How to test underground power wire

[idaho04]

I sure appreciate your responses, I am learning from it. Well, we burried the wire (2/2 aluminium Stevens?) directly without conduit. Before I got your replies I went and did the test again and found out some new info: the bad wire shows power at the end but looks weak (using simple tester), definitely weaker than the othe hot. When I switch one of its breakers on, the power disappears. There does not seem to be anything wrong with the in-the-barn circuit because this does not happen with the other hot. I did noticed that the panel in my shop has a ground cable going to the groundstick but my barn panel does not, would this be a clue? But why would one hot work and the other not?

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] I'm guessing that there is not enough of a conductor remaining to carry any significant amount of current. It's possible that all you are getting on the meter is bleed-over from the hot side of the break; as soon as you close the load side breaker it reduces the voltage to zero. Having a ground rod at each remote building sub panel is a good idea. Whenever you run to a remote site, plop in a ground rod just for good measure. If the sub panel is in the same building, you must carry a white neutral AND a green ground to the sub, and also "float" the neutral in the sub. The ground rod at the main is then the only ground and that is where green and white can tie together. [img]/forums/images/icons/tongue.gif[/img]

[egon]

Aluminum wire.

Maybe check the connections at the start of the run??? [img]/forums/images/icons/confused.gif[/img] [img]/forums/images/icons/confused.gif[/img]

Egon [img]/forums/images/icons/grin.gif[/img]

[Pat]

You shouldn't connect aluminum conductors to just any piece of stuff at random.
You should be sure the "stuff" is intended to be contacted by aluminum (may be labeled Al/Cu or Al-Cu or whatever. You should also use an approved anti-oxidation/corrosion paste IAW the MFG's instructions.

When you have a long parallel run of conductors, one conductor can induce a voltage into the other. For example: an AC hot wire running next to a wire not connected (or broken somewhere in the run) will have the non-connected wire showing a voltage when checked with a high impedance device (voltmeter or similar.) However if you try to draw meaningful power from the "parasite" source the voltage will drop way down and you will not get meaningful power. This is due to the high impedance of the parasitic source in case anyone cares.


Hi, Dave!

Pat

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] I'm reading, and reading, and reading, your posts, Pat; and learning, and learning, and learning stuff, as always. There is currently a show running on the SPEED channel, titled 101 cars that you MUST drive. They featured a Sunbeam Tiger recently, and I thought about you. They have had some real interesting rides on the show. [img]/forums/images/icons/smile.gif[/img] OHHHHH do I ever hate direct-buried cable. I do, oh yes I do. [img]/forums/images/icons/tongue.gif[/img] Just went to an auction and bagged a nice Freon Recovery/Recycling/Recharging machine; a Robinaire. [img]/forums/images/icons/cool.gif[/img] At long last I am GREEN. [img]/forums/images/icons/crazy.gif[/img] Kermit the Frog is BROWN compared to me. [img]/forums/images/icons/smile.gif[/img]

[idaho04]

Well, today I did some more investigating. At the main power panel both hot legs are powered properly at 123V. At the barn, one hot measures 122V and the second (bad) one 98V, disconnected from the panel (no interference). That seems to be my problem. As I said before, the 3 wires (awg2 aluminum Stevens) are 800' long, loosely twisted and buried at least 2' in the ground, no conduit. I am no aware of any damage to the wires. The bad wire must be leaking to the ground?

[egon]

Durned, it couldn't be something simple. [img]/forums/images/icons/grin.gif[/img]

Will it be digging time?
[img]/forums/images/icons/frown.gif[/img] [img]/forums/images/icons/frown.gif[/img]
Egon [img]/forums/images/icons/grin.gif[/img]

[JazzDad]

Pat, don't forget to explain how to match the impedance to the TDR.

[Pat]

Nah, you do it Jazz, I gotta do some other stuff and am willing to share the stage. Besides, my head is so swollen up right now from Dave patting me on the back I'm afraid to load it any more with thinking.

Pat

[jimbrown]

Well if it was Az I would say look for gopher holes. The suckers like to eat insulation. They eat my poly pipe for drip irrigation.