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32
USER MANUAL
Figure 18
– Connecting diagram and phase shift at the phase method of
cable insulation failure locating
Connect one lead of the GT-15 Transmitter to a damaged conductor
(see Figure 18). The opposite end shall be protected. The second
lead of the Transmitter shall be grounded with a pin placed at the
distance of no less than 5m from the cable. Preset the double
frequency «
φ
».
Select the TRACE mode and frequency of the «φ 8928» on the
Receiver. Stand directly over the utility line at the beginning of the
tested plot. Make sure that you are not closer than 20m to the point
of connection of the Transmitter. Press the «
» button on
the Receiver to reset the phase indications. Move along the target
line, directly over it, and control the position with the null scale; take
phase readings carefully. The phase may change smoothly. The
phase readings will rise abruptly by several scale units behind the
area of insulation failure. When you pass the area with damaged
insulation, the phase readings will change smoothly.
The failures of this method are as follows:
phase fluctuation within the areas of damaged insulation is less
obvious than signal fluctuation by the insulation control sensor
tracing method;
interferences from adjacent utilities.
5.3.4
Tracing the area of wire break
In case the cable is inaccessible or protected with metal armature,
perform a high- voltage burn-down of the cable to achieve stable
short-circuit of the broken conductor to the adjacent wire or armature.
To make further search follow the steps.
