Overcurrent protection on only one phase
Overcurrent protection on only one phase
(OP)
I have a 3-phase, y-connected generator, 400volt. Overcurrent protection is provided in one phase only. Does this provide adequate protection?
Any comments?
Any comments?





RE: Overcurrent protection on only one phase
Unfortunately I cannot open the docx file. try a doc or pdf and tell us more...
rasevskii
RE: Overcurrent protection on only one phase
David Castor
www.cvoes.com
RE: Overcurrent protection on only one phase
Otherwise it is not sufficient as dpc said.
Rafiq Bulsara
http://www.srengineersct.com
RE: Overcurrent protection on only one phase
"Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic — and this we know it is, for certain — then it is a mere question of time when men will succeed in attaching their machinery to the very wheelwork of nature". – Nikola Tesla
RE: Overcurrent protection on only one phase
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Overcurrent protection on only one phase
David Castor
www.cvoes.com
RE: Overcurrent protection on only one phase
Rafiq Bulsara
http://www.srengineersct.com
RE: Overcurrent protection on only one phase
The manufacturer supplies thousands of similar units into the Japanese/Australasian market.
RE: Overcurrent protection on only one phase
Rafiq Bulsara
http://www.srengineersct.com
RE: Overcurrent protection on only one phase
There's a time and place for lean manufacturing design, this is neither the time or place.
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RE: Overcurrent protection on only one phase
I just don't know why they have only used one CT, and what sort of prorection that provides. i would think that it would only provide adequate protection the the load was perfectly balanced across phases.
The manufacturer uses 2 CTs on most other (larger) of its generators.
RE: Overcurrent protection on only one phase
I've been lurking for a few years, enjoying the posts and interesting ideas. I finally decided today was the day to see if I could help out. I've been hanging around industrial grade generators for a lot of years and possibly I have an informed opinion.
First I'll make some guesses (and I could easily be all wet):
The generator is at least 50kw and not more than 500kw - probably closer to 100kw - 300kw.
The driver is on the small side for the rated output.
I don't see any external inputs for voltage (field current), so it is likely there is also no external governor input for frequency. The unit is likely not designed for parallel operation.
The manuals with the generator show the output connected to a circuit breaker feeding the premises distribution system.
It could meet easily NEC445. The guiding light for overload protection is 445.12 and that is pretty vague. A small driver with a under frequency trip on the governor might be enough.
As for selling in the US, there is nothing I saw in the thread that would violate UL2200. But since it is 400v and likely 50Hz - it probably would not sell many.
So, based on my guesses, and the posts from the OP, the short answer is, "No this is not adequate protection". But these are design issues, and once the installation meets these, it will be in excess of the regualtory requirements.
Assuming you are going to use the gen on a grounded wye, 3phase overload protection is a must. It is possible to overload the system heavily on one or two phases and not exceed the driver capability. Since you have to protect the conductors from the gen to the first over current device, set the first OCP small enough to trip the gen CB inside of it's damage curve.
Also you will want a under voltage/over voltage to keep the gen from damaging the loads if the AVR fails
Any protection past these has to do with the cost of replacing the generator structure and if it is cost effective to rewind the gen as opposed to replacment. The issue is that if the generator faults, how quickly do you want the fire put out?
Hope I helped.
ice
RE: Overcurrent protection on only one phase
There does not seem to be a PMG so voltage collapse may be expected to provide some protection.
Bill
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Jimmy Carter