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Recent content by VTer

  1. VTer

    Thermal Resistivity of Soil

    Thank you all for your responses. I also reached out to the cable ampacity software company and it appears that there is no standards or guides on this at this time. We will run a few iterations and see the impact. It is interesting that there seems to be more of a push from the industry to do...
  2. VTer

    Thermal Resistivity of Soil

    dpc, Yes this is for ampacity calculations but for direct buried cables. I can run a sensitivity analysis but was just curious if anyone is familiar with any applicable standards or industry practice for use of soil thermal resistivity values for various moisture content. "Throughout space...
  3. VTer

    Thermal Resistivity of Soil

    Thanks 7anoter4. Interesting and helpful document but I could not find any discussion on the recommended soil thermal resistivity values based on the soil dry-out curves. "Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and this...
  4. VTer

    Thermal Resistivity of Soil

    The geotech reports typically include a dry out curve and tables with multiple values of thermal resistivity for a soil sample based on the percentage of water content. My understanding is that the 0% water content values are oven dry soil and not practical. Is there an industry standard for...
  5. VTer

    Zigzag TX rating - Westinghouse T&D vs IEEE C62.92

    Clarification to my previous post. Per C57.32-2015 table 14, for 1 min rating the continuous duty in percent of thermal current rating is 7%. For you zig-zag xfmr the equivalent kVA should be ~103kVA. Sorry about the confusion. "Throughout space there is energy. Is this energy static or...
  6. VTer

    Zigzag TX rating - Westinghouse T&D vs IEEE C62.92

    The kVA rating should be I_neutral continous/3*Vll*sqrt(3). If that is a short time withstand current than you need the Z0 value. "Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and this we know it is, for certain ù then it is...
  7. VTer

    Neutral Cable Sizing

    If you only have 3phase 3-wire loads, typical of many MCCs, you may not need the neutral. It really depends on your load. "Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and this we know it is, for certain ù then it is a mere...
  8. VTer

    One Ner per Substation for two Transformers

    @RRaghunath, Can you please elaborate? If multiple generators are operated in parallel and only one generator is connected to the NER, how are the rest of the generator neutrals grounded? "Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if...
  9. VTer

    TRANSFORMER TRIPPING

    The consideration on tripping operation should depend on the system arrangement. Tripping of the downstream devices may be required for multiple sources or parallel operation. "Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù and...
  10. VTer

    Xfmrs

    Typically 12470V systems are grounded and the utility does not necessarily provide a neutral conductor but this is something you need to confirm with the serving utility. Many times these systems are multi-grounded and I prefer to use concentric neutral conductors and ground the concentric...
  11. VTer

    Literature on Sizing Zig-Zag Transformers for Large Scale Solar Farms connected to the Grid

    Most utilities require grounding transformers to satisfy their effective grounding requirement. However most utilities apply the X0/X1<3 and R0/X1<1 criterium to meet this requirement which is inconsistent with the recommendations of C62.96.6. Standard C62.92.6 has some further discussion on...
  12. VTer

    NEC 110.26 Working Clearance

    Thanks for the response FacEngrPE but it appears that neither thread really addresses my questions about the working clearances of electrical equipment below say 1000V or 600V. "Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if kinetic ù...
  13. VTer

    NEC 110.26 Working Clearance

    Hi All, Is anyone aware of equivalent IEC or other international code/standard that may include the equivalent requirements for working clearances similar to those found in NEC 110.26? "Throughout space there is energy. Is this energy static or kinetic! If static our hopes are in vain; if...
  14. VTer

    Can someone think of a way to REDUCE the HIGH ARC FLASH numbers for this design?

    This may not apply but another point to consider is code compliance. In the NEC land you are limited by how much you can run your secondary conductors without over-current protection. From that aspect you may need to provide some over current protection which will also help reduce your arc flash...
  15. VTer

    Selection of Transformer to Supply a Cyclic Load

    Hi All, Thank you for the feedback, this is a great discussion. My initial questions was regarding shorter duration cyclic loads in terms of cycles and seconds, not so much longer term overload conditions. For example, 50kVA at 450ms then 200kVA at 50ms and so on. The comment on "additional"...
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