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5.1.3
Multiple Fault Patterns
The signal pattern created by two faults in a line is depicted in
Figure 5-3
. The two
faults are shown without the ground point. Notice that from a distance the two faults will
have the appearance of a single fault due to the equipotential circle around them both. As
you get closer, the individual faults become apparent. There is an area between two
faults where the A-Frame may give a false indication of another fault. This is caused by
the two faults canceling each other. Errors can be avoided in this situation by following
the procedure described in Section 7.7. We recommend that multiple faults be attacked
one at a time, i.e., whenever a fault is positively located, it should be repaired before
looking for the other faults.
F1
F2
Figure 5-3: Multiple Fault Signal Patterns
5.1.4 Distortion Due to Adjacent Conductors
Whenever an un-insulated adjacent conductor lies between a fault and the ground return
point; the return current tends to concentrate on the conductor instead of flowing through
the earth. This can cause shrinkage of the signal pattern near the fault, which would tend
to reduce the detectable signal away from the fault. By tracing the faulty conductor first
and looking for adjacent conductors before locating the fault, possible problems such as
this can be avoided.
