Design of Corona Rings for Insulation Stability of 500kV HVDC Polymer Insulators

HVDC (High Voltage Direct Current) transmission systems are efficient for long-distance, high-capacity power transfer and asynchronous network interconnection. However, insulation design is challenging due to localized polarization and space charge effects in steady-state conditions, and high electrical stress in transient conditions. This study focuses on designing corona rings for 500kV HVDC transmission systems, addressing all electrical stresses encountered under both steady-state and transient-state to enhance insulation reliability. Using COMSOL Multiphysics, three key corona ring parameters were optimized to mitigate electrical stresses. Finite element analysis showed maximum electric fields were concentrated near metal fittings and sheds under steady-state conditions, and at the triple junctions under transient-state. Before corona ring installation, safety factors were critically low at 0.5 in steady-state and 0.1 in transient conditions. The optimized corona ring increased safetyfactors to 2.5 and 3.3 in steady-state, and 1.3 and 1.2 in transient-state. These results demonstrate the optimized corona ring effectively mitigates electric field concentrations, enhances safetyfactors, and extends the operational life of polymer insulators, ensuring reliability under extreme conditions.