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  1. C

    Discolored Copper

    Hopefully that is whats causing it. I'm also thinking it may have something to do with the annealing process, or that the copper was overheated. But its just a wild guess. FWIW I bought a 2100 watt UK hair dryer with 0.75mm2 flex. When I ran the dryer the cord didn't even seem to get warm...
  2. C

    Discolored Copper

    Not seen in the UK? I suspect you guys have better quality control. Or perhaps your copper tends to be more pure. I'm clueless to be honest, but at the same time I can't help but think your copper is held to higher standards in some way or another.
  3. C

    Discolored Copper

    Earth wires are tinned in modern romex cable. I've seen brown, reddish, bronze and even silver colored copper in romex on occasion.
  4. C

    Discolored Copper

    Does anyone know what causes this? Is the wire safe to use? Does it have the same conductivity and anneal as "regular" copper? For that matter does this occur with UK rolls of twin and earth?
  5. C

    Confused about Zs 5 second disconnection time

    I'd have to disagree. If the person is outside in the back lot, on wet grass, the person will see those 25 volts drop across the neutral in addition to the internal R2 volt drop at the outside socket. A local earth rod does not change that unless you are standing on the earth rod itself. In...
  6. C

    Confused about Zs 5 second disconnection time

    Right, supply impedance determines PFC. Same applies to touch voltage. The lower the transformer Z the higher voltage at its output for a short circuit inside the building.
  7. C

    Confused about Zs 5 second disconnection time

    Right, but you're leaving out the source impedance regarding touch potential. The greater the voltage dip at the spades of the transformer during a fault the longer the disconnection time is permitted in theory and in practice.
  8. C

    Confused about Zs 5 second disconnection time

    OCPS? I'm having trouble grasping how perspective fault current is more accurate in determining disconnection time. I would think instead the ratio of the trafo impedance/alternator compared to the impedance of the conductors leading up to the fault point. Correct, in many cases R2 is of...
  9. C

    Confused about Zs 5 second disconnection time

    Neat, cool, and easy to do. :) I disagree. Disconnection time is dictated by R1+R2.
  10. C

    Confused about Zs 5 second disconnection time

    I obtained 80% regarding coefficient C from IEC 61200-413: My understanding is that C is derived from the voltage drop of the transformer while a L-E short circuit is occurring at the far end of a circuit inside a building. Typically a short circuit on a 16-32 amp branch circuit will on...
  11. C

    Confused about Zs 5 second disconnection time

    So basically with Ze, I turn the transformer into an series reactor+resistor (in vector form?) and assume 230 volts infinite on the other side of the trafo? That makes more sense. The 0.8 vs 5 second time threw me off a bit... in regards to the physics...
  12. C

    Confused about Zs 5 second disconnection time

    I understand, but my point is that with larger circuits (lower Z) the voltage at the trafo will dip, so technically 230 volts is not an accurate number or the 80% multiplier.
  13. C

    Confused about Zs 5 second disconnection time

    My apologies. I was thinking about Ze. Ze is small relative to R1+ R2 in 2.5mm2 cable so the voltage stays near nominal at the trafo during a fault at the socket. But a fault on 120mm2 cable pulls the voltage down at the transformer terminals to half or less.
  14. C

    Confused about Zs 5 second disconnection time

    Running some calcs I'm confused about what Zs to use when calculating 5 second disconnection times. In circuits with 1.5mm2-4mm2 cable a fault doesn't seem to pull the voltage down much at the trafo terminals so from an ohms law perspective the current magnitude reflects simple V/(R1 + R2)=I...
  15. C

    To Parellel or Not to Parellel

    What happens when a gen trips off line? How is load shared between the two without one drifting off?
  16. C

    To Parellel or Not to Parellel

    The units are rated 0.8 PF. Load PF will be a bit higher than that. The 100kw units are being replaced with 200kw units so when gen 1A or 2A fails the ATS can automatically transfer to 1B or 2B without overloading them.
  17. C

    To Parellel or Not to Parellel

    You can with paralleling switchgear. These aren't that large... try 3000kw. Polarized face >> ?
  18. C

    To Parellel or Not to Parellel

    If you had to provide onsite power via generators, how would you design the system? Parallel the gens or have them run the building in separately divided systems? 100kw units will go to 200kw providing full back-up to 1A and 2A.
  19. C

    Earthing Conductor Size- Good?

    Shoot me a PM, I'll send you my Email.
  20. C

    Earthing Conductor Size- Good?

    Ok, now I'm confused.

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