Transcript The D.C. Scout Battery Distribution System Ground Locator

Presented by: H.J. Arnett Industries, LLC
D.C. Scout Purpose
 The D.C. Scout is used for locating resistive or non-
resistive current paths from DC Battery Distribution
System to building ground without de-energizing
components or loads in the system.
Battery +/- Lead
(-)
(+)
D.C. SCOUT
LOAD
Building Ground Lead
Current Flow
D.C. Scout Description
 Instrument consists of two basic parts:
A) Pulser Unit, used to pulsate current through
the DC battery – DC Scout – building ground loop
B) Pulse Detector Unit, used to detect pulses
generated by the Pulser Unit in the DC battery – DC
Scout – building ground loop
Operational Overview
 The D.C. Scout repeatedly opens and closes (pulses) the
closed circuit, established when D.C. Scout is connected.
Current flows from the (+) battery pole, through the wire
shorted to building ground, through the D.C. Scout
building ground lead, then back through the D.C. Scout +/battery lead to the negative battery post.
Pulse Detector
Battery +/- Lead
(-)
(+)
A
LOAD
D.C. SCOUT
B
Building Ground Lead
C
Current Flow
 Note that the ground detection system battery is the source of the
current flow, not the Scout.
Operational Overview
 The D.C. Scout Detector Unit can then detect and
show these pulses on the Detector Unit Meter where
the Pulse Detector Current Transformer Probe is
clipped over a wire in the current path.
 This systematic approach of noting where pulses have
been detected, then moving down the wire to where
pulses are not detected, pinpoints the ground fault
location.
D.C. Scout Precautions
 Always wear proper Personal Protection Equipment
when working on and around energized circuits
 Work involves energized circuits
 Inspect all energized equipment for proper installation
and functions before initializing work
D.C. Scout Limitations
 D.C. Scout Pulser Unit should be connected in parallel with
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grounded circuit (positive or negative ground); it will have full
battery voltage across it for a solid ground or partial voltage
across it for a resistive ground.
Pulse amplitude will be set for a minimum of 5 mA to a
maximum of 200 mA DC.
D.C. Scout Pulser Unit has two in-line fuses to ensure protection
of D.C. Scout and system it is analyzing. If more sensitive
protection is desired, a lower amperage quick-blow fuse may be
substituted; this would limit output capacity of D.C. Scout.
Under no circumstances should a fuse rating of more than 250
mA be installed in BATT FUSE or GRND FUSE fuseholders.
With both Switches A and B on, there is no current limiting
resistors in circuit and it is possible to quickly blow D.C. Scout
Pulser Units BATT FUSE or GRND FUSE.
Operation Instructions
 Follow all tag out and safety procedures for working on
energized circuits.
 Ensure all systems operators are aware of fault
situation and procedures to follow
 Determine if Ground is Positive (+) or Negative (-)
 Controls on D.C. Scout Unit will be set to locate the
problem. If it is a Positive Ground, set controls to (+)
GRD, or (-) GRD
Operation Instructions
 Set controls on the pulser unit as follows:
 If ground is positive (+), set Meter Switch C to (+).
 If ground is negative (-), set Meter Switch C to (-).
 Set pulse amplitude adjust control to minimum current
position.
 Set pulser ON/OFF switch to OFF.
 Verify fuses for battery fuse and ground fuse are 100 mA
(1/10A).
 Plug in D.C. Scout pulser Unit 120 VAC power cord.
Meter Switch CPositive or Negative
Ground Switch
Operation Instructions
 Set controls on the Pulser Unit as follows:
 If ground is positive (+), connect D.C. Scout Pulser Unit as follows:
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Connect black BLDG GROUND lead to building ground wire.
Connect red BATT. +/- lead to negative (-) bus.
 If ground is negative (-), connect D.C. Scout Pulser Unit as follow:
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Connect black BLDG GROUND lead to building ground wire.
Connect red BATT. +/- lead to positive (+) bus.
Negative Bus
Connection
Building Ground
Connection
Operation Instructions
 Adjust D.C. Scout Pulser Unit as follows:
 NOTE – A solid ground has zero resistance to ground. A
resistive ground will show up on both positive and negative
indicators, but one will show more strongly than other.
 If system voltage is 24, 48, 125 VDC with a solid ground:
 Set Switch A - ON (closed).
 Set Switch B - OFF.
 Set 5K/55K switch to 5K.
 Set 30mA/300mA meter range
 switch to 300mA.
Switch A and B
Operation Instructions
 Adjust D.C. Scout Pulser Unit as follows:
 If system voltage is 250 VDC with a solid ground:
 Set Switch A - OFF.
 Set Switch B - OFF.
 Set 5K/55K switch to 5K.
 Set 30mA/300mA meter range
switch to 300mA.
Switch A and B
Operation Instructions
 Adjust D.C. Scout Pulser Unit as follows:
 If system voltage is 24, 48, 125 or 250 VDC with a
resistive ground:
 Set Switch A - OFF.
 Set Switch B - OFF.
 Set 5K/55K switch to 55K.
 Set 30mA/300mA meter
range switch to 30 mA.
Switch A and B
Operations Instructions
 The D.C. Scout package has an External Pulse Indicator
Lamp. This lamp is handy for seeing when each pulse from
the Pulser Unit occurs, even when the user may be 40 yards
or more away from the Pulser Unit.
 Plug the External Pulser Lamp jack into the Pulser Unit
External Lamp Output plug. The lamp has velcro backing
to place it in the upper right side of the units lid when
open.
Operation Instructions
 Set up D.C. Scout Pulse Detector Unit
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as follows:
Plug pulse detector unit current
transformer probe into banana jacks
of on back of Pulse Detector Unit.
Turn on pulse detector unit by pulling
out on balance control knob.
Adjust balance control until meter
needle is centered on meter.
Perform a battery check by pressing
red button on back of unit; meter
needle should deflect to BATT OK
position on meter face.
Clamp current transformer probe
around red BATT +/- lead of pulser
unit.
Operations Instructions
 Set pulser ON/OFF switch to ON.
 NOTE – If turning on pulser causes any relay actuations,
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this relay and its wiring should be thoroughly investigated
to ensure these components are not the cause of ground
fault.
Adjust pulse frequency adjust control for desired pulse rate.
Slowest rate is a good place to start.
CAUTION – Do not adjust pulse amplitude to exceed 100
mA.
NOTE – Meter range switch may be changed to either scale
as required for adjustment.
Using pulse amplitude adjust control, adjust pulse meter to
read a minimum of 5 mA to a maximum of 100 mA.
Operation Instructions
 NOTE – In some cases, DC Scout Pulser Unit Pulse
Meter will not register minimum detectable ground
current of 4 to 5 mA (i.e., a highly resistive ground).
For this reason, manufacturer specifies DC Scout is
only effective for use on ground currents that generate
 5 mA reading.
 If a minimum of 5 mA cannot be obtained, perform
following:
 Turn pulse amplitude adjust control to minimum.
 Set both Switches A and B to ON.
 Slowly adjust pulse amplitude adjust control to 5 mA.
Operation Instructions
 The Pulse Detector unit meter needle
should begin deflecting left and right.
 Adjust sensitivity knob, on back of pulse
detector unit, for a wide deflection both
ways from center mark on meter scale.
 Clamp pulse detector probe around load
wires to trace pulse to grounded circuit.
 The Pulse Detector Unit meter needle
should now be deflecting right then left of
the meter center for each Pulse Unit pulse.
If the meter needle deflects to the left on
each pulse, reverse the clamp on direction
of the Detector Unit Probe.
Tracing the Fault
• Expose the load wire in the distribution panels, using caution to avoid
tripping any circuit breakers or disconnecting switches.
• Clamp the Detector Probe around each load wire and note the wire or
wires, which have pulses that coincide with the generated pulses.
Determine the locations of the panels or devices these circuits feed.
Continue to follow the pulses until the grounded wire or device is
found. BE SYSTEMATIC AND USE YOUR PRINTS.
Usage Tips
 At times there can be difficulty discerning between the
desired pulses on the Detector Meter and random
pulses, or “noise.”
 For those pulses/spikes, which are circulating from (-) to
(+) in the circuit, clamp the D.C. Scout’s Pulse Detector
Probe around both (-) and (+) wires at the same time. The
circulating pulses will cancel out and you should see only
the D.C. Scout’s pulse, which is not circulating on both the
(+) and (-) wires.
Usage Tips
 For those pulses/spikes that are radiating down a wire
and are not circulating, move down the wire, if possible,
to get away from noisy systems such as choppers, and
inverters. It may be necessary to decreases the
sensitivity of the Pulse Detector and increase the
amplitude of the D.C. Scout’s pulse in order to override
the remaining interference.
 The “Pulse Frequency Adjust” control on the D.C. Scout
Pulser Unit can be adjusted so that the frequency of the
Scout’s pulses stand out from the existing noise.
Additional Applications
 Locating A.C. Grounds:
 The D.C. Scout can be used to locate grounds on A.C.
system up to 480 volts, provided the following conditions
are met.
 The A.C. circuit must be totally de-energized and
disconnected from its source. This means all phase
leads and the neutral lead, if used.
 A 130 Volt D.C power supply must be available that is
capable of supplying 200 mA of current. This D.C.
voltage must be isolated from ground. This means that
the (+) and (-) leads each read zero (0) volts to ground
when energized.
Additional Applications
 Ground locating on Fire Alarm and Marine Systems:
 The D.C. Scout has been used successfully to locate
grounds on fire alarm systems, using the procedures
outlined.
 These procedures will be useful for marine systems as
well.
 We welcome comments, reports, and questions from
users.