Distribution class transformer insulation evaluation under distorted voltage waveforms

The smart grid with state of the art technology is expected to facilitate ease of dispersed generators (DGs) connected to the distribution network. However, the fast switching power converter based interface of dispersed DGs to the distribution network is a potential source of harmonic injection; hence a considerable distortion in the voltage waveforms. With increased DG penetration, such harmonics may become a potential source of high frequency; high dv/dt stresses on the insulation system of vital power system. Additional stresses implies faster degradation rate of insulation system. Understanding such harmonic based stresses will help in designing an improved insulation system to withstand high stresses created by the switching devices. The paper presents the electric field simulation results, of a transformer model winding, which is a representative of a typical distribution class transformer, under various distorted voltage waveforms.