Quality Analysis of Ceramic Insulators Under Steep Front Impulse Voltage

Abstract

The insulators used in power transmission and distribution networks are meant to provide electrical isolation and mechanical support to the power lines. Hence, the insulators are exposed to continuous electromechanical stresses. These insulators are also expected to withstand abnormal electrical stresses like system generated switching impulses and natural lightning impulses. Failure of ceramic insulators in the field due to puncturing is often reported. The methodology to analyse the impulse puncture strength of the ceramic insulator is stipulated in IEC 61211/2004-11. In the present work, cap-and-pin type insulators from five different manufacturers are subjected to standard stipulated steep front impulse voltage test. After the test, one sample of healthy insulator from each manufacturer and samples of failed insulator are subjected to Scanning Electron Microscopy and Energy Dispersive Spectroscopy. It is observed that the presence of impurities reduces the dielectric strength of the ceramic insulator resulting in its puncture.