The electricity delivered to your home or business is typically generated in large centralized power plants (see the figure below). Power travels long distances via high-voltage transmission lines, which are interconnected in a network or grid.
From the transmission system, electricity travels to distribution substations. From these substations, distribution lines, operating at lower voltage levels, disperse the power throughout cities and neighborhoods. For safety, each distribution line is protected by a circuit breaker in the substation.
The electricity then travels from the distribution line through a service transformer near your home or business. Electricity enters the building through either overhead or underground wires that connect to the meter. CenterPoint Energy reads this meter each month and reports the information to your retail electric provider. Typically, ownership and responsibility of the wires are transferred from CenterPoint Energy to the customer near the meter (referred to as the point of service).
From the point of service, power flows along conductors to the main panel, which contains the main breaker. The main breaker provides protection for the entire building.
In industrial or commercial facilities, the main panel may also be the point of origin for circuits providing heating, ventilation, and air conditioning, as well as lighting. Furthermore, the main panel may supply feeder circuits for sub panels and dry-type transformers. The dry-type transformers step the voltage down to lower levels for branch circuits, which supply convenience receptacles throughout the facility. The figure below illustrates the paths traveled within a commercial facility.
In the figures, you can see the long and complex path electricity takes from the centralized generating plant all the way to your home or business. Unfortunately, due to the length of this path, many events can happen which interrupt the flow of power or degrade its quality as it travels to its destination.