| Arc Flash Forum https://brainfiller.com/arcflashforum/ |
|
| Arc flash calculations when Ibf greater than 65kA at 690V AC https://brainfiller.com/arcflashforum/viewtopic.php?f=15&t=6415 |
Page 1 of 1 |
| Author: | Andy Whittaker [ Wed Mar 18, 2026 4:43 am ] |
| Post subject: | Arc flash calculations when Ibf greater than 65kA at 690V AC |
What calculation methods would you revert to if your bolted fault current is out of the new range for IEEE 1584 2018. I have a system at 690V with a Ibf at 70kA. These values were within the range 1584-2002 but it is out of range for the 2018 version. Within EasyPower I can default to Ralph Lee or force to use IEEE. My concerns are that Ralph Lee will not include busbar configuration, enclosure size and electrode gap. Thanks in advance for any input. |
|
| Author: | bbaumer [ Wed Mar 18, 2026 6:20 am ] |
| Post subject: | Re: Arc flash calculations when Ibf greater than 65kA at 690 |
This may not be of much help but a few observations from looking through 1584-2018. Maybe Jim will see this and chime in. He is much more of an authority on this than me. 1. I don't see that they ran any tests at 690V, but they did run a few hundred tests at 600V. The next test voltage level was 2-3kV and then up from there. 2. They only tested under 600V up to 80kA and say they extrapolated results out to 106kA for developing the formulas. 3. They only tested over 600V up to 65kA but did not use the same approach by extrapolating to greater than 65kA. Not sure why. 65kA is pretty close to 70kA though for what it's worth. It it were me, I would first make sure whatever it is you are calculating IE for actually needs to be labeled per the NEC, IEEE and NFPA 70E criteria. Is it likely to require inspection and maintenance while energized exposing workers to live parts? If the answer to that is yes, I would do a test calc at 599V and another at 690V using the IEEE formulas and another using Lee. Lee formulas may only be in open air. Not sure. If the results are close, I would probably go with the worst case, notify the customer and get their direction on how they want to proceed and note and CYA the heck out of the situation in my report including what was done at customers direction. OR Discuss with the customer prohibiting live work on that equipment and labeling it that way. No live work permitted. |
|
| Author: | stevenal [ Wed Mar 18, 2026 11:54 am ] |
| Post subject: | Re: Arc flash calculations when Ibf greater than 65kA at 690 |
bbaumer wrote: Discuss with the customer prohibiting live work on that equipment and labeling it that way. No live work permitted. Since testing for absence of voltage is considered to be live work, such a label would prohibit all work. ArcPro should be able to give an answer. |
|
| Author: | bbaumer [ Wed Mar 18, 2026 1:31 pm ] |
| Post subject: | Re: Arc flash calculations when Ibf greater than 65kA at 690 |
stevenal wrote: bbaumer wrote: Discuss with the customer prohibiting live work on that equipment and labeling it that way. No live work permitted. Since testing for absence of voltage is considered to be live work, such a label would prohibit all work. ArcPro should be able to give an answer. True. They would have to install test ports for meter probes or one of those Panduit permanent absence of voltage boxes in that case. |
|
| Author: | Andy Whittaker [ Thu Mar 19, 2026 3:26 am ] |
| Post subject: | Re: Arc flash calculations when Ibf greater than 65kA at 690 |
Thanks for the advice. Unfortunately live working (proving for dead) and manual switching of MCCB's while doors are open after maintenance is required. (in remote locations too) I had already compared the results between Ralph Lee and IEEE and IEEE was around 10cal/cm² greater. After checking at 599V and 690V using IEEE and the 690V is only 3cal/cm² greater but in the same PPE categories. This is due to the change in arcing current. Out of interest and have checked the results using ETAP and that will run IEEE 1584-2018 at 690V at 69kA. Looks like the cut off for ETAP is 70kA for some reason. After all the checks I will be discussing the findings and limitations with the client and will be recommending using IEEE 1584-2018. If we were doing the calculations before the 2018 update we would have used IEEE and not Ralph Lee as the 2002 calculations didn't have the 65kA limit at 690V. Thanks for your suggestions and feed back. Cheers Andy |
|
| Page 1 of 1 | All times are UTC - 7 hours |
| Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/ |
|