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| IEEE 1584 - 2018.....Last Equation in Standard https://brainfiller.com/arcflashforum/viewtopic.php?f=8&t=5303 |
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| Author: | ebowles [ Thu May 07, 2020 2:28 pm ] |
| Post subject: | IEEE 1584 - 2018.....Last Equation in Standard |
I apologize in advance if this has been asked, but can someone make heads or tails out of the very last equation in the Standard (also on the last page)? From what I can tell, it doesn't appear mathematically correct as it seems to be missing a term. Perhaps it's just my copy, but I don't think so. Any clarification would be greatly appreciated! Thanks in advance. Ernie Bowles EB Consulting |
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| Author: | arcad [ Mon May 11, 2020 5:13 pm ] |
| Post subject: | Re: IEEE 1584 - 2018.....Last Equation in Standard |
ebowles wrote: I apologize in advance if this has been asked, but can someone make heads or tails out of the very last equation in the Standard (also on the last page)? From what I can tell, it doesn't appear mathematically correct as it seems to be missing a term. Perhaps it's just my copy, but I don't think so. Any clarification would be greatly appreciated! Thanks in advance. Ernie Bowles EB Consulting could you please let me know what equation you are questioning exactly? |
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| Author: | ebowles [ Mon May 18, 2020 8:51 am ] |
| Post subject: | Re: IEEE 1584 - 2018.....Last Equation in Standard |
Annex I - Development of Special Model for Circuit Breakers Equation I.4, solving for Ibf.....should there not be a term after "log"? All I see is an exponent that I can't really read. Thanks! |
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| Author: | Jim Phillips (brainfiller) [ Tue May 19, 2020 10:00 am ] |
| Post subject: | Re: IEEE 1584 - 2018.....Last Equation in Standard |
ebowles wrote: Annex I - Development of Special Model for Circuit Breakers Equation I.4, solving for Ibf.....should there not be a term after "log"? All I see is an exponent that I can't really read. Thanks! I believe it may be a typo (unofficially - I have not confirmed with the committee yet) This is verbatim (almost) from the 2002 Edition of IEEE 1584 page 62. In that edition the equation was: Ibf = I1 = 10^(log * I1) It looks like in the 2018 edition a superscript was lost. "log" should be part of the superscript. log * I1 not log^I1 Good catch - thanks. I will report back once I confirm. |
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| Author: | ebowles [ Tue May 19, 2020 10:51 am ] |
| Post subject: | Re: IEEE 1584 - 2018.....Last Equation in Standard |
Thank you Jim.....I'm glad I was able to make a contribution  One other question while you're on topic.....the equation itself, to me, doesn't make sense......the term I1 is being solved for as a function of itself.....it's like having an equation such as X = 4X instead of X = 4Y......in the first equation, if X = 2, then it can't also be equal to 8. I'll look forward to your response, and thanks! Ernie Bowles EB Consulting |
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| Author: | Jim Phillips (brainfiller) [ Tue May 19, 2020 2:27 pm ] |
| Post subject: | Re: IEEE 1584 - 2018.....Last Equation in Standard |
ebowles wrote: Thank you Jim.....I'm glad I was able to make a contribution One other question while you're on topic.....the equation itself, to me, doesn't make sense......the term I1 is being solved for as a function of itself.....it's like having an equation such as X = 4X instead of X = 4Y......in the first equation, if X = 2, then it can't also be equal to 8. I'll look forward to your response, and thanks! Ernie Bowles EB Consulting After considerable thought my conclusion is - you might be the first to have actually read Annex I  This material is a carry over from the 2002 standard and the information was from a specific manufacturer and from what I understand was based on that manufacturer's devices. I believe it was an attempt to simplify what was known in 2002 and of course we know orders of magnitude more now. Specific to your question: I agree equation I.4 seems like something is not correct. It is the same equation from 2002. I don't know if the "dot" should be a different operator such as + or what happened. I believe the people behind the original work are no longer involved. The simple (?) solution is ignore it and focus on the 2018 equations. Great question Ernie, it certainly got me scratching my head! (which now hurts) btw, this is my personal view and can't be taken as an official position of IEEE or any other standards organization. Thanks - Jim |
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| Author: | arcad [ Wed May 20, 2020 7:34 am ] |
| Post subject: | Re: IEEE 1584 - 2018.....Last Equation in Standard |
ebowles wrote: Annex I - Development of Special Model for Circuit Breakers Equation I.4, solving for Ibf.....should there not be a term after "log"? All I see is an exponent that I can't really read. Thanks! yes indeed the only way the equation makes sense is if it reads Ibf = I1 = 10^(log * I1) not Ibf = I1 = 10*log^ I1 |
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