DC Ground Fault Location
GFAL - A and GFAL-B
User's Manual
By Samco Engineering
Table of contents
Sections
1.0
Introduction
2.0
GFAL- A, Description
3.0 GFAL- A,
Display meters
4.0 GFAL-
A, Control switches
5.0
GFAL- A, Field applications
6.0 GFAL-
A, Specifications
7.0 GFAL-
A, Appendix A, Battery Pack Maintenance
8.0
GFAL- A, Appendix B, Special application
Find the value of the fault resistance from
each polarity
9.0
GFAL- A, Warranty and Contact Information
10.0 GFAL-
B, DC Ground fault tracker unit
11.0
GFAL- B, Applications
12.0
GFAL- B, Specifications
13.0
GFAL- B, Appendix C, Battery Pack Maintenance
14.0
Appendix D, GFAL-A/B Method “Locating DC ground Faults”
15.0
Locating DC ground faults
16.0
Contact and training Information
1.0 –
Introduction
Hardware
The GFAL-A/B method to
indicate and locate DC ground faults is made up of two instruments,
the GFAL-A (Fig.1)
is the interrupter
unit, also this unit can be use on its own as a DC ground fault analyzer
instrument, it connect to the DC
distribution system with
a 3 cable harness.
The GFAL-B
(Fig.2) is the seek out unit, it has a removable sensor that wrap around
the conductors for troubleshooting purpose,
this unit require the
GFAL-A to locate DC ground faults.
Present methodology to indicate
DC ground faults
The existence
of a DC ground fault in a multi-feeder DC distribution system is commonly
indicated by voltmeters.
The voltmeters are attached
to the DC distribution system and will indicate ground faults; however,
if a second ground fault
with an equivalent resistance
is present on the opposite polarity the voltage equilibrium with respect
to ground is restore and
the voltmeters will fail
to indicate the ground faults.
There are
many other variations of this voltage imbalance measurements procedure,
a few examples are: the replacement of
voltmeters with light
bulbs, ground fault detector/alarm relays, or a current meter connected
at the center point of a voltage divider.
The major
problem with all the cited DC ground fault indication methods is
that they use the voltage imbalance technology for
indication.
Consequently, as mentioned
earlier, these methods and instruments will have erroneous or no
indication at all on multiple ground faults
if those faults are located
on opposite polarity.
After the
DC ground fault it has been detected by the monitor equipment, the
fault has to be located in order to correct the problem.
To find
the location of these faults is a very difficult task without having
the proper method, instrument and personal training in the art
of locating DC ground
faults.
The penalty for not locating these faults in a timely manner
could include a complete system shutdown costing hundred of thousand
of dollars per
day.
GFAL- A, DC Ground fault
Analyzer unit
Fig 1
2.0 – GFAL- A, Description
There
are 2 Input Connectors
1) CHARGER
Input
connector for the 12-18 VDC adapter.
The Green
LED next to the connector will light up when the charging adapter
is connected.
The Red
LED BATT LOW will light up when the battery need to be recharge.
2) PROBE
Input
connector for the positive and negative polarity and site ground of
the DC system under test.
3.0 –
GFAL- A, Display meters
There are 2 display meters
1)
VOLTS
The
voltmeter displays the AC or DC voltage from the point of connections
of the PROBE.
Remark
The voltmeter display is in volts e.g. 002 display representing 2 volts
disregard the zeros on the left side.
2)
MILLIAMPS
Display
the pseudo fault current from the PROBE point of contact trough the
Instrument
Remark
The
display is in milliamps, 02.0 mA represent 2.0 mA, disregard the zeros
on the left side
4.0 – GFAL- A, Control
switches
FUNCTION SELECT, 6 position switch
Remark
With the FUNCTION SELECT Switch in positions 2-6 the green LED at
the upper left corner of the FUNCTION SELECT
switch box should light
up, (otherwise the internal battery of the Instrument is discharged
or disable).
1)
OFF
In this
position, the GFAL-A instrument is turn off.
Remark
The battery recharge
function can be performed (and is recommended) with the FUNCTION SELECT
switch in the OFF position
2)
AC CONT
Read
the AC voltage from the DC system under test with respect to site
ground.
Remark
To perform this test,
the red (+) cable has to be attached to the system under test.
3)
POS/NEG
Read
the voltage between the Positive Polarity with respect to the Negative
Polarity of the DC system under test.
4)
POS/GND
Read
the DC voltage between the Positive Polarity with respect to site
ground of the system under test.
Remark
Also, enable the POS
POLARITY TO GND and the NEG POLARITY TO GND switches.
5)
NEG/GND
Read the DC voltage between the Negative Polarity with respect
to site ground of the system under test.
Remark
Also, enable the POS
POLARITY TO GND and the NEG POLARITY TO GND switches.
6)
LOC
Initiate
the interrupter function of the GFAL-A. Also, enable the POS POLARITY
TO GND and the
NEG POLARITY TO GND
switches.
The cycle
has two stages, for 6 seconds the ground fault circuit is open and
for 6 seconds the ground fault circuit is close.
Remark
When the LOC position
is selected the blue LED at the upper left corner of the LOC FLASH
PULSE wil be on for about 1 second
POS POLARITY TO GND , 7 position
switch
1 )
OFF
Disconnect
all the pseudo fault resistances from the positive polarity with respect
to site ground
2)
80
Insert
a 80 Kohm resistor from the positive polarity to ground
3)
60
Insert
a 60 Kohm resistor from the positive polarity to ground
4)
40
Insert
a 40 Kohm resistor from the positive polarity to ground
5) 20
Insert
a 20 Kohm resistor from the positive polarity to ground
6)
10
Insert a 10 Kohm resistor from the positive polarity to ground
7)
5
Insert
a 5 Kohm resistor from the positive polarity to ground
Remark
IF the FUNCTION SELECT
switch is at position POS/GND or NEG/GND and the POS POLARITY TO GND
switch is at any
position among 2-7,
the red LED in the box POS POLARITY TO GND will light up, indicating
that a pseudo fault resistance
from the GFAL-A is connected
to the positive polarity of the distribution system with respect to
site ground.
NEG POLARITY TO GND
, 7 position switch
1)
OFF
Disconnect all the pseudo fault resistances from the negative polarity
with respect to site ground
2)
80
Insert
a 80 Kohm resistor from the negative polarity to ground
3)
60
Insert
a 60 Kohm resistor from the negative polarity
to ground
4)
40
Insert
a 40 Kohm resistor from the negative polarity
to ground
5)
20
Insert
a 20 Kohm resistor from the negative polarity
to ground
6)
10
Insert a 10 Kohm resistor from the negative polarity
to ground
7)
5
Insert
a 5 Kohm resistor from the negative polarity
to ground
Remark
IF
the FUNCTION SELECT switch is at position POS/GND or NEG/GND and the
NEG POLARITY TO GND switch is at any
position
among 2-7, the red LED in the box NEG POLARITY TO GND will light up,
indicating that a pseudo fault resistance
from the
GFAL-A is connected to the negative polarity of the distribution system
with respect to site ground.
LOC, 3 position
switch
This switch increase (FAST) or
decrease (SLOW) momentarily the frequency
of the PULSE TRACKER to synchronize the
GFAL-A with the GFAL-B
At the center position the switch is
off
5.0 –
GFAL- A, Field applications
Application # 1 AC voltage on DC distribution
systems
Test
Directly read
AC voltage respect to site ground on DC distribution systems.
Used for
Verify the amount
of AC Voltage that exists between the DC distribution system with
respect to site ground.
It also will indicate
the presence of DC ground fault spikes in the DC distribution systems.
Caution:
“Phantom” Earth Grounds
A path to ground
through UPS can result in extremely hazardous AC voltages being present
between the DC system and the
grounded racks and switchgear enclosures.
This condition in case
of person come in direct contact with any conductor of the DC distribution
system can result in a
fatal shot.
Application # 2 DC
Voltage between polarities
Test
Directly read the DC voltage between the
positive polarity of a DC distribution system with respect to the negative
polarity.
Used
for
This test will verify any site voltage indication
attached to the DC distribution system.
Application
# 3 Positive voltage respect to site ground.
Test
Directly read the DC
voltage between the positive polarity with respect to site ground.
Used for
This test will verify any site
voltmeter(s) attached to the DC distribution system, and there is
not crossover contamination
between two battery independent systems.
Application # 4
Negative voltage respect to site Gnd.
Test
Directly read the DC
voltage between the negative polarity respect to site ground.
Used for
This test will verify
any site voltmeter(s) attached to the DC distribution system, and
there is not crossover
contamination between two battery independent systems.
Application # 5 DC alarm trip
points of operation
Test
By introducing a variable
resistance between a polarity of a DC system and site ground.
Used for
It will test the operation
and response of the DC alarm system.
If the site DC Alarm it is
properly working should trip when the introduced resistance is below
the set point
needed to trip the alarm.
Disconnected, out of commission
and out of specifications site DC alarms are quickly exposed by the
GFAL-A instrument, if the alarm does not respond
when the test resistance value is below the trip point
specify for the alarm.
Application # 6 Finding
the value of fault resistance from each polarity of a battery distribution
system
with respect to site ground.
Test
By performing two field
tests, the second test with the help of a pseudo resistor from the
GFAL-A unit connected between
the DC system with respect to site ground
and the use of calculation, the value of the fault resistance from each
polarity with
respect to site ground could be found.
Used
for
The voltage imbalance
readings on DC system are normally performed by voltmeter(s).
The voltmeter(s) data can not give
information on the actual value of the fault
resistance that exists from each polarity respect to site ground.
One resistance respect to ground
in one polarity cancels the effect (voltage imbalance cancellation)
from another resistance
respect to ground over the other polarity.
Note
To know
how to perform this method use Appendix B
Application
# 7 Extreme DC system voltages respect to
site ground
Test
The GFAL-A can determent
if the readings of 0.0 VDC from one polarity, and full DC voltage reading
from the other polarity,
with respect to site ground is the result
of a short circuit of one of the polarity with respect to ground, an
instrument failure
or is the result of an open connection from
the site ground detector unit.
Used
for
When a short circuit
occurs in a DC distribution system the voltage imbalance readings are:
full battery voltage from the polarity
without the short circuit and near 0.0 VDC
from the polarity with the short circuit.
When one side of a relay on
a DC alarm system fails open or a resistor on a voltage divider fails
open, the voltage imbalance
readings are; full battery voltage from the
polarity with the open resistance and near 0.0 VDC from the other polarity.
Remark
The point is that an open connection
and a short circuit to ground will yield the similar voltage readings
from the DC system with
respect to site ground.
The reliability of a DC System
having an open relay or resistor is totally opposite to the reliability
of the same system having a short
circuit from one polarity to ground.
Application
# 8 Predict Maintenance
Program
Test
Performing periodic
readings and creating data base files from both polarities of a DC
System.
Important data to collect are:
DC Voltage between polarities and respect to site ground, AC contamination
in the DC system,
DC ground fault resistance from each polarity
and DC Alarm system response and operation.
Used for
The base line readings from
a good working DC system are a very important data to have when grounds
fault materialize.
Application # 9 Miscellaneous
Applications
Help identify and quantified DC
ground faults on DC systems.
Can create balance or imbalance loads respect
to site ground on a DC systems up to 6 different values, from 5 K Ohm
to 80 K Ohm
With the help of a DC external power
source can analyze de-energize circuits.
With the help of a decade
resistor box can increase the input impedance of the Instrument respect
to site ground.
Useful to train technical people
on DC Ground fault theory and troubleshooting.
6.0 –
GFAL- A, Specifications
Operating DC range
12
to 270 VDC
Impedance Range
5 K to 10 M Ohm (5% accuracy)
Switching pseudo grounds
By opto-isolation, “Cold Switching”
Accuracy (full scale)
Minimum
5%
Environmental
30 to 125 Degrees F
Power source input
12-18
VDC
Internal battery life
24
hr (Rechargeable)
Display (volts and mA)
2, 3 ½ Digit LCD
Dimensions
12” x 7.5” x 11”
Weight
6 Lb.
Case (2 colors)
Gray and yellow
Warranty
1 yr.
Parts and Labor
7.0 – GFAL- A, Appendix A, Battery Pack
Maintenance
The internal battery assembly
consists of four (4) Nickel Cadmium (Ni-Cad) cells.
The voltage of the pack is
approximate 5.6 VDC at full charge.
Charging the Pack
If the red
LED BATT LOW turns on is time to recharge the battery pack.
A battery charging adapter unit is furnished
with the GFAL-A, the adapter has a nominal output voltage of 12-18
VDC and
a current capacity no less of 500 mA.
Continuously charging the batteries
will not damage the Instrument or the battery pack.
Also, it is recommended to
leave the charging unit a least one-day prior to using the Instrument.
It is no recommended to use
the GFAL-A when the BATT LOW alarm LED is light up, to continue operating
the instrument.
Install the charging
unit and when the BATT LOW alarm LED turns off the GFAL-A is ready
to be use again.
If the battery assembly is
completely discharged the Instrument has to be charge for a least
2 hr. before can be use.
The GFAL-A can be used with
the charger connected to the main AC line.
The GFAL-A should provide 24
hr of continuos operation when the battery pack is full charge.
Battery
pack replacement
Remove only the 10 screws around
the edge of the front panel.
The battery pack is attached
to the PCC, remove the tie-wrap and installs a new pack
It is recommended to leave
the charging unit a least one-day prior to using the Instrument.
If after 2 hr. of charging
the Instrument the BATT LOW alarm turns off the GFAL-A can be use with
the charging AC adapter
unit connected to the AC power.
Battery
Specifications
Voltage at full charge:
5.6 VDC
Current Capacity:
1600 mA
CAUTION:
Replace the battery pack only
with Nicad batteries with the same nominal voltage and current capacity
to avoid damaging the Instrument.
8.0 – GFAL- A, Appendix B, Special application
To find the value of fault
resistances from each polarity with respect to site ground on a DC
distribution system.
Let calculate these fault
resistance in a 130 VDC distribution system with a predominant negative
ground fault.
Note: All the voltage readings
are in absolute value no signs attach to the readings.
1) Measuring the voltage of
the Positive polarity with respect to site ground:
Vp = 90.0 V
2) Measuring the voltage of
the Negative polarity with respect to site ground:
Vn = 40.0 V
From the positive polarity
of the GFAL-A select a resistor Rfix with respect to ground that will
change the distribution system
positive voltage with respect to ground for
no more of 5% to 10% of it original value, assume that this resistor
is:
Rfix = 40 K Ohm
There will be some voltages
changes with respect to site ground now.
Voltage from the Positive polarity
with respect to ground after the Rfix resistor has been installed
Vpc = 81.0
V
Voltage from the Negative polarity
with respect to ground after the Rfix resistor has been installed
Vnc = 49.0
V
To calculate the fault resistance
from the negative polarity (Rneg)
Rneg = Rfix (Vnc / Vpc - Vn
/ Vp)
Rneg = 40 K (49.0 / 81.0 -
40.0 / 90.0)
Rneg = 40 K (0.605 - 0.444)
= 6.44 Kohm
To calculate the fault resistance
from the positive polarity (Rpos)
Rpos = Rneg ( Vp / Vn ) = 6.44
K ( 90.0 / 40.0) = 14.49 Kohm
If there is a predominant positive
ground fault just apply the same procedure, however install the fix
resistor
Rfix in the negative polarity to do the calculations.
Note: If some resistance of
knowing value still attached to the DC distribution system with respect
to site ground,
by an extra step in the calculation the value
of the fault resistances with respect to ground from each polarity
can accurately
be calculated.
Consult Samco Engineering to
obtain these extra steps.
9.0 – GFAL- A, Warranty and Contact Information
Samco Engineering warrants
this product the GFAL-A to be free from defects in material and workmanship
for a period of 1 year from the date of shipment.
LIMITATION OF WARRANTY
This warranty does not apply
to defects resulting from unauthorized modification or misuse of the
Instrument.
This warranty does not apply
to the replacement of the battery unit.
This warranty is instead of
all other warranties, expressed or implied.
Repairs will be made
and the instrument returned with transportation prepaid.
REMARK
Samco Engineering shall not
be liable for any indirect, special or consequential damages resulting
from the use
of this instrument.
Contact
Information:
Samco Engineering
Fountain Valley,
CA 92708
Phone: (714) 235 - 5901
E-mail: samcoeng@aol.com
Web-site: http://www.samcoeng.com
GFAL- B, DC Ground fault locator unit
Fig 2
10.0 – GFAL- B
Introduction
The GFAL-A/B
method to indicate and locate DC ground faults is made up of two
instruments.
Instrument A
GFAL-A is the
interrupter unit, this unit also can be use as a separate DC ground
fault analyzer instrument.
Instrument B
The GFAL-B is
the “tracker” instrument, this unit require the GFAL-A to operate.
10.1)
Description
Input connectors on the GFAL-B
CHARGER
Input connector
for the 12-18 VDC battery charger unit.
The green LED will be
on when the charger unit is connected to the GFAL-B.
SENSOR
Input connector for
the sensor test probe.
10.2)
Switch
POWER switch
In the ON position turn
the unit on, in the OFF position turn the unit off.
With the POWER switch at the
OFF position it is OK to re-charge the battery assembly.
10.3)
Display
Alphanumeric
display, MILLIAMPS
For software, battery low and
milliamps information.
The default or maximum mA current
that can be display is plus (+) or minus (–) 50.0 mA.
PULSE
TRACKER LED (blue color)
Will be briefly on (every 12
seconds a part) at the beginner of each tracking pulse cycle and will
be off for the
rest of the cycle.
CHARGER
LED
The charger LED will be illuminate
when the power adapter is connected to the power main.
11)
GFAL- B, Applications
The unique application of the
GFAL-B instrument is to track with the attached sensor unit the signal
produce by
the GFAL-A throughout the DC distribution
system to locate the ground fault.
If there are one or several
ground faults in the range of the instrument specification, it will
locate these faults.
12)
GFAL- B, Specifications
Operating DC range
12 to 270
VDC
Impedance Range
No load to the DC system
Environmental
30 to 125 Degrees F
Power source input
12-18
VDC
Internal battery life
24
hr (Rechargeable)
Display
LCD
Alphanumeric
Dimensions
12” x 7.5” x 11”
Weight
4 Lb.
Case (2 colors)
Gray and yellow
Warranty
1 yr. Parts and
Labor
13) GFAL-
B, Appendix C, Battery Pack Maintenance
The internal battery assembly
consists of four (4) Nickel Cadmium (Ni-cad) cells.
The final voltage of the pack
at full charge is approximate 5.6 VDC.
Charging the Pack
If the letter “b” (low battery
alarm indication) appears in the alphanumeric display, is time to
recharge the battery pack.
A battery charging adapter
unit is furnish with the GFAL-B, the adapter has a nominal output
voltage of 12 to 18 VDC
and a current capacity no less of 500 mA
Continuously charging the batteries
will not damage the Instrument or the battery pack.
The GFAL-B can be used with
the charger connected to the main AC line
Is recommended to leave the
charging unit connect to the GFAL-B a least one-day in advance to use
the Instrument.
It is not recommended to use
the GFAL-B when the letter “b” is displayed.
To continue operating the Instrument,
install the charging unit and when the “b” alarm disappear, the GFAL-B
is ready
to be use again.
If the battery assembly is
completely discharged, will be no alphanumeric display, the Instrument
has to be charge for
a least 2 hr. before can be use.
When the battery pack is full
charge, the GFAL-B should provide 24 hr of continuos operation.
Battery pack replacement
Remove only
the 4 screws around the edge of the front panel.
The battery pack is attached
to the PCC, remove the tie-wrap and install a new pack
It is recommended to leave
the charging unit a least one-day prior to using the Instrument.
Battery Specifications
Voltage at full charge:
5.6 VDC
Current Capacity:
1600 mA.
CAUTION
Replace the battery
pack only with Nicad batteries with the same nominal voltage and current
capacity to avoid
damaging the Instrument.
14.0 –
Appendix D, GFAL-A/B Method “Locating DC ground Faults”
14.1)
Introduction
The GFAL-A (Fig.1)
unit provides the means to analyze the DC distribution system
by introducing
a fix resistor to site ground and complete
an electrical circuit through the site ground fault resistance and the
battery system (Fig.3).
Also, makeup synchronization
with the detector unit GFAL-B (Fig.2) via the LOC FLASH PULSE switch,
and front
panel FLASH PULSE LED visualization.
14.2)
Troubleshooting a DC Distribution System
To begin troubleshooting a
DC DS Install the GFAL-A in a location close to the Battery Room or
main DC circuit breaker
panel.
CAUTION
Take all necessary precautions when making connections
or working on DC DS energized line or equipment.
The operation of the GFAL-A
Interrupter will disrupt the Control Room DC ground fault display and
or DC alarm system.
Always communicate with the control room operator
before install and turn on the GFAL-A interrupter.
Before attach the interrupter
to the DC DS disconnect as possible any instrumentation or electrical
apparatus that has
resistance between the DC
distribution system and site ground e.g. voltmeter,
DC alarm light bulbs or relays.
This operation will eliminate
unwanted activation of such equipment and will increase the sensitivity
and range of the
troubleshooting procedure.
A) Set the GFAL-A FUNCTION
SELECT switch on the OFF position.
Connect
the PROBE GREEN ground cable to site ground.
Connect
the PROBE RED positive cable to the battery positive polarity.
Connect
the PROBE BLACK negative cable to the battery negative polarity.
B) Turn the GFAL-A FUNCTION
SELECT switch to the AC/CONT position.
Verify that
the AC voltage with respect to the site ground is within the limits
established by the site DC DS specifications.
Normally
this reading should be no more than 5.0 VAC in DC DS, however UPS installations
without input transformer
could have a substantial
VAC reading.
C) Turn the GFAL-A FUNCTION
SELECT switch to the POS/NEG position.
Verify
that the positive polarity voltage with respect to the negative polarity
voltage is within the limits established by the site
DC DS specifications.
D) Turn the GFAL-A FUNCTION SELECT switch
to the POS/GND position.
Verify
that the positive polarity voltage with respect to site ground is within
the limits established by the site DC DS specifications.
Normally
this reading is half of the battery voltage plus or minus 10%.
If
the voltage reading of the positive polarity is bigger for more than
10% of the voltage reading of the negative polarity,
then the distri-bution
system has a predominantly negative fault.
Remark
Using the voltage imbalance
as an indication of DC ground fault activity is valid only if the method
to calculate the ground fault
from each polarity is applied
first and the value of the fault resistance from each polarity is
reveal.
Look at:
Application 8.0 – GFAL-A Appendix B
To find
the value of the fault resistance from each polarity with respect
to site ground on a DC distribution system.
E) Turn the GFAL-A FUNCTION
SELECT switch to the NEG/GND position.
Verify that
the negative polarity voltage with respect to site ground is within
the limits established by the site
DC DS specifications.
Normally
this reading is half of the battery voltage plus or minus 10%.
If the voltage
reading of the positive polarity is smaller for more than 10% of the
voltage reading of the negative polarity,
then the distri-bution system
has a predominantly positive fault.
F) How to
locate a predominant positive fault
For a predominant
positive fault set the FUNCTION SELECT switch to the NEG/GND position.
Set the
NEG POLARITY TO GND switch to the 80 K-OHM position.
If the MILLIAMPS
display is less than 03.0 mA rotate the NEG POLARITY TO GND switch to
60 K-OHM position
or less till the reading
is more than 03.0 mA.
It is recommended
no to increase the tracing current for more than 10.0 mA.
14.3)
GFAL- B, Set up
The
Ground Fault Analyzer and Locator GFAL-B (Fig. 2) is a hand held microprocessor
based unit, that provide
a display signal with a
Blue LED to help synchronize the GFAL-A, takes the signals from the attach
PROBE sensor
and display fault current
measurements in mA.
A)
Synchronization procedure
A
synchronize visual signal is needed to synchronize the GFAL-A with the
GFAL- B.
The
GFAL-A and the GFAL-B repeats a cycle every 12 seconds, where 6 seconds
are used for test and 6 seconds are
used for reference.
Because
there is not hardware connection or a transmitted signal between the
two units the synchronization process
is accomplish by direct
operator intervention.
Turn the
POWER switch of the GFAL-B to the ON position.
When the
PULSE TRACKER LED on the GFAL-B turn momentarily on is an indication
that the test cycle has begun
and the reference part of
the cycle has ended.
After the
PULSE TRACKER LED on the GFAL-B turn on and them off wait for
approximate 5 seconds, them rotate
the FUNCTION SELECT switch
on the GFAL-A to the LOC position.
On the next several
cycles of the two units there will be a shift between the FLASH PULSE
LED on the GFAL-A and
the PULSE TRACKER LED on
the GFAL-B.
By activating
the GFAL-A PULSE TRACKER switch to the FAST or SLOW position, the
cycle on the GFAL-A and
GFAL-B should be available
to synchronize.
Hint
If
the FLASH PULSE LED on the GFAL-A turn on before the PULSE TRACKER
LED in the GFAL-B turn on, move
the PULSE TRACKER switch
to the SLOW position.
If the FLASH
PULSE LED on the GFAL-A turn on after the PULSE TRACKER LED in the GFAL-B
turn on, move
the PULSE TRACKER switch
to the FAST position.
When the two flashing LED’s
turn on and off about the same time the two unit are synchronize
15.0)
Locating DC ground faults
15.1) Install
the GFAL-A as explained in Appendix D
15.2)
Synchronize the 2 units as explained in Appendix D
15.3) Connect
the magnetic sensor attach to the GFAL-B around the positive and
negative cable of a branch of a DC
distribution system where a search for a ground fault is suspected
to exist.
The main DC breaker panel is the best choice for
this initiation task.
Wait for at least four complete cycles and observe
the GFAL-B MILLIAMPS reading.
If no fault exists in the first branch tested, select
another branch until the ground fault has been located.
If the MILLIAMPS reading on the GFAL-B is continuously
more than + or - 3 mA a branch with a ground fault
has been identify.
NOTE: It
is very possible that more the one branch will have ground fault, in
this case adding all the reading from the
GFAL-B should be near or
equal to the reading of the GFAL-A.
15.4)
At the end of the test
Disconnect the GFAL-A and reinstall any equipment
or apparatus removed before ground fault troubleshooting.
Inform the Control Room or supervisor authority immediately
after finishing troubleshooting.
16.0)
Contact Information
:
Samco Engineering
Fountain Valley, CA 92708
Phone: (714) 235 - 5901
E-mail: samcoeng@aol.com
Web-site: http://www.samcoeng.com
Return to Home page
2008