Impact Assessment of Electric Vehicles Charging on the Loss of Life of Distribution Transformers

Electrification of the transport sector is an essential component of the energy transition. However, the arrival of large numbers of Electric Vehicles (EVs) may negatively impact grid components. Expressly, steep peak demands from the uncoordinated charging of EVs will stress distribution transformers. This situation is aggravated depending on the ambient temperature since high temperatures reduce the transformer's operating range, and very low temperatures increase the energy demand of the EVs. In this context, this paper proposes an impact assessment methodology to consider the temperature effects jointly on EVs' demand and transformers' loss of life. Firstly, a time-series modeling process characterizes the EV charging profile and its dependency on ambient temperature. Secondly, a transformer's expected loss of life is computed as a function of its hotspot temperature, according to the IEC 60076–7 standard. Experiment results on actual data show an increase of 36% in EVs' energy demand as ambient temperature drops from 25°C to -15°C. The cold temperatures are likely to increase the transformers' operating range and help them to support longer peak demands. Thus, results suggest that transformers' degradation is significantly higher in summer sessions, more than one hundred times.