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  1. R

    What is an isolation transformer

    I always thought it'd be dangerous to ground the primary side since it's at such high voltage. So maybe isolation transformers allow you to ground the secondary side, rather than, as you say, allowing the primary to float when you have a grounded secondary?
  2. R

    What is an isolation transformer

    When lightning strikes near power lines, it breaks down the air which shorts the power lines, but why would this have an effect on the load? The short and the load are in parallel, so the load should not be affected. When you have two things in parallel what happens to one branch should not...
  3. R

    What is an isolation transformer

    What other coupling does a transformer have other than magnetic? I thought that was the definition of transformer, two windings that don't touch but share flux. That makes sense. So can the definition of an isolation transformer be a transformer that is not tapped, i.e., the transformer has...
  4. R

    What is an isolation transformer

    Does anyone know what is meant by electrical isolation? From this schematic: url=http://upload.wikimedia.org/wikipedia/en/1/12/Swer.gif I don't see the significance of calling the transformer an "isolation transformer". What is the difference between a transformer and an isolation...
  5. R

    How does mains electricity work?

    I got it from the link that was given by berekeman in this thread. The very last paragraph says: I can sort of understand how internet operates: some companies build a network of cables that cross the country, and charge ISPs to connect to this backbone. They sell usage of their lines to ISPs...
  6. R

    How does mains electricity work?

    Thanks. I find it interesting that the reason for separating the electric industry into power plants, transmission lines, substations, primary and secondary distribution, is to prevent a monopoly of the entire electric industry. But I find that odd, as I'd imagine that power plants have a...
  7. R

    How does mains electricity work?

    I don't see how the secondary center conductor (the middle black wire) is connected to neutral/ground. That middle black wire seems to end at a dielectric spacer that separates a ground wire (the wire where you can see the braids) from other wires.
  8. R

    How does mains electricity work?

    Could someone confirm if what I'm saying about this picture is correct: http://en.wikipedia.org/wiki/File:Polemount-singlephase-closeup.jpg http://en.wikipedia.org/wiki/File:Polemount-singlephase-closeup.jpg There are three thick insulated black wires which are the split phase secondary...
  9. R

    400 kv power line

    Thanks, makes sense now. When I see two conductors with a spacer in between them, I usually think they're at different voltages. But I didn't stop to think what type of insulator could withstand 400 kv, so they're not at different voltages.
  10. R

    400 kv power line

    Here's a link to a picture of a 400 kV pole: http://www.emfs.info/Sources+of+EMFs/Overhead+power+lines/Parts+of+a+power+line.htm Call the 3 phases A, B, and C. Are the phases transmitted in pairs, AB, BC, and AC? Because in the pictures of the power lines I've seen, they are sent in pairs...
  11. R

    400 kv power line

    Why do 400 kv power lines have 6 pairs of wires, 3 on each side? Shouldn't there only need to be 4 wires, a ground/neutral wire and 3 wires for 3 phases?
  12. R

    Grabbing the ends of a transmission line

    Are you talking about the internal impedance of the generator? I wasn't aware you had to match that to the transmission line. So the internal impedance of the generator should match the 50Ω impedance of the line, ideally? If it matches, then the voltage at output would be around twice the...
  13. R

    Grabbing the ends of a transmission line

    I have a formula for the impedance that a generator connected to a line and load sees: Z=Z_0 \frac{Z_l \cos(kl)+iZ_0\sin(kl)}{Z_0\cos(kl)+iZ_l \sin(kl)} where Zo is the impedance of the line (characteristic impedance) and Zl is the impedance of the load. So at half wave-length this would...
  14. R

    Grabbing the ends of a transmission line

    A 1000 ohm resistor and a 50 ohm line is a huge mismatch of impedance, so I'm not sure you can say the power from the generator is equal to to the power burned by the resistor, since a lot of that power would be reflected. Although for a quarter-wavelength line you can't get any power from a...
  15. R

    Grabbing the ends of a transmission line

    Transmission lines. There's an experiment done at 41 minutes, 30 seconds into this video: http://ocw.mit.edu/courses/physics/8-03-physics-iii-vibrations-and-waves-fall-2004/video-lectures/lecture-16/ that attaches a light bulb to two wires coming out of an AC generator. As the light...
  16. R

    Grabbing the ends of a transmission line

    If you have a two-wire transmission line that is open-ended at the load, and connected to an alternating voltage generator at the source, then the voltage between the open ends can be as high as twice the voltage of the generator. However, if the two ends are shorted, then the voltage would be...
  17. R

    Ground fault power line

    Right, but if you don't ground that point in the circuit, and touch the circuit, then you're just as safe. In this case, Vfinger=Vfeet, since current can't flow out of your feet since the system is not connected to the ground.
  18. R

    Ground fault power line

    That makes sense. I was reading this website: http://www.allaboutcircuits.com/vol_1/chpt_3/3.html and they make no mention about circuit breakers at all! It begins in the middle of the page with the paragraph: "Circuit grounding ensures that at least one point in the circuit will be safe to...
  19. R

    Ground fault power line

    In power lines, the neutral wire is tied to ground, causing a hazard if you touch the ground and the hot wire simultaneously. It seems it would be much better not to ground the neutral wire, so that you only get shocked if you touch the hot wire and the neutral wire simultaneously. An...
  20. R

    Ground fault power line

    If a hot power line hits the ground, and you are touching the neutral line with your hands and the ground with your feet, would you get shocked? Also, same question, except the lines are coming out of a grounded portable generator instead of the electric company.
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