Download DC Scout Operations Procedures

CNS OPERATIONS MANUAL
MAINTENANCE PROCEDURE 7.3.27.2
125/250 VDC SYSTEM GROUND LOCATOR
1.
2.
3.
USE: REFERENCE
QUALITY: QAPD RELATED
EFFECTIVE: 3/27/03
APPROVAL: ITR-RDM
OWNER: MNT-E SUPT
DEPARTMENT: MNT-E
RISK SIGNIFICANT PROCEDURE 1
P&I: 1
PURPOSE ......................................................................................................................... 1
PRECAUTIONS AND LIMITATIONS ................................................................................. 1
INSTRUCTIONS ................................................................................................................ 2
ATTACHMENT 1
ILLUSTRATIONS .............................................................................. 5
ATTACHMENT 2
SIGN-OFF AND REVIEW SHEET..................................................... 7
ATTACHMENT 3
INFORMATION SHEET .................................................................... 9
REVISION VERIFICATION:
(initial use + every 7 days)
REV.
DATE
CHANGES
1
7/31/01
Reformatted per latest 0-PWG-01 guidance. Updated EBS
terminology.
2
3/27/03
Corrected typo. Added NOTES and enhanced instructions. Added
Vendor Manual to References.
1. PURPOSE
1.1 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. The procedure is not intended for use on the 125 VDC PMIS and
Security Distribution Systems.
2. PRECAUTIONS AND LIMITATIONS
2.1 Work involves energized circuits.
2.2 D.C. Scout Pulser Unit should be connected in parallel with 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.
2.3 Pulse amplitude will be set for a minimum of 5 mA to a maximum of 100 mA DC.
2.4 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.
2.5 Under no circumstances should a fuse rating of more than 100 mA be installed in
BATT FUSE or GRND FUSE fuseholders.
PROCEDURE 7.3.27.2
REVISION 2
PAGE 1 OF 9
2.6 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.
3. INSTRUCTIONS
3.1 Have Operations Caution Tag ground detection switches on associated charger to
ensure switches are not operated while checking for grounds.
NOTE – Pulling metering fuses will de-enerize local and remote voltmeters, and ground
detection relay and lights for associated switchgear.
3.2 Obtain Clearance Order for metering fuses in top right cubicle of associated
switchgear.
3.3 (QC Witness) Mark and lift Leads P and N on K6 (GDA) relay in associated charger.
3.4 Determine if ground is positive (+) or negative (-).
3.5 Set controls on pulser unit as follows:
3.5.1 If ground is positive (+), set Meter Switch C to (+).
3.5.2 If ground is negative (-), set Meter Switch C to (-).
3.5.3 Set pulse amplitude adjust control to minimum current position.
3.5.4 Set pulser ON/OFF switch to OFF.
3.5.5 Verify fuses for battery fuse and ground fuse are 100 mA (1/10A).
3.5.6 Plug in D.C. Scout Pulser Unit 120 VAC power cord.
3.6 If ground is positive (+), connect D.C. Scout Pulser Unit as follows:
3.6.1 Connect black BLDG GROUND lead to building ground wire.
3.6.2 Connect red BATT. +/- lead to negative (-) bus.
3.7 If ground is negative (-), connect D.C. Scout Pulser Unit as follow:
3.7.1 Connect black BLDG GROUND lead to building ground wire.
3.7.2 Connect red BATT. +/- lead to positive (+) bus.
3.8 Adjust D.C. Scout Pulser Unit as follow:
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.
3.8.1 If system voltage is 125 VDC with a solid ground:
3.8.1.1 Set Switch A - ON (closed).
PROCEDURE 7.3.27.2
REVISION 2
PAGE 2 OF 9
3.8.1.2 Set Switch B - OFF.
3.8.1.3 Set 5K/55K switch to 5K.
3.8.1.4 Set 30mA/300mA meter range switch to 300mA.
3.8.2 If system voltage is 250 VDC with a solid ground:
3.8.2.1 Set Switch A - OFF.
3.8.2.2 Set Switch B - OFF.
3.8.2.3 Set 5K/55K switch to 5K.
3.8.2.4 Set 30mA/300mA meter range switch to 300mA.
3.8.3 If system voltage is 125 or 250 VDC with a resistive ground:
3.8.3.1 Set Switch A - OFF.
3.8.3.2 Set Switch B - OFF.
3.8.3.3 Set 5K/55K switch to 55K.
3.8.3.4 Set 30mA/300mA meter range switch to 30 mA.
3.9 Set up D.C. Scout Pulse Detector Unit as follows:
3.9.1 Plug pulse detector unit current transformer probe into banana jacks of on back
of Pulse Detector Unit.
3.9.2 Turn on pulse detector unit by pulling out on balance control knob.
3.9.3 Adjust balance control until meter needle is centered on meter.
3.9.4 Perform a battery check by pressing red button on back of unit; meter needle
should deflect to BATT OK position on meter face.
3.9.5 Clamp current transformer probe around red BATT +/- lead of pulser unit.
NOTE – If turning on pulser causes any relay actuations, this relay and its wiring
should be thoroughly investigated to ensure these components are not cause of
ground fault.
3.9.6 Set pulser ON/OFF switch to ON.
3.9.7 Adjust pulse frequency adjust control for desired pulse rate.
PROCEDURE 7.3.27.2
REVISION 2
PAGE 3 OF 9
CAUTION – Do not adjust pulse amplitude to exceed 100 mA.
NOTE – Meter range switch may be changed to either scale as required for
adjustment.
3.9.8 Using pulse amplitude adjust control, adjust pulse meter to read a minimum of
5 mA to a maximum of 100 mA.
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.
3.9.9 If a minimum of 5 mA cannot be obtained, perform following:
3.9.9.1 Turn pulse amplitude adjust control to minimum.
3.9.9.2 Set both Switches A and B to ON.
3.9.9.3 Slowly adjust pulse amplitude adjust control to 5 mA.
3.9.10 Pulse detector unit meter needle should deflect right, then left of meter center
for each pulser unit pulse.
3.9.11 If meter needle deflects to left on each pulse, reverse clamp on direction of
current transformer probe.
3.9.12 Adjust sensitivity knob, on back of pulse detector unit, for a wide deflection both
ways from center mark on meter scale.
3.10 Clamp pulse detector probe around load wires to trace pulse to grounded circuit.
3.11 Land leads as follows:
3.11.1 Ensure lugs are free of damage and correctly installed. Replace lugs per
Procedure 7.3.28.1, as necessary.
3.11.2 (QC Witness) Land Leads P and N on K6 (GDA) relay in associated charger.
3.12 Ensure test equipment removed and covers installed.
3.13 Release Clearance Order for metering fuses in top right cubicle of associated
switchgear.
3.14 Notify Operations that Caution Tags for ground detection switches on associated
charger can be removed.
PROCEDURE 7.3.27.2
REVISION 2
PAGE 4 OF 9
ATTACHMENT 1
ATTACHMENT 1
ILLUSTRATIONS
ILLUSTRATIONS
Figure 1 - D.C. SCOUT CONNECTION WITH POSITIVE GROUND
PROCEDURE 7.3.27.2
REVISION 2
PAGE 5 OF 9
ATTACHMENT 1
ILLUSTRATIONS
Figure 2 - D.C. SCOUT CONNECTION WITH NEGATIVE GROUND
PROCEDURE 7.3.27.2
REVISION 2
PAGE 6 OF 9
ATTACHMENT 2
ATTACHMENT 2
SIGN-OFF AND REVIEW SHEET
SIGN-OFF AND REVIEW SHEET
Work Order Number:
Performed By/Date
Verified By/Date
Verification Step
3.3 (QC) Leads P and N lifted on K6 (GDA) relay.
3.11.2 (QC) Leads P and N landed on K6 (GDA)
relay.
Initials
Printed Name
Initials
Printed Name
/
/
/
/
/
/
/
/
Supervision Review:
Date:
RECORDS
Attachment 2 is sent to CNS Records (quality record upon Supervision review signature).
PROCEDURE 7.3.27.2
REVISION 2
PAGE 7 OF 9
ATTACHMENT 2
SIGN-OFF AND REVIEW SHEET
Initial/date by each discrepancy or resolution listed.
#
DISCREPANCIES
PROCEDURE 7.3.27.2
#
REVISION 2
RESOLUTIONS
PAGE 8 OF 9
ATTACHMENT 3
ATTACHMENT 3
INFORMATION SHEET
INFORMATION SHEET
1. REFERENCES
1.1 VENDOR MANUALS
1.1.1 CNS Number 1740, DC Scout DC Battery Ground Locator.
1.2 PROCEDURES
1.2.1 Maintenance Procedure 7.3.28.1, EQ and Essential Lead Removal/Installation
and Lug Installation.
1.3 MISCELLANEOUS
1.3.1 1 CR-CNS-2008-5767 CA-84, Add Risk Significant Flag. Affects Risk Flag.
PROCEDURE 7.3.27.2
REVISION 2
PAGE 9 OF 9