Primary Distribution Box: Serves as the main distribution box for a construction site or project (usually only one). 4kV to the distribution cabinet (primary distribution cabinet), then the outgoing line is led to the distribution box (secondary distribution box) in each building, and finally the outgoing line is led to the distribution cabinet. With secondary selective service, each distribution transformer must be able to supply the entire load for maximum reliability benefits. Spot Networks are used for customers with the highest reliability requirements. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between 2 kV and 33 kV. Utilities may have some control over and access to the energy stored in electric vehicles attached to the grid. The equipment within these boxes varies: primary distribution cabinets usually contain isolating switches, circuit breakers, and residual current devices (RCDs); secondary cabinets contain large three-phase circuit breakers; tertiary cabinets contain single-phase circuit breakers.
