The Experts below are selected from a list of 171 Experts worldwide ranked by ideXlab platform

Xing Liang Jiang - One of the best experts on this subject based on the ideXlab platform.

  • A Predictive Model for Dry-Growth Icing on Composite Insulators under Natural Conditions
    MDPI AG, 2018
    Co-Authors: Xing Liang Jiang, Zhongyi Yang, Conglai I
    Abstract:

    Icing can adversely influence electric power system security. Two main issues are caused by icing: the overload of transmission lines, and the reduction in the insulation ability of the Insulators. Most previous research has focused on the flashover characteristics of ice-covered Insulators, but research on the icing process of the Insulator is seriously lacking. Considering the effect of icing shape, the outer airflow field of an Insulator was calculated and the local collision efficiencies of water droplets (β1) were investigated according to the Lagrange algorithm. The simulation showed that the values of β1 on the Insulator edge and rod are much higher than on the Insulator surface, and both were significantly influenced by the wind speed and median volume diameter (MVD) of the water droplets. Based on thermal balance equations, a dynamic dry-growth icing model was established. Using the natural icing conditions of Xuefeng Mountain (China) as an example, validation experiments were conducted on a Composite Insulator and the climate parameters measured by multi-cylinders were used to model the icing shape and mass. The results indicate that high wind speed and low temperature increase icing rate; the icing was mainly concentrated on the windward side and the greatest horizontal thickness was generally on the Insulator edge. The dry-growth model had an average error lower than 25% for icing thickness and an average error lower than 20% for icing mass, which were affected by icing roughness

  • AC flashover performance of different shed configurations of Composite Insulators under fan-shaped non-uniform pollution
    Institution of Engineering and Technology, 2018
    Co-Authors: Zhiji Zhang, Xinha Qiao, Yi Zhang, Liang Tia, Dongdong Zhang, Xing Liang Jiang
    Abstract:

    Currently, it is founded that under unidirectional wind and certain landform, Composite Insulators are always fan-shaped non-uniformly polluted. In this paper, artificial pollution tests on three types of Composite Insulators with different shed configurations and under various fan-shaped non-uniform pollution conditions were carried out. Then the flashover performances of Composite Insulators, porcelain Insulators and glass Insulators were compared. Results indicate that there is a big difference between ac flashover performance of Composite Insulators under non-uninform pollution and uninform pollution. The flashover voltage of Composite Insulator is largely influenced by salt deposit density (SDD), the ratio of SDD of windward side to leeward side (W/L), the occupation ratio of leeward side k and the shed configurations. The relationship between SDD and U(50) still meets negative power function when Composite Insulator is fan-shaped non-uninform polluted. There is a reduction of 17.8–27.6% in the flashover strength when the ratio W/L of SDD decreases from 1/1 to 1/15. The shed configurations of Composite Insulators have great effects on the flashover performance. Composite Insulators always have better withstand property compared to glass and porcelain Insulators under either uniform pollution or fan-shaped non-uniform pollution

  • Non-Uniform Distribution of Contamination on Composite Insulators in HVDC Transmission Lines
    MDPI AG, 2018
    Co-Authors: Zhiji Zhang, Xinha Qiao, Shenghua Yang, Xing Liang Jiang
    Abstract:

    In recent years, the air particulate pollutants formed by the combustion of fossil fuels and the emission of industrial waste gases have constantly been produced, and the polluted particles deposit also seriously affects social production and people’s lives. For instance, pollution-induced flashover is seriously threatening the safe operation of the power system, while Insulator pollution non-uniformity has great influence on the flashover voltage of Insulators. Therefore, in this paper both field contamination experiments of HVDC (High Voltage Direct Current) transmission lines and wind tunnel contamination simulation tests were conducted, and pollution non-uniformity coefficient KT/B, KW/L and KH/M were proposed and obtained. The results showed that the degree of contamination on top surface and leeward side is heavier than that on bottom surface and windward side. Thus, in the DC energized condition, contamination along the string is also non-uniform, and serious pollution occurs mainly in the high voltage terminal. In order to explain the uneven distribution phenomenon along the string, the coupling-physics model of Composite Insulator string was established and using the finite element method, the electric field around the Insulator was simulated. Furthermore, basing on the field charging theory, the value of electric field force on particles around the Insulator surface was calculated and the mechanism of non-uniformity along the Insulator sting was then explained. The results are very important for guiding insulation design and field anti-pollution works

  • Investigation of flashover voltage and non-uniform pollution correction coefficient of short samples of Composite Insulator intended for ±800kV UHVDC
    IEEE Transactions on Dielectrics and Electrical Insulation, 2010
    Co-Authors: Xing Liang Jiang, Zhijin Zhang, Jianlin Hu, Shaohua Wang, Qin Hu
    Abstract:

    Differences in the amount of pollution on the top and bottom surfaces of an Insulator have a great influence on the dc pollution flashover voltage. Up to now, many investigations have been carried out on non-uniform pollution flashover performance of porcelain and glass Insulators, but very few on Composite Insulators. In this paper the influence of non-uniform pollution distribution on dc Composite Insulators on their flashover performance was analyzed, and a correction formula for the non-uniform pollution flashover voltage was proposed, based on artificial pollution tests carried out on short samples of a Composite Insulator intended for ±800kV UHVDC. The test results showed that, when the ratio (T/B) of the salt deposit density (SDD) on the top surface to that on the bottom surface is between 1/1 and 1/10, the value of the characteristic exponent a indicating the effect of SDD on the flashover voltage ranges from 0.22 to 0.255. The value of a is nearly independent of T/B. However, the flashover voltage U50 decreases with the increase in T/B. The correction formula indicating the influence of non-uniform pollution distribution on the flashover voltage could be expressed as K=1 - b×log(T/B). For the tested Composite Insulators, the factor b was 0.141 to 0.156, which is smaller than that of porcelain or glass Insulator. That is to say, the influence of T/B on the flashover voltage of the Composite Insulator is weaker than those on the porcelain and glass Insulators. [ABSTRACT FROM AUTHOR]

Yanfeng Gao - One of the best experts on this subject based on the ideXlab platform.

  • Effects of liquids immersion and drying on the surface properties of HTV silicone rubber: characterisation by contact angle and surface physical morphology
    Institution of Engineering and Technology, 2019
    Co-Authors: Yanfeng Gao, Xidong Liang, Yingya Liu, Yuanji Cai
    Abstract:

    High-temperature vulcanised (HTV) silicone rubber Composite Insulator has been widely used in extra-high and ultra-high transmission lines due to its excellent electrical and mechanical performance. In practice use, liquids may encounter the Composite Insulator intermittently and can lead to the degradation and deterioration of silicone rubber. In the present research, the effects of liquids immersion and subsequent drying on the surface properties of HTV silicone rubber were investigated by means of the contact angle measurement and surface physical morphology measurement which was further analysed in terms of the discrete wavelet transform method, multiresolution signal decomposition algorithm, and three-dimensional fractal dimension calculation. Based on the experimental results, the mechanism of the loss and recovery of the hydrophobicity of HTV silicone rubber surface during the liquids immersion and subsequent drying processes were further explained by taking into consideration the embedded water molecules (and/or hydrated ions) on the HTV silicone rubber surface and the synergy of the increase in roughness/fractal dimension and low molecular weight siloxanes diffusion. This study is helpful for better understanding of the change of surface properties of HTV silicone rubber caused by environmental and electrical stresses

  • decay like fracture mechanism of silicone rubber Composite Insulator
    IEEE Transactions on Dielectrics and Electrical Insulation, 2018
    Co-Authors: Xidong Liang, Yanfeng Gao
    Abstract:

    In recent years, a new kind of abnormal fracture phenomena of Composite Insulator occurred in high voltage transmission lines in several countries, which was totally different from brittle fracture and normal fracture. According to the general characteristic features of the fracture, this type of failure was named decay-like fracture of Composite Insulator by the author. In this paper, a decay-like fractured Composite Insulator was investigated and microscopic physic-chemical properties of decay-like fractured Fiber Reinforced Plastic (FRP) core rod were analyzed. Scanning Electron Microscope (SEM), Thermal Gravimetric Analysis (TGA) and Fourier Transform Infrared (FTIR) Spectroscopy methods were employed to explain the microscopic morphology characteristics and chemical component changes of decay-like fractured Composite Insulator, and to further explain the reasons for the name of decay-like fracture in terms of "crisp" and "decay-like". The main microscopic feature of decay-like fracture is the degradation and deterioration of the epoxy resin matrix in FRP rod. The mechanism of decay-like fracture of Composite Insulator could be summarized as follows. Due to the liquids penetration into the sheath-core interface, hydrolysis of silane coupling agent with bad quality leads to poor adhesion strength and interface voids, which results in distortion of electric field at the sheath-core interface. Under the combined action of damp condition and high electric field, discharge and current appear along the FRP rod surface. Epoxy resin matrix is eroded in the presence of discharge and current, and then is soften, melt, evaporated. Meanwhile, ion-exchange and hydrolysis process happen between glass fibers under the combined action of mechanical stress and nitric acid produced by discharge in the presence of moisture. Fiber-resin interface in FRP rod is separated owing to the erosion of epoxy resin. The degradation direction of the decay-like fracture is from outside to inside of FRP rod, and the interface between silicone rubber sheath and FRP rod is confirmed to be the initial deterioration area of the decay-like fracture. The criterion to distinguish the differences between the decay-like fracture, brittle fracture and normal fracture depends on whether the epoxy resin matrix is degraded and deteriorated or not.

  • failure analysis of decay like fracture of Composite Insulator
    IEEE Transactions on Dielectrics and Electrical Insulation, 2014
    Co-Authors: Jiafu Wang, Xidong Liang, Yanfeng Gao
    Abstract:

    In recent years, a new type of Composite Insulator mechanical failure appeared in high voltage transmission lines, which is a type of severe accident for power system, but only few studies on it have been reported all over the world. In this paper, this type of failure was named Decay-like Fracture by summarizing and analyzing the general features, and the decay-like fracture of Composite Insulator was treated and studied as a new type of Composite Insulator mechanical failure. By analyzing some field failed Composite Insulators in China, main features of decay-like fracture were then summarized. The fracture spot of decay-like fractured Insulator became crisp and looked like decayed wood. The mechanisms of the normal fracture and brittle fracture of Composite Insulator cannot explain decay-like fracture, and boron-free Fiber Reinforced Plastic (FRP) core which has been widely used to prevent brittle fracture could not prevent decay-like fracture. Decay-like fracture is not a pure mechanical failure. The discharging and surface micro current on the core surface would finally lead to mechanical fracture of Composite Insulator. But the process and mechanism of decay-like fracture still need further researches.

Gubanski Stanislaw - One of the best experts on this subject based on the ideXlab platform.

  • Surface Potential Decay on Material Samples Taken From In-service Aged (U) HVDC Silicone Rubber Composite Insulators
    2017
    Co-Authors: Chao Yua, Xie Congzhe, Li Licheng, Xu Xiangdong, Gubanski Stanislaw
    Abstract:

    Surface potential decay characteristics of specimens extracted from in-service aged and reference UHVDC Composite Insulator sheds are reported and analyzed in this paper. In the experiments, surfaces of the Insulator samples were charged by dc corona and the decay was recorded utilizing a non-contact technique. In addition, surface and bulk conductivities of the specimens were determined and used for analyzing by means of computer simulations their impact on the potential distribution profiles and its decay. Based on the performed experiments, trap density distributions, mobility of charge carriers and field dependent bulk conductivities are deduced for the investigated samples with the aim to evaluate the ageing severity

  • Surface Potential Decay on Material Samples Taken From In-service Aged HVDC Silicone Rubber Composite
    2017
    Co-Authors: Yua Chengyi, Xie Congzhe, Li Licheng, Xu Xiangdong, Gubanski Stanislaw
    Abstract:

    Surface potential decay characteristics of specimens extracted from in-service aged and reference HVDC Composite Insulator sheds are reported and analyzed in this paper. In the experiments, surfaces of the Insulator samples were charged by dc corona and the decay was recorded utilizing a non-contact technique. In addition, surface and bulk conductivities of the specimens were determined and used for analyzing by means of computer simulations their impact on the potential distribution profiles and its decay. Based on the performed experiments, trap density distributions, mobility of charge carriers and field dependent bulk conductivities are deduced for the investigated samples with the aim to evaluate the ageing severity

Xidong Liang - One of the best experts on this subject based on the ideXlab platform.

  • Effects of liquids immersion and drying on the surface properties of HTV silicone rubber: characterisation by contact angle and surface physical morphology
    Institution of Engineering and Technology, 2019
    Co-Authors: Yanfeng Gao, Xidong Liang, Yingya Liu, Yuanji Cai
    Abstract:

    High-temperature vulcanised (HTV) silicone rubber Composite Insulator has been widely used in extra-high and ultra-high transmission lines due to its excellent electrical and mechanical performance. In practice use, liquids may encounter the Composite Insulator intermittently and can lead to the degradation and deterioration of silicone rubber. In the present research, the effects of liquids immersion and subsequent drying on the surface properties of HTV silicone rubber were investigated by means of the contact angle measurement and surface physical morphology measurement which was further analysed in terms of the discrete wavelet transform method, multiresolution signal decomposition algorithm, and three-dimensional fractal dimension calculation. Based on the experimental results, the mechanism of the loss and recovery of the hydrophobicity of HTV silicone rubber surface during the liquids immersion and subsequent drying processes were further explained by taking into consideration the embedded water molecules (and/or hydrated ions) on the HTV silicone rubber surface and the synergy of the increase in roughness/fractal dimension and low molecular weight siloxanes diffusion. This study is helpful for better understanding of the change of surface properties of HTV silicone rubber caused by environmental and electrical stresses

  • decay like fracture mechanism of silicone rubber Composite Insulator
    IEEE Transactions on Dielectrics and Electrical Insulation, 2018
    Co-Authors: Xidong Liang, Yanfeng Gao
    Abstract:

    In recent years, a new kind of abnormal fracture phenomena of Composite Insulator occurred in high voltage transmission lines in several countries, which was totally different from brittle fracture and normal fracture. According to the general characteristic features of the fracture, this type of failure was named decay-like fracture of Composite Insulator by the author. In this paper, a decay-like fractured Composite Insulator was investigated and microscopic physic-chemical properties of decay-like fractured Fiber Reinforced Plastic (FRP) core rod were analyzed. Scanning Electron Microscope (SEM), Thermal Gravimetric Analysis (TGA) and Fourier Transform Infrared (FTIR) Spectroscopy methods were employed to explain the microscopic morphology characteristics and chemical component changes of decay-like fractured Composite Insulator, and to further explain the reasons for the name of decay-like fracture in terms of "crisp" and "decay-like". The main microscopic feature of decay-like fracture is the degradation and deterioration of the epoxy resin matrix in FRP rod. The mechanism of decay-like fracture of Composite Insulator could be summarized as follows. Due to the liquids penetration into the sheath-core interface, hydrolysis of silane coupling agent with bad quality leads to poor adhesion strength and interface voids, which results in distortion of electric field at the sheath-core interface. Under the combined action of damp condition and high electric field, discharge and current appear along the FRP rod surface. Epoxy resin matrix is eroded in the presence of discharge and current, and then is soften, melt, evaporated. Meanwhile, ion-exchange and hydrolysis process happen between glass fibers under the combined action of mechanical stress and nitric acid produced by discharge in the presence of moisture. Fiber-resin interface in FRP rod is separated owing to the erosion of epoxy resin. The degradation direction of the decay-like fracture is from outside to inside of FRP rod, and the interface between silicone rubber sheath and FRP rod is confirmed to be the initial deterioration area of the decay-like fracture. The criterion to distinguish the differences between the decay-like fracture, brittle fracture and normal fracture depends on whether the epoxy resin matrix is degraded and deteriorated or not.

  • failure analysis of decay like fracture of Composite Insulator
    IEEE Transactions on Dielectrics and Electrical Insulation, 2014
    Co-Authors: Jiafu Wang, Xidong Liang, Yanfeng Gao
    Abstract:

    In recent years, a new type of Composite Insulator mechanical failure appeared in high voltage transmission lines, which is a type of severe accident for power system, but only few studies on it have been reported all over the world. In this paper, this type of failure was named Decay-like Fracture by summarizing and analyzing the general features, and the decay-like fracture of Composite Insulator was treated and studied as a new type of Composite Insulator mechanical failure. By analyzing some field failed Composite Insulators in China, main features of decay-like fracture were then summarized. The fracture spot of decay-like fractured Insulator became crisp and looked like decayed wood. The mechanisms of the normal fracture and brittle fracture of Composite Insulator cannot explain decay-like fracture, and boron-free Fiber Reinforced Plastic (FRP) core which has been widely used to prevent brittle fracture could not prevent decay-like fracture. Decay-like fracture is not a pure mechanical failure. The discharging and surface micro current on the core surface would finally lead to mechanical fracture of Composite Insulator. But the process and mechanism of decay-like fracture still need further researches.

Xu Xiangdong - One of the best experts on this subject based on the ideXlab platform.

  • Surface Potential Decay on Material Samples Taken From In-service Aged (U) HVDC Silicone Rubber Composite Insulators
    2017
    Co-Authors: Chao Yua, Xie Congzhe, Li Licheng, Xu Xiangdong, Gubanski Stanislaw
    Abstract:

    Surface potential decay characteristics of specimens extracted from in-service aged and reference UHVDC Composite Insulator sheds are reported and analyzed in this paper. In the experiments, surfaces of the Insulator samples were charged by dc corona and the decay was recorded utilizing a non-contact technique. In addition, surface and bulk conductivities of the specimens were determined and used for analyzing by means of computer simulations their impact on the potential distribution profiles and its decay. Based on the performed experiments, trap density distributions, mobility of charge carriers and field dependent bulk conductivities are deduced for the investigated samples with the aim to evaluate the ageing severity

  • Surface Potential Decay on Material Samples Taken From In-service Aged HVDC Silicone Rubber Composite
    2017
    Co-Authors: Yua Chengyi, Xie Congzhe, Li Licheng, Xu Xiangdong, Gubanski Stanislaw
    Abstract:

    Surface potential decay characteristics of specimens extracted from in-service aged and reference HVDC Composite Insulator sheds are reported and analyzed in this paper. In the experiments, surfaces of the Insulator samples were charged by dc corona and the decay was recorded utilizing a non-contact technique. In addition, surface and bulk conductivities of the specimens were determined and used for analyzing by means of computer simulations their impact on the potential distribution profiles and its decay. Based on the performed experiments, trap density distributions, mobility of charge carriers and field dependent bulk conductivities are deduced for the investigated samples with the aim to evaluate the ageing severity