High-Voltage Cables

Discussion in 'General Electronics Chat' started by horsebox, Jun 30, 2007.

  1. horsebox

    Thread Starter Active Member

    Jun 9, 2007
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    I just read that if a man was hanging off a high voltage cable he wouldn't get an electric shock because theres no potential difference between him and the cable. It then said if he was to put his foot on the metal tower which is grounded and insulated from the cable he would short circuit the insulation and create a potential difference of 14 kV and be toasted.

    Considering the fact that the high voltage cable has 14 kV wouldn't there already be a huge potential difference between it and the man hanging off it since a man doesn't have anywhere near 14 kV in his body?

    I know that the ground is neutral and when somebody is electrocuted the electricity uses the body as a conductor to get to the ground but wouldn't somebody hanging off the electrical wire positively charged compared to the electrical wire?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,170
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    If no current flows there is no potential difference. No potential difference means the same thing as all points are at the same voltage.
     
  3. horsebox

    Thread Starter Active Member

    Jun 9, 2007
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    Wouldn't there be a potential difference between the cable and the mans shoes?
     
  4. recca02

    Senior Member

    Apr 2, 2007
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    unless connected to ground or the circuit is completed,no voltage difference is there between to points.
    consider a high resistance to replace the man connected to +ve of the battery but no connection is made to -ve the terminal voltage is same as that of the source.
    a return path for the current is required or else the man reaches the same potential as that of the terminal
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
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    The notion of electricity "going to ground" is a common misconception. Current always goes back to the source from which it came - in many cases it goes back through ground.

    When the man is hanging from the 14KV wire, his potential is also 14KV. 14 - 14 = 0, so no current will pass through the man. The man's shoes will also be at the same 14KV potential. This is no different from a bird landing on the wire. As soon as part of the body touches something at a different potential, then different parts of the body will be at different potentials. That's when current will flow.
     
  6. mrmeval

    Distinguished Member

    Jun 30, 2006
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  7. recca02

    Senior Member

    Apr 2, 2007
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    good vid,
    what was the spark flying was it flow of electron to bring thebody at same potential?
     
  8. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    Recca,

    I suspect that spark was the static generated by the helo's rotating blades.

    You always have a wand to do that discharge when working with anything from a helo ... like a rescue basket.

    You can get a spark when working with energized towers, which is why when you climb an energized tower, you firmly grasp it when your on the fiberglass ladder.

    Of course the higher the potential, the greater the distance for the spark to reach out.
     
  9. recca02

    Senior Member

    Apr 2, 2007
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    thanks mr joe :)
     
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