Steam Generator ( boiler ) is very important equipment at thermal power units , Boiler is the steam supply for the unit to rotate the turbine’s rotor , hence produce electricity at Generator’s stator.
Boiler usually equipped with solar and Main gas firing equipments , and you can imagine that huge boiler disappear in seconds unless operator take his precaution from operation hazards., hence Boiler always equipped with a protection relays to trip the boiler out of service if hazards conditions has happened , these relays are enclosed at huge protection system is called ( Master Fuel Trip ).
From its name ( Master Fuel Trip ) , it produces trip signal for fuel systems from operation , then trip the boiler out of service away from danger. this relay needs many conditions to operate , these conditions will be found at the following figure.