electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
It depends in the voltage, but In the case of 480/277 the answer is yes.
Getting a delta secondary from a wye transformer
- Thread starter mhowlett
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I don't see how you can go your own way on this. You have to go in the direction the manufacturer supports. There is no new generator without MDGF trip ? There are the liability and warranty issues of not following the manufacturer's instructions.
Does the new generator replace an old generator for a like to like swap ? Is there is already a connection point on the main bus for the old generator ? Was the existing protection controls all connected and operational, functional?
There is so much to look at and consider before even ... Look for some fresh eyes and minds. This is a very specialized and highly engineered area.
The main service you have A and B main transformers with a tie, MTM ? Are A and B on the same primary circuit or is there some redundancy where A is up when B is down, true dual primary? How often does the power go out, when it does what is the cost?
If you have or can get a true dual primary from the utility, A is isolated from outages on B, statistically, downtime on the facility is a lot less.
With the new microprocessor protective controls, is it possible to get a new controls package for the breakers using as much of the existing installed equipment as possible?
You want to run the plant on generator when the utility is out. Or just maintain power to critical loads and wait for the utility to come back? How often does power loss happen and how long is it out? The utility may be able to improve the reliability or isolation of your existing circuit.
mhowlett
Member
- Location
- Lexington KY
There is no generator now. The two utility feeds are from separate primaries, but both have gone down for extended periods during bad weather events, thus the need for the generator as the third source. There are critical loads that can't go more than a couple hours without operating. They don't have to run everything concurrently but need the flexibility to operate any loads at the plant.
We really are stuck with this breaker issue. The manufacturer says the only way they can make it work with the GF is by replacing the two mains. They agree the MDGF is not code required but they won't install without it. They don't like the idea of disabling the GF either but can't argue that it's a solution that would be permitted by code.
We really are stuck with this breaker issue. The manufacturer says the only way they can make it work with the GF is by replacing the two mains. They agree the MDGF is not code required but they won't install without it. They don't like the idea of disabling the GF either but can't argue that it's a solution that would be permitted by code.
- Location
- Illinois
- Occupation
- retired electrician
Yes. 250.20(B)(2) only requires that system to be grounded where the neutral is used as a circuit conductor.
I see no reason why you can't remove the neutral bond, assuming there is not one internal to the transformer, and connect one of the legs to ground to have a grounded system.
On the supply side, the utility maintains outage reports. They may be able to look at the history for the plant's circuits and may be able to offer improvements to the statistical reliability or the isolation of A from B. I would guess it may have been a long time since this was looked at, but changes and future planned changes have taken place. There may be something they can do. Or plan to do in the future.
On the load side I would exhaust alternates also. Can you run just the critical loads and let the plant be down while waiting for the utility (to restore either A or B). You might be looking at a new emergency power distribution system that connects much further downstream, nearer to the loads with ATS's. You may be able to protect critical plant process while letting production go down.
The cost of plant downtime is a factor. But the engineers and not the bean counters should be making the engineering value decisions.
On the load side I would exhaust alternates also. Can you run just the critical loads and let the plant be down while waiting for the utility (to restore either A or B). You might be looking at a new emergency power distribution system that connects much further downstream, nearer to the loads with ATS's. You may be able to protect critical plant process while letting production go down.
The cost of plant downtime is a factor. But the engineers and not the bean counters should be making the engineering value decisions.
mhowlett
Member
- Location
- Lexington KY
Thanks, Don. That is what I was trying to figure out.
Dan, agree engineers should be making the design decisions. I hope to avoid going to a antiquated (but code permitted) system if at all possible.
Dan, agree engineers should be making the design decisions. I hope to avoid going to a antiquated (but code permitted) system if at all possible.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Is this the manufacturer's sales and marketing force or its power system engineering?
You may need to pay to have your full system evaluated and designed. Recently I have seen more HRG being put in rather than ungrounded or corner grounded.
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