Derating of dry power transformers in accordance with IEEE Std. C57.110 and EN 50541-2

Current and voltage harmonics generated by nonlinear elements in electric power systems cause increased heating of power transformers due to additional core losses, eddy current losses, skin effect, etc. Consequently, in some cases, derating the power transformer's maximum operating capacity must be done. This paper analyzes the necessity of derating dry power transformers following IEEE Std. C57.110 and EN 50541-2. Calculations are done for results measured at two locations: 1) PV power plant (voltage level 0.8 kV, the maximum measured power 1460 kVA), and 2) small hydropower plant supplying large nonlinear loads (voltage level 10 kV, the maximum measured power 840 kVA). More critical results are estimated using IEEE Std. C57.110 and in the case of the small hydropower plant supplying large nonlinear loads.