Protective tripping systems provide a defense against excursions beyond the safe operating limits by detecting an excursion beyond set points related to the safe operating limits (i.e. the onset of a hazard) and taking timely action to maintain or restore the equipment under control to a safe state.
A trip system may be very straight forward, involving a simple actuation of a final control element when the sensor detected a deviation from a safe operating limit. Often, the trip system is more complicated, with interlocks sequence involving several pieces of equipment.