Evaluation of Temporary Overvoltages in Power Systems due to Low Order Harmonic Resonances

TOVs due to low order harmonic resonances were not prevalent until recently. The phenomenon is becoming more probable due to the increasing usage of cables in transmission grids and other factors that contribute to the shift of resonances to low harmonic frequencies (e.g., 2^nd or 3^rd). If excited by a harmonic current, a TOV occurs containing both the power frequency component and a noticeable harmonic component. The withstand voltage in this condition is neither defined in the literature nor part of the standard equipment testing. The TB describes the phenomenon in detail, it presents various methods for its assessment and it provides modelling guidelines. Lastly, it proposes and explains different mitigation solutions.