Transformers are usually designed for nominal frequency and sinusoidal load current. Nowadays, usage of non-linear loads such as power electronics loads has extremely increased. These loads produce harmonic currents, which induce additional losses in transformer windings and other transformer parts and cause temperature rise, and ultimately can cause insulation deterioration, ageing and finally fast failing. The purpose of this paper effort to quantify the increasing in transformer
losses due to harmonic load current and the corresponding temperature rise in
transformer and study the effect of harmonics on loss of insulation life, total ownership cost of transformer, capacity of transformer and oil viscosity. An eddy current harmonic loss factor for transformer windings and harmonic loss factor for other stray loss are presented and used to calculate the transformer losses under harmonic load currents. The impact of transformer winding conductor size on
winding eddy current harmonic loss factor is presented. Three loads with different amount of harmonic content of load current are proposed in this paper.