Operating method for a gas turbine plant and plant operated accordingly

Gas turbine plant (1) operating method in which a generator (4) is driven by turbine (2) to produce a current with a predefined frequency (f0) and whereby a combustion air flow (L) is supplied, and the operating frequency (f(t)) is monitored in a time-resolved manner. If the operating frequency varies from the set frequency, an actuator signal is generated with which the volume flowrate of a liquid, especially water, which is injected into the air, is adjusted so that the net power output of the turbine is increased in order to reduce the frequency variation. The invention also relates to a corresponding gas turbine plant.