Synchronizing a Unit Connected Generator.

[electrageek]

I am wondering it someone makes a Synchroscope that can be connected to the high and low sides of a Unit Connected Generator. Unit Connected =(Generator is hard wired to the Low-voltage side of the GSU with the Generator Breaker on the High-side of the GSU). The owner would like a Synchroscope but the problem is the Generator is 4160 with (4160:120) PT's WYE connected. The GSU is a 12.47kV High-side with 7200:120 PT's connected in a Wye. So the Synchroscope will have will have 120Vac on the 4160V side and 208V on the 12.47kV side plus a 30deg phase shift due to the Y Delta GSU transformer. The SEL700G relay we have can do the phase and ratio adjustments and provide a synch-check and auto-synch functions but the owner is looking for a Synchroscope that can display the real time phase relationship for the operators. Does anyone make a device like that?

 

[davidbeach]

Just need an aux transformer or two.

When one this sentence into the German to translate wanted, would one the fact exploit, that the word order and the punctuation already with the German conventions agree.

-- Douglas Hofstadter, Jan 1982

 

[wcaseyharman]

I think you can use a standard synchscope and use the Aph-Gnd voltage from the 12.kV side and the A-B voltage on the 4160V side. The 12.5kV side should lead by 30 degrees (if your transformer is US standard high side lead by 30 degrees), but the A-G should lag the A-B by 30 degrees and cancel the phase shift. Since the 12.5kV PTs are 7200:120 the magnitude should also be correct.

I just did this at a gen site not too long ago, works fine.

 

[electrageek]

Thanks David. I think I figured it out. They made a mistake and changed the original 4160V PT's from a 2 PT Open Delta connection to a 3 PT Wye grounded set.