Our Steam turbine generator Power factor suddenly drops for two or three second then restores automatically.

Please let me know what it could be the problems. What important things i need to check in Generators.

 

The power factor suddenly "drops". That is an incomplete statement in that you haven't said if it "drops" in the leading or lagging direction, or what the magnitude of the "drop" is (from 0.98 lagging to o.78 lagging, for example). You should also tell us what load (kw or MW) the unit is producing when the "drops" occur.

Further still you need to indicate if the unit is being operated in Power Factor control mode or VAr control mode, or automatic- or manual voltage regulator mode.

Precipitous, sudden and/or intermittent changes in reactive current are most likely the result of some problem with the generator exciter, sometimes called the "AVR" (Automatic Voltage Regulator), or the inputs to the device (potential transformers; current transformers; VAr transducers; analog setpoint signals; etc.),

There is also the possibility that the instrumentation being observed is faulty or failing.