While most older homes have an overhead service connection, underground services are now the standard and are the favorite among homeowners for several reasons. These buried lines are more appealing to the eye and the surrounding landscape than power poles and overhead lines draped across the yard. Underground lines also don't have to contend with tree branches, which cause so many problems for overhead lines during inclement weather. But just like overhead service line feeders, there are rules that must be followed when installing underground lines, and underground feeders present their own dangers.
The Path to Power
For customers with overhead electrical service, the primary power comes from the utility company's power lines via a transformer mounted on the power pole. The heavy lines that hang between the transformer and the house are collectively called the service drop. These must be a minimum of 12 feet above a driveway. The point of attachment to a house's service connection should be a minimum of 10 feet above the ground. The service drop typically connects to the house at the top of a vertical pipe called a masthead or weatherhead. This connection point is called the service point and in many cases represents the dividing line between the utility and the customer. From the service point, the service entrance conductors carry the electricity to the home's service panel, or breaker box.
With underground service, the service lines between the utility transformer and the house are known as the service lateral, and the service entrance conductors often travel up to the service panel rather than down from the roof. The service lateral cables must be protected in the ground by conduit until they reach a depth of 4 feet. At this point, they often make the horizontal run to the house without conduit. This is why you must always "Call Before You Dig;" that is, call the 8-1-1 hotline to have all utility lines marked before you dig anywhere on your property. Trust me, you don't want to hit a 200-amp electrical cable with a shovel. If you do damage something, you'll have to likely pay a fine and the repair costs, if you survive the encounter.
Meter and Service Panel Connections
The service entrance conductors connect to a utility meter, which records all electricity used by the house. After the meter, there are three service conductor wires that come into a service panel: two hot feeder wires and a neutral wire that bonds to the case ground of the service. This ground is then connected and bonded to both the water piping within the home a ground rod driven into the earth near the service panel.