What component is primarily responsible for controlling turbine speed by adjusting steam admission?

• A. Stop valve
• B. Governor assembly
• C. Throttle pressure valve
• D. Auxiliary steam valve

Answer: (B)

Controlling turbine speed comes down to regulating how much steam can enter the turbine. The governor assembly is the device that senses the actual speed and automatically adjusts the main steam-inlet (throttle) valve to keep the speed at the desired setpoint. If the turbine speeds up, the governor reduces steam admission by partially closing the inlet valve; if it slows down, it opens the valve to admit more steam. This closed-loop action is what stabilizes speed under changing load.

The stop valve is mainly a safety shutoff used to stop steam flow in emergencies or trips, not for normal speed regulation. The throttle valve position is what the governor controls to adjust steam flow, and the auxiliary steam valve handles steam for non-turbine uses, not primary speed control.