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24
SERIES
Fault locating determines the position of an insulated break on an underground conductor. Some signal
will return to the Transmitter via the Ground Rod through a break in the insulation.
It is generally a good idea to locate the conductor path before attempting to fault locate. If, during
the path locate, an unusual amount of signal loss occurs, a part of the signal has escaped to ground in
the last several feet. Lower frequencies will generally show a greater signal loss at a fault, but higher
frequencies may be needed to locate if resistance is too high.
n
ote
:
Signal would go to ground at a grounded splice point, which would act as a fault during the
path and fault locate.
Once the path is determined and a general area where a fault is expected, additional current can be
forced to flow through the fault by disconnecting and isolating the far access point. If the current has
no path to ground at the far access point, it will be forced to seek ground at the fault. This will increase
the current in the soil at the fault and ease the detection of the fault.
BURIED CABLE
FAULT
RETURN PATH THROUGH SOIL
A
B
NEAR ACCESS POINT
FAR ACCESS POINT
EARTH
BLACK
RED
EARTH
EARTH
CABLE (END VIEW)
THE GROUND RETURN PROBE FRAME
SHOULD BE IN LINE WITH, AND
DIRECTLY ABOVE THE CABLE PATH.
CABLE (SIDE VIEW)
BOTH SPIKES SHOULD EVENLY
PENETRATE THE GROUND AND
MAKE GOOD ELECTRICAL CONTACT.
Set the Transmitter to fault mode by pressing and holding the frequency button for 10 seconds. When
released the DFF symbol on the LCD will be displayed.
Place the
a-
frame
connected to the receiver (or STAFF) into the ground between the ground rod and
the fault with the front spike toward the fault and the back spike toward the ground rod (Approx. 2
yards or 2 meters from ground rod).
Turn the
receIver
on. The receiver LCD should indicate DFF for fault mode. Press the
mode
button to
toggle out of
dff
mode and cycle back to
dff
mode. This will sync the receiver to the transmitted
signal. As you walk the path using the GRP, place the probe every three or four steps. The bar graph
will indicate the direction of the fault by blinking at the top for forward and the bottom for backward.
The
staff
will blink the appropriate arrow. As you near an area of high current concentration in the
soil, the Ground Rod or the fault, the center bars of the bar graph will blink faster or stay on. The
fault lies in the center of the Ground Return Probe spikes.
Circuitry between the ground spikes provides a path for current in the soil returning to the
G
round
r
od
. The current enters one spike of the
G
round
r
eturn
P
roBe
and exits the other spike. The GRP
should be inserted into the soil with consistent force and depth.
f
ault
l
oCating
With
the
a-frame
or
staff