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  1. JBinCA

    Infeed + Motor Fault Contribution

    I don't work in IEC standards, but I will say that the drives do not contribute to a fault in anything like the same way that the motor directly would. The drives may even be able to limit 1/2 currents. I know this is true of modern solar inverters. Definitely incorporate Waross's discussion...
  2. JBinCA

    Transformer differential, CT in the delta

    I'm agreeing with Stevenal on all points made: Many modern multiprocessor relays will compensate for the phase shift automaticaly. If your relay does not do this, you will have to compensate for the phase shift by CT secondary connection. Also agree that hiring a protection engineer would...
  3. JBinCA

    Multi-source Ground Fault / Modifified Differential Groud Fault

    Rafiq, I definitely understand limiting your time investment. My question is really about what equipment can but used for "Modified Differential Ground Fault (MDGF) / Multi-Source Ground Fault (MSGF)" in 480/277 systems. It appears that the answer is equipment listed to UL 1053. The best I...
  4. JBinCA

    Multi-source Ground Fault / Modifified Differential Groud Fault

    Rafiq, Thanks for the reply. 4 Pole ATS's would certainly solve the problem. Three factors have us leaning away 4 pole ATSs. 1. One of the 3 pole ATS's is integrally installed into the Main SWBD. Even if we could find a 4 pole unit to fit into the enclosure, the needed outage time is far...
  5. JBinCA

    Excel is amalgamating numbers.

    Try pasting from your application into a text editor first. Notepad for example. Then copy from notepad and paste to excel. Or save the notepad doc as yourfilename.csv and open it with excel.
  6. JBinCA

    Multi-source Ground Fault / Modifified Differential Groud Fault

    Greetings All, I'm consulting on an 480V 3ph 4W ~1.5 MVA system that powers a building and small data center on a university campus in the U.S. There are three power sources to this system, each with an independent bonding jumper. Each on a different SWBD. The system wasn't designed that...
  7. JBinCA

    Transformer Inrush

    PRC, Skosgurra is referring to the residual flux in the core - "where you left the core when switching off" JB
  8. JBinCA

    Basics of Soft start

    Jraef, I'd never considered it before, but the method you describe as "Sensing the back EMF" makes a lot of sense. I can't begin to understand, however, how it would come to be know as ""Sensing the back EMF". Anyone have any ideas about this? JBinCA
  9. JBinCA

    Zero Sequence current during XFMR inrush?

    Reactors can be used in the pre-insertion scheme that bronzeado mentions as well. Regards, JBinCA
  10. JBinCA

    Short Circuit Testing

    DanDel, That would be a test to measure 3Io, right? Thanks, JB
  11. JBinCA

    Zero Sequence current during XFMR inrush?

    dpc, Thanks again for the reply. I have not gotten accurate data on the GFD settings yet. I have been assuming that increasing the delay band is the right way to correct the problem. Regards, JB
  12. JBinCA

    Zero Sequence current during XFMR inrush?

    Davidbeach - Thanks for the response. Are the CTs in ICCBs not rated similar to protection class CTs? I can't remember reading it specifically, but I would think that they would be rated such that saturation would not occur until after 20 pu current. As to the general question, I understand...
  13. JBinCA

    stored energy motor operating mechanisms

    If the device is one of motor operators that mount on the front of MCCBs (as DPC thinks), it's worth pointing out that while the closing evolution is slow, the actualy closing of the contacts is not. The handle is moved slowly, but the contacts close rapidly once the handle gets to the right...
  14. JBinCA

    Zero Sequence current during XFMR inrush?

    Greetings All, I'd like to solicit opinions on the following question - Should there be any significant zero sequence (ground) current during the energization of a XFMR? The event which gives rise to my question is a ground fault trip that happened when the XFMR was energized with no...
  15. JBinCA

    strange specification for a ABB asyncronous generator

    Stevenal, good thinking. I was going to go with the low tech option - I think they screwed up when copying and pasting an old spec.
  16. JBinCA

    Red Book Statement

    Aren't there regulations specific to the mining industry that require ground current to be limited to much lower values than standard industrial systems would have? I know that Multilin and Schweitzer offer relays with a "sensitive ground" CT input that is provided for mining applications...
  17. JBinCA

    Communication or Application

    In regard to DJS's comment, not all GE 90/30 PLCs have CPU modules, some have the CPU embedded in the backplane. The backplane CPU models do not have the keyswitch. The power supply module should have three green lights on it: PWR; OK; and Run. If the run light is on, the code is running. It...
  18. JBinCA

    PLC software question

    You'll have lost the variable declarations and any comments that were in the original code. The variable declarations for inputs and outputs can be easily recreated by looking at what's wired to each, but if the code is sufficiently complicated as to require the use of multiple internal bits...
  19. JBinCA

    no load current

    It seems to me that everyone but Gunnar is missing the point. The OP seems to be asking why he's getting different results when attempting to perform the same test that was conducted prior to his motor leaving the shop. I think Gunnar is probably correct that a difference in voltage is the...
  20. JBinCA

    Co-gen Interconnection with local utility

    I'm going to second DavidBeaches recommendation - Hire a consultant. I recommend this if you're in the US more because every utility has their own requirements, interpretations of those requirements, and process for determining compliance with those requirements. A thorough understanding of...

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