Assessing the integrity and remaining service life of vintage high voltage ceramic insulators

Electric utilities are currently using millions of ceramic cap and pin type insulators that are either approaching or are beyond their intended service life. While the performance of these insulators has traditionally been very good, the number of observed problems has risen as the number of insulators in service for more than 30 to 50 years has increased significantly. Therefore, utilities are interested in identifying suitable 'stand-off' inspection methods and tools to assess the electrical and mechanical integrity and performance of ceramic insulators in an attempt to maintain the reliability of their power lines. Inspection, testing, and assessment methods are presented to allow utilities to assess the integrity of ceramic insulators on transmission lines in their delivery system. Methods were developed based on test data of 'aged' ceramic insulators, 'new' insulators not previously used in service, and experiences from a number of field inspections on actual transmission lines. Results indicate that the use of visual, infrared, and corona imaging of ceramic insulators in field conditions is likely to consistently identify 'problem' cap and pin type ceramic insulators making these technologies viable tools for the stand off inspection of these components.