Why do you need 12 gauge when you are drawing 100mA?
Also, what if you stick a magnetic metal in the coil to amplify the flux?
A Solution to the RWP for Exam 1 – Stealing Power (2006)
21–30 of 32 posts
Re: A Solution to the RWP for Exam 1 – Stealing Power (2006)
#22There's another part to this story I remember hearing, that there is a way to measure of impedance? capacitance? in this powerline to detect where the coil is. anyone now how that works?
For smaller transmission lines that operate at a higher frequency you would use a Time Domain Reflectometer. I don't know if it is practical for high voltage power transmission lines.
Re: A Solution to the RWP for Exam 1 – Stealing Power (2006)
#23> the payback period would be at least 1000 years Now I wonder if you could take advantage of the increase in copper price over the time, you might come out ahead
Perhaps your descendants might. But I think it's pretty certain you won't.
:-)
Re: A Solution to the RWP for Exam 1 – Stealing Power (2006)
#24Earlier quoted context omitted.
> A major missing detail is accounting for the other phase conductors in the transmission line. Good point. So for the customary 3-phase power lines the UNC exam is confusing and the given sample solution wrong. In reality you could steal much less than the already ridiculous amount in the exam. The German railways operate a 1-phase power grid. (After all 3-phase transmission makes only sense if you are able to balan…
"A 1-phase transmission line needs 2 conductors" Right, but for many single phase installations a ground/earth return is often employed. This often simplifies things and saves a lot of infrastructure costs. Whether it's single or 3-phase, calculating the coupling efficiency will, at best, only be a rough guesstimate unless great care is taken to accurately collect and collate all physical and electrical parameters. N…
> Right, but for many single phase installations a ground/earth return is often employed
Often? Not what I as a complete laymen in power transmission have observed.
The mentioned power grid of the German railways uses 2 conductors. Why they would pay nearly 100% more in infrastructure cost than just using ground as conductor for return current I have no idea. There must be a reason.
The Finnish railways don't have their own power grid, with the frequency being the same as the general grid they can get power from there. However, they have another way of seemingly wasting metal for a return conductor. Normally trains use the rails as return conductor. That seems "free" metal to use, because the train needs more than enough for it for mechanical reasons. However, Finnish railway lines have a second overhead wire next to the railway line and autotransformers or booster transformers (I don't understand the difference) to make sure the current is directed from the rails to the much thinner overhead return wire instead. The overhead wire being insulated from earth in contrast to the rails.
https://en.m.wikipedia.org/wiki/Split-phase_electric_power mentions the same (?) for British railways. As a reason for the extra effort they mention reducing transmission losses and reducing electro-magnetic interference to the environment.
I guess reducing electro-magnetic interference means that the "stealing" scenario from the original posting does really only work for 1-phase single wire power lines where the return current goes via earth. And even there not really well, as the article has shown.
The only place where I have seen single wire power lines is Iceland. 20 kV lines I guessed when I saw them.
> I reckon this article deliberately avoided the transmission line/multiphase effect to avoid that controversy or complicatlation.
I agree. But I would have expected that the assumptions/simplifications had been mentioned as part of the task description.
Re: A Solution to the RWP for Exam 1 – Stealing Power (2006)
#25I guess the stories of farmers stealing from the next door radio station are untrue too then. Another old urban legend down. Someone needs to do this for today's kids and harvesting 'water' from the air.
Here in Norway the usual way for a farmer to steal electricity was to get a couple of long poles with metal hooks on the end and just hook them over the line. At least that's what I was told by a colleague whose family owned a small farm. Of course that isn't suitable for voltages above the hundreds or possibly low thousands.
Re: A Solution to the RWP for Exam 1 – Stealing Power (2006)
#26Earlier quoted context omitted.
> A major missing detail is accounting for the other phase conductors in the transmission line. Good point. So for the customary 3-phase power lines the UNC exam is confusing and the given sample solution wrong. In reality you could steal much less than the already ridiculous amount in the exam. The German railways operate a 1-phase power grid. (After all 3-phase transmission makes only sense if you are able to balan…
> Isn't it so that when the max current flows in one direction in one conductor it will flow in the opposite direction in the other one? So what you can steal is determined by d1^2 - d2^2 where dn is your stealing coil's distance from conductor n? There are two wires because of Kirchoff's current law -- if the current goes out in one direction, it has to come back somehow. There are "single wire earth return" systems…
Yes, of course the field does not grow by the square of the distance.
Re: A Solution to the RWP for Exam 1 – Stealing Power (2006)
#27This was discussed in the squatting community I was in, London, 1984. The coil approach would get you lighting. I never had to do it, we had power. We argued about the wisdom of theft, when the electricity company would actually re-connect you to an illegally occupied house anyway. Why compound your problems with the law?
Years ago for a laugh I tried to stop the rotating aluminum disk in my power meter from rotating by holding a powerful ex-magnetron magnet near the one in the meter. It made not one iota of difference to the disk's rotation speed as the poles of the meter's magnet are so close to the disk that there was no way to alter the strength of the magnetic field that was at right angles on to the disk. Electricity utilities h…
Make a pin hole in the box with the disk right above the disk, unroll a paper clip, put it trough the pin hole. When the wire is against the disk it should stop. You can scotch the wire from the outside to maintain it in its exerting pressure position.
Re: A Solution to the RWP for Exam 1 – Stealing Power (2006)
#28I guess the stories of farmers stealing from the next door radio station are untrue too then. Another old urban legend down. Someone needs to do this for today's kids and harvesting 'water' from the air.
Here in Norway the usual way for a farmer to steal electricity was to get a couple of long poles with metal hooks on the end and just hook them over the line. At least that's what I was told by a colleague whose family owned a small farm. Of course that isn't suitable for voltages above the hundreds or possibly low thousands.
I heard attracting wasps with honey to lay nests in the spinning meter, also can't source that.
I think the main way is wires around the meter. How cool were these dudes stealing electricity from Edison, I liked Edison's firewall -
(1886) - "It was hardly worth while to maintain the continuous espionage necessary to detect and punish these pilferers, but the superintendent of the station, Mr. Chamberlain coupled in extra dynamos, and threw as great an increase of current over the system as the safety catches would permit, at various times for about one second while this current was passing; the incandescent lamps would give an unwanted glow, and every induction coil and motor surreptitiously attached to the system would receive an extra current designed to burn it. In this manner the system to occasionally cleared of all trespassers."
Re: A Solution to the RWP for Exam 1 – Stealing Power (2006)
#29There are groups looking to do this with low orbit drones and Cu wire. Steal from the core!
I'm not sure why you were modded down. Here's a link: https://pwg.gsfc.nasa.gov/Education/wtether.html
While you can of course use the space tether as a power generation device, generating small amounts of electrical power in space is easier done by solar panels. The space tether is usually envisaged to be operated the other way around, to convert electrical power from a solar panel into propulsive force. In any case, you aren't really taking power "from the core", it comes from your own kinetic energy.
Re: A Solution to the RWP for Exam 1 – Stealing Power (2006)
#30Earlier quoted context omitted.
Years ago for a laugh I tried to stop the rotating aluminum disk in my power meter from rotating by holding a powerful ex-magnetron magnet near the one in the meter. It made not one iota of difference to the disk's rotation speed as the poles of the meter's magnet are so close to the disk that there was no way to alter the strength of the magnetic field that was at right angles on to the disk. Electricity utilities h…
Make a pin hole in the box with the disk right above the disk, unroll a paper clip, put it trough the pin hole. When the wire is against the disk it should stop. You can scotch the wire from the outside to maintain it in its exerting pressure position.
Yeah, I've no problem actually doing that. But there's the problem of the meter guy noticing!
This was a proof of concept experiment after I had had a discussion about a decade ago with a friend of my then boss who in his younger years actually designed electricity meters - he was also president of my local IEEE chapter so he was highly regarded (unfortunately he's now dead).
Anyway, he challenged me to alter the metering rate on one of my meters (I've four 3-phase + off-peak) without actually tampering with the meter or breaking the lead seals. He said I'd have Buckley's chance and he was right.
He said they not only go to inordinate lengths in the design of meters to ensure that it's not possible to stop them but also that they don't change their rate (run slightly slow, etc.) when heated, cooled, exposed to magnetic fields etc., and that before a meter is approved it's tested by certifying authorities for strict compliance.
Mind you, some meter readers don't seem to give a damn. We rented some short-term space off site to the main factory (which itself was an old factory) and some of its meters no longer even have glass covering the dials and others had their lead seals missing altogether. Anyway whenever the meter reader turned up he was never the slightest bit concerned. The boss said for no one to fiddle, for as sure as eggs, someone will forget to remove the 'tweak' before the next reading and the consequences of that would be much more trouble/far outweigh any potential savings gained on the account. :-)