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window frame zapping

Discussion in 'Electrical Engineering' started by Mark Kelep, Mar 14, 2008.

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  1. Mark Kelep

    Mark Kelep Guest

    Hi all,
    I got a small shock (electrical and the other) while leaning against a steel
    window frame while handling speaker wires in a house today.
    The home is built with concrete walls and all windows are steel.
    I measured around 100 VAC between either speaker wire wrt the window frame
    with the amp on or off.
    I was able to light up an LED too, though the current couldnt have been much
    as I didnt use a limiting resistor and the LED didnt burn out.

    What the hell is going on??

    Hoping for some advice as to what to check.

    Thanks,
    Mark
     
  2. Guest

    | I got a small shock (electrical and the other) while leaning against a steel
    | window frame while handling speaker wires in a house today.
    | The home is built with concrete walls and all windows are steel.
    | I measured around 100 VAC between either speaker wire wrt the window frame
    | with the amp on or off.

    You seem to be posting from Australia, so I will assume your have 240 volts
    line-to-neutral/ground power system.

    Does the power plug on the amplifier have 2 prongs (ungrounded) or 3 prongs
    (grounded)? You can't reverse an AU plug, so check to see if the outlet or
    power cord into the amplifier is miswired.


    | I was able to light up an LED too, though the current couldnt have been much
    | as I didnt use a limiting resistor and the LED didnt burn out.
    |
    | What the hell is going on??

    If a 3 prong (grounded) plug is involved, and the ground wire is attached
    to the amplifier frame, as it should be, it may be the case that the ground
    wire in the outlet or branch circuit is NOT CONNECTED to the real ground.
    It would them be capacitively coupled to both the hot (240V) and neutral
    wires, giving you something about half way in between with very little
    current available.


    | Hoping for some advice as to what to check.

    Check to see what voltage you get between the GROUND slot of the outlet and
    the window frame. If nothing there, check the frame of the amplifier when
    it is plugged in, and also when it is unplugged. There is also the chance
    of another device in the A/V system causing this if more than one is present
    and they are interconnected. Pull all connections and test each one by one
    if that is the case.
     
  3. Mark Kelep

    Mark Kelep Guest


    ***Two prongs


    ***I did some checking, and pulling out the turntable (the only three
    pronged device) finally shut the LED down.
    I then measured between 'house earth' and the window.
    The same 100 volts was there and lit the LED as before.
    I'm guessing your theory involving Capacitance is having a role to play
    here.
    Is this due to to bad earthing? and am I likely to be paying for energy i'm
    not getting?
    What would be the best way to fix the problem?

    Cheers mate,
    Mark
     
  4. Guest

    | ***I did some checking, and pulling out the turntable (the only three
    | pronged device) finally shut the LED down.
    | I then measured between 'house earth' and the window.
    | The same 100 volts was there and lit the LED as before.
    | I'm guessing your theory involving Capacitance is having a role to play
    | here.
    | Is this due to to bad earthing? and am I likely to be paying for energy i'm
    | not getting?
    | What would be the best way to fix the problem?

    Yes, the earthing is likely to be faulty. There exists a remote possibility
    the window frame is energized some other way and the "house earth" is just
    the return for that energy in the window frame.

    It is not likely you are paying for energy you are not getting/using, since
    the current is so small. But that does not rule out some other fault.

    If the problem is what I believe to be most likely (a broken ground/earth
    wire somewhere between the outlet and the panel where the ground/earth is
    connected to the system neutral and the earth electrode(s)), it will not
    cause loss of energy unless something else is at fault. Such faults that
    could result in high leakage current or, worse, electrocution hazard to
    people, should result in the circuit breaker tripping off because of high
    current to the ground wire. With the broken ground/earth connection, that
    won't happen and if such a risk exists, it will persist.

    If the ground/earth wire were connected to neutral and ground correctly,
    any energy it is charged with through capacitive coupling would be drained
    fully to neutral and earth. It apparently is only "draining" through the
    capacitive coupling (and so it is about half way in voltage).

    To fix this, hire an electrician who has the appropriate license/permits in
    your location. It MAY be as simple as a loose connection in the outlet. It
    is more likely to be a loose connection in the electrical panel. Unless you
    are an electrician, you don't want to be messing around in there.
     
  5. G'Day, many homes in 'Oz' are not equipped with RCD breakers if they are of
    the older vintage. Simply a main switch and fuses. Also such homes used the
    metallic water supply piping for the earth electrode.If your home is such it
    would be a good idea to have a look at that connection, being careful not to
    touch the wire and the pipe if it is disconnected (to avoid shock). It
    should be visible as a brass clamp with a small identifying tag. If not sure
    consult a licensed tradesman!!

    Cheers ........ Rheilly P


    With the broken ground/earth connection, that
     
  6. Mark Kelep

    Mark Kelep Guest


    **** Thanks guys, problem solved. There were a couple of loosish wires at
    the power point. Nipped them up with an 'all steel' screw driver (haha
    kidding of cause) anyway all is well now. Time to check all the other points
    I reckon.
    Yep, it's a very basic set-up here with no protection apart from fuses.

    Just a quick question while i'm here.
    Is it true that both the Active and Neutral wires come in off the street?
    If thats the case, does that neutral simply terminate to ground at a sub
    station way before the power station or does it go all
    the way?
    On the other hand, does only an active come into the house and returns to
    ground at the house only.


    Thanks again,
    Mark
     
  7. Guest

    | Just a quick question while i'm here.
    | Is it true that both the Active and Neutral wires come in off the street?

    Yes.


    | If thats the case, does that neutral simply terminate to ground at a sub
    | station way before the power station or does it go all
    | the way?

    It could be isolated at a transformer by being grounded/earthed on the
    secondary side, and not connected across to the primary. However, at
    least in the USA, it is typically connected between primary and secondary.
    So the answer is, it very well could go all the way to the power station.
    There would be many points along the way where it would be earthed.


    | On the other hand, does only an active come into the house and returns to
    | ground at the house only.

    The power return is through the neutral, not earth. The neutral is earthed
    for various reasons/benefits. But it is usually earthed at only one point
    near where it enters the building. Duplicate earthing can cause problems
    such as return current flowing through the earthing electrodes, corroding
    them.

    Some very high voltage transmission power lines are designed to use earth
    itself as a return path. But this is rare.
     
  8. John G

    John G Guest

    Generally in Australia the system distribution, both the very hi voltage
    grid and the local street high voltage is 3 phase DELTA and hence no
    neutral.
    There is then a large 40kva or more transformer in the street, sometimes on
    a pole (outside my house) and sometimes in a box on a pad or hidden in
    buildings. These each serve more houses than the typical US pole pig.
    The neutral originates in the 3 phase WYE secondary output and is grounded
    there.
    The neutral is again connected to the ground at the building entry box and
    hopefully nowhere else.
    There are some hi voltage Single Wire Earth Return (SWER) systems in the
    bush and of course to work they have the neutral and the ground connected on
    both sides of the transformer at the consumer.

    Gloat (- for USA home workshop people, 3 phase 230/400 volt power is
    available anywhere (except at SWER instalations) just for the cost of
    installation or sometimes for free. Most ducted Air cons are 3 phase so lots
    of houses already have it installed.

    John G.
     
  9. Don Kelly

    Don Kelly Guest

    --

    Don Kelly
    remove the X to answer
    ----------------------------
    -------------
    Very high voltage lines do carry a neutral -usually in the form of overhead
    ground wires and multiple grounds as well as a counterpoise where needed- as
    they are usually connected Y. None that I know of use earth as the return
    path as the attempt is to keep the load well balanced at those levels. Do
    you have an example?

    There are some low voltage -say 7200V to earth rural lines taken off one
    phase of a Y system that have used earth as the return for single phase
    service- these are increasingly rare as the earth path is paralleled by a
    neutral which is grounded at every transformer along the line rather than
    use a ground path only. Corrosion doesn't appear to be a problem (as it
    would be with DC).
     
  10. Guest

    | Generally in Australia the system distribution, both the very hi voltage
    | grid and the local street high voltage is 3 phase DELTA and hence no
    | neutral.

    So the single phase pole pigs would have two insulation bushings for the
    primary connections?


    | There is then a large 40kva or more transformer in the street, sometimes on
    | a pole (outside my house) and sometimes in a box on a pad or hidden in
    | buildings. These each serve more houses than the typical US pole pig.

    How many houses can be served by one 40 kVA transformer down under?


    | Gloat (- for USA home workshop people, 3 phase 230/400 volt power is
    | available anywhere (except at SWER instalations) just for the cost of
    | installation or sometimes for free. Most ducted Air cons are 3 phase so lots
    | of houses already have it installed.

    Three phase is fine to have around if you don't have the penalty of having
    and odd voltage. I'm sure nothing for consumers is made designed to be
    run from 460 volts, so no one would have a reason to get 230/460 volt split
    phase power. The voltages would strictly be 230 and 400 (240 and 415 in
    legacy installations). In the USA and Canada, many consumer appliances use
    240 volts single phase. But you don't get that 240 volts where three phase
    power is provided in the form of the 120/208 volt system.
     
  11. John G

    John G Guest

    There are NO single phase pole pigs except the remote SWER installations.
    All street transformers are 3phase 3 wire in 4 wire out. and as far as I can
    find out higher voltage distribution transformers are alwys 3 wire in and 3
    wire out with only relatively light lightining protection wires at the top
    of some tower runs.
    It is hard to tell because the 4 wire 230/400 wireing is often looped with
    more than one transformer connected to a bigger group with hand operated
    disonnects for fault isolation.
    I think I undestand the various voltage problems with three phase and split
    120/240/208/
    Anything you are likely to buy here is either 1 phase 230v or 3 phase
    230/400.
    There are some legacy kitchen ovens that were 2 phase.
    Of course it is only a short while since we started to move to 230 from 240
    and some years ago Western Australia was 250.

    My comments about how easy it is to get 3phase were aimed, in jest, at home
    machinists in the US who buy commercial equipment then have to resort to
    some odd convertors to get them to run.

    John G.
     
  12. Vancouver Island is fed power from the main BC grid via a HVDC submarine
    cable. I think the voltage is around +- 200 kV. The rectifier station
    is a few miles from the coastline, and the HVDC is carried on towers to
    the point where the submarine cable comes ashore. This point is right
    next to the road access to the main ferry terminal, so it's quite
    visible. The overhead lines look a lot like standard HVAC, but there
    are only two conductors, not three.

    In addition, there's another single conductor that goes from the
    rectifier station to the shoreline of a nearby bay, where it connects to
    an array of ground rods. There's a fence around the ground rod array
    with warnings about dangerous voltages - not what you'd expect from
    obviously "grounded" electrodes.

    From various stuff I've read, I think this is what's going on:
    Normally, all the current is carried by the submarine cable conductors,
    and the ground rods do nothing. But if one of the conductors ever
    becomes open, the ground rods at this end (along with another array
    somewhere on Vancouver Island) provide a return path via sea water that
    would allow the remaining good conductor to deliver half the normal
    power. This much DC current would likely corrode the ground rods pretty
    fast, but is better than losing the entire cable capacity.

    These features can be seen (somewhat fuzzily) in Google Earth. The
    rectifier building is part of the substation at (49.090456
    -123.041981). (This is latitude/longitude in degrees) The terminal
    where the HVDC lines connect to the submarine cable is at (49.028194
    -123.100258). And I believe the ground array is what you see at
    (49.057122 -123.029581).

    (It's actually a bit more complicated than I described, because there
    are multiple submarine cables. There are older cables, lower in
    capacity, fed from a building in Tsawwassen, between 4 Ave and 5 Ave.
    The installations described above are for a more recent higher-capacity
    cable. And BC Hydro is in the process of adding yet another cable, but
    it's reusing the old Tsawwassen connection route).

    Dave
     
  13. Guest

    |
    | |>
    |> | Generally in Australia the system distribution, both the very hi voltage
    |> | grid and the local street high voltage is 3 phase DELTA and hence no
    |> | neutral.
    |>
    |> So the single phase pole pigs would have two insulation bushings for the
    |> primary connections?
    |
    | There are NO single phase pole pigs except the remote SWER installations.
    | All street transformers are 3phase 3 wire in 4 wire out. and as far as I can
    | find out higher voltage distribution transformers are alwys 3 wire in and 3
    | wire out with only relatively light lightining protection wires at the top
    | of some tower runs.

    Well, that certainly makes it much easier to get three phase service, even
    if most homes are only getting one or two phases from that transformer.

    But if there was a single phase one, it would have to be the two bushing
    type. Suppose you have a neighborhood area, but off to one side of it at
    some distance (say 1km) not suitable to run 230 volts directly, is a home
    isolated from the others. The closest place to feed it is from the same
    distribution going around these neighborhood streets, because that is also
    the way the road goes to that house. That distribution is delta, so there
    is no neutral handy. So you'd have to run at least two of the distribution
    wires out that 1 km road, and put a transformer out there. Would the do
    this with three wires and put a three phase transformer, anyway?


    |> | There is then a large 40kva or more transformer in the street, sometimes
    |> on
    |> | a pole (outside my house) and sometimes in a box on a pad or hidden in
    |> | buildings. These each serve more houses than the typical US pole pig.
    |>
    |
    |> How many houses can be served by one 40 kVA transformer down under?
    |
    | It is hard to tell because the 4 wire 230/400 wireing is often looped with
    | more than one transformer connected to a bigger group with hand operated
    | disonnects for fault isolation.

    So it forms a "networked service".


    |> | Gloat (- for USA home workshop people, 3 phase 230/400 volt power is
    |> | available anywhere (except at SWER instalations) just for the cost of
    |> | installation or sometimes for free. Most ducted Air cons are 3 phase so
    |> lots
    |> | of houses already have it installed.
    |>
    |> Three phase is fine to have around if you don't have the penalty of having
    |> and odd voltage. I'm sure nothing for consumers is made designed to be
    |> run from 460 volts, so no one would have a reason to get 230/460 volt
    |> split
    |> phase power. The voltages would strictly be 230 and 400 (240 and 415 in
    |> legacy installations). In the USA and Canada, many consumer appliances
    |> use
    |> 240 volts single phase. But you don't get that 240 volts where three
    |> phase
    |> power is provided in the form of the 120/208 volt system.
    |>
    | I think I undestand the various voltage problems with three phase and split
    | 120/240/208/
    | Anything you are likely to buy here is either 1 phase 230v or 3 phase
    | 230/400.

    What if you have a very high power device that can only be run single phase?
    Would that not be wired for 400 volts?


    | There are some legacy kitchen ovens that were 2 phase.
    | Of course it is only a short while since we started to move to 230 from 240
    | and some years ago Western Australia was 250.
    |
    | My comments about how easy it is to get 3phase were aimed, in jest, at home
    | machinists in the US who buy commercial equipment then have to resort to
    | some odd convertors to get them to run.

    And that is a well aimed jest. It is in fact a real issue. My grandfather
    did get 3 phase power for his wood shop, which was in a detached building
    on the side of the house distant from where the power came in. This was
    done in 1961. My guess is he had assumed the three phase power would be
    in the form of "center tapped delta" without him necessarily understanding
    the details (he was not an engineer, he was a school teacher of subjects
    wood shop and business math). But instead of getting center tapped delta
    he apparently got "208Y/120" and wired 3 phases underground to the shop and
    just 2 phases into the house. They had the "slow heating" problems with
    that lower line-to-line voltage on everything, and it was most problematic
    for my grandmother who was always doing cooking for many things. The house
    was one of those early "all electric" houses which had no gas service at
    all. My grandfather was trying to get the electric issues corrected for
    the next 11 years until he passed away. Perhaps the new owners afterwards
    would have not needed three phase and single asked for the service to be
    reverted to single phase.

    I posted a while back a description of the kind of electrical system I would
    have used if I could, back in time, have determined what it would be before
    all the economics locked us into what we have now. It would have been a
    system somewhere beteween what .US and .AU have now. But I would have also
    avoided using directly connected line-to-neutral light bulb connections.
    The service would have been either 144/288 or 288Y/166 with all utilization
    wired line to line. Incandescent lights would have been wired through a
    step down transformer to operate at 24 or 12 volts.

    OTOH, if the whole world had simply done 400Y/230, fewer issues would exist
    today. An electric stove could be wired to 230 volts at just 40 to 60 amps
    while if only single ended 120 volts were all that people got in .US then
    it would have needed 80 to 120 amps. So we needed that extra split phase
    to handle the extra voltage for a few big appliances. The problem comes from
    the need to have TWO single phase voltages, which cannot be reproduced using
    simple three phase wye/star systems. Eliminating that need solves it.
     
  14. Guest

    | From various stuff I've read, I think this is what's going on:
    | Normally, all the current is carried by the submarine cable conductors,
    | and the ground rods do nothing. But if one of the conductors ever
    | becomes open, the ground rods at this end (along with another array
    | somewhere on Vancouver Island) provide a return path via sea water that
    | would allow the remaining good conductor to deliver half the normal
    | power. This much DC current would likely corrode the ground rods pretty
    | fast, but is better than losing the entire cable capacity.

    And sound a bunch of alarms, too :)
     
  15. John G

    John G Guest


    Pity you did not ask this question 2 weeks ago.
    I have just come back from a 4000 km drive to Adelaide and could have taken
    more notice of installations closer to towns than those with SWER.
    I think some small phase to phase transformers may be used as you suggest.

    I dont know of any but I guess it is posible, like as I said some old
    kitchen ovens, and I do not know if you ever had them but houses had fire,
    gas or electric heated boilers for washing clothes before washing machines
    and I think some of them were also 2 phase.

    john g.
     

  16. I think the Bonneville to LA DC intertie ("Celilo link") is Earth
    return.

    http://en.wikipedia.org/wiki/Pacific_DC_Intertie

    I am not sure but The return on DC links is Earth in most cases I have
    seen.

    It makes sense. Cost and operation wise.
     

  17. DC links typically get converted back to AC for the distribution
    segments.

    So the converter station and the source make for only ONE path
    for the link.

    No "ground rods" are used for such huge power passes. It is a far
    different system.
     
  18. Guest

    | On 16 Mar 2008 17:18:58 GMT, wrote:
    |
    |>
    |>| From various stuff I've read, I think this is what's going on:
    |>| Normally, all the current is carried by the submarine cable conductors,
    |>| and the ground rods do nothing. But if one of the conductors ever
    |>| becomes open, the ground rods at this end (along with another array
    |>| somewhere on Vancouver Island) provide a return path via sea water that
    |>| would allow the remaining good conductor to deliver half the normal
    |>| power. This much DC current would likely corrode the ground rods pretty
    |>| fast, but is better than losing the entire cable capacity.
    |>
    |>And sound a bunch of alarms, too :)
    |
    |
    | DC links typically get converted back to AC for the distribution
    | segments.
    |
    | So the converter station and the source make for only ONE path
    | for the link.
    |
    | No "ground rods" are used for such huge power passes. It is a far
    | different system.

    Something has to be there in the ground. What do YOU think it is? Some
    metal that cannot be corroded? Some conductive ceramic?
     
  19. Guest

    | On Sun, 16 Mar 2008 07:00:04 +0000 (UTC), (Dave
    | Martindale) wrote:
    |
    |>Vancouver Island is fed power from the main BC grid via a HVDC submarine
    |>cable.
    |
    |
    | I think the Bonneville to LA DC intertie ("Celilo link") is Earth
    | return.
    |
    | http://en.wikipedia.org/wiki/Pacific_DC_Intertie
    |
    | I am not sure but The return on DC links is Earth in most cases I have
    | seen.
    |
    | It makes sense. Cost and operation wise.

    It can also introduce the possibility of getting free electricity from the
    ground for people in or near the path.
     

  20. For Megawatts? It ain't ground rods.

    It is likely a huge slab at each end that is some power station
    enhanced version of an ufer system sitting on a wet link to bedrock.
     
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