In a turbine equipped with an Electronic Overspeed trip system with 3 magnetic sensors, how many sensors must agree before a trip occurs?

In a turbine equipped with an Electronic Overspeed trip system that uses three magnetic sensors, the design is made to ensure reliability and accuracy in monitoring the turbine's speed. To prevent false tripping and to enhance safety, a majority voting system is utilized. In this case, two out of the three sensors must agree before a trip occurs. This means that if two sensors detect an overspeed condition while the third does not, the system will activate the trip to shut down the turbine.

This approach minimizes the risk of an unnecessary trip due to a single sensor malfunction, which might happen due to noise, a temporary glitch, or other issues. By requiring two sensors to agree, the system increases the likelihood that the detected overspeed condition is both real and critical, thereby providing a more stable and safe operating environment for the turbine. Therefore, the need for agreement among two sensors is a critical design feature that enhances the overall safety and reliability of the turbine operation.