VON SST15-832, Руководство по эксплуатации

Страница: 12 / 22

VON MODEL SST15-832 ARC REFLECTION SECTIONALIZING SYSTEM Page 10
VI-B HINTS AND TYPICAL TRACES
1. The radar must show the faulted cable ends before any attempt is made push
the START button which automatically puts out a high voltage pulse.
2. Remember that the magnitude of down blip at the fault can not be greater than the
magnitude of the up blip due to an open circuit at the same point.
3. If different types of cable are spliced together, the trace itself can go up or down after
the discontinuity at the splice.
4. The first step in sectionalizing using radar is to find both ends of the cables. This is
done by touching each end to ground and finding the left most point where the trace
changes direction.
5. Notice that locating the beginning of the cable by shorting it to ground requires the
most skill. Everything past the fault changes.
6. Notice that a short at the end of the cable is easy to find and locate.
7. Remember that the first major divergence between the reference trace and the
active trace is what you are looking for. The down blip at the fault may not be
down on the screen but only below the reference trace. In some faults at the
divergent point the captured trace is a straight line while the reference trace goes
up. This is most likely to happen on very short cable where the cable trace is
very wavy.
8. When the cable trace looks similar to the trace of the end of the test lead alone
then the faulted cable is very short (most likely burned in two pieces) Very short
runs have a large number of ups and downs in the waveform.