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  • Users: CoryA
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  1. CoryA

    XFMR Neutral GNDg Resistor sizing

    Hello JBUDA54, There is a paper that addresses neutral-grounding-resistor selection specifically. I'll add a link to it below. Ground-Fault Detection, Charging Current and Neutral-Grounding Resistor Selection I would suggest, however, that if the resistors are intact, their replacement may...
  2. CoryA

    Earth Leakage Relay and Earth Fault Relay

    I have often seen the term "earth leakage" define current flow that is below that of the protective relay's earth-fault pick-up setting. In this case, however, because the description is in regard to a relay, I believe the terms refer to the same thing. I am not sure what "LGR" refers to. A...
  3. CoryA

    Comparison of zig zag and open delta transformers

    I know that this post is fairly old, but it caught my eye when it popped up in a related Google search. I’d like to comment on zazmat’s post. I am not sure that one thing can be electrically smaller than another. Resistance grounding is more and more common today than in the past...
  4. CoryA

    Motor/System Charging current

    I've added a link below directing you to a document that will have some useful information for you raisinbran. Ground-Fault Detection, Charging Current and Neutral-Grounding Resistor Selection The paper addresses your enquiry in detail. --- Cory Anderson http://startco.ca/
  5. CoryA

    grading of overcurrent relay

    I have heard of several installations using a continuous-rated neutral-grounding resistor, and an appropriate zigzag transformer, to allow the system to operate with a ground fault. In either case, as Marmite suggested, ground-fault protection on downstream devices should be set to operate...
  6. CoryA

    Charging current

    You are correct vennivivi- in general the minimum neutral-grounding-resistor let-through current should be equal to, or larger than the system charging-current. The document linked below contains detailed information about the selection of a neutral-grounding resistor. Ground-Fault Detection...
  7. CoryA

    VFD Tripping ground fault relay

    Hello Simmi123, The SE-105 Ground-Fault Ground-Check Monitor is an analog relay with a ground-fault circuit low-pass filter having a frequency response of 25 to 400 Hz, and may be prone to harmonic frequencies developed by the VFD. The SE-325 Neutral-Grounding-Resistor Monitor could also be...
  8. CoryA

    Ground detection device to break circuit

    An SE-525 Earth-Leakage and Ground-Integrity Monitor may work here... SE-525 Earth-Leakage and Ground-Integrity Monitor A PDF version of the manual is available here. Are 8-A output contacts sufficient? --- Cory Anderson http://startco.ca/
  9. CoryA

    High Resistance Grounding Units

    There is an online schematic diagram showing how to high-resistance ground the neutral of a delta transformer as dpc suggested. I'll add the link below. Implementing Resistance Grounding on Ungrounded Systems You could skip the zigzag if you're grounding the neutral of a wye-connected...
  10. CoryA

    Ground Connection Monitor

    It just occurred to me that I may have misinterpreted your question nightfox1925. There are also a series of Startco ground-check monitors that may be applicable (SE-105, -107, -134C, -135). I was considering your inquiry more from a transformer-grounding perspective rather than a...
  11. CoryA

    Ground Connection Monitor

    The Startco relays you speak of are called neutral-grounding-resistor monitors. There is no mention of a grounding scheme here but... the SE-330-series monitor could be configured for a system with a solid ground (which is essentially a grounding resistor with a very, very small impedance)...
  12. CoryA

    Any Protective Relaying gurus here.

    Yes PnCTech44, you're in good hands with Eng-Tips. I am yet another electrical engineer involved with protective relaying that is a member of this forum. The folks here are very knowledgeable and active. I'm confident that any kind of networking you're looking to accomplish can be done so...
  13. CoryA

    Voltage limitation on Underground Cables at Mine Sites?

    I too am unaware of any such regulation. I did as you did majesus and looked through my copy of CSA M421-00 Use of Electricity in Mines - I found nothing. I understand that there are many coal mines in that region - in that regard a limitation on voltage seems to make sense. It seems to me...
  14. CoryA

    Earthing of Mobile Equipment

    Hello Goldyvb, Jim (lansford) is right about the United States MSHA requirements. You can read a little more about them at the following link. http://www.msha.gov/30cfr/18.47.htm Is this system in the United States? I’ll also add a link to a white paper that may be helpful...
  15. CoryA

    sizing conductor for NGR

    I found the following excerpt in my copy of the “Canadian Electrical Code Part I: Safety Standard for Electrical Installations.” 10-1108 Conductors used with neutral-grounding devices 1. The conductor connecting the neutral-grounding device to the neutral point of the transformer shall be (c)...
  16. CoryA

    MV VFD protection.

    There are some other options out there too. The Startco MPU-32 is a current-sensing motor-protection relay that can be set to monitor 50 Hz, 60 Hz, or varying frequencies. It samples at 32 samples per cycle, and can adjust its center frequency based on the detected zero crossings to maintain...
  17. CoryA

    Design of zig zag earthing transformer in an 11kV system

    I agree with RalphChristie’s line of questioning. If you were to utilize the Zigzag transformer so as to high-resistance-ground the system, you’ll only need one large enough to handle the let-through current of the neutral-grounding resistor. I’ll attach a document to this post that may be of...
  18. CoryA

    Grounding resistor

    There are definite advantages to incorporating high-resistance grounding in a great many applications, this being one of them. In an ungrounded three-phase system, a phase-to-ground fault does not produce ground-fault current because of the lack of a return path to its source. As a result...

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