The overspeed threshold is reached at N2 speed of what percentage?

The overspeed threshold is reached at N2 speed of what percentage?

• A. 118%
• B. 125%
• C. 130%
• D. 123%

Answer: (D)

Overspeed threshold is the speed at which the protection system trips to prevent damage to the turbine, expressed as a percentage of the N2 (the spool being monitored). This target provides a small safety margin above normal operating speeds so that a real runaway is stopped promptly, while avoiding nuisance trips during normal transients or startup. In this setup, the threshold is 123% of N2. That specific value reflects the plant’s chosen margin to safeguard the rotor from excessive stresses while still tolerating brief speed excursions. If the setting were higher, protection would react later and risk damage; if it were lower, trips could occur too often during normal operation. The other options represent plausible margins, but they aren’t the configured protection point for this system.

Overspeed threshold is the speed at which the protection system trips to prevent damage to the turbine, expressed as a percentage of the N2 (the spool being monitored). This target provides a small safety margin above normal operating speeds so that a real runaway is stopped promptly, while avoiding nuisance trips during normal transients or startup.

In this setup, the threshold is 123% of N2. That specific value reflects the plant’s chosen margin to safeguard the rotor from excessive stresses while still tolerating brief speed excursions. If the setting were higher, protection would react later and risk damage; if it were lower, trips could occur too often during normal operation. The other options represent plausible margins, but they aren’t the configured protection point for this system.