Microstructure based evaluation of field aged and new porcelain suspension insulators

Porcelain suspension insulators that were in service for up to 38 years on 115-500 kV transmission lines were evaluated for electrical and mechanical properties. The microstructure of the porcelain and cement was examined using analytical techniques like scanning electron microscopy and x-ray diffraction. It has been shown that insulators that performed well in service for many years had microstructural details that were notably different from those that exhibited significant reduction in residual electrical strength and punctured in the laboratory test. This information has been utilized to rank new insulators made presently that were obtained from the users.