight loss caused by composite degradation should not be neglected. A modified Langmuir model, taking Arrhenius Theory and the nonlinear aging characteristic of the composite into consideration, is proposed and can successfully describe the moisture diffusion process. Both the glass fibers and epoxy resin will degrade in the deionized water. The glass fibers show better resistance to degradation than the epoxy resin. The epoxy resin degrades from the glass fiber/epoxy resin interface and become fragments. For composite insulators, the water invasion through the ends should be avoided as far as possible, or the degradation of the UGFRE rod will result in decay-like fracture. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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13 pages, 6396 KiB  
Article
A Terahertz Identification Method for Internal Interface Structures of Polymers Based on the Long Short-Term Memory Classification Network
by Shushan Wang, Hongwei Mei, Jianjun Liu, Dabing Chen and Liming Wang
Polymers 2022, 14(13), 2611; https://doi.org/10.3390/polym14132611 - 27 Jun 2022
Cited by 1 | Viewed by 1331
Abstract
Polymers are used widely in the power system as insulating materials and are essential to the power grid’s security and stability. However, various insulation defects may occur in the polymer., which can lead to severe insulation accidents. Terahertz (THz) detection is a novel [...] Read more.
Polymers are used widely in the power system as insulating materials and are essential to the power grid’s security and stability. However, various insulation defects may occur in the polymer., which can lead to severe insulation accidents. Terahertz (THz) detection is a novel non-destructive testing (NDT) method that is able to detect the interface structures inside polymers. The large quantity of information in the THz waveform has potential for the identification of interface types, and the long short-term memory (LSTM) network is one of the most popular artificial intelligence methods for time series data like THz waveform. In this paper, the LSTM classification network was used to identify the internal interfaces of the polymer with the reflected THz pulses of the internal interfaces. The experiment verified that it is feasible to identify and image the void interfaces and impurity interfaces in the polymer using the proposed method. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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14 pages, 3195 KiB  
Article
Characteristics of Small-Molecule Migration of Silicone Rubber Insulator in Electrical Power Systems
by Xiaobo Meng, Gongmao Peng, Kang Niu, Xiaogang Wang, Hongwei Mei and Liming Wang
Polymers 2022, 14(13), 2519; https://doi.org/10.3390/polym14132519 - 21 Jun 2022
Cited by 2 | Viewed by 1281
Abstract
The migration of low-molecular-weight components of polysiloxane (small molecules) to the surface of high-temperature-vulcanizing silicone rubber (HTV-SR) ensures its hydrophobicity and tends to coat the surface of pollutants, which would otherwise lower hydrophobicity. The transferability of hydrophobicity will ensure the insulator maintains its [...] Read more.
The migration of low-molecular-weight components of polysiloxane (small molecules) to the surface of high-temperature-vulcanizing silicone rubber (HTV-SR) ensures its hydrophobicity and tends to coat the surface of pollutants, which would otherwise lower hydrophobicity. The transferability of hydrophobicity will ensure the insulator maintains its higher hydrophobicity after being coated with surface pollutants, thus providing the insulator with higher pollution flashover voltage. This migration process takes a certain time, and in this paper, the time characteristics of hydrophobicity transfer from HTV-SR coated with ten different inert materials were investigated. Ten different inert materials have different migration times and static contact angles, possibly due to the influence of pollution material characteristics on the characteristics of small-molecule migration. Thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), and gas chromatography–mass spectrometry (GC–MS) were used to analyze the migration of small molecules to the polluted surface. The evidence of small molecules migrating to the surface of the polluted material over time was found. Furthermore, the influence of pollution material characteristics on small-molecule migration was analyzed via SEM, specific surface area, and porosity. On that basis, the hydrophobicity migration characteristics of mixtures of kaolin and kieselguhr were also studied and compared to determine how best to simulate the behavior of natural pollution using artificial pollutants and their mixtures. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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25 pages, 5997 KiB  
Article
Research on Improving the Partial Discharge Initial Voltage of SiC/EP Composites by Utilizing Filler Surface Modification and Nanointerface Interaction
by Xupeng Song, Wei Yang, Shouchao Huo, Kun Wang, Yuanyuan Wu, Yun Chen, Jian Qiao, Boyang Shen and Xingming Bian
Polymers 2022, 14(11), 2297; https://doi.org/10.3390/polym14112297 - 05 Jun 2022
Cited by 3 | Viewed by 2014
Abstract
SiC/EP composites are promising insulating materials due to their high thermal conductivity, stable chemical properties, and nonlinear electrical conductivity. However, the compatibility of micron-sized SiC particles with the organic polymer matrix is poor, and defects such as air gaps may be introduced at [...] Read more.
SiC/EP composites are promising insulating materials due to their high thermal conductivity, stable chemical properties, and nonlinear electrical conductivity. However, the compatibility of micron-sized SiC particles with the organic polymer matrix is poor, and defects such as air gaps may be introduced at the interface, which reduces the partial discharge resistance of the composite materials. In order to improve the partial discharge initial voltage (PDIV) of SiC/EP composites, in this paper, SiC/EP composites with different proportions were prepared by surface modification of filler and compound of micro/nano particles. Firstly, a method of secondary modification of SiC particles was proposed, which was first modified by alkali washing and then silane coupling agent KH560, and the effectiveness of the modification was verified. Therefore, the interface bonding ability between the filler and the matrix was improved, the air gap defects at the interface were reduced, and the PDIV of the composite material was improved. When the filling ratio is 10 wt%, the PDIV was enhanced by 13.75%, and when the filling ratio was further increased, the improvement was reduced. In contrast, the introduction of nanoparticles into the composites can effectively improve the PDIV of composite materials. In this study, nanoparticles were used to form a shell-core structure in epoxy resins to exert their huge specific surface area and active surface properties, thereby changing the overall crosslinking properties of the composites. Through experimental research, the optimal micro-nano particle compounding ratio was explored. Under the optimal mixing ratio, the PDIV of the composite material can be increased by more than 90%. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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15 pages, 4850 KiB  
Article
Performance Evaluation of Cross-Linked Polyethylene Insulation of Operating 110 kV Power Cables
by Man Ding, Weifeng He, Jiahe Wang and Jinpeng Wang
Polymers 2022, 14(11), 2282; https://doi.org/10.3390/polym14112282 - 03 Jun 2022
Cited by 7 | Viewed by 1941
Abstract
The ageing characteristic of XLPE insulation of operating a 110 kV power cable with different service time is studied in this paper. The microscopic morphology of XLPE films from different cables were characterized by using Differential Scanning Calorimetry (DSC), X-ray Diffraction method (XRD), [...] Read more.
The ageing characteristic of XLPE insulation of operating a 110 kV power cable with different service time is studied in this paper. The microscopic morphology of XLPE films from different cables were characterized by using Differential Scanning Calorimetry (DSC), X-ray Diffraction method (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) methods, and the dielectric, mechanical, and electrical properties of XLPE were also measured. The relationship of several typical property parameters with the cable service time were established, and the ageing mechanism of XLPE insulation of the operating cable was also analyzed. It was found that XLPE insulation would endure a recrystallization process in the initial operation stage during which the microscopic morphology would become more perfect with higher crystallinity and denser crystal structure. Then, the thermal oxidation would dominate the ageing process of XLPE with the molecular chains broken and more micromolecular products generated after the cable had operated for more than 10–15 years. The AC breakdown strength decreases with the increase of cable service time, with lower decreasing rate in the initial operation stage and a larger rate after 10–15 years. The Pearson correlation coefficient between the cable service time with the characteristic parameters were calculated, and some of them were found to be effective to be used as indicators for operation state detection of operating power cables. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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10 pages, 2876 KiB  
Article
Investigation into Layer Number Effect on Breakdown Strength of Multi-Layer Polymer Films
by Liang Zhao, Binxiong Yu and Wei Shang
Polymers 2022, 14(9), 1653; https://doi.org/10.3390/polym14091653 - 20 Apr 2022
Cited by 4 | Viewed by 1347
Abstract
The layer number effect on electric breakdown strength (EBD) of multi-layer polymer films is investigated using 10-μm polypropylene (PP) films under a dc condition. The layer number, n, of the films during the test is as large as 120. [...] Read more.
The layer number effect on electric breakdown strength (EBD) of multi-layer polymer films is investigated using 10-μm polypropylene (PP) films under a dc condition. The layer number, n, of the films during the test is as large as 120. It is observed that the relation between EBD and n conforms to a minus power law, i.e., EBD(n) = E1′n−a, where the power exponent, a, is 0.27, E1′ is a constant. By reviewing the experimental data in references, it is found that the power law holds true for different types of polymers in different test conditions, but the value of a varies from 0.072 to 0.5. The variation of a is explained in perspective of the discontinuous structures within films and those between films. A small value of a means a good purity level of the film, which is due to the decrease of the size of the inter-layer defects. A large value of a means a poor purity level of the films, which is due to the increase of the amount of intra-layer defects. Both factors influence the value of a, leading to the variation of a. Full article
(This article belongs to the Special Issue Detection and Diagnosis of Polymer Composites for Electrical and Electronic Engineering Application)
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