Turbine trip

A turbine trip is the automatic safety shutdown of a power-generation turbine due to unexpected events. Due to the number of issues that may cause a trip, they are relatively common events. The term is common in both coal and nuclear power generation.
Many events can cause a turbine trip, including:

turbine overspeed condition where the turbine accelerates over its design speed, typically by 10%
low vacuum in the secondary cooling loop, or condenser
lubrication failure for any number of reasons
vibrations due to any number of issues

In order to trip the turbine, inlet steam must be removed from the feed. This is normally accomplished with dump valves that re-route the feed steam from the turbine inlet directly into the condensers.