Substation

A substation is the meeting point among the transmission grid and the distribution feeder system. This is where a fundamental change takes place within most T&D systems. A transmission and sub-transmission systems above the substation level commonly form a network (about that you will study in the further studies). But arranging a network configuration from the substation to the customer would simply be prohibitively expensive. Thus, most distribution systems are radial (also described in the next section), i.e., there is only one path by the other levels of the system.

Classically, a substation consists of high and low voltage racks and buses for power flow, circuit breakers at the transmission and distribution level, metering equipment and the control house, whereas the relaying, measurement and control equipment is located.  But the most significant piece of equipment that gives the substation its capacity rating is the substation transformer. It converts the incoming power from transmission voltage levels to the lower primary voltage for distribution. Very frequent, a substation has more than one transformer.

Expect from the transformer, a substation has other equipment like as lightning arrestors, isolators, etc. You will learn about the substation equipment in detail in further studies and the distribution transformers. Here we provide a brief introduction of the most critical component of a substation, the transformer.