DEVELOPMENT, MANUFACTURING AND SUPPLY OF INSTRUMENTATION
41
7. The sharp positive overfall of the «A8/A1» value by 3dB and
more indicates the possibility of defect existance(the resistance
is less than 5 kOhm). The sensor should be located straight
across the communication.
If you go through the same site in the opposite direction
(towards the generator), holding the receiver the same as before
with reset of the indication (using the button « »), negative
value of the reading (more than minus 3dB) will mean that there
is damage in the cable.
8. To validate the existance of the
damage, use 2contact method, using.
(the methodology in app. 2 of p.1.2)
4. Phase «two-frequency» method «
Δφ»
The contactless method of search for insulation defects of city cables with resistance less
than 10 kOhm. The smaller the distance till the end of the cable, the higher the sensitivity of the
method on this site. This method cannot be used in city because of high distortion of the signal.
Steps 1-3
are similar
to those in
p.3.
4. «Δφ»
shows - the change of the phase
difference
«φ
1024
– φ
8192», after the
resetting (in degrees reduced to the frequency
1024 Hz). The value
«Δφ»
is sharply changes,
when operator passes the place of leakage of
the signaling current into the ground.
Note
Δφ
indication can be negative, «running» in the
process of increase of distance from the
generator. It is recommended to periodically
reset such indications (exactly over the route),
using the button «
».
5. The «doubled» scale
shows levels (amplitudes) of
the frequency components of
the signal. At bottom - A8kHz,
at top - A1kHz. When levels of
the frequency components are
insufficient for determination
A8/A1, the inscriptions A8kHz
and A1kHz are correspondingly
«darkening», and the value «X0»
disappears.
6. There is no need to
continuously move along
the route, controlling
the signal. You can walk
around the place which
is hard to reach. If, while
returning to the route, A8/
A1 did not changed, it
means that there are no
damages on the surveyed
site.
Summary of Contents for AP-019.1
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