Induced draft fan RB control method based on induced draft fan system state monitoring

The invention relates to an induced draft fan RB control method based on induced draft fan system state monitoring. The induced draft fan RB control method comprises the steps that according to the unit furnace pressure, the induced draft fan inlet pressure and the induced draft fan motor current change condition, whether the induced draught system unusual service condition that an induced draft fan does not trip but output cannot be achieved occurs or not in the running process is judged; when the unusual service condition is detected, the induced draught system unusual RB is triggered in time, and a series of protection motions are done. Compared with the prior art, the induced draft fan RB control method has the beneficial effects that when the induced draft fan does not trip, the unusual service condition that the induced draft fan cannot output is judged in time, quick unit load shedding is achieved, and safe and stable running of a unit is maintained.