Simulation results relevant to realistic configurations of medium-voltage (MV) and low-voltage (LV) distribution systems provide useful information to evaluate both the expected level of power quality problems on LV networks due to lightning and the benefits achievable by a proper installation of protection devices. The paper describes a procedure to evaluate lightning overvoltages induced on MV lines by lightning strokes hitting the ground on the line vicinity and that are transferred through the MV-LV transformer on the LV network. To show how the high-frequency model of the transformer play a crucial role in the simulation of transferred overvoltages, the paper presents the results obtained by using two different models identified by means of laboratory measurements.