Calculation of air clearance in HVDC converter valve hall based on electro-thermal coupling model and deep learning of electric equipment image database

Abstract

Distribution of the radial electric and temperature field is an important parameter to characterize the performance of resin impregnated paper (RIP) high voltage direct current (HVDC) bushings. The upper discharge path is air insulated discharge, and its 50% impulse discharge voltage U50 can be calculated by lightning impulse withstand level and operation impulse withstand level, which can be corrected to 50% impulse flash-over voltage under standard atmospheric conditions, and the minimum safety clearance can be calculated according to the air clearance formula under standard meteorological conditions. In the paper, under 6250A current, the maximum temperature of fittings has reached 80 ℃, which exceeds the maximum operating temperature of 90 ℃ of the air medium bare aluminum alloy material in GB/T 11022 and the maximum temperature rise of 50 ℃ in relative environment, far exceeds the serious defect limit of hot spot temperature exceeding 80 ℃ in DL/T 664-2008 Code for Diagnosis and Application of Live Equipment, approaches critical defect limit of 110 ℃, and cannot meet the requirements for long-term operation reliability on site. The design and process are improved and optimized to improve the current carrying temperature rise performance. The results are in good agreement which proving validity of the finite element electro-thermal coupling model. Then the finite element model was used in the cone model which is much closer to the actual condenser structure. Optimization design for the condenser outer contour structure was also conducted to make sure that the hottest-spot temperature is close to 90℃ under rated operating condition, and the maximum radial E-field strength is approximately equal to 3.5kV/mm and distributed uniformly. Finally, the temperature rise and electrical performance test were carried out on RIP HVDC bushing prototype, which can vertify the feasibility of optimized design.