i-gard grounding.pdf
TRANSCRIPT
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Arc Flash Hazard: HRG Technology can play a role in prevention
Grounding
Why Ground?
Arc Flash Hazard: HRG Technology can play a role in prevention
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Industrial Power SystemGrounding Methods
Resistance Grounded
Arc Flash Hazard: HRG Technology can play a role in prevention
Industrial Power SystemGrounding Methods
Solidly Grounded
Arc Flash Hazard: HRG Technology can play a role in prevention
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Industrial Power SystemGrounding Methods
Solidly Grounded
Arc Flash Hazard: HRG Technology can play a role in prevention
Industrial Power SystemGrounding Methods
Solidly Grounded
Arc Flash Hazard: HRG Technology can play a role in prevention
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Industrial Power SystemGrounding Methods
Ungrounded
Arc Flash Hazard: HRG Technology can play a role in prevention
What are the main Hazards withUngrounded/Solidly Grounded?
Ungrounded: Method used to ground first powersystems
Very large transient over-voltage conditions may exist.Insulation not rated, therefore, hazard to personnel andequipment.
Very difficult to locate ground fault.Good chance of second ground fault on a different phase due toprolonged ground fault.
Solidly Grounded: Replaced Ungrounded Systems
Very high ground fault currents.Fault must be cleared, shutting down equipment.Generators may not be rated for ground fault .
Tremendous amount of arc flash / blast energy.Equipment and people are not rated for energy.
Arc Flash Hazard: HRG Technology can play a role in prevention
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Do others agree?To HRG or to not HRG?
IEEE Std 242-2001 (Buff Book)
Recommended Practice for Protection and
Coordination of Industrial and Commercial Power
Systems
8.2.5Ungrounded low-voltage systems employ ground detectors
to indicate a ground fault. These detectors show the
existence of a ground on the system and identify the faulted
phase, but do not locate the ground, which can be
anywhere on the entire system.
One disadvantage of the solidly grounded 480V systeminvolves the high magnitude of destructive, arcing
ground-fault currents that can occur. However, if thesecurrents are promptly interrupted, the equipment
damage is kept to acceptable levels.
Arc Flash Hazard: HRG Technology can play a role in prevention
Do others agree?To HRG or to not HRG?
IEEE Std 141-1993 (Red Book)
Recommended Practice for Electric Power
Distribution for Industrial Plants
7.2.4The solidly grounded system has the highest probability of
escalating into a phase-to-phase or three-phase arcing fault,
particularly for the 480V and 600V systems. The danger of
sustained arcing for phase-to-ground fault probability is also
high for the 480V and 600V systems, and low for the 208Vsystems. For this reason ground fault protection shall be
required for system over 1000A. A safety hazard existsfor solidly grounded systems from the severe flash, arc
burning, and blast hazard from any phase-to-ground
fault.
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What causes the Hazards inUngrounded Systems?
System Capacitance
Unable to discharge leading to transient over-
voltages
No direct return path for ground fault current
Prolonged fault conditions due to inability to quickly
locate fault.
NEC 250.21(B) Ground Detectors. Ungroundedalternating current systems as permitted in
250.21(A)(1) through (A)(4) operating at not less than
120 volts and not exceeding 1000 volts shall have
ground detectors installed on the system.
Arc Flash Hazard: HRG Technology can play a role in prevention
Ungrounded Systems
Ungrounded systems do not have an intentional
connection from the source generator or transformer to
ground
Typically a three wire delta system.
Can be a four wire system where the source neutral is
not connected to ground.
BA
C
BA
C
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Ungrounded Systems
Unintentionally grounded through system capacitance Such as cables, transformers, motors, surge suppressors, etc.
Total Capacitive Current
cbI + I + Ia0 =
Iab
IIc
3 Load
480V Delta Source
BA
C
cc c
c c c
caX
cXbccX
l-nV
a,b,cI =Xa,b,c
cc
cX = 277ohms
(typical)
a,b,c
[120 apart]
277V
Ground 0V
Arc Flash Hazard: HRG Technology can play a role in prevention
C
A B
480V Delta Source
3 Load
IfcI Ib aIc c c
cXccbX
cXa
Ground FaultsUnintentionally grounded through system capacitance
Such as cables, transformers, motors, surge suppressors, etc.
480V
Ground A
a
fI = a(I + I + I )b c
l-lV
bI =X
Total Capacitive Current
b cXI =c
Vl-l
c c c
c
cc
cc
I = 0A (short-circuited)
Arc Flash Hazard: HRG Technology can play a role in prevention
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Ground Faults
Ground Fault voltage distribution (voltage rise)
A
BC
G
C B
A
A
BC
G
a a a
ag
bg
cg
ng
N
N
N
ng
cg
bg
ag ag
bg
cg
ng
V = 277VV = 277VV = 277V
V = 0Va = 120
V = 138VV = 367VV = 367V
V = 138Va = 82
V = 0VV = 480VV = 480V
V = 277Va = 60
(0% Fault) (50% Fault) (100% Fault)
Arc Flash Hazard: HRG Technology can play a role in prevention
Ground FaultsGround Fault current distribution (current rise)
A
BC
G
C B
A
A
BC
G
a a a
ag
bg
cg
I
cg
bg
ag ag
bg
cg
If
IbgcgI
f
fI
Icg bgI
agI
(50% Fault)(0% Fault) (100% Fault)
I = 0.00AI = 1.73A
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Ground Faults
Arc Flash Hazard: HRG Technology can play a role in prevention
What Causes the Hazards in SolidlyGrounded Systems?
Very low impedance in ground patho High fault current
High fault energy
Ground Fault Coordinationo Long time delays on upstream devices
High fault energy
Arc Flash Hazard: HRG Technology can play a role in prevention
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Solidly Grounded Systems
Grounded systems have an intentional connection
from the source generator or transformer to ground
Typically a four wire delta system
Can be a three wire system where the source
neutral is not connected to loads
C
BA
N
Arc Flash Hazard: HRG Technology can play a role in prevention
Solidly Grounded Systems
Intentionally grounded through ground wire
caI + I + I = 0cb cc
Total Capacitive Current
IcacbIIcc
A B
C
3 Load
480V Wye Source
nI~0 ~277
Arc Flash Hazard: HRG Technology can play a role in prevention
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Arcing Grounded Systems
Arcing ground fault: Lower fault current, so OCPDsmay not clear fault. Delay will cause severe equipment
and personnel damage due to tremendous amount of
energy released.
Arcing ground faults are approximately 38% bolted faults.
No transient
over-voltagesHigh fault
current
Arc Flash Hazard: HRG Technology can play a role in prevention
Locating Ground Faults
Follow the Smoke!
Direct return to source provides over-current conditions thatallow for OCPD to operate, hence, clearing the fault.
OK, IF the following condition is met (and you like repairwork):
Acceptable Damage
People???
Equipment???
Costs??? Who decides???
Not OK, IF
You do not want to accept damaging people
You pay for equipment repairs
Arc Flash Hazard: HRG Technology can play a role in prevention
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Coordination Problems
Discussed Over-Voltage and Over-CurrentHazards ...
Now discuss time factor
Energy is also a function of time
E = volts * amps * time
Large radial systems have long time delays forcoordination
Arc Flash Hazard: HRG Technology can play a role in prevention
Coordination Problems
IG = Fault Current
(A)
Va = 100V (typical)
t = time (cycles)
Typical Transformer:
2500 kVA, 5% impedance
Ground condition Ig=23kA
KWC = 55,200
Acceptable???
24 Cycles
(0.4 seconds)
12 Cycles
(0.2 seconds)
6 Cycles
(0.1 seconds)
Arc Flash Hazard: HRG Technology can play a role in prevention
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Coordination Problems
A) 100 Kilowatt CyclesFault location identifiable at close inspection - spit marks on metal andsome smoke marks.
B) 2000 Kilowatt CyclesEquipment can usually be restored by painting smoke marks andrepairing punctures in insulation.
C) 6000 Kilowatt CyclesMinimal amount of damage, but fault more easily located.
D) 10,000 Kilowatt CyclesFault probably contained by the metal enclosure.
E) 20,000 Kilowatt Cycles
Fault probably burns through single thickness enclosure and spreads
to other sections.
F) Over 20,000 Kilowatt Cycles
Considerable destruction.
Arc Flash Hazard: HRG Technology can play a role in prevention
Hazards with Ungrounded and SolidlyGrounded
UngroundedSolidly-
Grounded
Transient
Over-VoltageHigh Risk Low Risk
Transient
Over-CurrentLow Risk High Risk
FaultLocation
High Risk(Good Luck)
High Risk(Follow Smoke)
High FaultEnergy
High Risk
(2nd Fault)High Risk
Arc Flash Hazard: HRG Technology can play a role in prevention
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High Resistance Grounding
How does HRG solve these hazards?
Inserts a resistor between neutral and ground
Eliminates 98% of Arc Flash / Blast Injuries
Source(Wye)
HRG C
BA
N
Arc Flash Hazard: HRG Technology can play a role in prevention
High Resistance Grounding
What if no neutral exists (i.e. delta systems)?A grounding transformer is installed (either a zig zag or a wye-
delta) from all three phases to create an artificial neutral for
grounding purposes only.
Arc Flash Hazard: HRG Technology can play a role in prevention
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High Resistance Grounding
Intentionally grounded through neutral resistor
cccIab
IIc
Ir
A B
C
3 Load
480V Wye Source
HRG
N
Vng0V
277V
Ground0V
Arc Flash Hazard: HRG Technology can play a role in prevention
High Resistance Grounding
cccIabIIcIr fI
A B
C
3 Load
HRG
480V Wye Source
N
Compared to Ungrounded Systems (voltage rise)
VngVan
(277V)
Additionalreturnpath,onlydifference
betweenUngroundedandHRG!
Ground A
480V
Arc Flash Hazard: HRG Technology can play a role in prevention
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High Resistance Grounding
Voltages:Normal Operation
Vag = 277VVbg = 277VVcg = 277VVng = 0V
Fault conditionsVag = 0V (Faulted phase is atground potential)Vbg = 480V
Vcg = 480VVng = 277V
Arc Flash Hazard: HRG Technology can play a role in prevention
High Resistance Grounding
cccIabIIcIr fI
A B
C
3 Load
HRG
480V Wye Source
aC
Resistor(HRG)inlieuofwireaddssignificantamountofresistancetolowergroundfaulttoa
predeterminedvaluepreventingdestructivefaultcurrentsandshutdown!
Importance of additional path versus Solidly Grounded
Arc Flash Hazard: HRG Technology can play a role in prevention
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High Resistance Grounding
Compared with Solidly Grounded (current rise)
cccIabIIcIr fI
A B
C
3 Load
HRG
480V Wye Source
Resistorinreturnpath,onlydifference
betweenSolidlyGroundedandHRG! 5.83A3.00A+5.00A
5.83A
Ground A
277
1.73A
55.4
5.00A
Arc Flash Hazard: HRG Technology can play a role in prevention
High Resistance Grounding
Currents:
Normal Operation:
Fault conditions;
AIII c
c
c
b
c
a 0)(
AV
R
VI
r
ng
r 0
4.55
0
AIIIII c
c
c
b
c
arf 0)( 22
AIII cccbca
9000.3)12073.16073.10()(
AV
R
VI
r
ng
r
000.54.55
277
AIIIII c
c
c
b
c
arf 83.5)( 22
AIf
3183.5000.59000.3
Arc Flash Hazard: HRG Technology can play a role in prevention
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High Resistance Grounding
ccbIIcIr
fI
A B
C
3 Load
HRG
480V Wye Source
aCc
Ia
Contactorshortsoutpartoftheresistorchangingtheresistance,hence,changingthecurrent.
Groundfaultcurrentnowisapulsesignalthatallowsfordetection!
Another advantage of return path: ground fault
location
Arc Flash Hazard: HRG Technology can play a role in prevention
High Resistance Grounding
ZSCT
Meter
ZSCT
MeterMeter
ZSCT
0A
55A
50A
50A80A
80A
50A 50A 50A
50A50A55A30A 30A 30A
30A30A30A
MotorMotor
5A
5A0A
5A
HRG
5A
480V Wye Source85A
C
BA
55.4ohms
Method to quickly locate ground faults.
Meter reading willalternate from 5Ato 10A every 2seconds.
Arc Flash Hazard: HRG Technology can play a role in prevention
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Ground Faults
Damage to Power System Components:
Thermal Damage (Irms)2 * t
Mechanical Damage (Ip)2
Comparison between S-G example and HRG
System Grounding
HRG
S-G
Ground Fault (A)
5
22,800
Damage to Equipment (1 sec)
1 per unit
(22,800 / 5)2 = 20.8x106 p.u.
SolidlyGroundedSystemshave20.8milliontimesmoredamagethanHRG!!!
Arc Flash Hazard: HRG Technology can play a role in prevention
Do Others Agree?To HRG or not HRG?
IEEE Std 142-1991 (Green Book)
Recommended Practice for Grounding of Industrial and
Commercial Power Systems
1.4.2 Numerous advantages are attributed to grounded
systems, including greater safety, freedom from
excessive system over-voltages that can occur on
ungrounded systems during arcing, resonant or near-
resonant ground faults, and easier detection and location of
ground faults when they do occur.
1.4.3 A system properly grounded by resistance is not
subject to destructive transient over-voltages.
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Do Others Agree?To HRG or not HRG?
IEEE Std 142-1991 (Green Book)Recommended Practice for Grounding of Industrial and CommercialPower Systems
1.4.3 The reasons for limiting the current by resistancegrounding may be one or more of the following.
1) To reduce burning and melting effects in faulted electricequipment, such as switchgear, transformers, cables, androtating machines.
2) To reduce mechanical stresses in circuits and apparatuscarrying fault currents.
3) To reduce electric-shock hazards to personnel caused
by stray ground-fault currents in the ground return path.
Arc Flash Hazard: HRG Technology can play a role in prevention
Do Others Agree?To HRG or not HRG?
IEEE Std 142-1991 (Green Book)Recommended Practice for Grounding of Industrial and CommercialPower Systems
1.4.3 The reasons for limiting the current by resistancegrounding may be one or more of the following.
4) To reduce the arc blast or flash hazard to personnel whomay have accidentally caused or who happen to be in closeproximity to the ground fault.
5) To reduce the momentary line-voltage dip occasioned bythe clearing of a ground fault.
6) To secure control of transient over-voltages while at thesame time avoiding the shutdown of a faulty circuit onthe occurrence of the first ground fault (high resistancegrounding).
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IEEE Std 141-1993 (Red Book)
Recommended Practice for Electric Power Distribution for
Industrial Plants
7.2.2 There is no arc flash hazard, as there is with solidly
grounded systems, since the fault current is limited to
approximately 5A.
Another benefit of high-resistance grounded systems is the
limitation of ground fault current to prevent damage toequipment. High values of ground faults on solidly groundedsystems can destroy the magnetic core of rotating machinery.
Do Others Agree?To HRG or not HRG?
Arc Flash Hazard: HRG Technology can play a role in prevention
Do Others Agree?To HRG or not HRG?
IEEE Std 242-2001 (Buff Book)
Recommended Practice for Electric Power Distribution for
Industrial Plants
8.2.5 Once the system is high-resistance grounded, over-
voltages are reduced; and modern, highly sensitive ground-fault protective equipment can identify the faulted feeder on
the first fault and open one or both feeders on the secondfault before arcing burndown does serious damage.
Arc Flash Hazard: HRG Technology can play a role in prevention
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Advanced High Resistance Grounding
SENTINEL/OHMNI DSP
The only SMART HRG
Selective instantaneous feeder
isolation 2nd fault
Mitigate 95-98% of arc flash
incidents - on 1st phase to
ground fault
Assisted fault location
Resistor-integrity monitoring
Time-selective feeder isolation
For more information pick up a product brochure or visit us at www.i-gard.com
Arc Flash Hazard: HRG Technology can play a role in prevention
Advanced High Resistance Grounding
Avoiding second ground fault
Arc Flash Hazard: HRG Technology can play a role in prevention
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Advanced High Resistance Grounding:Assisted Fault Location
SENTINEL/OHMNI DSP
The only SMART HRG
Phase Indication
MODBUS
TRIP TRIP
ZSCTZSCT
DSP HRG
. . . Several Feeders . . .
MotorMotor
Arc Flash Hazard: HRG Technology can play a role in prevention
Advanced High Resistance Grounding:Assisted Fault Location
SENTINEL/OHMNI DSP
The only SMART HRG
Feeder Indication
MODBUS
TRIP TRIP
ZSCTZSCT
DSP HRG
. . . Several Feeders . . .
MotorMotor
Arc Flash Hazard: HRG Technology can play a role in prevention
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Advanced High Resistance Grounding:Avoiding 2nd Ground Fault
SENTINEL/OHMNI DSP
The only SMART HRG
Options for Faulted
Feeder:
1) Alarm Only (No Trip)
OR
2) Trip with Time DelayMODBUS
TRIP TRIP
ZSCTZSCT
DSP HRG
. . . Several Feeders . . .
MotorMotor
Arc Flash Hazard: HRG Technology can play a role in prevention
Advanced High Resistance Grounding:Avoiding 2nd Ground Fault
SENTINEL/OHMNI DSP
The only SMART HRG
MODBUS
TRIP TRIP
ZSCTZSCTDSP HRG
. . . Several Feeders . . .
MotorMotor
2nd Ground Fault:
Prioritize Feeders
Trips least important,maintaining operation on
most important
Up to 50 Feeders
Arc Flash Hazard: HRG Technology can play a role in prevention
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Advanced High Resistance Grounding:Neutral Path
SENTINEL/OHMNI DSP
The only SMART HRG
System Ground Monitor:
Continually monitors
circuit from Neutral to
Ground
Alarms if OPEN circuit
Alarms if SHORT circuit
MODBUS
TRIP TRIP
ZSCTZSCT
DSP HRG
. . . Several Feeders . . .
MotorMotor
Arc Flash Hazard: HRG Technology can play a role in prevention
Advanced High Resistance Grounding:Neutral Path
SENTINEL/OHMNI DSP
The only SMART HRG
Remote Monitoring:
Tie into Internet
Monitor plant anywherein world
Notify maintenance orlocal qualified electrical
contractor to locateground fault
MODBUS
TRIP TRIP
ZSCTZSCT
DSP HRG
. . . Several Feeders . . .
MotorMotor
Arc Flash Hazard: HRG Technology can play a role in prevention
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Minimizing Second Simultaneous GroundFault
Arc Flash Hazard: HRG Technology can play a role in prevention
DSP Relay Double Ended Unit SubApplication
Arc Flash Hazard: HRG Technology can play a role in prevention
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Design Considerations when applyingHRG Systems
HRG is the best Grounding Method available todayoFirst developed with resistor and pulsing contactor (Analog)
oLeast Hazards of all grounding methods, but some still exist
Elevated Voltages
Trained Personnel
Cables, TVSSs, VFDs Insulation
Line-to-Neutral Loads
Phase-to-ground-to-phase Faults
Bypasses neutral grounding resistor
Single-poling circuit breakers
HRG Systems Resolve these Hazards
Arc Flash Hazard: HRG Technology can play a role in prevention
ASD, UPS
Arc Flash Hazard: HRG Technology can play a role in prevention
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ASD, UPS
-800
-600
-400
-200
0
200
400
600
800
0 200 400 600 800
AMPLITUDE
TIME
A-G B-G C-G N-G
Arc Flash Hazard: HRG Technology can play a role in prevention
ASD, UPS
Arc Flash Hazard: HRG Technology can play a role in prevention
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Design Considerations when ApplyingHRG Systems
NFPA 70: National Electrical Code (2005)
250.36/186 High-impedance grounded neutral systems in which agrounding impedance, usually a resistor, limits the ground-fault currentto a low value shall be permitted for 3-phase ac systems of 480 voltsto 1000 volts where all the following conditions are met:
1) The conditions of maintenance and supervisionensure that only qualified persons service theinstallation.2) Ground detectors are installed on the system.3) Line-to-neutral loads are not served .
Continuity of power is required.(Removed 2008).
Arc Flash Hazard: HRG Technology can play a role in prevention
Elevated Voltage Hazard
A B
C
3 Load
HRG
480V Wye Source
N
Maintenancemustbeawareofelevatedvoltagesandmethodtolocatefault. IFNOT,DO
NOTHAVETOMAINTAINPOWER. Allowedtotrip(sameasSG)butwithoutthehazards.
277V
0V
0V
480V
480V
Ground A
Properly rated equipment prevents Hazards.
Arc Flash Hazard: HRG Technology can play a role in prevention
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Elevated Voltage Hazard
A B
C
3 Load
HRG
480V Wye Source
N277V
0V
0V
480V
480V
Ground A
Properly rated equipment prevents Hazards.
Cables,TVSSs,VFDs,etc.andother
equipmentmustberatedforelevated
voltages(UngroundedSystems).
Arc Flash Hazard: HRG Technology can play a role in prevention
Resolve Cable Insulation Issue
600V CablesInsulation thickness based on mechanical strength, not electricalExtra thickness exceeds 600V electrical ratingTherefore, should be used on 600V systems (HRG)
1000V CablesOnly CSA listed, not UL
5000V CablesNon-shielded: Should be used on 2400V systems (HRG)Shielded: Should be used on 4160V systems (HRG)
8000V CablesNon-shielded: Should be used on 4160V systems (HRG)
Arc Flash Hazard: HRG Technology can play a role in prevention
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Resolve NEC Requirement
Add small 1:1transformer and solidlyground secondary for 1loads (i.e. lighting).
Arc Flash Hazard: HRG Technology can play a role in prevention
Resolve NEC Requirement
Advantages of 1:1 transformer
oAbility to retrofit HRG Systems
oOnly ~20% of facility / plant load is 1No neutral required from main source and mainswitchgear (cost savings,)
oSignificantly reduced risk of Arc Blast / Flash Hazard
Only small portion of power system is solidlygroundedLighting Ballasts
Arc Flash Hazard: HRG Technology can play a role in prevention
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Phase-to-Ground-to-Phase Fault
A B
C
3 Load
HRG
N
480V Wye Source 2000A/3P/65kAIC
Single-poling circuit breaker
During phase-ground-phase fault, single-pole of MCB has to clear the 480Vfault at 65kA. However, per UL 489, single-pole interrupting rating is only at20kAIC. HAZARDOUS?
Arc Flash Hazard: HRG Technology can play a role in prevention
Phase-to-Ground-to-Phase Fault
For condition to occur, all of the following must be true:1) One fault must be on line side of MCB
Very uncommon2) Low impedance per ground fault
Very uncommonGround faults are usually arcing faults (high impedance faultsper IEEE Std 241, 9.2.5)
3) Faults on different phases4) No other over-current protective devices in fault path
Very uncommonIf so, they will open: eliminating the single-pole interruption
Although remote, HAZARD may still exists:Should be considered during coordination studyDetect ground faults per NEC 250-36
Arc Flash Hazard: HRG Technology can play a role in prevention
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Resolving Hazard via New Technology
M M M M
DFM DFMDFM DFM DSM
First fault: Sound Alarm
Send signal
Second fault: Open feeder with lower
priority
Third fault: Open feeder with lower
priority
Arc Flash Hazard: HRG Technology can play a role in prevention
Additional Advancements in HRGSystems
Arc Flash Hazard: HRG Technology can play a role in prevention
Communications
RS232 (Serial) / RS485 (Modbus, Profibus) / TCP/IP
(Ethernet)
Control and monitor relay remotely via existing
SCADA system
Data Logging & Trending
Most ground faults are intermittent, so when you goto locate via pulse, fault may have cleared
Data log can link ground faults with equipment
starting or running
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Additional Advancements in HRGSystems
Arc Flash Hazard: HRG Technology can play a role in prevention
Filters Harmonics / Noise / RFMonitors fundamental voltage and current for ground faults
Avoids nuisance trippingMonitors 3rd harmonic voltage and current
High Harmonics may require de-rating resistorLow Harmonics may indicate ground fault near generatorneutral
Zone Selective InterlockingAllows coordination between interlocked protection relays on thesame system
Continuously measures system impedanceElectrical systems are perpetual systemsSystem capacitance may increase causing grounding resistor tobe incorrectly sized
Undesirable, higher fault current may flowTransient over-voltage may occur
To Summarize
Arc Flash Hazard: HRG Technology can play a role in prevention
Hazards with Ungrounded Systems
Severe transient over-voltages
Cannot efficiently locate ground faults
Hazards with Solidly-Grounded Systems
Very high fault currents and time delays
Causing severe arc blast / flash conditions
Ground fault coordination problems
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To Summarize
Arc Flash Hazard: HRG Technology can play a role in prevention
High-Resistance Grounded Systems
Best Grounding Method todayResolves Ungrounded hazards
Resolves Solidly-Grounded hazards
Technology continues to make HRG Systemssafer than any other grounding method, but needhelp
Continue to educate and train personnel (engr and maint.)NETA
Update standards and guideline that hinder HRGNEC
NFPA 70E and IEEE 1584
Optical or Pressure Detection
Arc Flash Hazard: HRG Technology can play a role in prevention
Which one is faster?
Speed of light = 300 x 106 meters/sec
Speed of sound =350 meters/sec
Pressure travels at the speed of sound
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Optical Arc Fault Detection
Arc Flash Hazard: HRG Technology can play a role in prevention
Relies on detecting a high- intensity light
Fastest method of arc detection
Can issue a command to trip in 1 ms to 7 ms
Detectors are light sensors.
Sensors local to the relay, rely on Fibre optic to
conduct light to the relay
Sensor remote to the relay, are hard wired to the
relay
Pressure Detection
Arc Flash Hazard: HRG Technology can play a role in prevention
Pressure wave of an arc travels at the speed of
sound
Ralph Lees research shows that arcing faults can
produce 20-1000 psi
Depending on placement of pressure sensors,
detection can be as fast as 8-18 ms
Can still trip in less than 100 ms
Commercially available
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Temperature Detection
Arc Flash Hazard: HRG Technology can play a role in prevention
Temperature detection is a slower technique to
detect the presence of an arc
This method is more effective as an early detection
system for series faults
Can easily detect loose connections by monitoring
the outgases of products produced by overheating
Distance
Arc Flash Hazard: HRG Technology can play a role in prevention
Effect on Personal Protective Equipment (PPE)
requirements
Remote operation inherently increases distance
from arc source
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Reduce Incident Energy
Arc Flash Hazard: HRG Technology can play a role in prevention
Reduce Time
Reduce Bolted Fault Current
Do both.
Reduce Incident Energy
Arc Flash Hazard: HRG Technology can play a role in prevention
Activate a current limiting device that will quickly
insert an impedance into the circuit on the
occurrence of an arc fault;
Can reduce the fault current from 50 kA to 0.4 kA in
approximately cycle.
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Reduce Incident Energy
Arc Flash Hazard: HRG Technology can play a role in prevention
This conceptual unit will reduce the incident energy
from 5.7 cal/cm2 to 0.9 cal/cm2
Thank You!
Questions?
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I-Gard CorporationHead Office7615 Kimbel St., Unit 1 Phone: 905.673.1553 Toll Free 1.888.737.4787Mississauga, Ontario Canada L5S 1A8 Fax: 905.673.8472 E-mail: [email protected]
Our business hours are Monday to Friday 9:00 a.m. to 5:00 p.m. (EST), if during thosehours you are not able to call us, simply send us an e-mail or leave us a message.
The following members of our inside sales team will be pleased to assist you:
Mr. Doug Gonyou [email protected] Mr. Edmundo Perich [email protected] Mrs. Kavita Raghunathan [email protected] Mr. Upul Herath [email protected]
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