Optimization and Improvement of ±800kV RIP Capacitor Type DC Bushing

The valve-side DC bushing of converter transformers serves as a critical insulation support and electrical connection component in UHV transmission systems. During operation, it endures harsh conditions such as high voltage, large current, and polarity reversal, with its performance directly determining the safety and reliability of the UHV transmission system. This paper focuses on researching surface flashover faults occurring in the gas cavity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 800 \text{kV}$</tex> epoxy resin-impregnated paper (RIP) capacitor type DC bushings applied to converter transformer valve-side (hereinafter referred to as “<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 800 \text{kV}$</tex> drytype DC bushings”). Through mechanism analysis of surface flashover and DC electric field simulation verification, approaches and solutions for optimization and improvement are proposed. Enhancement measures for the surface of the core flashover in gas cavity performance are adopted in three aspects: optimizing the core structure, shielding in the gas cavity, and improving assembly processes. The improved bushing has already passed all test verifications and operated reliably in DC transmission projects, providing a safe and reliable dry-type DC bushing solution for UHV transmission systems.