Seasonal Effects of Electric Vehicle Charging on the Aging of Distribution Transformers

Large-scale adoption of electric vehicles (EVs) will be accompanied by several technical, financial and environmental benefits. However, high penetration of EVs in residential neighborhoods is expected to overburden the local distribution network. Unregulated EV charging has the potential to reduce the lifespan of network equipment, most notably the distribution transformer. The loss of life of a transformer is a function of its internal temperature, which in turn depends on the kVA loading and ambient temperature. Transformer loading is influenced by the level of EV penetration while the ambient temperature varies seasonally. This paper examines the impact of domestic EV charging on the aging of a distribution transformer under multiple penetration levels during summer and winter. The transformer's thermal model is utilized to determine its internal temperature and the rate of aging under different loading levels. The simulation results clearly exhibit the variation in transformer aging with EV deployment under different seasons.

I. Introduction

The growth in popularity and acceptance of electric vehicles (EVs) among the public has ushered in the “decade for electric mobility” [1]. Although the superiority of EVs over combustion engine vehicles in terms of energy efficiency, running costs and carbon emissions is irrefutable, the electrical energy requirement represents a significant burden on the power system [2]. Supplying the electricity required to recharge numerous EV batteries simultaneously may lead to infeasible operating conditions on the power grid. The impact of EV charging loads is expected to be the most severe at the secondary distribution level [3] and the widespread deployment of these vehicles could become a significant challenge for distribution system operators in the future.