Modelling the impact of electrode roughness on net charge density in polyethylene

Abstract

Predicting the electric field distribution under dc stress within polymeric insulations remains a challenge, as space charge behaviour is still difficult to understand in these materials. Charge generation is often thought to arise from injection at the electrodes. Hence, surface roughness should be taken into account, as it strengthens the electric field locally and therefore promotes charge generation at some points. A charge transport model has been developed in 2D to account for surface roughness. The model is first validated with the help of previous results, obtained with a one dimensional charge transport model. Then, with simple shapes accounting for roughness, the simulated results show that surface roughness has a significant impact on the net space charge behaviour. The impact of shape, and size of protusions is presented, as well as a more realistic case were a large surface of the electrode is considered as rough.

Space Charge Behavior in Epoxy‐Based Dielectrics: Progress and Perspective

“…The basic BCT model regards the conduction process as Ohmic conduction with a constant mobility. [251][252][253][254] To better fit and explain the experimental results where space charge is involved, a hopping process has been employed in the modified BCT model. [80,241] The hopping conduction is essentially a combined action of thermal excitation and tunneling process where trapped carriers inside polymers "hop" from one trap site to another.…”

“…Charge Recombination: Instead of directly setting up the "recombination rate" to describe the charge neutralization process by some researchers, [247,252,254] Le Roy et al [260] defined the recombination rate as a function of the mobility following the Langevin relations [261,262]…”

“…Alison and Hill [79] Chen and Xu [258] Le Roy group [285] Le Roy et al [260] Laurent et al [247] Wu and Yin [283] Jin et al [254] Chen group [80] Le Roy et al [284] Peng group [251] Shimakawa et al [253] Hoang et al [252] Charge injection results that positive charge accumulation was less pronounced in PTFE than in LDPE. [93] Studies on charge injection characteristics of other polymers such as XLPE [91] and PE [274] have been reported as well.…”

“…Instead of directly setting up the “recombination rate” to describe the charge neutralization process by some researchers, [ 247,252,254 ] Le Roy et al. [ 260 ] defined the recombination rate as a function of the mobility following the Langevin relations [ 261,262 ] $$\[ \begin{array}{*{20}{c}}{{S_{{{\rm{i}}_1} - {{\rm{i}}_2}}} = \frac{{{\mu _{{{\rm{i}}_1}}} + {\mu _{{{\rm{i}}_2}}}}}{{{\varepsilon _0}{\varepsilon _{\rm{r}}}}}}\end{array} \]$$where S i1‐i2 is the ratio of recombination between two carriers (among free electrons (fe), free holes (fh), trapped electrons (te), and trapped holes (th)).…”

Impact of nanometric processes linked to charge generation on the macroscopic behaviour in polyethylene

“…These physical hypotheses are however too simple, and do not account for the particular material structure of the material at an interface, directly related to barrier injection, and/or energy states, and lastly to surface roughness. Experimental [1][2] and theoretical researches [3][4][5] have focused on this particular interface behaviour, but a lot remains to do. In the present paper, we propose a 2D charge transport model developed to account for different physical processes related to the interface: surface roughness, variation of the injection barrier height along the x axis related to a variation of the material structure, and an interfacial zone of 1 µm where the energy states are deeper and with a higher density.…”