Effects of Defect Locations and Loading Voltages on Breakdown Morphologies of GIL Tri-Post Insulators

The tri-post insulator, a vital component of Gas insulated transmission lines (GIL), plays a critical role in ensuring both electrical insulation and mechanical support in GIL systems. However, breakdown incidents involving tri-post insulators are not uncommon, and these failures pose significant risks to the safety and operational stability of GIL systems. In this study, we explore the effects of defect locations and applied voltages on the breakdown characteristics of tri-post insulators through detailed experimental investigations. The findings demonstrate that the morphology of the breakdown is strongly influenced by the distribution of electric fields. Specifically, defects on the ground (GND) side of the insulator lead to damage paths that align toward the central axis of the insulator post. On the other hand, defects located on the high-voltage (HV) side, particularly in the belly region, cause the damage path to exhibit a distinct three-stage progression: “internal-surface-internal.” Additionally, defects on the HV side result in a longer breakdown duration compared to those on the GND side. The applied voltage also plays a crucial role in the development of these damage channels, resulting in diverse breakdown morphologies under different loading voltages. This research offers valuable insights into the root causes of breakdown incidents and provides practical recommendations for optimizing the design of GIL insulators.