Electric Field and Temperature Distribution of the UHV Valve-side Bushing under Aluminum Foil Breakdown

Insulation defects affect the electric field and temperature distribution in the valve-side bushing during operation. It is necessary to analyze the influence of defects on the electric field and temperature distribution, which contributes to the subsequent assessment of the operating condition and the risk warning. An electro-thermal coupling simulation model is established based on a valve-side bushing of a real ± 800kV converter transformer. Aluminum foil breakdown defects are introduced by model material parameter equivalence. The results show that the introduction of aluminium foil breakdown defects disrupts the structure of the electric displacement vector of the bushing core, resulting in a nonlinear radial electric field distribution. This defect did not substantially change the heat transfer structure of the core and therefore had little effect on the temperature distribution. It contributes to the subsequent reversal of bushing defects and assessment of the insulation condition.