Evolution Characteristics of Dielectric Constant and Resistivity of Different Oil-impregnated Paperboard with Increasing Aging Time

As the key apparatus of HVDC transmission, converter transformers have a high insulation failure rate. Under the actual operating conditions of UHV converter transformers, the internal oil-impregnated paper material might gradually age due to the combined action of multiple physics such as large temperature gradient and electric field. However, there are few studies on the aging characteristics of key insulation parameters of KI50X, HI50X and S4 transformer oil-impregnated paperboard which are widely used. This paper studied the dielectric constant and material resistance characteristics of three transformer oil-impregnated paperboard after aging at a high temperature of 90°C 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 paperboards 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.