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| IEEE1584 Empirical Formulas for 40Hz System https://brainfiller.com/arcflashforum/viewtopic.php?f=23&t=3454 |
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| Author: | mattp [ Wed Sep 24, 2014 7:00 pm ] |
| Post subject: | IEEE1584 Empirical Formulas for 40Hz System |
Hi All, I am currently performing an arc flash study on a 40Hz system using SKM PTW v7. System voltage is 6.9kV stepped down to 550V. Given that the IEEE1584 empirical formulas only apply to 50Hz and 60Hz systems I'm a little cautious about the accuracy of the results being provided, although they seem to be reasonable. The fault levels and incident energies given by SKM are slightly lower for 40Hz than the same system computed at 50Hz (2-5%), and SKM automatically adjusts factors such as breaker opening time correctly (0.075sec on 40Hz equating to three cycles, where it would be 0.05sec on 60Hz). Given the observations above, the empirical origins of the formulas and the fact they do not take frequency into account (so even 50Hz and 60Hz systems use identical calculations) I am fairly comfortable with the numbers I am getting, however I would like to know if any others have experience performing the calculations at non-standard frequencies? Regards, Matt Pilgrim |
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