What is the primary function of a substation?

• A. Provide insulation for lines
• B. Increase voltage for transmission and decrease voltage for distribution
• C. Decrease voltage for transmission
• D. Generate electricity

Answer: (B)

Substations are built to change voltage levels as electricity moves from generation toward customers. The key idea is transforming voltages: stepping them up for efficient long-distance transmission, then stepping them down for safe, usable distribution. This voltage adjustment happens with transformers inside the substation, and it’s complemented by switching gear and protective devices to control and protect the flow of power.

That’s why the best choice is that a substation increases voltage for transmission and decreases voltage for distribution. It matches the way high voltages are used to minimize losses over long distances and then lowered to distribution levels suitable for homes and businesses.

The other options don’t fit this primary role: insulation is a necessary support function but not the defining purpose of a substation, generating electricity is the job of a power plant, and decreasing voltage for transmission would run opposite to how transmission systems are designed to operate.