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 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 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.

On charge accumulation in heterogeneous porous rocks under the influence of an external electric field

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. D271-D291 ◽  
Author(s):  
A. Revil
Keyword(s):  
Porous Media ◽  
Electric Field ◽  
Effective Permittivity ◽  
Low Frequency ◽  
Free Water ◽  
Planck Equation ◽  
Charge Accumulation ◽  
Porous Rocks ◽  
Stern Layer ◽  
Charge Polarization

Electric polarization is described as the sum of charge accumulations (free charge density) and orientation of polar molecules such as those of bound and free water molecules (bound charge polarization). Charge accumulation in porous materials cannot be described with Ohm’s law alone. Nonequilibrium thermodynamics or the upscaling of the local Nernst-Planck equation imply that the drift of ions in porous media is controlled by the gradient of their electrochemical potentials and not solely by the electric field. In porous media, electrochemical capacitance is at least six to eight orders of magnitude larger than electrostatic capacitance associated with bound charge polarization. In other words, the low-frequency ([Formula: see text]) effective permittivity entering Ampère’s law is six to eight orders of magnitude larger than high-frequency dielectric permittivity (measured for instance at 1 GHz). Low-frequency polarization of porous media, with no metallic particles (no electronic conductors and semiconductors) is controlled by polarization of the inner component of the electrical double layer coating the grains. This layer, called the “Stern layer,” plays a strong role in defining the cation exchange capacity of a material. A polarization model based on the polarization of the Stern layer explains a large number of experimental observations and could be used in the interpretation of hydro- and petroleum geophysical measurements.

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.

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