4FA9E878d01 - IEEE Transactions on Power Delivery, Vol. S,...

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IEEE Transactions on Power Delivery, Vol. S, No. 2, April 1990 Aging of Distritxition Composite Insulators under Environmental and Electrical Stresses S. M. de Oliveira Curitiba, Parana Varennes, Quebec C. H. de Tourreil, Senior Member, IEEE COPEULAC IREQ Canada Brasil ABSTRACT Seven types of commercially available distribution composite insulators with sheds made of EPR or epoxy resin were subjected to various functional aging tests recommended by the IEC or the IEEE. The influence of UV radiation on the aging of the shed materials was also evaluated. The usefulness of the various aging and diagnostic tests is discussed and a modification of the recommended test procedures is proposed in order to improve the evaluation of the long term performance of these insulators. 1- INTRODUCTION Composite insulators have now been used on distribution lines for several years. With the gradual improvement of their design, their reliability has also increased. There are now many models commercially available and new models will appear in the future. The user is faced with the difficult task to choose amongst the many models available which all perform satisfactorily when new. It is however difficult to establish how they will perform after several years of service. Aging of the insulator weathershed may lead to damages such as excessive chalking and crazing, erosion and tracking which affect the insulator performance ['I. Since the weathershed protects the FRP rod and provides the required leakage path its degradation will prevent the insulator to cope with the service conditions. The International Electrotechnical Commission (IEC) and the Institute of Electrical and Electronic Engineers (IEEE) are issuing recommendations regarding the testing of composite insulator^[^^^]. The present study examines two testing methods recommended by the IEC and the IEEE for the evaluation of the resistance to tracking and erosion of the insulator weathershed . The influence of the UV radiation is also evaluated. In service these insulators are subjected to aging stresses such as humidity, pollution and electrical field which act singly or in combination and can produce erosion and/or tracking of the weathershed. The IEC and the IEEE tests attempt to simulate in the laboratory these service conditions. In the IEC test the insulator is placed in a salt fog chamber and stressed for 1000 h with a voltage proportional to the leakage distance of the insulator. One of the methods recommended by the IEEE document has the insulators placed on a rotating wheel and for about 1000 h they are sequentially dipped in a saline bath and subjected to a given vo I tag e. d9 TD 408-5 PIJ;u) A paper recommended and approved hy the IEE'd Transmission and qistribution Committee of the IEEE Power Engineering Society for presentation at the IEEE/PES 1989 Transmission and Distribution Confsrence, !Jew Orleans, Louisiana, April 2 - 7, 1989. "lanuscript submitted January 6, 1988; made available for printiqg January 13, 1989. 2- TEST SPECIMENS AND TEST PROCEDURES 2.1 Test sDec imens
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4FA9E878d01 - IEEE Transactions on Power Delivery, Vol. S,...

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