
350 Cable Survey System
DPN 402197 © TSS (International) Ltd Page 2 of 4
C.1 TONE INJECTION
The TSS 350 Cable Survey System is an active cable location system that detects
the magnetic fields associated with a tone carried on the cable.
To perform a survey on a cable, the 350 System can use any tone frequency up to a
maximum of 200Hz. In theory therefore, the System could be used to survey a live
power cable because of the mains frequency ‘tone’ that it carries. In practice however
this may not be possible or desirable for the following reasons:
❐ The tone must be single-phase.
❐ There may be many local sources of interference at the same frequency.
By injecting a tone onto a cable, you may select a frequency in the range 10Hz to
200Hz that is relatively free from interference. Refer to sub-section 6.2.2 for instruc-
tions to change the detection frequency of the 350 System.
C.1.1 Frequency Selection
Selection of a suitable tone frequency and current will depend upon specific circum-
stances. Note the following guidelines:
Generally, a low frequency is better for long cable runs and a high frequency is better
for short cable runs.
To avoid strong interference affecting the survey, the 350 System provides some
advanced signal monitoring facilities. These allow you to examine the spectrum and
to set a tone frequency in a region of relatively low background noise.
C.1.2 Connection to the cable
Throughout the length of the cable, the tone-carrying conductor must be insulated
from sea water. Where applicable, provide a good ground connection at the end of
the cable farthest from the current source.
C.1.2.1 Short cables
For short cables (of less than approximately 100km, depending upon the capacitance
of the cable) you will need access to both ends of the cable:
Table C–1: Effects of tone frequency choice
Advantage Disadvantage
Increased tone
frequency
Increased detection ranges available from the
350 System.
Decreased transmission distance for the tone
along the cable length.
Increased tone
current
Increased detection ranges available from the
350 System.
Increased noise generation in repeaters of fibre-
optic cables.
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