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Author Topic: Induced voltage from high-tension lines  (Read 15708 times)

Mike Sokol

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Re: Induced voltage from high-tension lines
« Reply #10 on: February 15, 2014, 07:08:46 am »

He lit his barn with tuned circuits and small, low voltage bulbs.

Tuned circuits? Hmmmmm, that an interesting idea....  Is it possible that this coupling effect is essentially a big radio wave? If so, then it's a combination of magnetic and electric fields, just like a radio station broadcasting at 60 Hz.

From Wikipedia

The electromagnetic waves that compose electromagnetic radiation can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. This diagram shows a plane linearly polarized EMR wave propagating from left to right. The electric field is in a vertical plane and the magnetic field in a horizontal plane. The two types of fields in EMR waves are always in phase with each other with a fixed ratio of electric to magnetic field intensity.
« Last Edit: February 15, 2014, 07:15:30 am by Mike Sokol »
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John Roberts {JR}

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Re: Induced voltage from high-tension lines
« Reply #11 on: February 15, 2014, 10:44:37 am »

I'll bet somebody at the power company knows exactly. It is their business to keep the majority of energy inside the wires, loss is loss.

JR
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Mike Sokol

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Re: Induced voltage from high-tension lines
« Reply #12 on: February 15, 2014, 11:01:35 am »

I'll bet somebody at the power company knows exactly. It is their business to keep the majority of energy inside the wires, loss is loss.

JR
If only I could call up Tesla and ask him. I do know that one of the advantages promoted for the new DC smart grid is less losses than AC transmitted over long distance due to power factor issues. More fun stuff to study...
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Frank DeWitt

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Re: Induced voltage from high-tension lines
« Reply #13 on: February 15, 2014, 12:30:38 pm »

There is a story around here about a guy with a barn near one of those lines who was found to have a few terns of wire around the barn and a lot of power available to him.  Perhaps it is true.

Frank
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Mike Sokol

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Re: Induced voltage from high-tension lines
« Reply #14 on: February 15, 2014, 01:07:02 pm »

There is a story around here about a guy with a barn near one of those lines who was found to have a few terns of wire around the barn and a lot of power available to him.  Perhaps it is true.

Frank
I know that the power companies don't like buildings directly under their high-tension lines. And if you read the pdf link from Bonneville Power I referenced at the beginning of this thread they'll talk about grounding metal buildings under power lines and that holding an irrigation pipe in your hands (like a big horizontal antenna) can cause painful shocks. That why they recommend that farm workers drive a ground stake and clamp a ground wire to bundles of irrigation pipes. They also make mention of adding ground stakes to wire fences running under high tension lines.

But nothing that I've read really discusses just how much amperage and voltage is induced in these cases, perhaps because they're worried about low-life individuals stealing "free"  power. Even if a stage or RV under a line had 1,000 volts at 5 mA induced from this effect, that's only 5 watts of power. And 10,000 volts at 5 mA would still only be 50 watts of "free power" which hardly seems worth all the trouble.

I'm really interested in this subject mostly from the human shock perspective. I do know that 10,000 volts at 5 mA is probably what a lawn-mower magneto delivers to a spark plug. As a young kid (maybe 10 years old) I tried to stop a running lawn mower engine by pulling off the spark plug wire with my bare hand. That was a BIG shock that slammed me to the ground.
« Last Edit: February 15, 2014, 06:09:45 pm by Mike Sokol »
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John Roberts {JR}

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Re: Induced voltage from high-tension lines
« Reply #15 on: February 15, 2014, 01:25:50 pm »

If only I could call up Tesla and ask him. I do know that one of the advantages promoted for the new DC smart grid is less losses than AC transmitted over long distance due to power factor issues. More fun stuff to study...

For the record Tesla was pursuing wireless transmission of energy.

High voltage DC is used for contact points and power transfer between major different grids. AC is just too convenient for conversion up and down between different voltage levels to reduce IR losses.

The heat loss in the transformers is what those saboteurs used to knock out a power sub-station by shooting holes in the transformer oil tanks so the transformers would overheat.

JR
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Don't tune your drums half-ass. Listen to what a properly "cleared" drum sounds like.   http://circularscience.com/

Lyle Williams

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Re: Induced voltage from high-tension lines
« Reply #16 on: February 15, 2014, 02:25:36 pm »

Stealing power is done with large coils.  Both large in area and lots of turns.  The power transfer is inductive.
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Stephen Swaffer

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Re: Induced voltage from high-tension lines
« Reply #17 on: February 15, 2014, 03:55:07 pm »

But if you work near a transmission line, and drive one of the new electric cars, perhaps a coil built into the roof and parking under the line would save you the energy cost of driving to work each day? Just thinking outside the box....
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Deric Craig

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Re: Induced voltage from high-tension lines
« Reply #18 on: February 15, 2014, 04:05:39 pm »

Partial quote...

So if your stage is located anywhere under high-tension power lines, I would REALLY be sure it's grounded via an 8-ft ground rod and properly bonded to your generator neutral/ground.

Oh, yes.
I believe it was late Summer 2005, on a request for production at a fair in a neighboring county. The original provider was unable to be there and was a last minute notice.

My friend called me to assist with his rig and off we go.
Upon arrival at the permanent concrete stage platform in front of the grandstands, I cast a wary eye at the HV towers overhead, not very far behind the platform, running parallel to the stage. The droop between the steel towers was at its lowest point in the stage area. Observing the insulators, I was fairly sure it was 138 kV (common in my area). It was a dual 3 phase circuit with lines on both sides of the towers.

I remarked to my friend about the situation and said this could be interesting and my concern about his 30 foot long lighting truss being affected by induction from the high voltage parallel lines. He said lets get moving on assembling the truss to the lifts.

The stage was about 4 feet high and we placed the crank lifts on the ground in front of the stage and attached the truss. We cranked the truss up to 6 feet above the stage level to attach lighting.
I went up on the stage to start the process and proceeded to receive a fairly good wallop on the truss.

That was enough for me. I told the boss we HAVE to get this truss grounded. The electricians working for the county fair were there connecting our cams for our distro and they were summoned to the front of the stage and ended up with #4 copper connected to the lifts and running to a good ground to take care of the issue.

I did not take the time to meter the truss to see what level of voltage was inducted. The rest of the day and evening was uneventful and went well. Yes, the ground conductors remained until the truss was brought back down.   
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Mike Sokol

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Re: Induced voltage from high-tension lines
« Reply #19 on: February 15, 2014, 06:14:21 pm »

For the record Tesla was pursuing wireless transmission of energy.

Oh, yeah... 8)
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Mike Sokol
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Re: Induced voltage from high-tension lines
« Reply #19 on: February 15, 2014, 06:14:21 pm »


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