A calculation method and some features of transient field under polarity reversal voltage in HVDC insulation

Mathematical equations are derived for the transient electric field in insulation media with permittivity and resistivity during boundary excitation due to changing from one steady state to another, such as a polarity reversal voltage imposed on the insulation of HVDC apparatus. The equations are solved by the finite element method, and a program for calculating the transient field is developed. Calculated results of some illustrative examples, including a typical bushing barrier system of power converter transformers, verify the method. Some distinguishing features of the transient field are discussed.>