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UTILIZING TEST HOLES
as a  
CABLE FAULT LOCATING METHOD
 
     No one in this business wants to dig holes or excavate for no reason, but there are times when no other alternative exists. There are situations, especially on secondary voltage underground cable, where your fault locating equipment simply cannot pinpoint the break in the buried electric cable. When these situations occur you may have no other choice than to excavate and manually test the underground cable.
 
     The news is not all bad, however. If performed correctly and intelligently we can limit the amount of digging that is necessary to locate an underground cable fault. As a matter of fact;
 
Any Fault On Underground Electrical Cable Can Be Located By Excavating No More Than 7 Test Holes - Regardless Of The Length Of The Circuit!
 
     That's right - any fault can be found with 7 test holes or less, regardless of the length of the section. A few conditions should exist to make this method easier, but these conditions are simple:
 
  • You must know, without question, a point where the cable is good and a point where the cable is bad. This area becomes your section. This section should have been determined during the testing phase.

 

  • The entire section of the cable must be accurately traced and marked. Again, cable tracing should have been completed prior to fault locating. Since you will be excavating the circuit to test the underground cable it is very convenient to know exactly where the cable is.

 

  • It is also very helpful if the entire section of cable is in an area accessable for digging. If there are driveways or other obstructions along the section you may need to adjust your test hole locations accordingly.

 

The Test Hole Method

 

  • Determine the exact halfway point between where you know the cable to be good and you know the cable to be bad. On longer sections this may require measuring.

 

  • Excavate the underground cable at this point and test it. Remember, test the cable with a load applied to the circuit and do not cut the neutral cable at any time!

 

Regardless of the test result, the section of cable we are working with has just been cut in half - now wasn't that easy?

 

  • If the cable tested "good" at this test hole the fault lies between this point and the load.

 

  • If the cable tested "bad" at this test hole the fault lies between this point and the feed.

 

  • Determine another point halfway between your first test hole and either the feed or the load, depending on the test result and repeat the process. Each test hole excavated cuts the section in half.

 

  • Regardless of the length of the original section of underground cable, each test hole cuts that length in half. At a certain point, whether the cable fault has been located or not, two of these test holes will be close enough together to connect them with a trench and splice in a new piece of cable between them.

 

     After the first test hole has been completed and the cable tested it may become tempting to reconnect the Spitfire and attempt to pinpoint the fault. This may be a practical approach if the section is very long, but generally speaking it will be a waste of time. The circumstances that prevented the equipment from pinpointing the cable fault the first time still exist on the circuit.