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The thermal degradation behavior of glass fiber reinforced polymer (GFRP) in nitrogen atmosphere was studied in the present work by thermogravimetric analysis (TGA). The changes of GFRP during the thermal degradation process were characterized from both chemical composition and micro physical structure points of view by using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The steps of thermal degradation of GFRP in nitrogen were investigated in detail by analyzing the residues at different set temperatures, then the temperature ranges for the disappearance of methyl and aliphatic structure and the appearance of carbonyl and polyaromatic structure were determined with a temperature resolution of 20 °C. The changes of micro physical structure of GFRP during the thermal degradation in nitrogen involved the softening, melt, shrinkage, appearing of twisted and shrink lines, debonding of interface between glass fiber and epoxy resin matrix and releasing the pyrolyzed gas consecutively. Based on the results, the entire process of thermal degradation of GFRP from initial intact to final deterioration in nitrogen up to 800 °C was characterized, the present work is helpful for better understanding of the thermal degradation behavior of GFRP used in high voltage composite insulator as well as in other industry applications involving the temperature rising condition.

The abnormal heating of high voltage composite insulator seriously affects the safe and stable operation of the overhead transmission line. In order to understand and avoid such accidents, the thermal degradation behavior of glass fiber reinforced polymer (GFRP) core deserves special attention. In the present work, the thermogravimetric analysis (TGA) was used to simulate the thermal degradation process of GFRP materials. The non-oxidative environment (nitrogen) and oxidative environment (air) were both used for comparing the difference of thermal degradation of GFRP in these conditions. The changes of GFRP during the thermal degradation process were characterized from both chemical composition and micro physical structure points of view by using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). By comparing the final residues of GFRP after thermal degradation in nitrogen and in air up to 800 °C, it was found that the chemical reactions during thermal degradation of GFRP contains auto-oxidation, aliphatic structure scission and formation of polyaromatic. Based on the results, the entire process of thermal degradation of GFRP from initial intact to final deterioration was characterized, the present work is helpful for better understanding of the thermal degradation behavior of GFRP used in high voltage composite insulator as well as in other industry applications involving the temperature rising condition.

Dielectric response provides an effective method to investigate the microstructure and charge dynamic of dielectrics. In the present research, the single relaxation process or conductivity process is expressed equivalently as an electrical component, in terms of micro physical structure, these electrical components can be electrically connected to form an equivalent circuit characterizing the dielectric response feature. In general there are five types of electrical components that can be inserted in an equivalent circuit: (1) a loss peak component; (2) a quasi-dc component (QDC) component; (3) a charge diffusion component; (4) a frequency independent capacitance component; and (5) a dc conductivity component. The equivalent circuit method can represent a quantitative analysis of the dielectric response, reflect the relationship between microstructure of dielectric and the measured dielectric response. The present work is helpful for understanding the Equivalent circuit and providing a theoretical analysis method of detecting the microstructure of dielectric.

Breeze vibration, which is a threat to the safe operation of transmission lines, easily leads to the damage of wires and fittings. ACCC (Aluminum Conductor Composite Core Wire) is a kind of new material wire, which has the characteristics of capacity increasing, high strength, corrosion proof, small SAG, etc. Therefore, it becomes one of the solutions to improve response properties of compacted lines. However, under the influence of material property, brittle failure easily happens with the complex loads, and then fatigue damage would generates from wires and fittings under long vibration caused by aeolian vibration, so as to influence the safe operation of transmission lines. In this paper, test system of aeolian vibration is built, and aeolian vibration fatigue test of ACCC is studied with the system. Finally, the resistance to mechanical fatigue performance of ACCC is explored.

The pollution on the surface of high voltage insulator including a composite insulator, ceramic insulator and glass insulator may lead to the pollution flashover of electrical outdoor insulation, thus, the characteristics of pollution on the surface of high voltage insulator deserve detail investigated. In the present work, the characteristics of saturation pollution on high voltage insulator in North China were analyzed in terms of pollution particle size analysis, pollution particle morphology and chemical component analysis. Firstly, the equivalent salt deposit density (ESDD) was measured according to the IEC 60815, the results showed that the ESDD for composite insulator was larger than the ESDD for ceramic and glass insulators. Secondly, the particle size analysis showed that the distributions of pollution particle size on ceramic and glass insulators were almost the same, however, the distribution of pollution particle size on composite insulator was quite different from the former two, more specifically, the pollution particle with lager size can be observed on the surface of composite insulator. It should be noted that due to the diffusion of LMW and the interaction between the LMW and pollution, the ESDD on composite insulator was larger and the particle size on composite insulator was alas larger than that on ceramic insulator and glass insulator, therefore, the evaluation on the pollution performance of high voltage insulator should be more comprehensive. The present study is a case study of the pollution and is helpful for better understanding of the pollution characteristics on high voltage insulator used in North China.

In the present research, five filled HTV silicone rubber with different ATH filler content were manufactured and analyzed by TGA measurement in Argon atmosphere. The crystal structure of ATH filler was measured by XRD analysis, based on the XRD results, it can be confirmed that ATH filler used in this research is the Gibbsite. The weight loss process of HTV silicone rubber during the TGA process was identified, two loss peaks were observed in the derivative of TGA curve, one was attributed to the dehydration of ATH filler and the other one was attributed to the pyrolyzation of silicone rubber matrix. Furthermore, a calculation method for obtaining each component weight in HTV silicone rubber based on TGA results was proposed, based on this calculation method, the detailed content information of these five HTV silicone rubber was obtained. Based on this research, it can be concluded that the TGA analysis of filled HTV silicone rubber is an effective way to obtain the weight of each component in HTV silicone rubber.

Water diffusion and permeation are considered the major mechanism for describing the aging phenomena of high temperature vulcanizing silicone rubber used in outdoor high voltage composite insulator. In order to obtain an appropriate model to investigate the water molecule diffusion process into silicone rubber, as well as the diffusion characteristics of this process, molecular dynamics simulation method was employed to study the water diffusion process into HTV silicone rubber. The simulation results revealed that the ATH filler in the silicone rubber composites was the main waterabsorbing component in comparison with the silica filler. The elimination of surface hydroxyl groups on the silica filler surface can improve the hydrophobicity of the composites and therefore can contribute to reducing the amount of moisture absorbed in the composite. In actual HTV silicone rubber, the surface hydroxylation degree of silica was low, and PDMS would be wrapped on the silica surface, so silica should have less influence on the water absorption of the system than that of ATH filler. The present study is helpful for better understanding of water diffusion into HTV silicone rubber and into other composite containing different kind of filler used in electrical engineering.

In thunderstorm weather, lightning induction appears on the surface of ground objects, and then the positive glow corona is initiated, which influences the selection of lighting targets by lighting leader. So, it has great research value for lightning protection of AC/DC transmission lines. Here, a two-dimensional model of positive glow corona is established in COMSOL Multiphysics. From the simulation results of its development progress, corona current, ion distribution, and migration are revealed. The positive ions are in a round symmetric distribution at the initial stage of migration, but when the ions move farther away, ions become an elongated oval distribution. Also, most of the ions move to the thundercloud in the end. The positive ions accumulate above the transmission line and form a positive background, which has confinement and attenuation to electronic beam. Therefore, the probability of the electron avalanche converted into flowing is reduced. Meanwhile, the positive background promotes the compound of ions and electrons. As a result, the initiation of upward leader is suppressed and so the selection of lighting targets by lighting leader is influenced.

In the present paper, five filled HTV silicone rubber with different ATH filler content were characterized by mechanical measurement, FTIR analysis and XPS analysis. It has been found that the ATH filler had a bad combination effect with silicone rubber matrix, for the ATH filler without surface medication, the interaction between ATH filler and silicone rubber was physical interaction, the poor interaction leads to low mechanical performance of silicone rubber with ATH filler being added in the matrix. The addition of ATH filler leads to an increase of hydroxyl (-OH) and a decrease of Si (CH 3 ) 2 . The decrease of Si (CH 3 ) 2 with adding ATH filler into silicone rubber matrix indicated that the ATH filler has a spacing effect which can limit the crosslink of silicone rubber. Due to the migration of LMW, the surface of ATH filler will be covered by LWM, while the analysis depth of XPS is nm, so no Al element can be detected on the surface of silicone rubber. Thus, the XPS analysis is not suitable for detecting the ATH filler in silicone rubber. Based on this research, an in-depth understanding of the mechanical properties of silicone rubber with different ATH content as well as the related FTIR and XPS results have been obtained.