Station Configuration Question

[powertrainee]

Hi I have a question regarding a station configuration arrangement as seen in the attachment (sorry for the crude drawing). It involves two separate Tx lines supplying a a three winding transformer, which in turn supply two separate buses on both sides (and then of course, the individual feeders). I understand the concept of redundancy on which this configuration is derived, however, am I correct in saying a very very large circulating current would on each individual bus if the two voltages on either side were not exactly the same?

From my understanding, tapping operations are not quick. Thus, if the voltage on one Tx line suddenly dropped or rose, the two ends of the bus would be at a different potential for seconds.

Is there some sort of strict voltage regulating mechanism in place with these types of stations or am I missing something on a more fundamental level?

Thanks

 

[ScottyUK]

It would be very unusual to parallel the HV network through a station auxiliary power network, at least in this neighbourhood. I would suspect that there are breakers which are not shown on the drawing, and that there is normally a single feed to each bus with the other breaker being open, with the possible exception of short-term paralleling for load transfers from one transformer to the other. There may be a fast bus transfer scheme to keep any power loss to the absolute minimum.

If the system really is configured as you show then yes, there could be very large circulating currents. Overcurrent protection would need to be directional, or a zone protection (bus differential) scheme implemented, otherwise you don't have increased security, you just have a bigger bang when something goes wrong.


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If we learn from our mistakes I'm getting a great education!

 

[jghrist]

There are methods available to at least partially control circulating currents with LTC controls when paralleling transformers. See

http://www.beckwithelectric.com/docs/tech-papers/advxpara.pdf