As a main insulation material in high voltage DC power equipment

such as convertor transformer

oil-paper is influenced heavily by space charge under DC voltage. At the same time

the oil-paper insulation always undertakes temperature differences from inside to outside. However

it is still unknown that how the temperature differences affect space charge property of oil-paper insulation. On the basis of former experimental study

we developed a transport model based on bipolar charge transportation and trapping level of materials to simulate space charge property in oil-paper insulation. The temperature gradient effect

namely

the heterocharges accumulating near lower temperature side and further distort local electric field

was gotten by simulation in both single and double layers oil impregnated papers. By comparing calculation results and experimental results

we concluded that the simulation model was reliable. Using this model

the effects of mobility of carriers

thickness of oil impregnated paper

and the temperature of lower temperature electrode were further studied. The results show that the increase of the mobility of oil impregnated paper and the injection rate of electrodes with the increase of temperature is mainly responsible for temperature gradient effect. And the temperature gradient effect turns to be more severe with the increase of mobility of carriers and the decrease of thickness of oil impregnated paper and the temperature of lower temperature electrode.