Trapped space charges densities determination in a polyethylene conical connexion by the TSM method

E. Belgaroui1*, Y. Mlik1, A. Toureille2

1Laboratoire de Matériaux Céramiques, Composites et Polymères (LaMaCoP),

Département de Physique, Institut Préparatoire aux Etudes d’Ingénieurs de Sfax, B.P 805, Sfax, Tunisie

2L.E.M Université de Montpellier 2, Place Eugène Bataillon, 34095 Montpellier, France

* Corresponding author. E-mail : ezzeddine.belgaroui@ipeis.rnu.tn

Received : 05 September 2003; revised version accepted : 27 March 2004

Abstract

In this paper, we are interested to the characterization of space charges by the thermal step method (TSM), for a cylindrical axis symmetrical dielectric material having a variable thickness. The polyethylene conical connections, which possess the previous geometrical characteristics, are often exposed to the electrical breakdown phenomenon during the tests of the dielectric rigidity. This phenomenon can be provoked by the accumulation of space charges in the conical volume of the polyethylene. To concrete the study and to understand the influence of this geometry on the space charge distributions within the material, we have applied the TSM method to a polyethylene conical connection. The experimental results show the influence of this geometry on the dynamic of the TSM current signals. The trapped space charge profiles have been determined by numerical technique that is previously validated with analytical models for a dielectric material having the shape of a parallelepiped. Initially, we have proceeded to a new validation of the numerical technique with analytical model for a cylindrical axis symmetrical dielectric. The results of the validation are in a good agreement. The previous numerical technique has been improved, and the obtained space charge density profiles in the conical connection show the effect of this geometry. Also, they underline the existence of gradients of charges according to the axis of the conical connection. These results are original and constitute a new contribution to the studies of the TSM method. They can help to the comprehension of the electrical breakdown apparition which is related to the local accumulations of the space charges within the dielectric.

Keywords : Dielectric; Piezoelectric; Ferroelectric; Antiferroelectric .

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