Standby Generator with Stepup Transformer

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natfuelbill

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Customer receives 4160V from utility as a primary voltage, and desires permanent backup generator during outages. Utilization voltage is 240.
Loading is 200kW. Genset would be a low voltage unit with larger larger kW.
Any code references for this generator feeding a step-up transformer say 480-4160V and taking 4160 V electric service both into a 4160 open transistion automatic transfer switch and refeeding customer owned step-down transformer?
 
Just wondering but what would be the big advantage of this? Cost of 4160 volt transfer switch would be higher that a 240 volt unit. Everytime you transform voltages you have losses. The further "down" in the system you can locate an auto transfer switch the more reliability you bring...... Can't quite tell why we'd want to do this..........
 
Article 490 is devoted to equipment operating above 600 volts and various individual articles have specific requirements for above 600 volt operation. I still question whether this is the best for a customer concerned about reliability. You are going to be relying on that customer owned step down transformer plus some of the 4160 volt distribution. Imagine a transformer failure or a failure on the 4160 volt system. You couldn't get the generator power to the load. Of course if the generator is a long way from the load I see where this would provide something.....
 
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I've seen one just like this in the UK, but it was 11KV, with an 850KVA genset. It was this way as the site (a hospital) was physically a big site, and there were several 11KV/415V transformers, as I suspect the OP's installation will have. I've described it in more detail on this board somewhere.

For certain kinds of installations this is the only realistic approach, LV doesn't travel well over long distances.
 
Low voltage transfer switch options are also being considered but has issues with limited available space.

The 4160 V option solves the space issue.
 
natfuelbill said:
Low voltage transfer switch options are also being considered but has issues with limited available space.

The 4160 V option solves the space issue.
Click to expand...


Yes, but probably at an increased cost, and reduced reliability.

But if that's what the owner wants, I don't see anything code wise that would prevent this. I would just make sure the owner knows the issues involved.

Steve
 
natfuelbill said:
Low voltage transfer switch options are also being considered but has issues with limited available space.

The 4160 V option solves the space issue.
Click to expand...

You can get an ATS in a Nema 3 or 4 enclosure and mount ouside.... if it would help. This might raise security issues but is available........
 
Someone cautioned to be careful of generator sizing when feeding step-up transformer. No details, just a caution. Any words of wisdom out there?
 
natfuelbill said:
Someone cautioned to be careful of generator sizing when feeding step-up transformer. No details, just a caution. Any words of wisdom out there?
Click to expand...

A transformer will have an inrush current that the generator would need to supply. I'm thinking this is around 6 times full load. A generator sizing program would help. I'm thinking a concern might be that the generator starts, come up to speed and voltage, then transfers, then the voltage will sag when the transformer is first energized. But generators can be sized to handle this.....
 
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