substation bus synchronization

[deltawhy]

I work in commercial and light industrial electrical design, so my experience with HV is limited. I have a question regarding bus synchronization. I have dealt with small scale generator synchronization of up to 1MVA, but nothing else. I am wondering, how is it substations synchronize the incoming power from multiple sources if there is no way to alter the incoming phase angle (ie. they are not able to control the generator governors from multiple sources).

Thanks

 

[davidbeach]

Generally all the sources are synchronized already as they are all part of a much larger network.

 

[dpc]

There may be a synch-check relay to guard against unexpected disaster due to stability issues, rolled phases, etc, but there is no way to synchronize one system to another at a substation. They are either in synch or they aren't.

 

[deltawhy]

So if I am reading this correctly, even large networks with inter-ties have a minimal phase angle difference? I am finding the technicalities of this hard to grasp. In the event of a fault on a bus being fed from multiple sources, one source could come out of steady state stability, and thus be out of synch with all loads it feeds. Seems like a very big problem, no?

 

[PaulSaul]

Not a very big problem in an interconnected system (an infinite bus). a fly cannot eat up an elephant

 

[tlrols]

Synch check relays will auto-synch you if voltages and phase angles randomly get within the acceptable breaker close parameters. Having synch'd at stations without generation I can tell you that sometimes the synch relay times out without a breaker closure. In these cases what you tend to do is start moving generation around to bring phase angles in close together, or you open breakers and close breakers to move the synchronization point closer to a resource that can affect voltage and phase angle. Keep in mind that a circuit breaker will happily close across a phase angle of 180 degrees...the power system will complain, but a properly sized circuit breaker will not.