In order to study the electrical field distribution in oil paper composite insulation under different voltages

a simplified insulation structure model of oil paper is established

and the electrical field distribution is analyzed by way of finite element analysis method. The law of the electrical field distribution in oil paper composite insulation at different voltages and the influence factors are summarized. The breakdown features of oil paper insulation structure at different temperature and at various voltages are tested. It is shown by the result that

although the factor of breakdown feature of oil paper structure is more and complicated

it has regularity. The electric breakdown in oil paper insulation structure is the main reason of causing transformer fault

the study can provide theory reference for insulation design of transformer.