Negative space charge and electric field intensity in polymeric insulators at low temperatures

1998 ◽  
Vol 40 (6) ◽  
pp. 1066-1070
Author(s):  
V. A. Zakrevskiĭ ◽  
N. T. Sudar’
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Field Intensity ◽  
Low Temperatures ◽  
Electric Field Intensity ◽  
Polymeric Insulators ◽  
Negative Space

scholarly journals Numerical Analysis of Space Charge Behavior and Transient Electric Field under Polarity Reversal of HVDC Extruded Cable

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2845
Author(s):  
Sun-Jin Kim ◽  
Bang-Wook Lee
Keyword(s):  
Steady State ◽  
Electric Field ◽  
Space Charge ◽  
Field Intensity ◽  
Electric Potential ◽  
Electric Field Intensity ◽  
Dielectric Breakdown ◽  
Operating Conditions ◽  
Polarity Reversal ◽  
Transient Electric Field

The superimposed transient electric field generated by polarity reversal causes severe stress to the high-voltage direct current (HVDC) cable insulation. Especially for polymeric insulation materials, space charge accumulation is prominent, which strengthens local electric field intensity. In order to avoid the risk of dielectric breakdown resulting from an intensified electric field caused by space charge behavior, several numerical analyses have been conducted using the Bipolar Charge Transport (BCT) model. However, these studies have only considered a unidirectional electric field assuming only steady state operating conditions, and there are few works that have analyzed space charge behavior during transient states, especially for the polarity reversal period. In order to analyze the charge behavior under polarity reversal, it is necessary to establish the boundary condition considering the direction and intensity of the field. Therefore, in this paper, we proposed a modified model connecting the steady state to the polarity reversal state, and the transient electric field was investigated depending on the electric potential zero duration. Since space charge behavior is influenced by temperature, different load currents were considered. From the simulation results, it was observed that the capacitive field was dominant on the electric field distribution during the polarity reversal. In addition, the long electric potential zero duration and high load currents could contribute to form a homo-charge at the conductor within the time of polarity reversal, resulting in a noticeable decrease in the maximum electric field intensity.

Effect of Electrical Trees on the Distribution of Electric Field and Space Charge in Cross-linked Polyethylene Cables

2020 ◽  
Vol 13 ◽  
Author(s):  
Yasha Li ◽  
Huiyao Wang ◽  
Kai Chen ◽  
Jiamao Chen
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
Three Dimensional ◽  
Trunk Length ◽  
Xlpe Cable ◽  
Insulation Aging ◽  
Electrical Trees ◽  
Distribution Of Electric Field

Background: Electrical trees can affect the distribution of electric field and space charge in cross-linked polyethylene (XLPE) cables, and play an important role in insulation aging and breakdown of cables. Therefore, it is important to study the influence of electrical trees in cables. Methods: In this study, the finite element method of second-order tetrahedral element and electromagnetic theory method are used for calculation. A model of XLPE cable with three-dimensional electrical trees is taken as an example for calculation. Results: The results shows that the longer the trunk length is, the greater the electric field intensity at the end of the branch is; the farther the electrical trees are from the insulation side of the high voltage, the more the electric field intensity of each location decreases. Conclusion: With the increase of the resistivity of the trees, the electric field intensity and charge density tend to be stable at the end of the tree.

High-speed isotachophoresis. Analytical aspects of the steady-state longitudinal temperature profiles

1979 ◽  
Vol 44 (3) ◽  
pp. 841-853 ◽  
Author(s):  
Zbyněk Ryšlavý ◽  
Petr Boček ◽  
Miroslav Deml ◽  
Jaroslav Janák
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Electric Field ◽  
Field Intensity ◽  
Electric Field Intensity ◽  
Minor Component ◽  
Physical Models ◽  
Temperature Profiles ◽  
Longitudinal Temperature ◽  
Continuous Character

The problem of the longitudinal temperature distribution was solved and the bearing of the temperature profiles on the qualitative characteristics of the zones and on the interpretation of the record of the separation obtained from a universal detector was considered. Two approximative physical models were applied to the solution: in the first model, the temperature dependences of the mobilities are taken into account, the continuous character of the electric field intensity at the boundary being neglected; in the other model, the continuous character of the electric field intensity is allowed for. From a comparison of the two models it follows that in practice, the variations of the mobilities with the temperature are the principal factor affecting the shape of the temperature profiles, the assumption of a discontinuous jump of the electric field intensity at the boundary being a good approximation to the reality. It was deduced theoretically and verified experimentally that the longitudinal profiles can appreciably affect the longitudinal variation of the effective mobilities in the zone, with an infavourable influence upon the qualitative interpretation of the record. Pronounced effects can appear during the analyses of the minor components, where in the corresponding short zone a temperature distribution occurs due to the influence of the temperatures of the neighbouring zones such that the temperature in the zone of interest in fact does not attain a constant value in axial direction. The minor component does not possess the steady-state mobility throughout the zone, which makes the identification of the zone rather difficult.

POLARON IN A QUANTUM DOT UNDER AN ELECTRIC FIELD

2007 ◽  
Vol 21 (24) ◽  
pp. 1635-1642
Author(s):  
MIAN LIU ◽  
WENDONG MA ◽  
ZIJUN LI
Keyword(s):  
Quantum Dot ◽  
Electric Field ◽  
Field Intensity ◽  
Ground State Energy ◽  
Ground State ◽  
Electric Field Intensity ◽  
State Energy ◽  
Theoretical Study ◽  
The Moment ◽  
Transformation Methods

We conducted a theoretical study on the properties of a polaron with electron-LO phonon strong-coupling in a cylindrical quantum dot under an electric field using linear combination operator and unitary transformation methods. The changing relations between the ground state energy of the polaron in the quantum dot and the electric field intensity, restricted intensity, and cylindrical height were derived. The numerical results show that the polar of the quantum dot is enlarged with increasing restricted intensity and decreasing cylindrical height, and with cylindrical height at 0 ~ 5 nm , the polar of the quantum dot is strongest. The ground state energy decreases with increasing electric field intensity, and at the moment of just adding electric field, quantum polarization is strongest.

scholarly journals Effects of Flash Sintering Parameters on Performance of Ceramic Insulator

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1157
Author(s):  
Yong Liu ◽  
Xingwang Huang
Keyword(s):  
Grain Size ◽  
Electric Field ◽  
Field Intensity ◽  
Current Density ◽  
Electric Field Intensity ◽  
Unit Cell ◽  
Uniform Structure ◽  
Ceramic Insulator ◽  
Flash Sintering ◽  
Ceramic Insulators

Ceramic outdoor insulators play an important role in electrical insulation and mechanical support because of good chemical and thermal stability, which have been widely used in power systems. However, the brittleness and surface discharge of ceramic material greatly limit the application of ceramic insulators. From the perspective of sintering technology, flash sintering technology is used to improve the performance of ceramic insulators. In this paper, the simulation model of producing the ceramic insulator by the flash sintering technology was set up. Material Studio was used to study the influence of electric field intensity and temperature on the alumina unit cell. COMSOL was used to study the influence of electric field intensity and current density on sintering speed, density and grain size. Obtained results showed that under high temperature and high voltage, the volume of the unit cell becomes smaller and the atoms are arranged more closely. The increase of current density can result in higher ceramic density and larger grain size. With the electric field intensity increasing, incubation time shows a decreasing tendency and energy consumption is reduced. Ceramic insulators with a higher uniform structure and a smaller grain size can show better dielectric performance and higher flashover voltage.

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