Impact of EV home charger on distribution transformer overloading in an urban area

Concentration of electric vehicles (EV) in an urban area can cause distribution transformer overloading because of their charging behaviors and the resulting power demand. This paper assesses the impact of EV home charging on transformer overloading considering two critical factors, which are penetration level and driving performance. Test scenarios are confined by a low-voltage distribution system with household load profiles. Test results show that the transformer overloading indexes are unacceptable when EV penetration level reaches 75 percent. The overloading indexes become significantly poorer when the EV driving performance is lower. Additionally, there are unsuccessful charge events in all tested cases. The assessment can provide guidelines for a power utility to devise necessary monitoring and control scheme to accommodate the EV penetration, and to plan for upsizing the distribution transformer in an appropriate time.