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 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 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 Acetylated SEBS Enhanced DC Insulation Performances of Polyethylene

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1033 ◽  
Author(s):  
Wei Dong ◽  
Xuan Wang ◽  
Zaixing Jiang ◽  
Bo Tian ◽  
Yuguang Liu ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Field Strength ◽  
Space Charge ◽  
Aromatic Compounds ◽  
Breakdown Strength ◽  
Charge Accumulation ◽  
New Approach ◽  
Functional Units ◽  
Poly Ethylene ◽  
Accumulation Characteristics

Acetophenone can significantly improve the dielectric properties of polyethylene (PE) insulation materials. However, it easily migrates from the PE due to its poor compatibility with the material, which limits its application. In this paper, the functional units of acetophenone were modified in polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) by an acetylation reaction, and SEBS was used as the carrier to inhibit the migration of acetophenone. The number of functional units in the acetylated SEBS (Ac-SEBS) was measured by 1H NMR and the effect of the acetylation degree of SEBS on its compatibility with PE was studied. Meanwhile, the effects of Ac-SEBS on PE’s direct current (DC) breakdown strength and space charge accumulation characteristics were investigated. It is demonstrated that Ac-SEBS can significantly improve the field strength of the DC breakdown and inhibit the accumulation of space charge in the PE matrix. This work provides a new approach for the application of aromatic compounds as voltage stabilizers in DC insulation cable materials.

scholarly journals Polyethylene/Graphene Nanoplatelet Nanocomposite-Based Insulating Materials for Effective Reduction of Space Charge Accumulation in High-Voltage Direct-Current Cables

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Ji Sun Park ◽  
Young Sun Kim ◽  
Hyun-Jung Jung ◽  
Daseul Park ◽  
Jee Young Yoo ◽  
...  
Keyword(s):  
Space Charge ◽  
Electric Fields ◽  
Healing Process ◽  
Field Enhancement ◽  
Hydrophobic Surface ◽  
Threshold Concentration ◽  
Charge Accumulation ◽  
Organic Modifiers ◽  
Defect Healing ◽  
Optical Absorption Measurement

We have demonstrated a straightforward hydrophobic surface modification of graphene nanoplatelets (GNPs) through a defect-healing process to fabricate well-dispersed insulating low-density polyethylene (LDPE)/GNP nanocomposites and have confirmed their effective suppression of space charge accumulation. Without any organic modifiers, GNPs containing oxygen-based functional groups at the edges were successfully reduced at optimal high-temperature defect-healing condition and modified to have hydrophobic surface properties similar to those of the LDPE matrix. The degree of dispersion and the reproducibility of the mechanically melt-mixed LDPE/GNP nanocomposites were immediately analyzed by thickness-normalized optical absorption measurement. In the LDPE matrix, below the percolation threshold concentration, well-dispersed GNP fillers effectively acted as trapping sites under high electric fields, resulting in the successful suppression of packet-like space charge accumulation (field enhancement factor=1.04 @ 0.1 wt% LDPE/GNP nanocomposite).

scholarly journals PP/PP-HI/Silica nanocomposites for HVDC cable insulation: Are silica clusters beneficial for space charge accumulation?

2021 ◽  
pp. 107186
Author(s):  
Xiaozhen He ◽  
Ilkka Rytöluoto ◽  
Paolo Seri ◽  
Rafal Anyszka ◽  
Amirhossein Mahtabani ◽  
...  
Keyword(s):  
Space Charge ◽  
Charge Accumulation ◽  
Cable Insulation ◽  
Silica Nanocomposites ◽  
Silica Clusters

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.

scholarly journals The Effects of Nano Fillers on Space Charge Distribution in Cross-Linked Polyethylene

2017 ◽  
Vol 7 (6) ◽  
pp. 3147
Author(s):  
A. N. Ramani ◽  
A. M. Ariffin ◽  
Gobinath Vijian ◽  
Ahmad Basri Abd Ghani
Keyword(s):  
Space Charge ◽  
Charge Distribution ◽  
Room Temperature ◽  
Electrical Breakdown ◽  
Research Work ◽  
Field Enhancement ◽  
Insulation Material ◽  
Charge Accumulation ◽  
Space Charge Distribution ◽  
Local Electric Field Enhancement

The performance of polymeric insulation will be distorted by the accumulation of space charge. This will lead to local electric field enhancement within the insulation material that can cause degradation and electrical breakdown. The introduction of nanofillers in the insulation material is expected to reduce the space charge effect. However, there is a need to analyze potential nanofillers to determine the best option. Therefore, the objective of this research work is to examine two types of nanofillers for Cross-Linked Polyethylene (XLPE); Zinc Oxide (ZnO) and Acrylic (PA40). The effects of these nanofillers were measured using the Pulsed-Electro Acoustic (PEA) method. The development of space charge is observed at three different DC voltage levels in room temperature. The results show that hetero charge distribution is dominant in pure XLPE materials. The use of both nanofiller types have significant effect in decreasing the space charge accumulation. With nanofillers, the charge profile changed to homo-charge distribution, suppressing the space charge formation. Comparison<br />between both the nanofillers show that PA40 has better suppression performance than ZnO.

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