Criteria for the diagnostic of polluted ceramic insulators based on the leakage current monitoring technique

Ceramic insulators installed in a 400 kV line located in a semidesertic area in Monterrey, Mexico have registered flashover caused during critical pollution (high amount of low solubility material) and wetting conditions (dense fog). In previous studies, the contaminant deposited on these insulators was chemically and electrically reproduced in the laboratory and the wetting conditions needed to cause the flashover at nominal voltage were also determined. To get more information, five different profiles of glass and porcelain insulators and several on-line leakage current monitors were installed in this line to determine the pollution accumulation process. Pollution tests were carried out in laboratory using the same insulator profiles in order to determine the leakage current patterns during critical conditions. The obtained values are being used to compare the performance of the insulators installed in the field with the purpose of providing preventive maintenance indicators. The maximum leakage current levels have been defined for the different profiles and a tighten relation between ESDD and leakage current has been obtained. The current levels have been used as a sign of alarm for the maintenance of this line during several years.