Three-Dimensional Modeling and Calculation of the Electric and Thermal Field Distribution in Composite Insulators with Different Types of Defects

In recent years, several incidents of abnormal heating in composite insulators have been witnessed during operation, which is regarded as the early stage of FRP rod degradation. The abnormal heating behavior generally stems from the increase of leakage current inside the composite insulators, and the increased current density is closely related to the specific defects or failures located in different domains. This paper deals with several types of defects in composite insulators, calculates the current density distribution in each case with a three-dimensional finite element model, and analyzes the concentration areas of local electric field or current density. Potential partial discharge and local heating behaviors are analyzed. It is also concluded that the radial current in the silicone rubber sheath caused by the distorted potential distribution along the degraded rod-sheath interface is one of the possible reasons for the lateral punch holes in the failed silicone rubber sheath. This study provides theoretical support in failure identification of composite insulators based on the IR thermal detection.