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  1. 7anoter4

    Fiberglass Conduit

    The IEC Standard 60287-1-1 chapter 1.4.2 Buried cables where partial drying-out of the soil occurs presents the calculation in the case when the soil is drying around a power cable run underground directly buried in the soil. There is different study to state the critical temperature in...
  2. 7anoter4

    Fiberglass Conduit

    It is very interesting how each part of the heat evacuation way reacts on variable heat load, indeed. All the known cable ampacity calculation standards consider steady state load-as far as I know. However, in order to provide a good protection of power cables there are standards which present a...
  3. 7anoter4

    Step-up transformer = Star-grounded LV / Star-grounded HV. How to calculate EPR?

    I agree with cherryg. The short-circuit current which does EPR rise it is only medium voltage current, since the low voltage current flows only through the grounding grid. The EPR =Iearth*Zgrounding So, the standard it is not IEC-60364-1 but EN 50522.
  4. 7anoter4

    Fiberglass Conduit

    According to Neher&McGrath Table VII Constants for Use in Equations 41 and 41(A) [for cables temperature rise in a pipe-duct or conduit- calculations] it is not a big difference between metallic and fiber pipes. However, the thermal resistance [see Table VI Thermal Resistivity of Various...
  5. 7anoter4

    Can someone guide me on how to determine the influence of substation GPR on a nearby pipeline?

    If no OHLine is close then the GPR fades exponential with the distance.See, for instance, the attached table from ENA EREC S34 Vx=ρI/(2.pi().r).arcsin(r/x) Formula P6.3 [Annex B]
  6. 7anoter4

    Directly from 30 kV to 0.4 kV? Or step down the voltage in stages, typically from 30 kV to 6 kV, then from 6 kV to 0.4 kV.

    In a power station of 700 MW coal fired steam turbine where the most of equipment Is of 1 to 20 MW rated power-see the boiler air draft fan, for instance- the main auxiliary distribution is 6 or 10 kV and not the low voltage [0.4-0.48-0.690] so you have here 6 kV already. But, if you have to...
  7. 7anoter4

    UHV/EHV Cables in aerial rack distance to Coke/Blast Furnace Gas

    You said: The main goal is to calculate the minimum distance between UHV/EHV cables and that pipe. If the transmission line goes parallel with the pipeline, induced voltages and currents are present in the pipe. There is a book[EL-904-V1+V2] as a result of the collaboration of EPRI [Electric...
  8. 7anoter4

    UHV/EHV Cables in aerial rack distance to Coke/Blast Furnace Gas

    The gas resulting from the melting process may be conveyed to another place to be used. For a power station gas turbine [fuel], for instance. No power cable should be above the gas conduit. On the Blast Furnace Complex, where I was, 110 kV cables ran underground. See NFPA 850 7.2 Fuel Handling —...
  9. 7anoter4

    UHV/EHV Cables in aerial rack distance to Coke/Blast Furnace Gas

    Usually, the coke used in a Blast Furnace is conveyed as solid particles of 100-200 grams from the storage to the highest level of the blast furnace and introduced from here together with the ore and other materials through open conveyors. If the cables are insulated, shielded, and grounded, no...
  10. 7anoter4

    Experience with Subterranean Transmission Lines (161kV+)

    Around 1970, I was a young engineer in a vast Siderurgica [steel manufacturing] complex. I was responsible for 110 and 10 kV distribution maintenance [with some 130 technicians, most of them]. The complex contained 4 blast furnaces, a steel plant, and 4 thick sheet metal rolling mills [and many...
  11. 7anoter4

    UHV/EHV Cables in aerial rack distance to Coke/Blast Furnace Gas

    NEC art.503.10 for wiring above coke field. NESC Rule 234. Clearance of wires, conductors, cables, and equipment from buildings, bridges, rail cars, swimming pools, and other installations However Jpascp said: Is there any standard that refers to the minimum distance between UHV/EHV Cables and...
  12. 7anoter4

    L-G Fault Zero Sequence Current in un-faulted phases

    More correctly, sorry!
  13. 7anoter4

    L-G Fault Zero Sequence Current in un-faulted phases

    You are right, waross .Thank you ! Wrong side of the star point.
  14. 7anoter4

    L-G Fault Zero Sequence Current in un-faulted phases

    If we follow, for instance, IEC 60909-0 the short-circuit current is: 4.2 Initial symmetrical short-circuit current I”k I"k=sqrt(3)*c*Un/(Z1+Z2+Zo) For a far-from-generator short circuit , the absolute value is calculated by: I"k=sqrt(3)*c*Un/(2*Z1+Zo) That means if the short-circuit is phase A...
  15. 7anoter4

    Cable bus sequence values

    In my opinion, it is like the transmission line parameter calculation where inductance Lx=2/10^7*ln(GMD/GMRx) H/m For imperial units, see -for instance: LINE&CABLE PARAMETER CALCULATION
  16. 7anoter4

    Gas tight cables - Gel as filler

    See-for information only: gastite_di_guide PDF (www.gastite.com)
  17. 7anoter4

    Txf DGA sampling question

    See-for information: tv0009-fa-oljeprøve-2019_a4_engelsk PDF (new.abb.com)
  18. 7anoter4

    70:250.30(A)(1) Exception 2

    In my opinion, the art.250.30 A(1) System Bonding Jumper requests a single SSBJ at the source enclosure, and Art.250.30 A(1) exception 2, permits 2 SSBJ: one at the source and the second at the disconnector side. In this case, we may not connect these two SSJBs with a bonding wire in order to...
  19. 7anoter4

    Protection Functions

    In my opinion all the symbols except Ursd and df/dt are IEC 60617 protection graphical symbols. Ursd may be Residual Voltage Relay and df/dt it has to be rate of change ROCOF relay .
  20. 7anoter4

    Buried Earthing Grid in Concrete Foundations - German Philosophy

    See also BS 7430:2011 9.5.8.5 Structural steelwork

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