Influence of electrolytic and crevice corrosion on mechanical resistance of porcelain insulators

Abstract Porcelain insulators are widely used in transmission lines; however, their durability and considerable overall maintenance cost have become problems over the years. In this work, porcelain insulators were collected from various locations in South Korea and classified according to their length of service. Mechanical and electrical load tests were performed, and the failure load and damaged region were recorded for each specimen. The fast degradation of the pin in porcelain insulators exceeding 50 years in operation was notable because there was no pin breakage among the samples in service for less than 50 years. Moreover, the failure of 73.68% of all porcelain insulators in service for 54 years occurred in the pin. The average failure load of these samples was 14% lower than that of samples in use for 45 years. To confirm the pin’s deterioration mechanism over time, a mechanical analysis of the reduction in the pin cross-section was performed using the finite element analysis method. Applied loads of 45, 75, and 95 kN resulted in stresses of 170, 285, and 350 MPa, respectively, in the bottom half part of the pin exposed to air. To calculate the stresses due to corrosion, the model was redrawn considering diameter reductions of 0.6, 1.2, 1.8, and 2.4 mm. The stress fields were found to considerably affect the corroded zone even in the case of the sample with a 0.6-mm reduction in diameter. Accordingly, a novel degradation mechanism is proposed in this study. Previous studies that focused on the critical areas of the porcelain insulator found that the exposed pin side was easily damaged by the external load. The current findings revealing an unfamiliar porcelain deterioration mechanism may aid in the formulation of a better design to mitigate the problems described above.