Which item is not part of the traction power system?

• A. Overhead catenary.
• B. Pantograph.
• C. Traction power substation.
• D. Rolling stock.

Answer: (D)

The key idea here is the distinction between the power delivery network and the vehicle that uses that power. The traction power system consists of the infrastructure that provides and controls electrical energy for trains. The overhead catenary is the live conductor that carries the current. The pantograph is the device on the train that makes contact with that conductor to draw the current. The traction power substation houses transformers, converters, and switchgear to supply and regulate the voltage fed to the line.

Rolling stock is the train itself—the equipment with traction motors and onboard systems that consumes the electrical energy. It relies on the traction power system to operate but is not part of the power delivery network. So the item not part of the traction power system is the rolling stock.