Hi,

I have seen a configuration of a dead bus synchronization that once the Generator Breaker is closed. the Valve will have about 2 % constant kick added to the valve output. I understand that this kick shall be when synchronizing to a live bus so the generator can some power once the breaker closed. but is this configuration on having a valve kicked when sync to dead bus is correct?

Thanks in advance for your reply

 

Ahmed,

Remember that even though a "dead bus" doesn't have any current flowing there can still be a load or loads which are anxiously waiting to be powered and which were not isolated from the bus or shut off when the bus went dead. These loads may be immediately energized as soon as the generator is closed on to the dead bus. So, some "kick" might be warranted though too much might not be good, either.

If the "dead bus" has no load or loads connected to it, then it would seem a "kick" of any level might not be warranted.

Isn't the real question, though, when a generator is closed on to a dead bus (not synchronized to--because there is nothing to synchronize to), should it be in Isochronous governor mode or Droop governor mode? Because if it is in Isochronous governor mode then even if a load or loads are present and energized as soon as the bus is energized the Isochronous governor mode should automatically adjust the energy flow-rate to try to maintain rated frequency and no "kick" should be required.

A "kick" such as you describe is often used when synchronizing a generator in Droop governor mode to a system or grid with other generators to prevent a reverse power trip. But, that same thing can be accomplished by synchronizing with the speed reference just slightly higher than synchronous speed and once the generator breaker is closed the difference will translate to "forward" power. (In other words, when the synchroscope is rotating rather quickly in the clockwise direction the speed reference is greater than synchronous speed, and when the breaker closes that extra fuel will become amps flowing out of the generator.)

If a generator with its prime mover operating in Droop governor mode is closed on to a dead bus with a load or loads "waiting" to be powered then what will happen is the frequency will drop in proportion the percentage of load versus the Droop percentage and some operator--or some load control scheme--will have to increase energy flow-rate to get the frequency back to rated. And, and changes in load will have to be countered by the operator or the load control scheme as long as the unit remains in Droop governor mode. Frequency control will be "automatic" with the governor in Isochronous mode and no operator or "outside" intervention will be required.

So, your question doesn't account for two possibilities, the first of which is the governor mode of the generator-set immediately after generator breaker closure, and the second is the presence (or absence) of any load or loads connected to the dead bus which will be energized as soon as the bus is energized.

Hope this helps!

 

Thanks CSA for your reply, much appreciated, actually now the confusion cleared. The Generator will on Isoc. Mode once the breaker closed to a dead bus, and no loads will be connected at that time as loads shall be connected gradually by some operation procedure. and I believe now as per your reply there is no need for a kick.

Thanks
Ahmed

 

Ahmed,

You're welcome, and glad to be of help.

And thank you for the feedback. It's always good to hear if the information provided was useful--or not. Sometimes it's difficult to understand exactly what the question was, or we just don't have enough information to be specific. So, thank you for taking the time to write back.