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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.
