Abstract The gas‐insulated switchgear (GIS) has been widely used in modern ultra‐high voltage systems. However, once it fails, its fully enclosed feature brings challenges in its diagnosis and maintenance. As the failure rate of GIS due to insulator failure has been increasing in recent years, it is necessary and important to understand the commonly existing defects presented in the insulator. First, the manufacturing process of GIS insulators is introduced here. The defect types commonly existing in the insulator are categorised. The failure of GIS due to insulator defects that occurred in recent years are reviewed and discussed. The content in this study is useful for engineers and scientists to study on the GIS solid insulation defects and their failure mechanisms.
