LAUSR

Abstract High-voltage insulators operating at 154 kV and 25,000 lbs and having service periods ranging from 0 to 53 years were considered to study the failure mechanism based on the composition of ceramic materials. Thermal and mechanical load tests (T&M) were conducted to accelerate the aging and determine the remaining mechanical strength of the aged insulators. Based on load tests (M&E), it was observed that 38 cristobalite samples approaching or completing 50 years of service failed the mechanical load test and exhibited degraded microstructures and insulation resistances of 1200 and 970 MΩ, respectively. Alumina insulators showed a 4% improvement in mechanical strength and 11% increase in hardness compared with the cristobalite samples. A compositional study (X-ray fluorescence) was performed to determine the elemental composition of both the superior and inferior samples to correlate their probabilities of failure P(F) with the wt (%) of SiO2, Al2O3, and Fe2O3 present in the ceramic insulators.