By analyzing an abnormal incident of steam turbo-generator's speed rise under unit's turning gear operation state

this paper presents concrete accident treatment schemes and finds the main causes of the accident.The results show that steam channeling between turbine's inner and outer cylinder by drainage system was the major reason for the turbine speed's sudden rise.After the defected drainage pipes were directly introduced to the condenser

the fault was eliminated and the turbine speed returned to normal.Thus the unit load rejection test was successfully carried out.The analyses and disposals of the accident can be good references for unit's design

overhaul and operation and will be a good caution action for some unit's techniques reconstruction and new building projects.