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Overhead wiring?


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  #21  
Old 10-15-2016, 12:08:24 PM
len k len k is offline
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Default Re: Overhead wiring?

Pet animals and young children are the real risk.
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  #22  
Old 10-15-2016, 12:17:48 PM
Birken Vogt Birken Vogt is offline
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Default Re: Overhead wiring?

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Can always do like one staker did step up voltage to couple KV and run 2 small bare wires overhead like utility does.
I'd like to see this. Link?
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  #23  
Old 10-15-2016, 12:35:48 PM
len k len k is offline
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Default Re: Overhead wiring?

Pic of it was on the Stak ~ 3 months ago, don't remember who had it. Think it was in the woods. Small gauge bare stainless?? wires were about 1-2 feet apart, small white knob type porcelain insulators. Did concern me that the wires were small enough gauge to be taken out by a falling branch, then they would be on ground. Not sure if current breaker would trip then.

As a kid in late spring I've put a 1 ft steel rod in ground and connected it to 120 hot to get worms for fishing to come out of ground, think it drew under 3 amps, maybe 1 amp. Was pretty low current, soil was clay. Wore rubbers and kept my feet together. Had to keep reminding myself when I saw a big worm I wanted to reach for , pull the plug first. . Surprising how fast they disappeared back in their holes when I shut AC off.

Last edited by len k; 10-15-2016 at 01:02:54 PM.
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  #24  
Old 10-15-2016, 12:59:03 PM
nothingbutdarts nothingbutdarts is offline
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Default Re: Overhead wiring?

Nope, not looking to use bare wire!

I'll do more digging today and see how that goes and decide.
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  #25  
Old 10-15-2016, 01:59:23 PM
Vanman Vanman is online now
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Default Re: Overhead wiring?

Was thinking about this last night, just for fun.

One way to improve the safety dramatically- though probably at some expense of reliability- would be to have a mid-point tap on the secondary of the step up transformer, and ground it through a very high resistance.

Connect the coil of a relay across this resistance, and arrange the circuit such that if the relay pulls in, it trips the circuit off line. Thus the slightest ground fault takes the circuit off line. A high voltage GFI.

Also for fun, I calculated that 5 KVA could be transmitted one mile using 15 KV with only ~4% loss using #34 wire! *Ridiculously* fragile, but illustrates the usefulness of high voltage.
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  #26  
Old 10-15-2016, 03:32:34 PM
len k len k is offline
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Default Re: Overhead wiring?

Old subs supposedly had a version of that , but they just leave the power on and use an indicator light to highlight trouble that a hot is grounded.

Some country ( Australia ??) uses a system of only one hi-voltage wire. And a ground rod for the return current to save wire costs out in the boonies. Actually that was the system I briefly thought about using.
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  #27  
Old 10-15-2016, 08:25:53 PM
soundbos soundbos is offline
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Default Re: Overhead wiring?

Quote:
Originally Posted by len k View Post

Some country ( Australia ??) uses a system of only one hi-voltage wire. And a ground rod for the return current to save wire costs out in the boonies. Actually that was the system I briefly thought about using.
The feed to my brothers house is 1 wire to a transformer and earth ground and this is only 6 years ago in Illinoise
I think it is 6kv

Butch
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  #28  
Old 10-15-2016, 08:37:49 PM
len k len k is offline
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Default Re: Overhead wiring?

In the Australia system I read the wire was MANY MANY miles long. So they used some type of voltage regulation at the user's step down transformer, to compensate for losses in the hi-voltage wire. Maybe an automatic multitap transformer.

And they did a special ground rod , think they used salts to increase soil conductivity to get a good ground. Since if had poor ground connection to earth the rod could be hot WRT earth under your feet, if you touched it.
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  #29  
Old 10-15-2016, 09:05:15 PM
SoTexRattler SoTexRattler is offline
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Default Re: Overhead wiring?

Yeah, a couple small "Pole Pigs" connected back-to-back would carry 120/240V 5kva a LONG way with little loss.
5KVA over #34 wire @15KV you say? COOL! That would definitely open up a wide choice for HV conductors!
Tiny pole pigs they use for powering a single billboard or traffic light out in the country would be perfect.
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  #30  
Old 10-16-2016, 03:48:56 AM
turtmaster turtmaster is offline
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Default Re: Overhead wiring?

i have also always wanted to run a mini high voltage line

one problem that one might have with using a microwave transformer is i think that the way they are designed with respects to it's losses that it would get hot quickly under load


also here is a link to a homemade mini high voltage transmission line in Chile

https://ludens.cl/paradise/turbine/turbine.html


also the Australian system is called "single wire earth return" sometimes no. 10 fence wire is used
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  #31  
Old 10-16-2016, 08:53:53 AM
Kevin K Kevin K is offline
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Default Re: Overhead wiring?

That problem has been faced by radio amateurs over the years: how to economically get power up to the repeater shack at the top of the hill. The solution: a couple of pole pigs and two lengths of RG-8 coax cable strung through the trees to carry the high voltage.

RG-8 is typically good for 10Kv.

http://www.spellmanhv.com/Technical-...on-Notes/AN-07
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  #32  
Old 10-16-2016, 09:36:10 AM
PopsGarage PopsGarage is offline
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Default Re: Overhead wiring?

WOW that some system that they built!!

Bob
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  #33  
Old 10-16-2016, 11:36:33 AM
armandh armandh is offline
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Default Re: Overhead wiring?

the DIY hydro has a problem, no quick over speed shutoff of the water.

load banking the excess might work for a while but if the load ever comes off;
Pelton wheel cups will become self extracting.
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  #34  
Old 10-16-2016, 12:25:56 PM
Vanman Vanman is online now
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Default Re: Overhead wiring?

If the turbine is designed properly, the no load speed will twice the running speed. If the generator is four pole, the no load speed will be 3000 rpm, likely safe for all components.

What I don't like is that speed regulation is purely by auxiliary load. So the generator is always running with load, no matter what. And it's made in China. So...... Wonder how long it will last under those conditions.

Keith
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  #35  
Old 10-16-2016, 12:40:27 PM
Birken Vogt Birken Vogt is offline
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Default Re: Overhead wiring?

All the off grid hydros that I work on regulate with auxiliary load although they use either GM alternators or some kind of strange permanent magnet motor run in reverse. They have their problems but burning up does not seem to be one of them.
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  #36  
Old 10-16-2016, 12:53:30 PM
len k len k is offline
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Default Re: Overhead wiring?

Water Turbine
Nice pics of how to wind your own transformer.

The solution of HZ control by variable load VS variable water flow is an interesting economic tradeoff. There was a thread here about a USA located mini-hydroplant ~ 10kw where they used variable water flow valves to control HZ. would expect water spool valves to wear/corrode and lock up.

Maybe a better solution is to use that new type of gen that makes constant HZ with variable rpm. Basically a DC gen with field excitation that runs at 60 hz not DC, plus some electronic switching (IGBT) of output to make the negative potion of the sinewave.

I'ld like to see an additional water slinger disk next to the gen to keep it's bearing dry.


High Voltage wires strung thru air
By using high voltage the IR losses are so low you can use SMALL gauge wire. So at this point the wire size is dictated by mechanical not electrical issues. Wind loading, ice loading, small tree branches breaking and hanging up on wire, ect. Would expect you don't need to use copper wire, except maybe as a coating for corrosion protection.


MW transformer
I once took a MW transformer and modified it to make 440 VAC output instead of normal ~ 1,000-1,500 VAC, to test power a fan in a hanging 10kw electric box heater. Basically I removed about 66% of the secondary, I also knocked out the 2 magnetic shorting laminations between the primary and secondary. I didn't use a fan on it , it ran hot even though load was low. And I think it was an older one, not the new small ones.

Last edited by len k; 10-16-2016 at 08:20:11 PM.
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  #37  
Old 10-16-2016, 03:17:02 PM
Vanman Vanman is online now
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Default Re: Overhead wiring?

Quote:
Originally Posted by len k View Post
Would expect you don't need to use copper wire, except maybe as a coating for corrosion protection.
True, although wire made of materials with a higher magnetic permeability- such as iron or steel- present a greater inductive reactance than other materials, such as copper or aluminum.

It doesn't mean that these metals can't be used, only that their characteristics must be accounted for.

Keith
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  #38  
Old 10-16-2016, 04:08:12 PM
len k len k is offline
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Default Re: Overhead wiring?

Not sure but I have a gut feeling when wires are separated by a good distance (maybe 6-12+ inches) then inductance from loop area dominates, and extra inductance from mass of ferrous metal is negligible by comparison.

Loop area being the wire length times distance between the conductors.

Think utilitys use aluminum instead of steel because it doesn't rust, and let the live wire fall down.

Last edited by len k; 10-17-2016 at 11:55:44 AM.
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  #39  
Old 10-17-2016, 08:01:48 AM
PopsGarage PopsGarage is offline
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Default Re: Overhead wiring?

and it is much lighter, span between poles can be longer.

Bob
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  #40  
Old 10-17-2016, 03:32:34 PM
dalmatiangirl61 dalmatiangirl61 is offline
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Default Re: Overhead wiring?

Find a rental yard that has one of these http://www.ebay.com/itm/14-Ditch-Wit...EAAOSwQYZWwm5i
I think they even come with a beer, er uh, beverage holder.
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