Vivax Metrotech vLoc3 Series User manual

vLoc3 Series A-frame User Guide V1.1
The vLoc3 series A-frame accessory is used to detect ground faults on pipes and cables. In the
case of pipes, the faults consist of coating defects. In the case of cables, faults are usually caused
by insulation damage allowing the metallic sheath (or internal conductor) to become in contact
with the ground.
It is intended to be used with the vLoc3 range of receivers and will require a fault find frequency
applied to the faulty conductor from a Vivax-Metrotech compatible transmitter.
vLoc3 Series A-frame Overview
Using the vLoc3 Series A-frame Fault Finding Accessory
P/N:4.04.000110
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Accessory A-frame receiver
Rubber spike cover
Interconnect cable
Quick guide
A-frame soft carry bag
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Note
Fault finding requires a non standard frequency. Historically there have been many versions of
fault finding frequencies. Some of these are listed below:
- 3/6Hz Fault find (Used to detect faults on pipelines)
- Signal Select Fault find (Good for fault finding on short runs such as power networks)
- SD Fault find (General purpose fault finding)
- 8kFF (General purpose fault find with good results on short and long runs and has good sensitivity)
For the purposes of this manual 8kFF is concentrated on as it gives the best overall performance.
To detect a damaged section, the line should be isolated and have all ground bonding removed. This
will ensure that the ground fault is not masked by deliberate bonding to ground. The A-frame cannot
distinguish between these two situations.
After isolating the line, use a Vivax-Metrotech transmitter with DC resistance measuring function, or a
dedicated resistance measuring device to confirm that there is a fault to ground. The A-frame will
typically detect faults up to 2 Mohm (depending on the distance from transmitter, soil conditions etc.)
Connect the transmitter to the target line using the red lead. A ground stake needs to be pushed into
the ground and the black cable clipped to it. Try to place the ground stake as far as possible from the
line to be evaluated. This ensures return currents do not distort the results. Switch on the transmitter
and select either 8kFF low or 8kFF high. Use 8kFF high if the line to be surveyed is long or the fault
resistance is high. Make sure the receiver and transmitter are set for the same FF type, i.e. 8kFF.
Plug in the analogue A-frame to the receiver accessory socket. When the receiver is switched on, it
will automatically default to the A-frame screen.
55
8kFF LOW
mA
26 dB
8KFF
Log
6

The above image is for reference only and may differ from actual image
Remove the rubber spike covers from the A-frame. Walk along the route of the line placing
the spikes of the A-frame in the ground (with the green leg pointing away from the transmitter
connection point) every two or three paces. If starting near the transmitter, the arrow on the
display will point away from the ground point. As the distance from the transmitter increases,
the dB reading will reduce and eventually the arrow will fluctuate or disappear altogether.
This is because the fault location is further along the line. Use the left/right arrows to ensure
the A-frame is positioned over the line and continue placing the A-frame in the ground every
two or three paces. If necessary, use long presses on the “M” pushbutton to enter the
locate screen allowing the user to confirm the position of the target line. Use a long press
on the “M” pushbutton again to re-enter the A-frame mode.
(Note that the A-frame is not shown connected to the receiver so as to simplify the diagram)
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26 dB
8KFF
Log
6
20 dB
8KFF
Log
6
26 dB
8KFF
Log
6

Disclaimer: Product and accessory specification and availability information is subject to change without prior
notice.
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Eventually the A-frame will detect the fault signal and the “Fault Find” arrow will point forward.
Continue moving forward, it may be worth reducing the distance between measurements points
as the fault is neared. The dB reading will increase as the fault is neared. Maximum reading will
be just before and just after the fault. When over the fault, the dB reading will drop, and the
arrow will flip backward indicating that the position of the fault has been passed.
Carefully place the A-frame before and after the fault to pinpoint the position. Repeating this
across the line direction will pinpoint the fault laterally. The fault will be at the point where the
lateral fault is identified.
Vivax-Metrotech Corp. (Headquarters)
3251 Olcott Street, Santa Clara, CA 95054, USA
T/Free: [phone]
Tel: [phone]
Fax: [phone]
Email: [email protected]
Website: www.vivax-metrotech.com
Visit us at www.vivax-metrotech.com to view our full product line and worldwide locations.
WARNING
Always disconnect or isolate target/faulty/suspected cables before
connecting the transmitter to it. Never attach the transmitter to live cables.
TIP
If it is suspected that there is just one fault, insert the A-frame approximately
one meter from the earth stake. Note the dB reading - this is approximately
the maximum dB reading that will be measured over the fault.