fault in 200 amp direct burial cable

2 replies [Last post]
david49@infowest.com's picture
Joined: 2014-03-16

I have a  200 amp aluminum direct burial cable running about a 1,000 ft, which powers a pump. At the meter we have 110 volts on each leg and 240 volts between legs. At the pump I have 110 volts on each leg and 0 volts between legs. Of course the pump does not run. I assume this is caused by the insulation being removed by a rodent. How do I find the exact location of my problem?

darrin's picture
Joined: 2013-12-02

If I was you, I would hand dig the entire length. When you get to the service end, land one wire one one phase and the other on a different leg/ phase. Call an electrician in the morning.after your Chiropractor. LOL

mdshunk's picture
Joined: 2014-03-14

There are many types of instruments in the marketplace for finding the fault location on buried cables, but two methods seem to prevail. One is the typical buried cable locator tool, such as many contractors and utility locate techs use. The signal will drop out, or change in nature, at the point of the fault or open. Some of these buried cable locators have additional special functions that can help find opens a little more accurately, but even the most crude tool will get you within a backhoe bucket's width of the open.

The other method is what I use, called a "thumper" for slang. It sends a high voltage impluse down the cable, which will actually "thump" earth in the location of the fault. You can feel it in the soles of your boots, and you know exactly where to dig.

Don't be so quick to blame rodents on your failure. Direct buried aluminium cable, while certainly popular, falls in to the "incredibly bad idea" category for me. More often, you'll find a rock or stone has worked its way through the insulation, the aluminium starts to corrode, and the aluminium is actually fouled for many feet on each side of the actual failure. I think most would agree that pipe and wire provides a more sturdy and more serviceable installation. When you perform your repair (think Raychem, please), fill under and around the cable with flowable fill material like sand or stone dust before the earth is replaced.

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