Research on insulation characteristics of multi-layers dielectrics under polarity reversal based on field-circuit coupling method

The polarity reversal (PR) is a special working condition of equipments in high voltage direct current (HVDC) transmission. The insulation of HVDC equipments must withstand the electric field stress safely caused by the PR voltage in operation or during a dielectric test at factory. Mathematical model of dielectrics under PR was established in this paper with field-circuit coupling method. A three-layers of flat dielectrics model was taken as an example for analyzing insulation characteristics. In the calculation of the transient electric field, the permittivity ε and conductivity γ of the dielectrics in the insulation structure were taking into account. The characteristics of space charge at the interfaces of the different dielectrics as well as temporal variation laws of the electric field distribution were analyzed. The results in this paper could be provided references for the insulation design of HVDC equipments.