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. After stepping down the voltage through the transformer's low-voltage side (0. 4kV), power distribution is achieved through three levels of distribution boxes: the main distribution board, secondary distribution boards, and tertiary distribution boards. Now, let's look at how consumers use electrical power. "Two-level protection" mainly refers to the use of leakage protection. Power Distribution Equipment is a term generally used to describe any apparatus used for the generation, transmission, distribution, or control of electrical energy. This section concentrates upon commonly used power distribution equipment: Panelboards, Switchboards, Low-Voltage Motor Control.
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