Metrotech 9800XT SFL2 Series, Руководство по эксплуатации

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5 PRINCIPLES OF OPERATION
5.1 Functional Theory
Even an experienced user needs to review the basics of sheath fault locating before
proceeding. This will improve the changes of finding the fault and save valuable time.
Comparing electrical current to water flowing through a pipe applies extremely well to
fault locating. Trying to find a leak in a water pipe, you might seal off one end, pump
water into the other, and look for water to appear near the leak. The principles of sheath
fault locating are identical. The cable equivalent of sealing off the pipe is to lift all
connections at both ends of the cable, creating a high resistance open condition. The
“water” in this case is the current flowing through the cable towards the fault. We look
for the current “leak” with an A-Frame”
Both ends of the cable must be disconnected from ground.
The SFL Transmitter applies a low frequency signal (4.8 Hz) between and isolated
conductor with an earth fault and another ground point. This induces a signal into the
ground from the fault location. This signal pattern is detected by the A-Frame Receiver
contact probes.
A typical hookup for locating a sheath fault, also called a shield-to-earth fault, is
illustrated in
Figure 5-1 .