utility company fault rating
utility company fault rating
(OP)
what happens or what can be done if the utility company current fault rating (13,000) is greater than the current fault rating of the equipment installed (10,000)?
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utility company fault rating
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utility company fault ratingutility company fault rating(OP)
what happens or what can be done if the utility company current fault rating (13,000) is greater than the current fault rating of the equipment installed (10,000)?
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RE: utility company fault rating
RE: utility company fault rating
RE: utility company fault rating
You might also check to see if you can get a series rating by installing a main fuse that is a listed combination with your downstream breaker.
RE: utility company fault rating
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RE: utility company fault rating
More information may help formulate more practical solutions. Plus where are you and the site located?
RE: utility company fault rating
What equipment exactly is rated at 10k? If it is the protective equipment just downstream of the utility, then you have a problem. If the 10k rating is for protective equipment farther downstream (breakers in a lighting or receptalce panel for example), then you may be okay. But you would need to perform a fault calc to be sure.
Give us some more details and I'm sure folks here can help.
RE: utility company fault rating
respectfully
RE: utility company fault rating
After the point-of-service we have the end box, 800A trans s cabinet (50 KAIC), 800A s/s(200KAIC) then the mdp at 10KAIC
thank you
RE: utility company fault rating
What and where is the main disconnect device (fuse or circuit breakers) in above two?
What type is MDP? I assume breakers is it is 10000 AIC.
If the main device is the fusible switch, you may be able to find out (from manufactures of the MDP) if the breakres in them are series rated (UL listed) with fuses in the main device (should be Class L) for higher AIC rating.
As others mentioned if you take in to account the cables between POS to the MDP it may be sufficient to drop SC current available at MDP but it needs to be calcaulated.
Sounds like it's time to involve a professional electrical engineer in this case or replace the MDP with a 22KAIC rated one.
RE: utility company fault rating
800 amp current transformer and 800 amp service switch.
RE: utility company fault rating
I believe there is a mistake in your 2nd last post (200kAIC for service switch). If is 20kAIC, then it seems OK for 13.7kA fault level. What is the cable size and no. of cables/phase from Service switch to 10kA MDP (I think it is Main Distribution Panel). If the length is more than (roughly) 50 meters, I think you won't be in problem.
Expert comments are welcome.
SMA
RE: utility company fault rating
the new electric service is 4-4/0 MCM CU UG service to P/L.
the main distribution panel is 20 ft away (in the same room)
thanks
RE: utility company fault rating
thanks
RE: utility company fault rating
2. Problem may be not only the equipment in MDP, but also in subsequent switchboards if their breaking capacity is low (6kA or less). MDP is quite close to end box. In order to be sure, I would think about cascading the equipment instead changing the equipment in MDP. Cascading provides circuit breakers placed downstream of a limiting circuit breaker with an enhanced breaking capacity. The limiting circuit-breaker helps the circuit breaker placed downstream by limiting high short-circuit currents. Cascading makes it possible to use a circuit breaker with a breaking capacity lower than the short circuit current calculated at its installation point.
This means that I would install limiting circuit breaker instead of service switch. Important: cascading should be implemented only by using circuit breakers predefined tables made by their manufacturer. You should be able to find them in Schneider Electric, Siemens, ABB or GE site or in their catalogs.
RE: utility company fault rating
RE: utility company fault rating
Sorry David, there must be some misunderstanding.
I think that you are wrong, since the cascading was officially implemented in IEC 60947-2 and NFC 15-100, &434.3.1 (with that specific term). If you open catalogs from this year from, for example ''Schneider Electric'', you will find the same term ''cascading'' and the same tables as in previous documentation.
RE: utility company fault rating
RE: utility company fault rating
Side issue: Under what conditions does one use 10% over voltage to calculate fault duty?