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  1. DBL-E

    In cross bonding, why is there a voltage gradient between grounded and bonded points of sheath

    Are you referring to a measurement of the sheath voltages at the midpoint of the earth cross-bonding locations? It due to the induction from the current carrying phases, and each phase has its vector that you will measure a different induced sheath voltage from. as you get closer to the earth...
  2. DBL-E

    Substation/HV grounding - Please let me know if my understanding is correct

    First off the best resource of this would be reading the IEEE Std 80, as it provides all the background information on the research and criteria used for HV substation grounding in many regions of the world. Now to answer/clarify your understanding- “People and Non-current carrying metallic...
  3. DBL-E

    Step/touch potentials inside the ground grid Vs at the edges

    yes, in North America and other regions we use a multi-grounded neutral for distribution, and many areas have shield wires providing a metallic connection from the substation grid to the tower grounds. With that metallic connection you would see a transferred voltage that exposes the public to...
  4. DBL-E

    Step/touch potentials inside the ground grid Vs at the edges

    As Jghrist mentioned, you can increase the mesh outside the property line, (you can see the person walking on the edge is near the 'drop off' of the GPR, while within the substation you can add another conductor to make the soil voltage closer to the GPR of the ground grid. At the periphery...
  5. DBL-E

    Step/touch potentials inside the ground grid Vs at the edges

    Conceptually they are the same inside and outside the fenceline, but do elaborate if you had something specific in mind. For a touch voltage, as Cranky108 mentions, you have to be within reach of something to touch. Inside the station there is more equipment to make contact with while outside...
  6. DBL-E

    Power plant tripped by lightning

    I'm going to second what FacEngrPE and really emphasize reviewing how the devices may have operated/failed as well as Kiribanda recommending the audit to verify your equipment is bonded and grounded. Sounds like you might be in an area outside north america, so earthing might be the better word...
  7. DBL-E

    Are Neutral Ground Resistor for 100 MW + PV sites common and what are the pros/cons?

    Most PV solar sites I have provided the relay settings range from 20-300 MW with a collector substation feeding multiple 12-34 kV circuits. At the substation there is typically a wye-delta-wye transformer without a neutral ground resistor. Discussing coordination with another engineer at a...
  8. DBL-E

    Plant Grounding - Step and Touch Voltage

    First off, if you have a PV site larger than 5 MW, then the plant should be designed to meet IEEE touch/step voltage criteria per the NESC. The IEEE 80 guide provides the calculations for touch/step limit as well as the background on the concepts of grounding. The IEEE 80 guide provides...
  9. DBL-E

    Earthing design of 50 MW PV Plant and 30/220kV Substation ( separated 7 km)

    I'm not an admin, nor very familiar with best practices on the forum BUT is suspect someone on this can give us advice on consolidating highly similar posts. IEEE 2778 is a short guide applicable for PV grounding, really giving guidance for applying the IEEE Std 80 concepts to PV. I know there...
  10. DBL-E

    Transference of earth fault currents to PV Plant Earthing System from interconnect substation

    I saw you other, similar post, and just wanted to get back on this one as well. Typically grounding systems mutually benefit by interconnecting, as you reduce the grid resistance and lower the GPR. As your colleagues point out, making that connection does transfer the potential out to the PV...
  11. DBL-E

    CDEGS HIFREQ Cable Design Voltage Potential Calculations

    I believe when you go to the output, I think there is a selection to plot metal properties/results OR soil values with the profiles(like step/touch voltages). The 'potential' of the sheath should be able to be selected based on the 'conductor name'... but I can't recall if you give each phase...
  12. DBL-E

    transmission line nears railway

    If you are just referring to clearance requirements, that is NESC (and there are states that have specific requirements like California). You can probably ask for support from PLS-CADD if you are using their program to design the t-line. As Waross mentioned, there is an 'AC Interference' study...
  13. DBL-E

    CYMgrd or ETAP simulation of PV and SS earthing grid interconnected.

    The problem you are seeing is a limitation of simpler analysis programs that have an 'equipotential plane' assumption. Essentially ignoring the voltage drop that occurs in the metal earthing/grounding system. With a well meshed earthing system, these tool can be reasonably accurate up to a...
  14. DBL-E

    EMF Software Options for Underground Circuits

    OK, I would recommend you ask them about the specific cables you are using before doing a purchase. The only part that caught my attention is in the website it says 'the induced currents are neglected', which if you have a concentric neutral or dedicated ground conductor that is a significant...
  15. DBL-E

    EMF Software Options for Underground Circuits

    When you are looking at EMF studies, what are you looking to see as a result of a study? If you are looking at underground circuits, its really just the magnetic field that propagates, and then you consider proximity of the phases having cancelation of each other's fields. I see Cyme as a...
  16. DBL-E

    grounding grid observation profile in CDEGS

    You are understanding IEEE 80 correctly, if there is nothing to touch there is not a touch hazard (even if software indicates the potential is there). You can ignore the colorful spot, but I want to highlight common oversights- -- Is there surfacing (rock) considered in the compliance criteria...
  17. DBL-E

    Mitigation of Transferred Potential

    Similar to the ground rods comparison, the separate between Grid A and Grid B will be based on their maximum dimension (as well as the soil structure), as that drives the zone/sphere of influence of the soil potential. I'm not aware of a guide/standard that is direct to your question, however...
  18. DBL-E

    What kind of fault current calculation is required during ground grid design

    Just to add to jghrist, the SLG and DLG have zero sequence and can produce GPR that result in touch and step voltages. Often the maximum SLG fault is what you will study, unless there is a long fault clearing that can actually drive the grounding design. As with many engineering studies, there...
  19. DBL-E

    Grounding Grid Design Using Plant Grid???

    The IEEE Std 80 really provides criteria for touch, step, and hand to hand voltage thresholds. The connection to the plant grid as others mentioned there are benefits in providing a direct metallic bond between the grids (reduce the impedance -> reduce GPR -> reduce touch/step voltages). IEEE 80...
  20. DBL-E

    GPR in Concrete

    As jghrist commented, utility scale grounding studies are typically done with software. The IEEE Std 80 equations help to show how the grounding system conceptually works through the equations, but those calculations have assumptions (assumes a superconductors and no voltage drop in the grid...

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