Power supply, telephone, TV or data lines often cover long distances, far from any protected areas, and are connected to very sensitive equipment. This condition makes the lines especially receptive to overvoltages, which will then be transmitted by conduction to the connected equipment.
Care must be taken with overhead lines that connect sensitive equipment even in protected environments, as it is likely that dangerous voltages may be induced. It is also important to take into account that lightning and power switching generate high magnitude electromagnetic fields, thus inducing currents in the conductors placed inside the field.
Finally, lightning effects can enter through the earthing system, changing the voltage reference of all the equipment connected to it or to the power supply line itself.
In addition, when there are several buildings in the same area, the risk can increase due to the higher number of possible interconnections.