Locating short in power line to well

[wykubotaguy]

Don't know exactly what a tdr is? I am an electrician and we have a locator with the a frame unit and it will locate line breaks and shorts down to 20ft. The line locator is not spot on exact so your break could be 1-2 feet either direction from his locate. But in my opinion, you already paid 195 for the locate and you said the length to pump is approx 110 ft? Get new pump wire or cable (whatever pump company recommends), probably cost you 350 to 400 and put in new line with conduit. Total cost by yourself $450-650.

 

[Rob-D]

Wheatstone bridge

National High Magnetic Field Laboratory - Wheatstone Bridge Tutorial

With the 4th resistor being your wire, you can determine extremely accurately how far away the short is.

However, there are times when a wire will not show a short without a load, but when load is applied, the wire fails. Using a megger to test the insulation can show if the insulation is breaking down.

With all that said, I would run new wires in conduit and forget about it.

You can't do it! Sorry, there's no way of knowing the resistance of the short, wheatstone bridge or not!
The best you can do is the ratio method I showed below because that takes into account the resistance of the short.

Rob

 

[Pilot]

After due consideration, including everybody's input here as well as guys I know, the plan is to dig a trench and put in a new wire inside conduit.

Cat-driver: System works fine with temporary above ground wire and the existing underground wire has shorts, to it's not the pump or water level. System was checked out by a well service guy who ran the temp power line after replacing components in the control box that blew--relay, capacitor, etc.

Thanks for everybody's input. It'll be awhile before the work is done, the weather turned on us the day after the system failed. It's snowing and 32 now, forecast to see high teens in a couple days with precip every day for the 7 day forecast. It will improve, the job will get done and life will be back to normal.

 

[techman]

Don't know exactly what a tdr is?

Just FYI A TDR is Time Domain Reflectometer. Resistance measurements are limited, since copper's resistance changes with temperature, and if the short is not a dead short, the readings can be bogus.

In a TDR, a pulse of 1 to 100 nS is applied to the end of the wire. A short, broken wire or even a resistance across the conductors will result in a reflection of the pulse. This is read and displayed. By the nature of the reflected signal, you can tell if it is a short, open or resistive short. The telco and cable guys use them to locate wire problems and to pinpoint the location.

Paul

 

[Rob-D]

Just FYI A TDR is Time Domain Reflectometer. Resistance measurements are limited, since copper's resistance changes with temperature, and if the short is not a dead short, the readings can be bogus.

In a TDR, a pulse of 1 to 100 nS is applied to the end of the wire. A short, broken wire or even a resistance across the conductors will result in a reflection of the pulse. This is read and displayed. By the nature of the reflected signal, you can tell if it is a short, open or resistive short. The telco and cable guys use them to locate wire problems and to pinpoint the location.

Paul

Thanks for the info, I didn't know about the instrument or how it works.

Good luck Pilot!

Rob

 

[manganos]

Fix it yet? I love the talk of Wheatstone Bridges and TDR's lol. I was a cable splicer turned engineer for Bell Atlantic/ VZ. Took the last buyout in July 10 and haven't looked back.

I'm with the others. I'd also put everything back to normal and see if you are getting the Voltage at the pump end just to confirm the wire is bad.


Next time put it in conduit/innerduct and run a few pullstrings with it.

Good luck and let us know what you do!

 

[Pilot]

Well, the well job is finally done. Had to replace the pressure tank as well. Came out pretty spendy, but I paid for most of the work.

Here's how it broke down:

Locator service: $195.
Trench, dug & filled by a 19 year old who needed the money who was willing to work in the wind and rain at 35 degrees and dig down thru 2 ft. of sticky clay soil, $152.
Materials, about $355 and that's with a 10% vet's discount at HD.
Electrician, an Air Guard retiree who does this kind of work as a retirement business and only charges $35 an hour, $326. I helped some, but we chatted a lot and the chat time is in the bill.
Well company, 2 visits, check the system, hook up temp power, then return to install new tank, $768.

Total, $1,796.

Then about 3 days after the job was done, the garage door broke This hasn't been a very good month and it's only half over!

But now the well works, the trench is filled in waiting for peat moss and grass seed, the garage door is fixed...so it's back to normal. Life is good.

 

[DougM]

Pilot.....In this Job that was just completed the one that WORKED the hardest was paid the least hmmmmm