Transmission Substations are used to...

• A. Step-down voltage for local distribution.
• B. A hub for customer service calls.
• C. A substation that steps down voltage for local use.
• D. Step-up voltage for transmission over long distances.

Answer: (D)

The main idea is that transmission substations raise voltage for efficient long-distance transmission. Power is generated at relatively low voltages, and sending it over long distances would waste a lot of energy as heat if kept at those levels. By stepping the voltage up through transformers at a transmission substation, the current is reduced for the same power, which lowers I²R losses in the lines and makes it practical to carry electricity over long distances. This high-voltage transmission then feeds into other substations that step the voltage back down for local distribution to homes and businesses. So the essential function is to increase voltage to transmission levels, not to serve as a local-step-down facility or a customer service hub.