Getting power from transmision lines electromagnetic field 2

[Bronzeado]

Hi folks,

In developing countries, corridor of transmission lines run nearby small villages with no electricity. This seems to be very unfair to people from those villages.

There is an ideia of getting power (1-2kW) from the electromagnetis field of the transmission lines to feed those village. I wonder if somebody has information on this kind of development.

Best regards,

Herivelto Bronzeado

 

[MikeHalloran]

It's a very, very, bad idea, because when you've gotten close enough to pull significant energy from the field, you've already been electrocuted by an arc from the line to the tower frame or whatever else you're standing on.

Don't even _think_ about doing it.



Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

Would you be proposing the same thing if it was a pipeline going by the village?

Besides it's stealing clear and simple.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LaffeyDD724]

Such a practice is unlawful in the USA, I would be hesitant to consider such a practice considering it may be against the law and concidering the negative safety aspects of it as well.
Tom

None of us is as smart as all of us.

 

[Skogsgurra]

Isn't it even more unfair to other villages? Those who cannot benefit from the beauty of modern power transmission technology?

Can't really see the "unfairness" in having a power line nearby and no power. I have a rail-road not far away. Lots of cars, fuel, frozen food, wine, timber. And I don't get any of it...

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

I don't think that Bronzeado is advocating stealing power. I think that he is looking for a viable way to provide service to villages.
I looked into the feasibility of providing power in a similar situation in Canada years ago. You can extract small amounts of energy by inductive coupling, but not enough to service a village.
They method needed is an economical transformer. I went looking for a suitable used transformer.
I considered having a used transformer rewound for the voltage needed. What I found was that for any given voltage there is a minimum size transformer. It has to do with the size and physical strength of the windings, and the size of the tank to provide space for the high voltage bushings. If the winding conductor diameter is below a certain size it will be destroyed by the first fault. It may not even survive energization stresses.
With a 133kV transmission line past the settlement, the smallest transformer that could feasibly be used was worth more as scrap metal than the village could afford.
I suspect that the same economics will still prevail.
When a line is grounded out for maintenance there will often be a voltage and current induced by parallel, energized, lines. There is often enough energy to kill men and livestock, but not much more. And also the extremely high source impedance will make regulation virtually impossible.
However, a challenge for some of the Gurus here: If a fourth line was added, parallel to one of the existing phases, how much energy could be linked per mile?
Possibly a distribution type transformer may be designed so that the induced voltage is kept to a value that the transformer will endure.
The next hurdle is controlling the voltage without excess waste.
As an idea, how about several miles of parallel line with a transformer at each end. One transformer will supply the load, and the other will have switching on the secondary to control the current (and, by inference, the voltage) at the other transformer depending on the load.
I haven't had my second cup of coffee yet. Maybe I will come up with some more suggestions later, but maybe not.
Back to you, Gentlemen.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

I can see that my post was "edited for clarity". OK, I accept that. But I still find the question way out of any engineering topic. For many reasons. Not only ethical and practical but also beacause it seems to represent the famous "free lunch" tom some individuals. I have heard this being discussed over and over by so many laymen that I am getting tired of it.

I respect your (always) positive attitude, Bill. But I cannot play this game.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

Hello Gunnar.
Respectfully, I believe that you may have misunderstood my intent. I was not advocating a free lunch or stealing power.
I was suggesting that we discuss a possible "outside the box" solution whereby utilities could supply and charge for small amounts of electrical energy to small settlements.
The capital cost of tapping a transmission line starts in the millions of dollars. Out of the question for small communities.
I am thinking in the range of possibly 10 KVA to 50 KVA.
A line parallel to one phase would be an air core transformer in parallel with a capacitor. While the energy available would be small, it would be several times greater than the energy induced in a parallel transmission line.
I am thinking something along the lines of two 15 KVA x 35 kV distribution transformers. The transformers would each have one high voltage bushing grounded, and have the other bushings joined by a length of conductor a safe distance from one phase. One transformer would supply the load and the other would control the voltage by varying an impedance across the secondary terminals. Similar to a distribution transformer used for high resistance grounding of a high voltage transformer.
I agree with you, Gunnar, stealing power is not proper.
However I see this as a challenge to supply small amounts of power in a way that it may be safely used and sold at a reasonable price.
I usually agree with you, Gunnar. When I don't agree with you, I still respect you. I feel that way about most of the regulars here.
Respectfully

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Bronzeado]

Thank you Bill for really get the gist of my ideia.

For those who did not get my point at first glance, I am sorry for not make myself clear.

For your information, I work for a state owner utility in the Noertheast of Brazil (Companhia Hidro Elétrica do São Francisco - CHESF,

http://www.chesf.gov.br)

that generate arround 10 GVA) and supply almost 60 million people.

We have more than 18.000 km of transmission lines runnig across an very poor and dry region with a lot of very small villages without electricity and with dificulties to get water.

There exist a governamental program in Brazil called "Light for All" that intend to supply electricity to arround 12 million people that live in remote villages without it. I am talking about a basic need (electricity)that should be the prime mover to run other "bussiness" in this poor region, mainly pumping water from wells.

Itsmoked, if you were aware of the situation of this region I am talking about, I think you could propose a program like "Water for All", where peolple could access water from passing pipelines. At least, the planners should think in a way to give access to all those living nearby a pipeline or a tranmission line. I am still talking about a very basic need - water and electricity.

As Bill said, I am not advocate to steal power or (taking a ride in your saying) water. What I am trying to know
is how can we get energy to supply safely (but not reliable) a remote small village neaby transmission lines.

How to charge for this service, control the supply voltage and protect people and equipmente is another matter that chalenge us.

I would very much appreciate your thought on that.

Best regards,

Herivelto Bronzeado

 

[Skogsgurra]

I can see where this may fit in, Bill. Your island?

But, given the fact that the transmission lines usually are three-phase and therefore produce near zil flux as soon as you get a few yards from it. And also given the fact that cables grow and shrink with temperature and sometimes "dance" violently in stormy weather. Plus the fact that line current is not very constant.

Given all those circumstances, I see no real practical solution to this proposition.

One solution could be to let the induced current charge a DC link with whatever power it can suck from the transmission line and feed this highly variable DC voltage to an inverter that produces the needed three-phase - perhaps even single phase AC will do?

I still think that a DG set or a solar panel plus accumulator/inverter would be the better solution. It is standard, it is available, it is proven, it is legal - what is wrong with that?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[jraef]

Bronzeado,

Rather that delve into the ethical issue, let's tackle the physics. There is no "free lunch" when it comes to power, electrical or otherwise. What the proponents of this idea (whomever they may be) are probably thinking is that, by somehow tapping into the EM field they hear of that exists around the conductors anyway, they can extract power without affecting the transmission lines themselves. That is just not the case.

First off, it would need to be an AC transmission line and a lot of high voltage lines are DC. If it were DC, the only way to extract power that I can think of would be to have some sort of coil moving in the EM field and where is the power going to come from for moving that coil? So let's move on to the assumption of an AC line.

As mentioned earlier, in order to extract any usable amount of energy from the EM field, i.e. with a transformer coupling across the lines of force, the transformer would need to be very very close to the lines, essentially an "air core transformer". In fact, it would need to be too close to be done safely; why do you think those towers are so high?

Lastly, assuming you solved that logistical dilema by sacrificing a few brave souls on a wooden platform, now you have the "no free lunch" part of it. When you do successfully couple your air-core power transformer to the EM fields around the lines, they will have an effect on the lines themselves, i.e. the back emf of your transformer will couple to the transmission lines and add impedance. That means less power will flow through those lines to the loads downstream and thus the transmission losses will be increased. Someone always pays for those losses, usually the supplier or maybe in your case, the Government. Nonetheless, it is not "free" and it is definitely unsafe.

So if the Government is truly interested in supplying power to these villages, they will need to tap off of the lines in a safe manner with a sub-station. That is exactly what those are for. Expensive? Yes, but if there were safer ways to do it less expensively, believe me, that would be the standard!


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[itsmoked]

I see. Thanks for clearing up the ethical aspect Bronzeado. We often see potential thieves here with the same question.

Leave it to waross to see the correct intent. (Atta boy.)

I have ot agree with Skogs on the solar angle. There are several good solar powered pump setups available. Solar trackers and MPPT (Maximum Power Point Tracking) controllers to get the biggest bang out of any solar arrays.

Lights are much more coefficient now in LEDs or Compact Fluorescent that little solar arrays can provide a lot of basic night lighting.

I was just given a flashlight that is made for poor/remote countries/people. It provides about 8Hrs of light after a day in the sun.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Hi Gunnar, no, not my island. We have a 13,800 distribution system and can hang distribution transformers wherever we need.
Hi jraef, As I understand the issue, Bronzeado works for the utility. The challenge is to supply AND CHARGE for small amounts of energy that will not support the expense of a conventional sub station.
Back to Bronzeado's issue. I assume that the amounts of power to be extracted are so small as to be insignificant as far as system through put is concerned.
Any thoughts on how much power we could extract with a bushing CT? Can we push one up to 5 KVA or 10 KVA? 25 KVA will support a fair sized villiage. No electric stoves or hot water, just lights and entertainment equipment.
If we determine that a CT is capable of extracting enough power, then we will work on controlling it. Gunnar's DC link and inverter may work well.
Bronzeado, what are your typical voltages and currents on the transmission lines under consideration.
What range of variation will there be with the current.
BTW, folks, if DG was economically feasible it would have been installed when oil was $50 a barrel, not now at over $100 a barrel.
I spent some time with a solar array in the Moskito Coast some years ago. it left me with a negative feeling towards solar. The new generation of grid tie inverters and net metering are making a believer out of me, but the cost of stand alone systems with battery banks seemed to be excessively expensive to me. Even with a donated system, replacing an average of 20% of the batteries anually is a factor that never seems to be considered. Yes, I know, there are better batteries, but the cost seemed to be proportional so the annual cost was about the same.
And, as for diesel, on the island, generating with diesel, the delivered cost is now $0.42 US per kWHr. The cost of fuel to run a self owned set is about one half of this. Nevertheless, the many folk who have their own backup sets have found that the cost of ownership is over twice the cost of the fuel. They buy energy from the grid and only run their own sets when the grid is down.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[davidbeach]

Even if you could come up with a means of coupling to one phase (which I would not recommend trying) under normal, steady state, conditions you still have big problems to deal with. The first is that your coupling is proportional to the current flowing in the line; this will vary all over the place. Then consider the impact of your little coupling device when there is a ground fault on the coupled phase. One ground fault could blow out your whole system, and ground faults happen.

 

[cranky108]

Although not much power could be gained, CCVT's and larger CC equipment has been used in the US for feeding tower top cell phone stations. The issue is with surges, and that can be delt with by arresters and a small ground grid tied to the static wires.

On the other hand there is only static wires where there is lightning.

Although somewhat costly Kuhlman makes station power transformers for taps on the transmission voltage (100KVA at up to 230kv).

 

[Skogsgurra]

Interesting discussion. Still, its raison d'etre seems to be the feeling that "there's something I could get for nothing - please let me have it!"

I remember this being discussed when I was a kid. And that is REALLY a long time ago. The idea is not new in any way. There is no solution to it as far as I know. Why do you think that is so?



Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Bronzeado]

Bill, your thought match up 150% with mine:

1. "The challenge is to supply AND CHARGE for small amounts of energy that will not support the expense of a conventional sub station."
2. "...the amounts of power to be extracted are so small as to be insignificant as far as system through put is concerned."
3. "If we determine that a CT is capable of extracting enough power, then we will work on controlling it."

The typical voltage on our transmission lines are 230kV and 500kV. The current varies from 0A to 300A.

Gunnar, I agree with you that the fact that line current is not very constant is a big issue in this matter.
Regarding to the cable "dance" and the null magnetic field, they may be avoid if an "air core transformer" is installed on a isolated platform nearby the lateral cable, with fixed distance from the cable.

Jraej, there will be no "free lunch". People would pay for this service at a price which should take into consideration the poor reliability and quality.

David, during a ground fault in the transmission line, the secondary winding of the coupling device could be short-circuited initially by a varistor and then by a "circuit closer" (circuit breaker). This action will protect the "system".

Cranky108, thank you for the information.

Regards,

Herivelto Bronzeado

 

[davidbeach]

It sounds like Brazil needs to repeat what the Rural Electrification Administration did in the US in the 30's and 40's. Power was provided to areas, because it was important to do so, where the loads were too small and too far apart to economically justify doing so.

 

[Skogsgurra]

I have (reluctantly) taken a sceptic and conservative view on this. I really do not like to make things seem more difficult and impossible than they are.

It will probably be possible to build an isolated platform and put a piece of conductor close to the transmission line so that varying distance would not be a problem. But the safety distance when dealing with 230 and 500 kV is such that the induction between the "primary" and "secondary" will be very small - if you do not apply system voltage insulation. And then, you could just as well use a transformer. With much better results.

Since I have a set-up to measure inductance between parallel conductors, I modified it somewhat to measure actual induced voltage when running 60 A AC in one conductor and measuring the other. The results are not encouraging. That is the reason why this "Power Line Tap" hasn't been used in practice - even if people have talked about it for at least sixty years (that is how far back my memory serves).

Test results in the attached pdf. Comments invited.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[slavag]

Just my 0.00002$.
Gunnar, great!!!

From my point of view, only solar solution in this case.
Regards.
Slava