DEVELOPMENT, MANUFACTURING AND SUPPLY OF INSTRUMENTATION
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3. Amplitude «two-frequency» method
«ΔA»
This method was added for contactless search of insulation defects of city cables with
resistance less than 5 kOhm. The smaller the distance to the end of the cable, the higher the
sensitivity of the method on this site.
The method decription:
the two-frequency signal is transmitted from the generator. The ratio
of two-frequency signal amplitudes remains stable, if there is no damages in cable. At presence of
damage, the ratio of amplitudes in the place of damage is changed.
1. Exit output of the generator
should be connected to the
«start» of communication (more
distant from the supposed place
of the defect). The other output
of the generator is grounded on
the maximum possible distance
from the communication. The
«end» of the communication is
not grounded.
2. The transmitter in the mode «2F»
sends to the communication the
signals of two frequencies (1024Hz
and 8192Hz) simultaneously.
3. The defect localisation is performed in
direction «from generator».
4. The value «A8/A1» is sharply changes, when operator
passes the place of leakage of the signal current into the ground.
Note
A8/A1 indication can have negative value. In such cases it
recommended to reset indication periodically, using the button
«
».
5. The «double» 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
«X.XdB» 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.
Table 8
Содержание AP-019.1
Страница 1: ......
