Page 12 - EngineerIt April 2021

MEASUREMENT AND INSTRUMENTATION

Cable locator for failsafe cable

fault diagnostics

By Lourenco Menezes, Comtest Sales Account Manager

Accidentally hitting a power cable during a project can lead to costly
repairs and create seriously hazardous safety situations. Digging in the
wrong place can also lead to significant and unnecessary delays, not to
mention run-on costs for the project.

he Amprobe rugged and durable Features of the AMPROBE UAT-600 series
UAT600 series is specifically The locating kit comes complete and ready for use with a transmitter, receiver, test lead kit,
Tdesigned to accurately pinpoint batteries and additional fuses, all in a mobile, protective duffle bag. The UAT-620 kit also
underground utilities and buried services up includes a Signal Clamp for transmitting a signal when it is not possible to make electrical
to 30m deep and has accuracy to a depth contact with the cable to be traced. For applications where ground fault locating is required,
of 6m - ideal for locating pipes and cables. the UAT-600 Transmitter can be used in combination with the optional A- Frame accessory.
Mines generally use Thumper
technology for cable fault location - a Main applications
portable high voltage (+25kV) surge • Locates energised 50/60 Hz cables carrying current
generator into the cable. At the fault, a • Identifies the location of all metallic utilities: pipes*, energised and de-energized cables
high-current arc makes a thumping sound. • Traces individual pipes* or cables (energised or de-energized)
Disadvantages of thumping are that it is very
time-consuming, and the cable, exposed to Three testing modes for wide range of applications
high voltage surges, may be degraded and • Passive power mode (50/60 Hz) – tracing energised lines conducting current (no
will definitely require re-insulation. It also Transmitter necessary)
can’t find short circuit faults. • Passive radio mode (RF) – using surrounding radio waves to trace underground
In December 2020, a Free State Gold utilities (no Transmitter necessary)
Mine had a damaged cable incident, • Active mode using UAT-600-T Transmitter
and the breach needed to be pinpointed
urgently. An external Thumper contractor
was called in and the eventual diagnosis
was that the damaged cable was at a length
of 120m. An excavation team was called
in and dug to that length. Unfortunately,
no breach in the cable was found. A new
channel was then dug at 60m and still
no fault was found. On the third tracing
attempt they located the breach across the
road and on a different cable.
The consequence of the cable breach/
fault was numerous days of lost production,
and the cost of the Thumper analysis. For
the cost of an AMPROBE UAT600 cable
locator, the mine would not only have
reduced the risks associated with the test,
but have an instrument that is able to give
an accurate reading, location diagnosis and
solution within a day.

EngineerIT | April 2021 | 10