Effects of defect locations and loading voltages on breakdown of GIL tri-post insulators

The gas insulated transmission lines (GIL) are critical components of power transmission systems, where insulators provide both electrical insulation and mechanical support. However, breakdown failures of insulators frequently occur, posing a threat to the safety of power systems. The highlights of this paper are as follows: • Systematic studies were conducted on the breakdown processes and underlying mechanisms of GIL insulators. • A numerical model was proposed to simulate the breakdown process of the GIL insulator. • Experimental and simulation results successfully replicate a real-world GIL failure case. The tri-post insulator is a critical component in Gas Insulated Transmission Lines (GIL). However, breakdown incidents involving tri-post insulators are frequent, posing risks to the safety and reliability of GIL systems. This paper investigates the effects of defect locations and loading voltages on the progression of damage channels in tri-post insulators through both experimental and simulation methods. Results show that the development of damage channels in insulators is influenced by electric field lines. Specifically, when the defect is located on the ground (GND) side of the insulator, the damage channel converges toward the center axis of the post. Conversely, when the defect is on the high-voltage (HV) side in the belly, the damage channel is divided into three segments: “internal-surface-internal.” The progression speed of the damage channel is influenced by the electric field strength at its front end, leading to shorter breakdown time and more side branches as the channel develops. When the defect is on the HV side, the breakdown duration is longer than when it is on the GND side. Additionally, loading voltage also affects the development of damage channels, resulting in varying breakdown morphologies within insulators. The findings of this study provide valuable insights for identifying the origins of breakdown faults and optimizing the design of GIL insulators.