Switchboards usually consist of two basic elements: the service section, where the cable and conduit or bus duct enters the switchboard, and the distribution section, where power from the service section is divided into feeders and branch circuits.
The service section typically contains the main lugs, to which the incoming line can be connected to a main disconnect and overcurrent protection device. In many applications, the service section will also house the utility's watt-hour meter (usually referred to as the utility metering compartment) as well as ammeters and voltmeters for the user. These are indicated on the diagram shown here along with potential and current transformers used for stepping down the current and voltage for the meters.
When incoming power lines enter a switchboard from underground, a separate pull section may be required, through which the cable or busway can pass, to connect with the lugs at the top of the switchboard.
From the "service" section, current passes along busbars to the distribution section where it connects to the busbars from which individual branch and feeder circuits are tapped. Each branch or feeder circuit has its own disconnect and overcurrent protection device (either a circuit breaker or fused switch) which forms the connection between the busbars and the feeder or branch circuits.
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