scholarly journals Effects of Trapping Characteristics on Space Charge and Electric Field Distributions in HVDC Cable under Electrothermal Stress

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1313
Author(s):  
Fuqiang Tian ◽  
Shuting Zhang ◽  
Chunyi Hou
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Trap Depth ◽  
Trap Density ◽  
Strong Impact ◽  
Charge Accumulation ◽  
Term Operation ◽  
High Voltage Direct Current ◽  
Field Distortion ◽  
Evolution Behavior

Space charge behavior has a strong impact on the long-term operation reliability of high voltage–direct current (HVDC) cables. This study intended to reveal the effect of trap density and depth on the space charge and electric field evolution behavior in HVDC cable insulation under different load currents and voltages by combined numerical bipolar charge transport (BCT) and thermal field simulation. The results show that when the load current is 1800 A (normal value), the temperature difference between the inside and the outside of the insulation is 20 °C, space charge accumulation and electric field distortion become more serious with the increase in the trap depth (Et) from 0.80 to 1.20 eV for the trap densities (Nt) of 10 × 1019 and 80 × 1019 m−3, and become more serious with the increase in Nt from 10 × 1019 to 1000 × 1019 m−3 for Et = 0.94 eV. Simultaneously decreasing trap depth and trap density (such as Et = 0.80 eV, Nt = 10 × 1019 m−3) or increasing trap depth and trap density (such as Et = 1.20 eV, Nt = 1000 × 1019 m−3), space charge accumulation can be effectively suppressed along with capacitive electric field distribution for different load currents (1800 A, 2100 A and 2600 A) and voltages (320 kV and 592 kV). Furthermore, we can draw the conclusion that increasing bulk conduction current by simultaneously decreasing the trap depth and density or decreasing injection current from conductor by regulating the interface electric field via simultaneously increasing the trap depth and density can both effectively suppress space charge accumulations in HVDC cables. Thus, space charge and electric field can be readily regulated by the trap characteristics.

scholarly journals Frequency and Temperature-Dependent Space Charge Characteristics of a Solid Polymer under Unipolar Electrical Stresses of Different Waveforms

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3401
Author(s):  
Hanwen Ren ◽  
Qingmin Li ◽  
Yasuhiro Tanaka ◽  
Hiroaki Miyake ◽  
Haoyu Gao ◽  
...  
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Positive Charge ◽  
Low Frequency ◽  
Solid Polymer ◽  
Charge Accumulation ◽  
Temperature Dependent ◽  
Rectangular Wave ◽  
Field Distortion ◽  
Half Wave

In this paper, we studied the space charge phenomena of a solid polymer under thermal and electrical stresses with different frequencies and waveforms. By analyzing the parameter selection method of a protection capacitor and resistor, the newly built pulsed electro-acoustic (PEA) system can be used for special electrical stresses under 500 Hz, based on which the charge phenomena are studied in detail under positive and negative DC and half-wave sine and rectangular wave voltages. Experimental results show that the charge accumulated in the polyimide polymer under DC conditions mainly comes from the grounded electrode side, and the amount of charge accumulated with electric field distortion becomes larger in a high-temperature environment. At room temperature, positive charges tend to accumulate in low-frequency conditions under positive rectangular wave voltages, while they easily appear under high-frequency situations of negative ones. In contrast, the maximum electric field distortion and charge accumulation under both half-wave sine voltages occur at 10 Hz. When the measurement temperature increases, the accumulated positive charge decreases, with a more negative charge appearing under rectangular wave voltages, while a more positive charge accumulates at different frequencies of half-wave sine voltages. Therefore, our study of the charge characteristics under different voltage and temperature conditions can provide a reference for applications in the corresponding environments.

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.

The Simulation of Electret Effect in Zn0.7Cd0.3S Layers

2005 ◽  
Vol 10 (1) ◽  
pp. 77-82
Author(s):  
F. Kuliešius ◽  
S. Tamošiūnas ◽  
A. Žindulis
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Charge Accumulation ◽  
Contact Mode ◽  
Charge Formation ◽  
Electret Effect

The regularities of the dark discharge in ionic contact mode as well as of the thermoelectret effect have been investigated for Zn0.7Cd0.3S layers. The peculiarities of electret charge formation as well as the electret voltage dependences on poling electric field, polarisation time and temperature have been analysed in Zn0.7Cd0.3S layers during the present work. The model of space charge accumulation have been proposed.

scholarly journals Space Charge Characteristics of Polypropylene Modified by Rare Earth Nucleating Agent for β Crystallization

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 42 ◽  
Author(s):  
Jiaming Yang ◽  
Mingze Gao ◽  
Hong Zhao ◽  
Shilin Liu ◽  
Ming Hu ◽  
...  
Keyword(s):  
Rare Earth ◽  
Space Charge ◽  
Impact Resistance ◽  
Nucleating Agent ◽  
Mechanical Analysis ◽  
Mechanical Relaxation ◽  
Charge Accumulation ◽  
Depolarization Current ◽  
High Voltage Direct Current ◽  
Lamellar Crystals

Compared to cross-linked polyethylene, polypropylene has a thermoplastic property and the advantage of recycling. However, the poor impact resistance at low temperature and the corresponding space charge problem restrict the application of polypropylene with the extruded high voltage direct current (HVDC) cable. Sufficient introduction of the β form of the polypropylene crystal can significantly improve impact resistance at low temperatures. Although it has been widely applied in insulation engineering, the effect of β-crystal on the space charge characteristics of polypropylene has rarely been researched until now. In this paper, a rare earth nucleating agent of β-crystal is employed to modify the performance of polypropylene to investigate the effects of nucleating agent content on β-crystalline, mechanical relaxation, trap, and space charge characteristics of polypropylene. The results of differential scanning calorimeter (DSC) and X-ray diffraction (XRD) tests indicate that the relative content of β-crystal in modified polypropylene increases gradually with the increasing concentration of the nucleating agent, approaching 43.5% when the nucleating agent content has been raised to 0.2 wt %, suggesting appreciable efficiency of the nucleating agent utilized in our research. Scanning electron microscopy (SEM) is utilized to characterize the morphology of β-crystal spherulites, which illustrates that the β-spherulites are in bunchy shape, and the lamellar crystals are parallel to each other without an obvious boundary between them. The results of the space charge test demonstrate that the modified polypropylene can substantially suppress space charge accumulation, which is attributed to an increment of β-crystal content by adopting a rare earth nucleating agent. It is indicated from dynamic mechanical analysis (DMA) measurements that the enhancement of β-crystalline in modified polypropylene can distinctly increase and decrease the β and α relaxation losses, respectively, which proves that the defects in β-crystal and amorphous regions are reduced and increased respectively. Thermally stimulated depolarization current tests further confirm that the number of traps caused by defects in the β-form of polypropylene crystal declines definitely, which dominantly accounts for the suppression of space charge accumulation.

scholarly journals Space Charge Accumulation Characteristics in HVDC Cable under Temperature Gradient

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5571
Author(s):  
Yifan Zhou ◽  
Wei Wang ◽  
Tailong Guo
Keyword(s):  
Temperature Gradient ◽  
Space Charge ◽  
Charge Accumulation ◽  
Cable Insulation ◽  
Xlpe Cable ◽  
Conductivity Model ◽  
High Voltage Direct Current ◽  
Dc Electric Field ◽  
Higher Temperature ◽  
Bipolar Charge

One of the main issues that affect the development of high-voltage direct-current (HVDC) cable insulation is the accumulation of space charge. The load operation of an HVDC cable leads to the formation of a radially distributed temperature gradient (TG) across the insulation. In this study, the space charge accumulation in a cross-linked polyethylene (XLPE) cable is measured under a DC electric field and TG using the pulsed electro-acoustic (PEA) method, and the effect of the TG on the space charge behavior is investigated. In addition, the bipolar charge transport (BCT) model and the conductivity model based on an improved cylindrical geometry are used to simulate the charge behavior in the HVDC XLPE cable under TG, and the experimental and simulated results are compared. The results show that the higher temperature of the cable conductor promotes the accumulation of homocharge near the side of high temperature. Additionally, with the increase of the TG, not only does more heterocharge accumulates adjacent to the side of low temperature, but more space charge also extends into the bulk of the cable insulation. More attention should be paid to the conductor shield layer and the insulation shield layer in HVDC cables. Moreover, the BCT model can more accurately describe the experimental results than the conductivity model.

Sign in / Sign up

Export Citation Format

Share Document