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 Post subject: Etap arc flash study
PostPosted: Mon Dec 06, 2010 9:09 pm 
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Dear Sir

I am doing the Arc flash Study via ETAP 6.0 version .
The probelm that I have faced during study is the main Generating bus PPE value exceed the limit .

The analysis show PPE Exceed limit with Incident Energy 1.1 cal/cm2 and working distance 5.75 ft .

Need to know what is the cause and how to resolve the problem .


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PostPosted: Mon Dec 06, 2010 9:16 pm 
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The program you are using showed 1.1 cal/cm2 and 5.75 feet? I am assuming you are thinkin it is low (being the Generator Bus)?

The company I work with just had their's done and several of their studies showed Incident Energy over 20 cal, with one of the one's I have seen so far at 47 cal/cm2... That was on a 480 volt bus, but the 5 kv bus has 5.6 cal/cm2...

Fault Clearing time, Fault Currents and the distance away from the fault are the factors influencing your calculation.


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PostPosted: Tue Dec 07, 2010 5:19 am 
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ASAD wrote:
Dear Sir

I am doing the Arc flash Study via ETAP 6.0 version .
The probelm that I have faced during study is the mian Generating bus PPE value exceed the limit .

The analysis show PPE Exceed limit with Incident Energy 1.1 cal/cm2 and working distance 5.75 ft .

Need to know what is the cause and how to resolve the problem .


I guess some details would help. Is this "Main Generating Bus" on the load side of a breaker on which the source side is a generator? What is the size of the generator? What are the voltages and generator parameters?

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Barry Donovan, P.E.
www.workplacesafetysolutions.com


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PostPosted: Thu Dec 09, 2010 7:28 pm 
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ETAP 7.1 activation code

Does anyone have 7.1 ACTIVATION CODE

PLEASE HELP


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PostPosted: Fri Dec 10, 2010 10:13 am 
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[quote="ASAD"].....The analysis show PPE Exceed limit with Incident Energy 1.1 cal/cm2 and working distance 5.75 ft ....QUOTE]

I am a little confused. If you only have 1.1 Cal/cm2, then it should not be dangerous. Is the working distance you have listed the working distance or the AF boundary? If it is the AF boundary, then something is wrong. You would not have a low AF energy value with a large AF boundary.

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Robert Fuhr, P.E.; P.Eng.
PowerStudies


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PostPosted: Sun Dec 12, 2010 5:35 pm 
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I use Etap 7.5... started out with ver. 6.0. Sounds like you have something wrong with the input data or an incorrect program setting. Almost sounds like the fault clearing time is missing because there is no PD in the circuit, so the program can't determine FCT. Usually Etap will indicate "Unknown FCT" on the offending bus. I know from experience with Etap (as with most canned software programs) you can get some very flaky results with incorrect program settings and data. Have you tried do the calculations by hand? Exceeds max PPE at 1.1 cal/cm^ @ 5.75 ft is not right. Post the bus parameters, voltage, clearing times, etc., and I'll run the numbers and see if I can figure out what's wrong.


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PostPosted: Tue Mar 15, 2011 2:28 pm 
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The PPE limit is exceeded when the calculated incident energy is greater than 40 cal/cm┬▓. The information you have provided is perhaps related to the Flash Protect Boundary. In any case, you need to clear the fault faster. Check your source protective device and its settings and adjust it so that the arc is cleared faster.


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PostPosted: Tue Mar 15, 2011 2:29 pm 
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ASAD wrote:
Dear Sir

I am doing the Arc flash Study via ETAP 6.0 version .
The probelm that I have faced during study is the main Generating bus PPE value exceed the limit .

The analysis show PPE Exceed limit with Incident Energy 1.1 cal/cm2 and working distance 5.75 ft .

Need to know what is the cause and how to resolve the problem .

The PPE limit is exceeded when the calculated incident energy is greater than 40 cal/cm┬▓. The information you have provided is perhaps related to the Flash Protect Boundary. In any case, you need to clear the fault faster. Check your source protective device and its settings and adjust it so that the arc is cleared faster.


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PostPosted: Tue Jul 19, 2011 6:17 am 
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Sounds like you have a setting set wrong in the study case editor. Make sure the short circuit study case editor under the AF data tab that you have the NFPA 70E 2009 checked and not User-Defined Values. If you do have user defined values then you will have to go to project-> settings -> arc flash -> hazard/risk categories and adjust it there if you intend to use the user-defined values. Good Luck.


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