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| Electric Utility Data for the Arc Flash Study https://brainfiller.com/arcflashforum/viewtopic.php?f=33&t=1789 |
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| Author: | Jim Phillips (brainfiller) [ Sun Jul 24, 2011 5:01 pm ] |
| Post subject: | Electric Utility Data for the Arc Flash Study |
This week’s question is a follow up on a earlier forum discussion. (Please don’t use names of people or companies) Have you ever had difficulty obtaining data from the electric utility company?
Stories are welcome! |
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| Author: | K. Engholm [ Mon Jul 25, 2011 7:42 am ] |
| Post subject: | |
I voted "sometimes" It's not always that they don't provide data, it is often that they don't provide correct data. When I am provided a short circuit current of 50,000 Amps at 480 volts and I know I have a 1000 kVA transformer, I question the data immediately. It usually comes down to the utility passing along their view of worst case which is a big infinite bus with a lot of cushion added . |
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| Author: | jghrist [ Mon Jul 25, 2011 10:20 am ] |
| Post subject: | |
We don't usually have a problem getting maximum fault current data, but getting minimum can be a problem. We also have problems sometimes getting protective device data, particularly if the device is an internal transformer primary fuse. |
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| Author: | M. Ambrose [ Mon Jul 25, 2011 2:05 pm ] |
| Post subject: | |
jghrist wrote: We don't usually have a problem getting maximum fault current data, but getting minimum can be a problem. We also have problems sometimes getting protective device data, particularly if the device is an internal transformer primary fuse.
We have had a few problems with protective device data. In one case the utility did not want to provide their relay settings because they might change them.  After a bit of discussion we finally obtained them.
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| Author: | BCR_1962 [ Mon Jul 25, 2011 9:47 pm ] |
| Post subject: | |
We get meaningful data perhaps 2/3 of the time. One of the major providers here in the midwest has a policy not to provide this information to secondary metered customers. We frequently see them use the secondary fault current (from an infinate bus calc) and put this value in for the utilties available fault current. Sometimes it can be a little hard to explain to customers that the 51kA figure provided by the utility on a 12.5 kV system is not the "real value". None the less, I keep pushing for actual values. If nothing else, I am earning a reputation as a first rate pest to these utilities.
Bob Ragsdale, P.E. |
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| Author: | Kim L. [ Tue Jul 26, 2011 1:47 pm ] |
| Post subject: | |
We have had similar problems in the past. Not too often fortunately but now and then we get what seems to be an infinite bus calculation. |
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| Author: | stevenal [ Wed Jul 27, 2011 12:49 pm ] |
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Yes it is with difficulty cause I'm the guy that generates it. |
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| Author: | Jim Phillips (brainfiller) [ Wed Jul 27, 2011 5:33 pm ] |
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stevenal wrote: Yes it is with difficulty cause I'm the guy that generates it.
Yes, that was my group too years (too many) ago. I had a reasonable sized staff but since utilites went through all their downsizing years back, I'm not sure how they are keeping up.
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| Author: | SArni01 [ Fri Feb 24, 2012 9:26 am ] |
| Post subject: | |
So knowing you have less than optimal data to run a study, what do people typically do to mitigate their risk/obtain more conservative values for the Arc Flash study? I'm especially interested in the case where the utility cannot provide data other than infinte bus. |
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| Author: | gilmomoney [ Fri Mar 16, 2012 10:54 am ] |
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maybe during this economic deprssion, the utility companies will be able to catch up with their models, until the next boom time. i think for a period of time there, there was so much construction going on that the engineers at the utility companies were running around just putting out fires, and didn't have the time to update their system and as-construct drawings. i hope it will change before big-brother steps in with more regulation in response to local utility complaints. |
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| Author: | Gary B [ Fri Mar 16, 2012 9:19 pm ] |
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Never had a problem getting a number from the utility (having worked for them in the past ) but also understand the limitations of what they can offer (having worked for them in the past ) .Ayone who thinks utility information is accurate, does not understand how they operate. Only way to contend with this is to bracket what information is given with what might be plausible extremes. |
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