Understanding the effects of electric vehicle charging on the distribution voltages

This paper evaluates effects of the distribution circuit parameters on the primary and secondary circuit voltages due to EV loads. The distribution circuit parameters considered here are; location of the service transformer with respect to the substation and location of the EV loads within the secondary service. The voltage analysis is carried out using a 13.8 kV distribution feeder dominated by residential loads. The study reveals that EV charging affects the secondary voltage more significantly than the primary voltage. The short-circuit capacity even at the remote end of the primary distribution line is adequately high; hence, preventing EV loads from affecting its primary voltage. When four 240V/16A EV loads in a secondary service nearby and remote from the substation are charging, the additional voltage drops in their respective primary voltages are 0.023% and 0.13%. However, because the short-circuit capacity at the secondary service wire for both locations (remote/nearby) is significantly lower, additional voltage drops of approximately 4.5% occur in the secondary service voltages. The study also reveals that a single EV load installed on a distant load node from a service transformer leads to comparatively higher additional voltage drop (1.7%) than an EV on a nearby load node (0.81%) in the same secondary service.