generator motoring 100%

[rasevskii]

@odlanor:

Yes. The 32R backup has to be enabled, as you have done, even with the load order. Suppose that, for some reason, the governor does not open the guide vanes(wicket gates) upon GCB closure, then the 32R signals (alarms) that situation. If the operator does nothing, the unit will trip safely on 32R backup.

In such a large station, with many units, if things go wrong all at once (line disturbance?) then you are protected against motoring.

Are you involved in the commissioning at site?

Another thing is, with such large low head low speed units, there must be a lot of turbulance at around no-load gate setting, which will make a short time setting of 32R more difficult.

What is the head in meters and the RPM of theses units?

rasevskii

 

[odlanor]

rasevskii
32R: Thank you.

commissioning: NO

H/RPM: 15.2 m / 94.7 rpm

 

[odlanor]

rasevskii

.... Suppose that, for some reason, the governor does not open the guide vanes(wicket gates) upon GCB closure, then the 32R signals (alarms)...

If guide vanes is closed, rotor is not running and GCB can not close. It assume to energize a generator stopped. You should trip GCB not alarm.

There is a Inadvertent Energization protection with instantaneous trip.

I did not understand the reasoning

 

[rasevskii]

No, I meant that if the governor failed to open the wicket gates beyond the no-load position (unit running at speed-no-load)after the GCB had closed, then you might get a motoring condition.

rasevskii

 

[odlanor]

Another cause of reverse power can occur during synchronization. If the frequency of the machine to be synchronized is slightly lesser than the bus bar frequency and the breaker is closed, power will flow from the bus bar to the machine. Hence, during synchronization(forward), frequency of the incoming machine is kept slight higher than that of the bus bar i.e. the synchroscope is made to rotate in the "Too fast" direction. This ensures that the machine takes on load as soon as the breaker is closed.

 

[odlanor]

To finish this thread:
Attached is a motorization table with hydroturbine 100%, extracted from GE instruction GEI-33891.