Evaluation of aged ceramic insulators from distribution lines

Summary

This paper presents the test results performed on old and new ceramic insulators to discover the reasons for the actual great number of fails. The dielectric tests were performed on glass and porcelain cap and pin insulators and porcelain pin type, new, with 10 years and with 20 years of operation and showed that both new as aged insulators had withstand lightning impulse test if the approval criterion was the withstand voltage presents in catalogs, but several insulators can be considered as failed if the criterion for approval is changed to the value of U50% also presents in the catalogues. In addition, several aged cap and pin insulators had better performance than the new ones of the same manufacturer. The verification of the cap-and-pin insulator dimensions indicated that the new insulators had reduced the dimension of theirs cap and this reduction should probably be responsible for the worst performance in impulse tests. The power frequency test showed that some new and aged insulators did not have good performance in this test. To verify the vandalism problem with porcelain pin insulators, an adaptation was carried out on the machine developed for the impact test on cap and pin insulators and this adaptation allowed to evaluate the mechanical performance of the pin insulators against the impact of a rock. The results indicated that the age of the insulators have influence in their performance. Although it was not possible to evaluate the influence of aging on cap-and-pin insulators due to reduction of the cap dimensions of new insulators, the dielectric test results indicated that the manufacturers of cap-and-pin insulators need to make a review in their catalogs to show the real test values of the new insulators. A future study can be done to verify if this cap reduction can be the responsible for the actual corrosion problems. The manufacturers of pin type insulators should set new design criteria or change components to improve their performance against impact and reduce the effect of aging.

Additional informations

Authors

D.R. DE MELLO

Keywords

aging, ceramic insulator, lightning impulse, power frequecy test