09_laurent_cable_aged - IEEE Transactions on Dielectrics...

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IEEE Transactions on Dielectrics and Electrical Insulation Vol. 16, No. 4; August 2009 1070-9878/09/$25.00 © 2009 IEEE 1189 Semi-quantitative Analysis of Photoluminescence in Thermoelectrically Aged Cables: II-Analysis of a Population of Cables G. Teyssedre 1,2 , C. Laurent 1,2 1 Université de Toulouse ; UPS, INPT ; LAPLACE (Laboratoire Plasma et Conversion d’Energie) ; 118 route de Narbonne, F-31062 Toulouse cedex 9, France. 2 CNRS ; LAPLACE ; F-31062 Toulouse, France. and G.C. Montanari Department of Electrical Engineering, University of Bologna, Viale Risorgimento, 2, 40136 Bologna, Italy ABSTRACT A set of thermo-electrically aged cross-linked polyethylene-insulated HVAC cables has been characterized by photoluminescence measurements. The photoluminescence spectra have been decomposed into a set of seven bands representing the response of three contributions to the emission: bulk cross-linked polyethylene emission, fluorescence of the antioxidant used in the semi-conducting screens of the cables, peaking at 400 nm, and an emission at 540 nm that has been correlated to the yellowing of the cables observed during thermal ageing. From the analysis of the cable radius dependence of these emissions, it is shown that traces of the antioxidant can be found in the 14 mm-thick insulation after less than 5000 h of ageing at 90 °C. The emissions related to the antioxidant and to yellowing appear dependent on the cable manufacturing process. Index Terms Cross-linked polyethylene, high-voltage cable, antioxidant, diffusion. 1 INTRODUCTION POLYMER insulated HVAC cables have been developed for 30 years or so, and there is now an increasing demand for the development of diagnosis tools for evaluating the reliability, and ideally the remaining life time, of installed lines. In a similar way as for paper-oil insulated cables, one can imagine various routes for evaluating the quality of synthetic insulation cables, going from electrical testing at the system level using e.g. partial discharges or charging current measurements, to morphological or chemical characterization of the insulating material. Concerning the chemical analysis route, there are at least three important issues to consider for developing diagnosis tools. First, the materials that are considered, usually crosslinked polyethylene (XLPE) have complex formulations, with a number of additive and residues due to the crosslinking process and anti- degradation agents, which means that the interpretation of analytical data is never easy, whatever the technique considered. The second issue concerns identifying changes in chemical or physical properties of the material with time and requires that the starting state be known. The point is that cable technologies have evolved over the years and we often do have not at our disposal data or samples relevant to the material for cable sections that have been installed for 30 years or so. The last issue concerns the marker itself. Under thermoelectric stresses, the material evolves regarding both its microstructural features and its composition,
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This note was uploaded on 06/11/2011 for the course ELECTRICAL 124 taught by Professor Ghjk during the Spring '11 term at Institute of Technology.

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09_laurent_cable_aged - IEEE Transactions on Dielectrics...

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