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Bush Tree

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Jingang Su – 1st expert on this subject based on the ideXlab platform

  • Effect of Crystalline Morphology on Electrical Tree Growth Characteristics of High-Density and Low-Density Polyethylene Blend Insulation
    IEEE Access, 2020
    Co-Authors: Zhonglei Li, Shuofan Zhou, Boxue Du, Jingang Su

    Abstract:

    The electrical Tree initiation and propagation behaviors are a key issue for the polyethylene-based cable insulation. This paper focuses on the effect of crystalline morphology on electrical Tree growth characteristics of high-density and low-density polyethylene (HDPE/LDPE) blend insulation. In this paper, the electrical Tree growth characteristics of HDPE/LDPE blends with HDPE mass fractions of 0, 10, 15, 20 wt% are investigated under repetitive impulse voltage at 40, 60, 80 °C. It is found that with the rise of HDPE content from 0 to 15 wt%, the growth rate and accumulated damage of electrical Tree decreases, with the morphology of electrical Tree tending to Bush Tree. The increasing of voltage amplitude improves the energy of injected charge while the temperature rise leads to the relaxation of molecular chain, which both result in the promotion of collision ionization, thus increasing the density of electrical Tree. Compared with branch Tree, Bush Tree illustrates better inhibition of discharge tracks due to uniform electric field at the end of branches. The crystalline characteristics of HDPE/LDPE blends indicate that the crystallinity increases with the addition of HDPE, and the blend comprising 15 wt% HDPE in an LDPE matrix apparently reduces the average size of spherulites and improves the distribution of spherulites evenly. The upsurge of crystal-amorphous interface leads to the increase of deep trap energy level density and the decrease of carrier mobility. Carrier injection and migration at the interface between crystalline and amorphous regions are restrained, thus inhibiting the growth of electrical Tree. It is concluded that the crystalline morphology modified by polymer blending has a significant effect on the electrical Tree growth characteristics.

  • Electrical performance of silicone rubber / SiO2 nanocomposites under low temperature
    Proceedings of 2014 International Symposium on Electrical Insulating Materials, 2014
    Co-Authors: Jingang Su, B. X. Du, Huanhuan Du

    Abstract:

    This paper investigated the electrical Tree growth process in SiR/SiO2 nanocomposites under the condition of low temperature. Samples were prepared by mixing nano-SiO2 into room temperature vulcanizing silicone rubber, with the content of 0, 0.5, 1, 1.5 and 2 wt% respectively. The experiment temperature ranged from – 30 °C to -90 °C. AC voltage with a frequency of 50 Hz was applied between a pair of needle-plate electrodes to investigate the electrical Tree at different temperatures. The experimental results reveal that both nanoparticles and low temperature environment have a significant impact on the electrical Tree growth characteristics of SiR/SiO2 composites. This paper studied electrical Tree growth characteristics from the aspects such as the patterns of electrical Tree, fractal dimension and the proportion of cumulative damage. It is suggested that there are both branch Tree and Bush Tree when the temperature is -30 °C or -60 °C, but only pine Tree when the temperature is -90 °C. It is also found that Tree structure is closely related to the crystalline state.

  • Effects of low temperature on Treeing phenomena of silicone rubber
    2013 IEEE International Conference on Solid Dielectrics (ICSD), 2013
    Co-Authors: Tao Han, Jingang Su, Boxue Du, Yu Gao

    Abstract:

    In this paper, room temperature vulcanized (RTV) silicone rubber (SiR) was employed as test sample to investigate the relationship between electrical Tree propagation characteristics and the low experiment temperature. Power frequency voltage was applied on the SiR specimens through the needle-plate electrode with the same radius of needle tips to initiate the electrical Tree at different low experiment temperatures. Both the structures and growth characteristics of electrical Tree in SiR were observed by using a digital camera and a microscope system. Obtained results show that electrical Tree in RTV SiR is white gap Tree channel which maybe composed of silicone compounds instead of carbonized channel in XLPE. Electrical Tree in SiR all initiate from single branch, and the width of initiative single branch channel varies a lot with the electrical Tree structure. The structure of at experiment temperature from 0 °C to -70 °C in RTV SiR can be classified into three categories, which are branch, Bush and pine branch Tree. The distribution of Tree structures changes with the experiment temperature. At the temperature of -70 °C, pine branch Tree take up a great proportion, however, Bush Tree becomes the dominant structure when the temperature rise up to -50 °C and -30 °C. All kinds of electrical Tree grow rapidly in the first beginning of the Treeing propagation, and this process lasts only a few minutes.

B. X. Du – 2nd expert on this subject based on the ideXlab platform

  • Effects of mechanical stress on Treeing growth characteristics in HTV silicone rubber
    IEEE Transactions on Dielectrics and Electrical Insulation, 2017
    Co-Authors: B. X. Du, J. G. Su, Jin Li

    Abstract:

    Tensile and compressive stress, produced by the spring clamp device and the banding force after the expansion of silicone rubber stress cone, can affect the electrical properties of silicone rubber in the cable accessories. Electrical Tree, one of the main electrical aging phenomena, is supposed to be related to the mechanical stress. In this paper, the Treeing growth characteristics considering the tensile and compressive stress were investigated by the pin-plane electrode system respectively. The tensile rate of silicone rubber ranged from 0% to 30%, while the compressive rate varied from 0% to 50%. The results indicate that both the tensile stress and compressive stress affect the Treeing propagation characteristics. The appearance probability of Bush Tree increases and it becomes the main Tree structure at higher tensile rate, while branch Tree turns into the main Tree structure at higher compressive rate. Electrical Tree initiation probability becomes higher and the initial time tends to be shorter under the tensile stress, while they show an opposite tendency under the compressive stress. Under tensile stress, the Tree length, fractal dimension and accumulated damage become lager as the tensile rate increasing, which indicates that the higher tensile rate accelerates the Treeing process. However, under the compressive stress, the Treeing growth process shows a converse trend, which demonstrates that the higher compressive rate retards the electrical Tree growth.

  • Temperature-dependent electrical Tree in silicone rubber under repetitive pulse voltage
    IEEE Transactions on Dielectrics and Electrical Insulation, 2017
    Co-Authors: B. X. Du, J. G. Su

    Abstract:

    Silicone rubber (SiR), which is employed as the main insulation materials in the cable accessories, faces the challenge of high temperature during the overload running process. Pulse voltage is inevitable during the switch operation process of the converters or lighting, which aggravates the operation state of the insulation materials. To understand the electrical Treeing process at the high temperature with repetitive pulse voltage considering the actual operating state, the needle-plate electrode system was stressed in the experiment. In the test, the ambient temperature (Tamb) was set to 30, 60, 90, 120 and 150 °C, while the pulse frequency was 5, 20, 100, 200 and 1000 Hz. Electrical Tree shapes, Tree length, fractal dimension (FD), Tree inception and Tree breakdown probability were studied to investigate electrical Tree growth characteristics. The results indicate that the Tree shapes are depended not only the temperature environment but also the pulse frequency. Higher pulse frequency and higher temperature facilitate Bush Tree shape to be generated. With the pulse frequency increasing, the Tree length becomes longer, while FD tends to be larger. However, the Tree length decreases as the FD increases with the temperature elevating at the same pulse amplitude. As more hot electrons to collide the molecular chain with pulse frequency increasing, the Tree inception and breakdown probability become higher. Nevertheless, the Tree inception probability tends to be larger as the mechanical property of silicone rubber drops with the temperature elevating, while breakdown probability becomes lower as the shorter Tree length grows for a given pulse number.

  • Effects of high temperature and pulse voltage on Treeing process in silicone rubber
    Proceedings of the 2016 IEEE International Conference on Dielectrics ICD 2016, 2016
    Co-Authors: J. G. Su, B. X. Du, Yang Yu, Tao Han, Jin Li, Yaguang Guo, Zongle Ma

    Abstract:

    © 2016 IEEE.High temperature environment produced in the process of high load, accompanying with pulse voltage generated by switching surges during the switch operation of the converters in the HVDC system, has an important influence on the electrical performance of silicone rubber (SiR) in the cable accessories. The pin-plane electrode system was employed in the test to investigate the Treeing characteristics in silicone rubber considering high temperature under repetitive pulse voltage. Results show that when the pulse frequency increases, the Tree length and fractal dimension tend to be larger and the main Tree morphologies are varied from branch Tree to Bush Tree with application 12 kV pulse amplitude at 30 °C. When the temperature becomes higher, the Tree length decreases while the fractal dimension shows a converse tendency. When the temperature is below 90 °C, both branch Tree and Bush Tree are appeared application 9 or 12 kV. However, when the temperature is above 90 °C, the Bush Tree becomes the lead Tree morphology at 200 Hz after 10000 pulse number.

J. G. Su – 3rd expert on this subject based on the ideXlab platform

  • Effects of mechanical stress on Treeing growth characteristics in HTV silicone rubber
    IEEE Transactions on Dielectrics and Electrical Insulation, 2017
    Co-Authors: B. X. Du, J. G. Su, Jin Li

    Abstract:

    Tensile and compressive stress, produced by the spring clamp device and the banding force after the expansion of silicone rubber stress cone, can affect the electrical properties of silicone rubber in the cable accessories. Electrical Tree, one of the main electrical aging phenomena, is supposed to be related to the mechanical stress. In this paper, the Treeing growth characteristics considering the tensile and compressive stress were investigated by the pin-plane electrode system respectively. The tensile rate of silicone rubber ranged from 0% to 30%, while the compressive rate varied from 0% to 50%. The results indicate that both the tensile stress and compressive stress affect the Treeing propagation characteristics. The appearance probability of Bush Tree increases and it becomes the main Tree structure at higher tensile rate, while branch Tree turns into the main Tree structure at higher compressive rate. Electrical Tree initiation probability becomes higher and the initial time tends to be shorter under the tensile stress, while they show an opposite tendency under the compressive stress. Under tensile stress, the Tree length, fractal dimension and accumulated damage become lager as the tensile rate increasing, which indicates that the higher tensile rate accelerates the Treeing process. However, under the compressive stress, the Treeing growth process shows a converse trend, which demonstrates that the higher compressive rate retards the electrical Tree growth.

  • Temperature-dependent electrical Tree in silicone rubber under repetitive pulse voltage
    IEEE Transactions on Dielectrics and Electrical Insulation, 2017
    Co-Authors: B. X. Du, J. G. Su

    Abstract:

    Silicone rubber (SiR), which is employed as the main insulation materials in the cable accessories, faces the challenge of high temperature during the overload running process. Pulse voltage is inevitable during the switch operation process of the converters or lighting, which aggravates the operation state of the insulation materials. To understand the electrical Treeing process at the high temperature with repetitive pulse voltage considering the actual operating state, the needle-plate electrode system was stressed in the experiment. In the test, the ambient temperature (Tamb) was set to 30, 60, 90, 120 and 150 °C, while the pulse frequency was 5, 20, 100, 200 and 1000 Hz. Electrical Tree shapes, Tree length, fractal dimension (FD), Tree inception and Tree breakdown probability were studied to investigate electrical Tree growth characteristics. The results indicate that the Tree shapes are depended not only the temperature environment but also the pulse frequency. Higher pulse frequency and higher temperature facilitate Bush Tree shape to be generated. With the pulse frequency increasing, the Tree length becomes longer, while FD tends to be larger. However, the Tree length decreases as the FD increases with the temperature elevating at the same pulse amplitude. As more hot electrons to collide the molecular chain with pulse frequency increasing, the Tree inception and breakdown probability become higher. Nevertheless, the Tree inception probability tends to be larger as the mechanical property of silicone rubber drops with the temperature elevating, while breakdown probability becomes lower as the shorter Tree length grows for a given pulse number.

  • Effects of high temperature and pulse voltage on Treeing process in silicone rubber
    Proceedings of the 2016 IEEE International Conference on Dielectrics ICD 2016, 2016
    Co-Authors: J. G. Su, B. X. Du, Yang Yu, Tao Han, Jin Li, Yaguang Guo, Zongle Ma

    Abstract:

    © 2016 IEEE.High temperature environment produced in the process of high load, accompanying with pulse voltage generated by switching surges during the switch operation of the converters in the HVDC system, has an important influence on the electrical performance of silicone rubber (SiR) in the cable accessories. The pin-plane electrode system was employed in the test to investigate the Treeing characteristics in silicone rubber considering high temperature under repetitive pulse voltage. Results show that when the pulse frequency increases, the Tree length and fractal dimension tend to be larger and the main Tree morphologies are varied from branch Tree to Bush Tree with application 12 kV pulse amplitude at 30 °C. When the temperature becomes higher, the Tree length decreases while the fractal dimension shows a converse tendency. When the temperature is below 90 °C, both branch Tree and Bush Tree are appeared application 9 or 12 kV. However, when the temperature is above 90 °C, the Bush Tree becomes the lead Tree morphology at 200 Hz after 10000 pulse number.