Impact Assessment of Electric Vehicle Charging on Distribution Transformers Including State-of-Charge

In this study, the impact of electric vehicle (EV) battery charging on distribution transformer (DT) is assessed in addition to the conventional loads connected to the grid. Current harmonic spectrums of different charging levels are used to analyze the effects of commercially available EV chargers on the losses, temperature rise and lifetime of a sample 1500 kVA transformer. The harmonic spectrum data take into account the state-of-charge (SOC) for more accuracy. The results for Level I/II chargers and Level III chargers are both discussed.