Abstract: The incorrect tripping accident of the excitationloss protection section III for the generator was occurred frequently. The reasons of the incorrect tripping of the excitationloss protection section III of the generator were analyzed. According the analysis, the reason of the incorrect tripping of excitationloss protection is that the operation mode of the unit primary system had been changed, but the binary input connection of excitation loss protection section III did not be modified relevantly. The measures to prevent incorrect tripping of excitationloss protection were put forward, which are helpful for ensuring the safe operation of the devices.

Key words: generator, excitation-loss protection section III, reason of incorrect tripping, analysis, preventive measure