Models of bipolar charge transport in polyethylene

Boufayed, F.; Teyssèdre, G.; Laurent, Christian; Roy, Séverine Le; Dissado, L.A.; Ségur, P.; Montanari, Gian Carlo

doi:10.1063/1.2375010

Cited by 162 publications

(140 citation statements)

References 27 publications

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“…(2) are reported in Table 1. These values are at least 2-3 orders of magnitude larger than the typical values of apparent-trap-controlled mobility coming from slow packets (typically10 -12 -10 -14 m 2 /Vs) [8,26]. Even using the local field in (2) the value of mobility is still very high.…”

Section: Evidence For Fast Charge Packetsmentioning

confidence: 90%

“…At other times, heterocharge is seen to accumulate close to electrodes. Models based on charge injection via a Schottky barrier, transport via either two levels of traps or a continuous exponential trap distribution, and presence or absence of an extraction barrier are able to reproduce many of the main features of space charge and conduction current that have been observed, though the details cannot yet be fully simulated [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…In this case a plane of negative ionization is transferred through the system as mobile holes released by the high field at the front of the plane move in the opposite direction to the plane and recombine with the ionized states at the rear of the plane. Simulations of the model for space charge accumulation described in [8] also gave a single charge packet occasionally that was related to fluctuations in the injection process. However, none of these theories or simulations is able to describe the large generality of cases of slow charge packets.…”

Section: Introductionmentioning

confidence: 99%

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Fast and slow charge packets in polymeric materials under DC stress

Fabiani

Montanari

Dissado

et al. 2009

IEEE Trans. Dielect. Electr. Insul.

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The presence of slow space charge packets crossing the insulation thickness from one electrode to the other and causing significant electrical field distortion has been reported already in several papers. They are activated in general by very high DC fields or, in highly polluted materials, by relatively low fields and constitute an important ageing factor, concerning DC electrical stress. It has been observed, in fact, that such packets can cause accelerated breakdown of insulation.The development of fast systems for space charge measurements has allowed the presence of almost instant heterocharge to be observed close to electrodes in certain field and temperature conditions, especially in cable models. This has been explained often by the separation of ionic charge populations, even though such heterocharge appears also in materials, such as Polyethylene or cross-linked Polyethylene that represent the best extra-clean technologies. The measurements reported here use a high speed technique to investigate the build up of heterocharge in model cables that have been treated to remove volatile chemical species. They show that in fact the heterocharge is built up by many very small and very fast charge packets (i.e. charge packets having a high mobility), which are injected from both electrodes and cross the insulation in less than one second. Because the packet charge is unable to exit the counter-electrode at the same rate at which it arrives, hetero-charge is built up within just a few seconds from the beginning of the polarization. The mobility of these charges, depending significantly on temperature, is estimated through observation of charge packets as a function of time, and compared with that of the already-known slow packets, generally occurring at higher fields with respect to fast packets. The basis for the interpretation and modelling of such phenomena is discussed.

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Section: Evidence For Fast Charge Packetsmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fast and slow charge packets in polymeric materials under DC stress

Fabiani

Montanari

Dissado

et al. 2009

IEEE Trans. Dielect. Electr. Insul.

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“…80 MV/m 18,24-27 however in those cases the pulses often show variations of amplitude both during transit and over a sequence of pulses, and more importantly a mobility (l ¼ 10 À16 -10 À15 m 2 V À1 s À1 ), and activation energy (1-1.2 eV) 13,27 close to that of the carriers in steady state currents. Explanations for these pulses have been proffered in terms of a negative differential resistance, 28 imbalance between injection/extraction and transport 29 or a dc-conductivity discontinuity. 30 However the current observations differ in the following important points: (a) the charge pulse always initiates from the electrode interface and contains a polarity specific quantity of carriers, and (b) the mobility of the carriers as a coherent group is many orders of magnitude higher than the carrier mobility determined from steady state currents in Polyethylene (l ¼ 10 À15 -10 À14 m 2 V À1 s À1 ).…”

Section: Resultsmentioning

confidence: 99%

Fast soliton-like charge pulses in insulating polymers

Dissado

Montanari

Fabiani

2011

Journal of Applied Physics

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A previously unknown mode of conduction is identified in insulating polymers at moderate fields (40-50 MV/m). This takes the form of coherent charged pulses with a mobility ($10 À10 m 2 V À1 s À1 ) several orders of magnitude larger than that traditionally associated with independent charge carriers ($10 À14 m 2 V À1 s À1 ). It is shown that this phenomenon is consistent with a mechanism in which a charged compression boundary is formed electro-mechanically during injection and thereafter travels as a coherent solitary wave (soliton) through the polymer.

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“…The source terms due to irradiation (electron beam and electron/hole pair generation in (4) and (6)) disappear during the relaxation period. Generation of positive or negative charges at the grounded electrode is possible through a modified Schottky law [18], the nature of injected carriers being function of the sign of the electric field: (9) where A is the Richardson constant, e the elementary charge, and w inj the injection barrier height. k B is the Boltzmann constant, T the temperature, and E(L,t) the electric field at the electrode at position L. The extraction of charges is possible at the grounded electrode, and follows an ohmic law.…”

Section: Model Equationsmentioning

confidence: 99%

Charge transport modelling in electron-beam irradiated dielectrics: a model for polyethylene

Roy¹,

Baudoin²,

Griseri³

et al. 2010

J. Phys. D: Appl. Phys.

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This paper proposes a numerical model for describing charge accumulation in electron-beam irradiated low density polyethylene. The model is bipolar, and based on a previous model dedicated to space charge accumulation in solid dielectrics under electrical stress. It encompasses the generation of positive and negative charges due to the electron beam and their transport in the insulation. A sensitivity analysis of the model to parameters specific to electron beam irradiation is performed in order to understand the impact of each process on the space charge distribution. At last, a direct comparison between time dependent space charge distribution issued from the model and from measurements is performed. The transport parameters used for the simulations are the same as those optimized for transportation in polyethylene under an external electric field giving a robustness in the modelling approach because of the constrains on fitting parameters that must comply to a set of experimental results.PACS Numbers: 72.20Ht, 72.20Jv 1. Introduction Solid dielectrics used as thermal blanket on geostationary satellites are submitted to the flow of several types of charged particles, and particularly to electrons. These materials can accumulate charges, building up the potential inside the dielectric, meaning a potential difference between different parts of the satellite. Electrostatic Surface Discharge (ESD) can occur, leading to possible damages of the electronics of the satellite [1]. In order to prevent such ESD to happen, it is necessary to understand the dynamics of the charge transport in solid dielectrics used in space environment. A number of studies have been carried out in this domain. Some are experimental, measuring the surface potential of the irradiated samples, the current flow during irradiation [2] and the space charge distribution after irradiation [3]. Recently, two original set-ups [4-5] to measure space charge distribution in electronbeam irradiated samples have been developed on the basis of the Pulsed Electro-Acoustic (PEA) method. With these experimental tools, it is now possible to observe the dynamic of charging and discharging in electron-beam irradiated materials. On the other hand, a number of works on theoretical background and simulation has been done in order to understand and reproduce the behaviour of charge in electron beam irradiated polymers [6][7][8][9]. Our very aim is to develop space charge modelling in electron beam irradiated materials in nonstationary conditions through an approach that closely associates experiment and numerical simulation. Within the first part of this paper, we briefly review the state-of-the-art on modelling charge transport in synthetic insulations under electron beam irradiation in order to establish the position of our approach. Then, we describe the proposed model, which has been adapted from a previous one [10] developed for space charge conduction in a Low Density Polyethylene (LDPE) under DC stress. The same set of transport parameters has b...

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Models of bipolar charge transport in polyethylene

Cited by 162 publications

References 27 publications

Fast and slow charge packets in polymeric materials under DC stress

Fast and slow charge packets in polymeric materials under DC stress

Fast soliton-like charge pulses in insulating polymers

Charge transport modelling in electron-beam irradiated dielectrics: a model for polyethylene

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