To determine the cause and location of a cable fault, it is necessary to locate the existing cable route. The first step is to research the as-built drawings to determine the installed cable route. Past history has shown that as-built information is, at best, sketchy and, in many cases, nonexistent. Cable location surveys should be conducted with the procedures described in Section 4.4.8. In locating and surveying the cable, some success has been achieved through the use of magnetometers. For example, the buried pipe and chain locator discussed in Section 2.2.8 may be used to track armored cables. A significant problem in the use of magnetometers is that they respond to any magnetic anomaly in the area, resulting in time lost checking on false readings. Another method is the use of a steel probing bar to locate the cable, but this method is very time consuming and costly.
An effective commercially available cable tracking system developed for UCT use consists of a diver-held electronic probe, a shore-based (dry) signal generator, and an underwater signal injector. This system provides the capability to locate the track cables on the beach as well as underwater. It also provides a mechanism to estimate the burial depth of cables. It is considered an "active" system in that it tracks a tone that is specifically placed on the conductors of the cable.
The probe, illustrated in Figure 5-3, is a submersible hand-held electronic device that is designed to detect a 25- and 1,024-hertz magnetic field. Depending on the strength (current level) of the impressed signal, the probe will track exposed or buried cable from about 100 feet away to its
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