scholarly journals Modified Molecular Chain Displacement Analysis Employing Electro-Mechanical Threshold Energy Condition for Direct Current Breakdown of Low-Density Polyethylene

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2746
Author(s):  
Minhee Kim ◽  
Se-Hee Lee
Keyword(s):  
Temperature Gradient ◽  
Space Charge ◽  
Breakdown Strength ◽  
Energy Condition ◽  
Threshold Energy ◽  
Molecular Chain ◽  
Polarity Reversal ◽  
Electrical Performance ◽  
Mechanical Threshold ◽  
Polymeric Insulators

In an HVDC environment, space charge accumulated in polymeric insulators causes severe electric field distortion and degradation of breakdown strength. To analyze the breakdown characteristics, here, the space charge distribution was numerically evaluated using the bipolar charge transport (BCT) model, considering the temperature gradient inside the polymeric insulator. In particular, we proposed an electro-mechanical threshold energy condition, resulting in the modified molecular chain displacement model. The temperature gradient accelerates to reduce the breakdown strength with the polarity-reversal voltage, except during the harshest condition, when the temperature of the entire polymeric insulator was 70 °C. The energy imbalance inside the insulator caused by polarity-reversal voltage reduced the breakdown strength by 82%. Finally, this numerical analysis model can be used universally to predict the breakdown strength of polymeric insulators in various environments, and help in evaluating the electrical performance of polymeric insulators.

Trap Property and Charge Transmission in PE

2020 ◽  
pp. 129-155
Keyword(s):  
Charge Transfer ◽  
Electrical Properties ◽  
Space Charge ◽  
Transfer Process ◽  
Breakdown Strength ◽  
Electrical Performance ◽  
Trap Level ◽  
Charge Transfer Process ◽  
Direct Current Conductivity ◽  
Trapping Process

The electrical properties of the dielectric are achieved by affecting the charge transfer process. The trap characteristics have an important influence on the electrical properties of the dielectric by affecting the charge transfer process. Aggregation and trap level characteristics of nanographene on low density polyethylene (LDPE). The direct current conductivity, breakdown strength, trap level distribution, space charge distribution, and charge mobility of nanocomposites were investigated. The experimental results show that the interface region between graphene and polymer introduces many deep traps in the forbidden band of nanocomposites, which can reduce the trapping process of charge and inhibit the accumulation of space charge. This indicates that the addition of nanoscale graphene has a significant improvement in the electrical performance of high voltage DC cables, which will provide a reference for production and application.

scholarly journals Enhanced Thermal Conductivity and Dielectric Properties of h-BN/LDPE Composites

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4738
Author(s):  
Lijuan He ◽  
Junji Zeng ◽  
Yuewu Huang ◽  
Xiong Yang ◽  
Dawei Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Space Charge ◽  
Direct Current ◽  
Breakdown Strength ◽  
Hexagonal Boron Nitride ◽  
Electrical Equipment ◽  
Electrical Performance ◽  
Suppression Effect ◽  
Thermally Conductive ◽  
Ldpe Composites

Low-density polyethylene (LDPE), as an excellent dielectric insulating material, is widely used in electrical equipment insulation, whereas its low thermal conductivity limits its further development and application. Hexagonal boron nitride (h-BN) filler was introduced into LDPE to tailor the properties of LDPE to make it more suitable for high-voltage direct current (HVDC) cable insulation application. We employed melt blending to prepare h-BN/LDPE thermally conductive composite insulation materials with different contents. We focused on investigating the micromorphology and structure, thermal properties, and electrical properties of h-BN/LDPE composites, and explained the space charge characteristics. The scanning electron microscope (SEM) results indicate that the h-BN filler has good dispersibility in the LDPE at a low loading (less than 3 phr (3 g of micron h-BN particles filled in 100g of LDPE)), as well as no heterogeneous phase formation. The results of thermal conductivity analysis show that the introduction of h-BN filler can significantly improve the thermal conductivity of composites. The thermal conductivity of the composite samples with 10 phr h-BN particles is as high as 0.51 W/(m·K), which is 57% higher than that of pure LDPE. The electrical performance illustrates that h-BN filler doping can significantly inhibit space charge injection and reduce space charge accumulation in LDPE. The interface effect between h-BN and the substrate reduces the carrier mobility, thereby suppressing the injection of charges of the same polarity and increasing the direct-current (DC) breakdown strength. h-BN/LDPE composite doped with 3 phr h-BN particles has excellent space charge suppression effect and high DC breakdown strength, which is 14.3% higher than that of pure LDPE.

scholarly journals Effect of Doping Microcapsules on Typical Electrical Performances of Self-Healing Polyethylene Insulating Composite

2019 ◽  
Vol 9 (15) ◽  
pp. 3039 ◽  
Author(s):  
Youyuan Wang ◽  
Yudong Li ◽  
Zhanxi Zhang ◽  
Yanfang Zhang
Keyword(s):  
Space Charge ◽  
Structural Damage ◽  
Carrier Transport ◽  
Breakdown Strength ◽  
Mechanical Damage ◽  
Electrical Performance ◽  
Self Healing ◽  
Nucleation Effect ◽  
Electrical Tree ◽  
Effect Of Doping

Polyethylene cables, as important transmission equipment of modern power grid, would inevitably be slightly damaged, which seriously threatens the safety of the power supply. This paper has pioneered the preparation and typical performances of a self-healing polyethylene insulating composite. The self-healing performance to structural damage was verified by tests of electrical and mechanical damage. The effect mechanism of doping microcapsules on the electrical performance of polyethylene was emphatically analyzed. The results show that in appropriate conditions (such as 60 °C/30 min), the composite can not only repair the electrical tree and scratches, but also restore the insulation strength of damaged area. The effect of doping microcapsules on the electrical performances of polyethylene, such as breakdown strength, volumetric resistivity, dielectric properties, and space charge characteristics, are mainly related to impurity and the interface of microcapsule. Polarization and ionization of impurities can reduce the electrical performance of polyethylene. The interface not only improves the microstructure of polyethylene (such as how the heterogeneous nucleation effect increases the number of crystal regions, and the anchoring effect enhances the stability of amorphous regions), but also increases the charge traps. Moreover, the microstructure and charge trap can affect the characteristics of carrier transport, material polarization, and space charge accumulation, thus improving the electrical performance of polyethylene. In addition, the important electrical performance of the composite can meet the basic application requirements of polyethylene insulating material, which has good application prospects.

scholarly journals Preparation Methods of Polypropylene/Nano-Silica/Styrene-Ethylene-Butylene-Styrene Composite and Its Effect on Electrical Properties

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 797 ◽  
Author(s):  
Mingze Gao ◽  
Jiaming Yang ◽  
Hong Zhao ◽  
Hui He ◽  
Ming Hu ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Space Charge ◽  
Composite System ◽  
Breakdown Strength ◽  
Nano Particles ◽  
Electrical Performance ◽  
Dispersion Characteristics ◽  
Ternary Composite ◽  
Nano Sio2 ◽  
Improvement Effect

Compared with traditional insulation materials, such as cross-linked polyethylene (XLPE), polypropylene (PP) is famous for its better recyclable and thermal properties, as well as its good electrical performance. However, the problem of poor impact strength has restricted the application of pure PP in high-voltage, direct current (HVDC) cables. In this paper, styrene-ethylene-butylene-styrene block copolymer (SEBS) was used as a toughening filler, and nano-SiO2 was expected to improve the electric properties of the nano-composite. By controlling the masterbatch system, the dispersion characteristics of nano-SiO2 in the ternary composite system were changed. When PP/SiO2 was used as the masterbatch and then blended with SEBS, nano-SiO2 tended to disperse in the PP phase, and the number of nano-particles in the SEBS phase was lower. When PP/SEBS was used as the masterbatch, nano-SiO2 was distributed in both the PP phase and the SEBS phase. When SEBS/SiO2 was used as the masterbatch, nano-SiO2 tended to be dispersed in the SEBS phase. The different dispersion characteristics of nano-SiO2 changed the crystallization and mechanical properties of the ternary composite system and produced different electrical performance improvement effects. The results of our experiment revealed that the space charge suppression capability was positively correlated with the direct current (DC) breakdown strength improvement effect. Compared with the DC performance of 500 kV commercial XLPE materials, the self-made PP-based ternary composite system has better space charge suppression effects and higher DC breakdown strength. When nano-SiO2 was more dispersed in the PP phase, the space charge improvement effect was best. When the nano-SiO2 particles were more dispersed in the SEBS phase, the expected electrical property improvement was not obtained. Scanning electron microscopy showed that the nano-SiO2 particles in the SEBS phase were more dispersed at the interface than in the SEBS matrix, indicating that the nano-particles were poorly dispersed, which may be a reason why the electrical properties of the composite system were not significantly improved.

Field distribution in polymeric MV-HVDC model cable under temperature gradient. Simulation and space charge measurements

2014 ◽  
Vol 17 (5-6) ◽  
pp. 307-325 ◽  
Author(s):  
Thi Thu Nga Vu ◽  
Gilbert Teyssedre ◽  
Bertrand Vissouvandin ◽  
Séverine Le Roy ◽  
Christian Laurent ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Space Charge ◽  
Field Distribution

Space charge characteristics in 160 kV DC XLPE cable under temperature gradient

2018 ◽  
Vol 25 (6) ◽  
pp. 2366-2374 ◽  
Author(s):  
Wang Xia ◽  
Chen Chi ◽  
Cheng Chuanhui ◽  
Wu Yang ◽  
Wu Kai ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Space Charge ◽  
Xlpe Cable

scholarly journals Effect of Temperature on Space Charge Distribution of Oil–Paper Insulation under DC and Polarity Reversal Voltage

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2271 ◽  
Author(s):  
Qingguo Chen ◽  
Jinfeng Zhang ◽  
Minghe Chi ◽  
Peng Tan ◽  
Wenxin Sun
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Electric Field Distribution ◽  
Operating Conditions ◽  
Polarity Reversal ◽  
Effect Of Temperature ◽  
Slow Decay ◽  
Voltage Polarity ◽  
Field Distortion ◽  
Paper Insulation

The electric field distortion caused by space charge is an important factor affecting the operation reliability of oil–paper insulation in a converter transformer. To study the accumulation and decay characteristics of the space charge within oil-impregnated pressboard under DC and polarity reversal voltage, and consider the possible operating conditions of the converter transformer, the space charge behavior of oil-impregnated pressboard was measured by the pulsed electro-acoustic (PEA) method in the temperature range from −20 °C to 60 °C. The effect of temperature on the accumulation and decay characteristics of space charge is also analyzed. The space charge accumulated within the pressboard at low temperature is mainly homocharge injected by the electrode, while heterocharge formed by ion dissociation counteracts some of the homocharge at high temperature. Thus, the space charge of pressboard first increases, then decreases, with an increase in temperature. However, slow decay of the space charge causes severe distortion of the electric field distribution in the pressboard during voltage polarity reversal.

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