Underground electric lines, though unseen, require space of their own. Planting shrubs and trees over underground lines is not recommended because of future maintenance that will be needed on these lines.
A 10-foot-wide strip centered directly over an underground line will provide enough space for future maintenance. Transformers located on the ground (which convert high electric voltage to a voltage usable by your household) also require extra space for maintenance. Leave an area of 8 feet in the front (the side marked with the Danger High Voltage sign) to be free of vines, shrubs, and trees.