Evolution Characteristics of Partial Discharge Inception Voltage and Breakdown Voltage of Different Oil-Impregnated Pressboard with Increasing Aging Time

As a key component of high-voltage DC transmission, the insulation failure rate of the converter transformer has remained high. The main insulation of the converter transformer is oil-paper composite insulation structure, its insulation performance is jointly determined by transformer oil and high-density transformer pressboard. Therefore, it is necessary to study the evolution of the electrical characteristics of oil and paper insulation under different working conditions in different aging conditions. This paper studied the partial discharge (PD) inception voltage (PDIV) characteristics and Breakdown characteristics of three transformer oil-impregnated pressboard after aging at a high temperature of 90 ℃ for 1 day, 7 days, 21 days, 28 days and 35 days. And we obtained the evolution law of the dielectric constant and resistance characteristics of the three oil-impregnated pressboards under long-term operating conditions, and compared the three transformer oils from different parameter perspectives, which could provide a basis and reference for the selection of insulating oils for converter transformers.