Transformer Questions

[hanksmith]

Sorry if this question has been posted before, I am having a hard time with the search on this one as I don't really know what to ask.

Currently looking at a transformer for a job I am working on and this transformer has to be able to to have power flow both ways. There is a generator on the secondary that during emergency situations will have to power site.

What issues would I have to take into accout when specifiying this transformer?

I spoke with a vendor and they stated that the only issue I would have to address is the bracing, guess the primary of a transformer is braced better to handle the inrush currents.

Thanks
Hank

 

[rbulsara]

Source grounding while fed by generator?

 

[jghrist]

Search Eng-Tips Forum for "transformer reverse" and you will get several relevant threads. There should be no problem as long as the vector group is correct and there is no LTC.

 

[davidbeach]

There is a Beckwith paper on the advantages and disadvantages of all of the transformer configurations when connecting generation to the utility. The utility may have a say in what you do; like they may not want you to have a transformer that is grounded wye on the utility side and delta on the generator side even though that may be the best configuration for the generator. It all just depends.

 

[NCTHAI]

General case, trasnformers can be used for power flow in both directions. What you need to consider is tap changers if installed on them - On Load Tap changers.

If you have OLTC installed and intend to use it, you need additional resistor for power flow in another direction.

also as suggested earlier, one needs to consider sutability of vector group, protections, earth connections and in rush current capability.

Thanks

NC