Studying the effect of aging temperature on space charge characteristics of oil-paper insulation in the different aging processes can provide experimental bases for space charge characteristics of oil-paper insulation of converter transformers while running for a long time under high temperature. Consequently

we studied the variations of space charge characteristics of oil-paper insulation with thermal aging under different ambient temperatures by using the pulsed electroacoustic method. The results show that space charge characteristics are different at different aging status

and there is no simple correspondence between the difference of space charge characteristics and the degree of aging. But the more seriously the oil-paper insulation is thermally aged

the deeper the trap energy level will be

hence more space charge is trapped

which can be speeded up by the increase of the ambient temperature. Thermal aging under different ambient temperatures will all lead to the change of real permittivity of oil-paper

which will affect space charge accumulation in return. Variations of space charge behavior and real permittivity of oil-paper insulation during thermal aging are sensitive to the ambient temperature of thermal aging

but the effect of ambient temperature does not fit the Arrhenius law very well

it may be caused by the rupture of chemical bonds and the formation of monomer chemical groups.