We have a power cable (AWG2) running underground from the main at the house to our barn about 800 feet away. Three wire cable brings two hots and a ground to the barn. One of the hots leaves the main but does not arive at the barn panel. I will need to find where the problem is. What is the best way? Are there any testers that I can use without stripping the insulation, or maybe without digging it out? Any advise will be appreciated.
[img]/forums/images/icons/tongue.gif[/img] Yes, there is. You can disconnect the cable at both ends, connect the spark plug wire from your tractor to the suspected leg. The take an AM radio that is slightly off-tuned and walk the line. You'll hear the static in the radio when you get to the break. I'm going on record as being a life-long opponent of the use of direct-burial cable, and THIS is why. A few hundred dollars worth of PVC conduit is CHEAP INSURANCE against power cable damage. [img]/forums/images/icons/tongue.gif[/img]
CJDave
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I'm going on record as being a life-long opponent of the use of direct-burial cable
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I'm with you. I know it's common for both electrical and telephone, but not something I would do on my own property.
I just buried two runs and although I considered direct burial I chose to use plastic conduit. Lowe's pricing helped drive my decision. Direct burial was $1.11 more per foot than the same 6-3 plus ground non burial. Plastic conduit was about 10-12 cents per foot so for a little work and some PVC glue I saved almost a dollar a foot for over 300 feet. That plus the fact that I didn't waste $ on burial cable running 80-90 feet inside a bld or having to put splices in the line.
If you have confirmed that the wire is in fact broken because it is connected to power ant one end but the wire at the other end is "dead" then a TDR would find the distance from the end of the cable to the break. I would use the TDR twice, once from each end of the suspect cable. The TDR will tell you how many feet from the end it is connected to it is to the break.
TDR stands for Time Domain Reflectometer. It is a standard piece of electronic test equipment, often built into a lineman's test set. It injects a signal into the line and measures the time for the reflected signal to bounce back. The signal is partially reflected by the broken end because it does not terminate the line in its own characteristic impedance. It is like wiggling a rope once and having the wiggle "bounce" back from the other end. Since you have a continuous cable of similar type you could use that to calibrate the TDR and get the difference between the intact and broken cables to a more accurate degree.
It might be harder to lay your hands on the TDR by far than it is to use it. I have one but we are not that close.
The spark plug wire thing with the AM radio does work sometimes. Tune the radio to a noisy place on the dial away from any recognizable stations. The little hand held radios work best. You may have to turn the radio around to point in different directions in order to note the difference in how strong the spark signal is.
You can also use a fence charger for an electric fence. Run a hot wire from the charger output to within a small fraction of an inch of the end of the cable in question so that the hot wire arcs to the cable with each pulse of the charger. Search with the AM radio just like with the spark plug version.
I found multiple wires from the meter when I was connecting a run to my well house. One of the runs was non bury Romex in 1/2 inch metal conduit to a foot below the surface and then just buried wire. The wire was BURNED off at the end of the conduit. I don't know how long it lasted but it was sure a DUMB thing for anyone to have done.
Pat
"I'm not from your planet, monkey boy!"
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?
[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]
CJDave
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]
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
"I'm not from your planet, monkey boy!"
[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]
CJDave
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?
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