The complete set of products can form a complete three-level protection system for construction electricity, achieving the goal of one machine, one switch, and one protection. A feeder usually begins with a feeder breaker at the distribution substation. Many feeders leave substation in a concrete ducts and are routed to a nearby pole. At this. Secondary distribution boxes, also known as sub-distribution boxes, generally serve specific power supply areas. The following electrical ratings are typical: As a result of locating power transformers and their close-coupled. The symbology (low voltage circuit breaker, low-voltage drawout circuit breaker, medium voltage switch, medium voltage breaker) reflects the most commonly-used equipment for each arrangement.