scholarly journals Space Charge Accumulation at Material Interfaces in HVDC Cable Insulation Part II—Simulations of Charge Transport

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1750
Author(s):  
Espen Doedens ◽  
E. Markus Jarvid ◽  
Raphaël Guffond ◽  
Yuriy V. Serdyuk
Keyword(s):  
Surface Roughness ◽  
Space Charge ◽  
Charge Transport ◽  
Transport Model ◽  
Charge Injection ◽  
Charge Trapping ◽  
Material Interfaces ◽  
Cable Insulation ◽  
High Voltage Direct Current ◽  
Cable Systems

Extruded high voltage direct current (HVDC) cable systems contain interfaces with poorly understood microscopic properties, particularly surface roughness. Modelling the effect of roughness on conduction in cable insulation is challenging, as the available results of macroscopic measurements give little information about microscopic charge distributions at material interfaces. In this work, macroscopic charge injection from interfaces is assessed by using a bipolar charge transport model, which is validated against a series of space charge measurements on cable peelings with different degrees of surface roughness. The electric field-dependent conduction and charge trapping effects stimulated by the injection current originating from rough surfaces are assessed. It is shown that by accounting for roughness enhanced charge injection with the parameters derived in part I of the paper, reasonable agreement between computed and measured results can be achieved at medium field strengths (10–40 kV/mm).

scholarly journals Space Charge Accumulation at Material Interfaces in HVDC Cable Insulation Part I—Experimental Study and Charge Injection Hypothesis

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2005
Author(s):  
Espen Doedens ◽  
E. Markus Jarvid ◽  
Raphaël Guffond ◽  
Yuriy V. Serdyuk
Keyword(s):  
Field Strength ◽  
Space Charge ◽  
Transport Model ◽  
Rough Surfaces ◽  
Charge Injection ◽  
Field Enhancement ◽  
Life Time ◽  
Charge Accumulation ◽  
Material Interfaces ◽  
Cable Insulation

On-site installation of accessories on extruded polymeric high voltage cables in a common practice. The procedure requires the shaping of the physical interface between the cable insulation surface and the pre-molded accessory body. On such interfaces, rough surfaces should be avoided in order to limit space charge accumulation in the insulation, which affects the cable performance by reducing insulation life-time, creating conditions for local field enhancement, and, respectively, the formation of possible breakdown path e.g. by electrical treeing. Space charge measurements on cable insulation peelings were undertaken to assess the space charge injection and accumulation on interfaces with varying degrees of surface roughness in order to improve understanding on this subject. The results of the measurements confirm the hypothesis regarding the enhancement of charge injection from rough surfaces when electric field strength exceeds a certain level. The accumulated charge density in the material is shown to strongly depend on the field strength and temperature in both polarization and subsequent depolarization measurements. These results emphasize that a bipolar charge transport model that incorporates field and temperature dependencies of charge injection, trapping, detrapping, and recombination processes needs to be adopted to accurately describe the observed electric conduction phenomena.

scholarly journals Space Charge Accumulation and Decay in Dielectric Materials with Dual Discrete Traps

2019 ◽  
Vol 9 (20) ◽  
pp. 4253 ◽  
Author(s):  
Zhaoliang Xing ◽  
Chong Zhang ◽  
Haozhe Cui ◽  
Yali Hai ◽  
Qingzhou Wu ◽  
...  
Keyword(s):  
Space Charge ◽  
Analytical Solutions ◽  
Charge Injection ◽  
Charge Trapping ◽  
Dielectric Materials ◽  
Dynamic Processes ◽  
Charge Accumulation ◽  
Charge Densities ◽  
Short Period ◽  
Trapped Charge

Charge trapping and de-trapping properties can affect space charge accumulation and electric field distortion behavior in polymers. Dielectric materials may contain different types of traps with different energy distributions, and it is of interest to investigate the charge trapping/de-trapping dynamic processes in dielectric materials containing multiple discrete trap centers. In the present work, we analyze the charge trapping/de-trapping dynamics in materials with two discrete traps in two cases where charges are injected continuously or only for a very short period. The time dependent trapped charge densities are obtained by the integration of parts in the case of continuous charge injection. In the case of instantaneous charge injection, we simplify the charge trapping/de-trapping equations and obtain the analytical solutions of trapped charge densities, quasi-free charge density, and effective carrier mobility. The analytical solutions are in good agreement with the numerical results. Then, the space charge dynamics in dielectric materials with two discrete trapping centers are studied by the bipolar charge transport (BCT) model, consisting of charge injection, charge migration, charge trapping, de-trapping, and recombination processes. The BCT outputs show the time evolution of spatial distributions of space charge densities. Moreover, we also achieve the charge densities at the same position in the sample as a function of time by the BCT model. It is found that the DC poling duration can affect the energy distribution of accumulated space charges. In addition, it is found that the coupling dynamic processes will establish a dynamic equilibrium rather than a thermodynamic equilibrium in the dielectric materials.

scholarly journals Evolution of Space Charges and Conductivity with DC Aging of Polyethylene-Synthetic and Natural Clay Composites

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Mahmoud Abou-Dakka
Keyword(s):  
Space Charge ◽  
Charge Transport ◽  
Percolation Threshold ◽  
Double Layers ◽  
Total Charge ◽  
Interaction Zone ◽  
Natural Clay ◽  
Material Interfaces ◽  
Space Charges ◽  
Synthetic Clay

The evolution of the space charge and conductivity with DC poling of two types of polypropylene-(PP-) based nanocomposites (PNCs) was investigated. The PNCs were manufactured with different concentrations of synthetic and natural organoclays. The optimal concentrations of nanofiller that can efficiently mitigate the space charge with DC aging time were 2-wt% for PP-natural-clay and between 2 and 4 wt% for the PP-synthetic-clay. Above these percentages charge transport through overlapping of nanoparticles can occur due to the interaction zone of double layers formed at the nanoparticle/host material interfaces. Under DC field the overlapping increases the conductivity of PNCs and minimizes the benefit of incorporating nanofillers into PP. The total charge stored in unfilled PP increased continuously with time reaching a maximum around 5000 h before decreasing but it also changed slightly in all filled specimens. It was perceived that the smaller the size of nanofiller platelets the more efficient the charge mitigation. The conductivity of specimens containing 6 wt% of natural clay and 8 wt% of synthetic clay reached≈6 times the level of the unfilled PP. This observation could be related and due to the crossing of the percolation threshold for these composites.

Development of a space-charge transport model for ion-exchange membranes

AIChE Journal ◽  
1990 ◽  
Vol 36 (7) ◽  
pp. 1061-1074 ◽  
Author(s):  
Angel G. Guzmán-Garcia ◽  
Peter N. Pintauro ◽  
Mark W. Verbrugge ◽  
Robert F. Hill
Keyword(s):  
Ion Exchange ◽  
Space Charge ◽  
Charge Transport ◽  
Transport Model ◽  
Ion Exchange Membranes

scholarly journals Improved space charge transport model in bi‐layer dielectrics—considering carrier dynamic equilibrium

High Voltage ◽  
2020 ◽  
Vol 5 (2) ◽  
pp. 176-183 ◽  
Author(s):  
Hucheng Liang ◽  
Boxue Du ◽  
Jin Li ◽  
Hang Yao ◽  
Zehua Wang
Keyword(s):  
Space Charge ◽  
Charge Transport ◽  
Transport Model ◽  
Dynamic Equilibrium ◽  
Carrier Dynamic

Multicomponent space-charge transport model for ion-exchange membranes

AIChE Journal ◽  
2000 ◽  
Vol 46 (6) ◽  
pp. 1177-1190 ◽  
Author(s):  
Yahan Yang ◽  
Peter N. Pintauro
Keyword(s):  
Ion Exchange ◽  
Space Charge ◽  
Charge Transport ◽  
Transport Model ◽  
Ion Exchange Membranes

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.

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