Steel wire carrying twelve volts ?

No.

Reply to
Richard J Kinch
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  Could I have some advice please.   I need to get a twelve volt, 1/2 amp supply five hundred metres up a hill. I do have a fence a metre high made from wooden posts and seven runs of Num eight (4 mil) galvanised steel wire. Is it feasible to use two of these wires to carry twelve volts that distance ? Thank you.  
Reply to
grumpyoldhori

I'd say yes.

Reply to
Don Foreman

If it was me, I run some trials. Id get a 12 volt car battery ,connect the positive to one of your galvanised wires then at the 500 meter point conect this wire to one say

2 strands down,come back to the battery and put a volt meter between the retun wire and the battery negative. this will show you the voltage losss/drop over the 1000m length. what ever this is, lets say for example 12 volts, youll then have to add another 6 volt battery to make the input voltage 18 to get 12 volts at the 500 meter point. Run the trialand let us all know what the values are. Even tho its up hill that shouldnt make much difference to what you get out. To replace or run a copper line 1000meters is a much better way to go. tho the cost wold be high. Depends where you are.
Reply to
Ted Frater

Like the others said, experiments will give you the answer for sure. But you can get a reasonable answer by calculating things ahead. For instance:

I shall make an assumption that resistivity of steel is the same as iron (1xe-7) and that your wire has a diameter of 2 mm (easy on the calculations and probably generous). This gives the resistance of a 500 m long steel wire as 16 ohms, give or take. Thus passing 0.5 Amp current will cause a drop of

8 V, leaving you with only 4V up the hill...

A copper wire of the same diameter and length is about ten times more conductive, thus the drop would be only 0.8V.

Reply to
Michael Koblic

If the duty cycle was fairly low, I would look at using a 12v SLA battery ( or maybe an old car battery), a small solar panel and a trickle charger to keep it toped up. As others have said, the resistance of the steel wire would be too high and the cost of running large enough copper conductors ( to minimise volt drop) that distance, would be too expensive. What is the application and estimated amount of use per day?

Reply to
Stephen Robinson

No.

Line losses will reduce the voltage at the far end way too low to use.

That's why we use AC voltage for distribution.

Richard

Reply to
cavelamb himself

Well most likely. Your steel wire has a higher ohms per foot than copper wire so the drop across the wire may be significant.

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Resistivity (?-m) at 20 °C Copper 1.72×10-8 Iron 1.0×10-7

I couldn't make sense of the units but basically it looks like steel wire is

17.2x worse a conductor than steel, so you now have a 8600 meter copper equivalent run.

formatting link
For copper, 0.6282 ohms per 1K feet. 8600 meter = ~28K feet, which yields

17.6 ohms per strand or 35.2 ohms for the circuit.

Now assuming your end load needs .5 amp you have a series circuit where a certain amount of voltage will be dropped across the fence. Right off the bat, that 12V input isn't going to be what you want.

Now your end load is 24 ohms, 6 watts assuming it needs all .5 amps. If the load is variable, well it gets messy. So assuming you need all .5 amps you have 24 ohms + 35.2 ohms in your series circuit. Right off the bat, it looks like 12v in isn't going to work and 24 isn't enough either.

So if you drop 12v across 24 ohms, you will have to drop 35.2/24 * 12v across the wire if my grasp of this is right. I've have a beer or two since it is the weekend so my thinking might be faulty ;)

E=IR E=.5 x 59.2 E= 29.6

Not sure I didn't blow something but it looks reasonable to me atm.

NN

Wes

So 17.6 volts across the circuit. That makes 17.6 + 12v = 29.6v P=IE I = P/E I = .5 / 29.6v

So yes this is doable, you just need to feed in a higher voltage to get what you need at the end. I'm not sure how legal putting 30V out on a fence is in your jurisdiction though.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Reply to
Wes

Running a Linksys wireless router on a hop for a microwave link. The output power is only 100mw. but the router draws five watts on average to power it's board etc. Running 24/7. Looked at solar and running copper wire, both came to around NZ $600 Which is why I am keen on using the steel wire if possible.

Reply to
grumpyoldhori

Probably need to start with 24 volts to get 12 at the top. It will have about 15+ ohms total resistance (~3000 feet of wire). Is the load constant? Like a lamp or such?

Is the wire insulated from the wood post? He could use 24 volts AC to a transformer at the top and convert to DC at the end.

Tom

Reply to
Tom M

Great, thanks for that, I am in New Zealand, trying to get internet access to a couple of isolated homes. It is a volunteer job and they not not have the money for the four solar setups needed. Of course we do have a lot of fences available to hold all the sheep in. I will have to check the legality, but I cannot see thirty volts DC being a problem.

Reply to
grumpyoldhori

Okay, the router comes with a 'universal' SMPS wall-wart, yes?

How about using TWO 230:24 (eg. 1A rating) transformers to send the power down your wires at 24VAC/50Hz, and step it up at the other end. The wall-wart will tolerate as low an input as 100VAC or so, so if the numbers we have for resistance are in the right ballpark you should be okay (easy enough to short them at one end and measure the (loop) resistance at the other. If it's around 35 ohms you should see around

150VAC at the output of the downstream transformer with a 6W load (if the 6W is from the nameplate, rather than measurement, expect to see a fair bit higher than that-- mabe 180 or 200VAC).

Although this may appear to be a more complex and expensive answer than some others, it should give you a stable regulated supply for the router, and at least has a good chance of surviving a nearby lightning strike (put an arrestor at each low voltage end, before the tranformer, as well as fuses or circuit breakers to protect against shorts). Going directly in with DC, I think you'll be buying, and configuring, a new router after every few electrical storms. The transformers provide isolation against common mode voltage (assuming the arrestor breaks down before the transformer insulation) and will saturate when presented with a high normal mode voltage.

Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

I wonder what the earth resistance is like? Potentially you could use all seven strands up, and the earth as a return. That also gives you plenty of redundancy if you lose a strand (but you have to keep them all insulated). As others have said, I would go for AC with a decent isolation system at the top end to protect the router against lightning.

Reply to
newshound

Thomas Edison never did agree with you on this issue.

Karl

Reply to
Karl Townsend

ted what has going up the hill got to do with it? please explain that, it really has me interested.

Stealth Pilot

Reply to
Stealth Pilot

YEAHbut - his didn't win.

Reply to
cavelamb himself

Yup, and HV DC transmission has advantages over AC transmission, and can contribute to overall system stability.

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250km undersea (Sweden to Germany) 450kVDC cable:
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$File/Project%20Baltic%20Cable%20450%20kV%20MIND%20subm-.pdf

Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

On Sat, 26 Apr 2008 16:33:32 +1200, with neither quill nor qualm, grumpyoldhori quickly quoth:

Sure, if you start with 110v or so.

Time to invest in a solar charger, Grumps.

-- Happiness in marriage is entirely a matter of chance. If the dispositions of the parties are ever so well known to each other or ever so similar beforehand, it does not advance their felicity in the least. They always continue to grow sufficiently unlike afterwards to have their share of vexation; and it is better to know as little as possible of the defects of the person with whom you are to pass your life. -- Jane Austen, Pride and Prejudice, 1811

Reply to
Larry Jaques

On Sat, 26 Apr 2008 06:29:29 -0500, with neither quill nor qualm, "Karl Townsend" quickly quoth:

No, but Westinghouse, using Uncle Nikola's technology, became the defacto standard around the world in no time at all. Uncle Tom, clinging tightly to Uncle Ben's technology, missed the boat on that one entirely. He lost a shitload of cash on that horserace, wot?

-- Happiness in marriage is entirely a matter of chance. If the dispositions of the parties are ever so well known to each other or ever so similar beforehand, it does not advance their felicity in the least. They always continue to grow sufficiently unlike afterwards to have their share of vexation; and it is better to know as little as possible of the defects of the person with whom you are to pass your life. -- Jane Austen, Pride and Prejudice, 1811

Reply to
Larry Jaques

Telephone systems run at 50 volts, and cause no particular safety problem. Likewise, power over ethernet uses ~50 volts.

In the US, the electrical code allows up to ~50 volt systems to be handled far more simply than power systems. It think that this rule is true worldwide.

So, the simplest system is two AC transformers, one to take the voltage down from 220 to about 48 volts, and another to take the voltage back up to 110 or 220 for the router, with three steel wire strands carrying one side of the 48-volt and three strands carrying the other side. The seventh strand is grounded and hooked to the center taps of the 48-volt windings, so the max voltage to ground is 24 volts.

You may need insulators to prevent outages during rainstorms.

You will need lightning protectors and individual fuses on both ends of both sets of 3 strands, for a total of four fuses and four lightning protectors. The ground strand should be grounded at both ends.

The 48 volts will help the cows to remember to not scratch on the fence.

Joe Gwinn

Reply to
Joseph Gwinn

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