3. Arc Flash Hazards
Molten Metal
Intense Heat
Droplets
35,000F
Flying Objects
& Shrapnel
Toxic Gases
Copper Solid to Intense
Vapor Expansion Light Flash
67,000 Times
Sound
Blast
Pressure
Wave
4. ARC FLASH
STANDARDS
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5. IEEE Standard 1584
Contains calculations used to determine
safe boundary distances for unprotected
personnel and the incident energy at the
working distance for qualified personnel
working on energized equipment.
6. IEEE Standard 1584
Incident Energy Calculation for
Arc Flash in a Cubic Box
E =1038.7D-1.4738 x T[0.0093F2-0.3453F+5.9675]
E = Incident Energy in cal/cm2
D = Distance to arcing point
T = Time to clear arcing fault
F = Available bolted fault short circuit current
7. NFPA-70E-2009
Standard for Electrical Safety
in the Workplace
Utilizes IEEE 1584 methods for
calculating incident energy on
specific electrical equipment and
provides guidelines for the PPE
clothing required based on the
incident energy level.
8. National Electric Code
Requires labeling of electrical equipment
to warn qualified personnel of the danger
of electric arc flash.
Refers to NFPA-70E as a guide for
quantifying the hazard.
11. OSHA 29 CFR Part 1910
1910.333 Selection and Use of Work Practices
Safety-related work practices to prevent injuries resulting
from either direct or indirect electrical contact, when
work is performed near or on equipment or circuits which
may be energized.
1910.335 Safeguards for Personal Protection
PPE shall be used to protect employees from
electrically related injuries while that employee is
working near exposed energized parts.
Subpart S, Appendix A
References NFPA-70E for
Electrical Safety Practices
12. ARC FLASH
PREVENTION
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14. Causes of Electric Arc Flash
Contact with Live Parts
Unsafe Work Procedures
Misoperation
Insufficient Maintenance
Overvoltages
Insulation Failure
Entry of Small Animals
15. Arc Flash Prevention
Maintain Sound Safety Practices
Prevent Entry of Critters
Use IEEE Metalclad Standards
Prevent Moisture Ingress
Proper Insulation System Design
Monitor for Partial Discharge
Monitor Bus Temperatures
16. IEEE Standard C37.20.7
“There is little likelihood of an internal arc in
equipment meeting the requirements of IEEE Standard
C37.20.1-2002 or IEEE Standard C37.20.3-2001. There
is even less likelihood of an internal arc in equipment
that has insulated bus, compartmentalization, barriers,
and interlocks, such as those described in IEEE
Standard C37.20.2-1999.”
Metalclad Switchgear Design Standard
17. Metal Enclosed Switchgear
Line
Terminals Uninsulated Bus
Load break
air switch
Everything in Same
Compartment
Exposed
Live Parts
with Fuse
Door Open
Load
Terminals
Ground bus
18. Metalclad Switchgear
Relay, Controls Primary buses and
and connections covered
Instrumentation with insulation
Shutters cover Main bus
Primaries when
Primary circuits,
no breaker installed
relays, meters,
and controls
isolated in own CT barrier CT
grounded metal Load
compartments bus
Movable
Shutters CT
Breaker
Compartment
Ground bus
19. Metalclad Switchgear
Relay, Controls
and
Instrumentation
Main bus
Steel barrier
CT
No primary circuits Load
exposed with bus
breaker installed Vacuum
CT
Breaker
Ground bus
20. Arc Flash Prevention
Maintain Good Safety Practices
Prevent Vermin Entry
Use IEEE Metalclad Standards
Prevent Moisture Ingress
Proper Insulation System Design
Monitor for Partial Discharge
Monitor Bus Temperatures
21. Moisture Prevention
IEEE Tested Enclosure Design
Use Extended Life Sealants
IEEE C37.20.2 Section 6.2.10
Ventilate Test Criteria
Cable Compartment
7.1 gallonsFilters/Screens rate
• Maintain per minute flow
60psi Dualwater pressure
• Use min Strip Heaters
10 ft. Min Distance from Joints
• Monitor Strip Heaters
Against 2 Surfaces at each Joint
• Seal Unintentional Openings
Apply Quality Protective Finish
22. Arc Flash Prevention
Maintain Good Safety Practices
Prevent Vermin Entry
Use IEEE Metalclad Standards
Prevent Moisture Ingress
Proper Insulation System Design
Monitor for Partial Discharge
Monitor Bus Temperatures
23. Insulation Materials
95kV BIL Rated Insulators
Fluidized Bed Epoxy Bus Insulation
Cycloaliphatic
bus supports
PVC
Insert
24. Arc Flash Prevention
Maintain Good Safety Practices
Prevent Vermin Entry
Use IEEE Metalclad Standards
Prevent Moisture Ingress
Proper Insulation System Design
Monitor for Partial Discharge
Monitor Bus Temperatures
25. Partial Discharge Monitoring
Signal
sent to
InsulGard
RFCT #1 detects partial Relay
discharges internal to
switchgear compartment.
RFCT #2 detects partial
discharges in Customer’s
cables up to 100 ft from
switchgear
27. Arc Flash Prevention
Maintain Good Safety Practices
Prevent Vermin Entry
Use IEEE Metalclad Standards
Prevent Moisture Ingress
Proper Insulation System Design
Monitor for Partial Discharge
Monitor Bus Temperatures
28. Temperature Monitoring
Bus
Joint Wireless Parasitically Powered
Temperature Detectors for
Medium Voltage Switchgear
Straight
(under development)
Bus
29. Output Through Internet
Protection system configuration
Temperature input from sensors
Current Input from CT’s
Calculate and Predict a Problem
Email/Alarm notification
30. ARC FLASH
PROTECTION
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31. Arc Flash Protection
Train Personnel
Wear Proper PPE
Install Warning Labels
Maintain Good Safety Practices
Build Sturdy Enclosure
Reduce the Human Interface
Redirect the Blast Energy
32. Safety Practices
De-Energize Equipment
Use Lockout/Tagout Procedures
Latch and Secure All Panels
Label Line and Load Side Bus
Isolate Potential Backfeeds
Open Tie Breaker/Redundant Sources
Ground De-Energized Conductors
33. Safety Practices
IEEE C37.20.6-2007 G&T TESTING STANDARD
First G&T Standard
Established Formal G&T Tests
BIL Withstand
AC Hipot 1-minute
Momentary For 10 Cycles Per
C37.20.2
K*I 2 Seconds Per C37.20.2
Interlocking (Upper & Lower)
500 Insertions and Removals
37. Arc Flash Protection
Train Personnel
Wear Proper PPE
Install Warning Labels
Maintain Good Safety Practices
Build Sturdy Enclosure
Reduce the Human Interface
Redirect the Blast Energy
38. Sturdy Enclosure Design
Use Only 11 Gauge Steel
Weld Cubicles
Two Walls Between Sections
Heavy Duty Door Hinges
Heavy Duty Door Latches
39. Arc Flash Protection
Train Personnel
Wear Proper PPE
Install Warning Labels
Maintain Good Safety Practices
Build Sturdy Enclosure
Reduce Human Interface
Redirect the Blast Energy
40. Reduce Human Interface
Opening & Closing Breaker
Relocate control switch
Use remote communications
Use local HMI
Use remote control station
Use Remote Operator
Use Time Delay Control Switch
48. IEEE Standard C37.20.7
A procedure for testing and evaluating
the performance of medium-voltage
metal-enclosed switchgear for internal
arcing faults and identifying the
capabilities of the equipment relative
to specific zones of protection.
NOT A DESIGN STANDARD
49. IEEE Standard C37.20.7
Arc-Resistant Definition:
“Equipment designed to withstand
the effects of an internal arcing
fault as indicated by successfully
meeting the requirements of IEEE
Standard C37.20.7-2007.”
50. IEEE Standard C37.20.7
Term Arc Resistant can be misleading.
In the event of an internal arcing fault,
the dangerous effects of the arc are
vented away from the zone of
protection for personnel.
Term Arc Venting is more accurate
53. Arc Venting Switchgear
Exhaust Vent Duct Design
Tested on the switchgear
Must vent to safe area
Fire rated at wall opening
No external air allowed in
Prevent buildup of ice and snow
Prevent critter ingress
54. IEEE Standard C37.20.7
“Not intended to provide this additional degree of
“Intended to provide an additional degree of
protection to operating personnel who, in thenormal
protection to the personnel performing normal
performance of their duties, would be required to
operating duties in close proximity to the equipment
open enclosure doors or panels or otherwise alter the
while equipment is operating under normal
equipment from its normal operating conditions.”
conditions”
55. IEEE Standard C37.20.7
IEEE does not require that metalclad
switchgear to be manufactured to
pass the IEEE Standard C37.20.7
Testing Procedures.
57. Zones of Protection
Type 1
Switchgear with arc-
resistant designs or
features at the freely
accessible front of the
equipment only.
58. Zones of Protection
Type 2
Switchgear with arc-
resistant designs or
features at the freely
accessible exterior
(front, back and sides)
of the equipment only.
59. Zones of Protection
Type 1B
That arcing does not
cause holes in the freely
accessible front of the
enclosure or in the walls
isolating the low-voltage
control or instrument
compartments.
60. Zones of Protection
Type 2B
That arcing does not
cause holes in the freely
accessible front, sides
and rear of the enclosure
or in the walls isolating
the low-voltage control or
instrument
compartments.
61. Zones of Protection
Type 1BC
Adds isolation from
effects of an internal
arcing fault between all
adjacent compartments
62. Zones of Protection
Type 2BC
Adds isolation from
effects of an internal
arcing fault between all
adjacent compartments
63. Arc Venting Switchgear
Considerations
Initial cost (up to 25% more)
Need breaker lift device
Must design room accordingly
Must seal all cable entries
Low voltage wiring protection
Loss of protection if door/panel open
64. IEEE Standard C37.20.7
Testing Does Not Address…
Protection against toxic gases
Protection against excessive sound
Arcing within components
Protection from above or below
65. ARC FLASH
MITIGATION
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66. Arc Flash Mitigation
Incident Energy Calculation
E =1038.7D-1.4738 x T[0.0093F2-0.3453F+5.9675]
E = Incident Energy in cal/cm2
D = Distance to arcing point
T = Time to clear arcing fault
F = Available short circuit current
67. Arc Flash Mitigation
Complete System Analysis
High Speed Differential Relay
Fast Bus Tripping
Maintenance Relay Settings
Arc Flash Detection
Hi-Speed Arc Terminator
3 Cycle Breakers
Current Limiting Fuses
70. Arc Flash Mitigation
Complete System Analysis
High Speed Bus Differential Relay
Fast Bus Tripping
Maintenance Relay Settings
Arc Flash Detection
Hi-Speed Arc Terminator
3 Cycle Breakers
Current Limiting Fuses
71. Maintenance Relay Settings
Relay Group Settings Feature can be enabled
by a contact input, communications or ARMs
Selector Switch to enable “Maintenance Mode”
protective settings when maintenance is being
performed on the equipment.
“Maintenance Mode” Protective Group settings
typically establish lower instantaneous pick-
ups that can be optimized to reduce trip delays
and increase sensitivity, but avoid nuisance
trips.
Remote and/or Local Visual Indication can be
provided to confirm the Relay is in Maintenance
Mode.
ARMs
Selector
Switch
TB2
FP5000
Relay Maintenance Mode
a b Indicating Light ARM’s Selector Switch
FP5000 Postion A Position B
Relay Settings Group 2 Group 1
Group Maintenance Mode Normal Mode
CI - 7
Relay Contact
CI - 8 CI-7 CI-8
Input
72. Arc Flash Mitigation
Complete System Analysis
High Speed Bus Differential Relay
Fast Bus Tripping
Maintenance Relay Settings
Arc Flash Detection
Hi-Speed Arc Terminator
3 Cycle Breakers
Current Limiting Fuses
73. Arc Flash Detection
Microprocessor based high speed relay
sends trip signal to breaker upon sensing
a light flash with high speed light sensors
installed in the
switchgear
compartments.
74. Arc Flash Detection
SEL-751A Feeder Protection Relay
Instantaneous Overcurrent
Timed Overcurrent
Instantaneous Neutral Overcurrent
Times Neutral Overcurrent
Undervoltage (Bus Side)
Overvoltage (Bus Side)
Undervoltage (Line Side)
Overvoltage (Line Side)
Over Frequency
Under Frequency
Syncronism Check
Auto-Reclosing
Arc-Flash Detection
Arc-Flash Overcurrent
81. Arc Flash Mitigation
Complete System Analysis
High Speed Bus Differential Relay
Fast Bus Tripping
Maintenance Relay Settings
Arc Flash Detection
Hi-Speed Arc Terminator
3 Cycle Breakers
Current Limiting Fuses
82. Arc Terminator
Detects presence of an arc flash with high
speed photo sensors and closes a high
speed switch that shorts out the the main
bus in the first ¼ cycle to create a parallel
path to the arc and quickly extinguish a
burning arc
92. Scheme Comparison
5 Cycle Breakers 3 Cycle Breakers
Arcing Percent Arcing Percent
Protection Scheme Time Reduction Time Reduction
Normal Coordination 800ms 0% 767ms 0%
Fast Bus Trip 170ms <79%> 137ms <83%>
Maintenance Settings 120ms <85%> 87ms <89%>
High Speed Differential 107ms <87%> 74ms <91%>
Arc Flash Detection 86ms <89%> 53ms <93%>
Arc Terminator 2.3ms <99.7%> 2.3ms <99.7%>
93. NFPA
Personal
Protective
Equipment
Requirements
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94. NFPA PPE Requirements
Incident Required
Energy PPE Minimum
Present Risk PPE Rating Protective Clothing Required to Prevent
(cal/cm2) Cat (cal/cm2) Onset of a Second Degree Burn
E ≤ 1.2 0 N/A Untreated Cotton
1.2 < E ≤ 4 1 4 FR Shirt + FR Pants
4<E≤8 2 8 Cotton Undergarments + FR Shirt + FR Pants
8 < E ≤ 25 3 25 Cotton Undergarments + FR Shirt + FR Pants
+ FR Coverall
25 < E ≤ 40 4 40 Cotton Underwear + FR Shirt + Pants
+ Multi-Layer Flash Suit (minimum of 3 layers)
E > 40 N/A N/A Too Dangerous to Work On
95. NFPA PPE Requirements
NO CALCULATION OF INCIDENT ENERGY
NFPA Table 130.7(C)(9) – 1Kv – 38Kv Switchgear
Tasks Performed on Energized Equipment Risk Cat
Inspections Outside Restricted Approach Boundary 3
Operate Circuit Breaker with Door Closed 2
Operate Circuit Breaker with Door Open 4
Operate Meter Switch 0
Work on Energized Electrical Conductors 4
Work on Exposed Control Energized Circuits <120V 2
Work on Exposed Control Energized Circuits >120V 4
Racking of Breakers with Door Open or Closed 4
Application of Safety Grounds After Voltage Test 4
Remove Covers to Expose Energized Conductors 4
Open Hinged Covers to Expose Energized Conductors 3
Open PT or SST Compartment 4
96. NFPA PPE Requirements
NO CALCULATION OF INCIDENT ENERGY
NFPA Table 130.7(C)(9) – 1Kv – 38Kv Switchgear
IF ARC RESISTANT SWITCHGEAR UTILIZED
(for clearing times less than 500ms)
Non AR AR Swgr
Tasks Performed on Energized Equipment Risk Cat Risk Cat
Operate Circuit Breaker with Door Closed 2 0
Operate Circuit Breaker with Door Open 4 4
Work on Energized Control Circuits <120V 2 0
Work on Energized Control Circuits >120V 4 4
Racking of Breakers with Door Open 4 4
Racking of Breakers with Door Closed 4 0
Insert or Withdraw Potential Transformers 4 0
97. E (cal/cm2) versus Fault Current
5 Cycle Breaker
Protection Scheme 25ka 40ka 50ka 63ka
Normal Coordination 13.30 29.70 50.50 89.30
Fast Bus Trip 2.83 6.32 10.73 18.97 PPE
E
Maintenance Settings 2.00 4.46 7.58 13.39 (cal/cm2) Cat
High Speed Differential 1.78 3.98 6.76 11.94 1.2 0
Arc Flash Detection 1.47 3.20 5.43 9.60 4 1
3 Cycle Breaker 8 2
Protection Scheme 25ka 40ka 50ka 63ka 25 3
Normal Coordination 12.75 28.5 48.40 85.60 40 4
Fast Bus Trip 2.28 5.09 8.65 15.29
>40 N/A
Maintenance Settings 1.45 3.23 5.49 9.71
High Speed Differential 1.23 2.75 4.67 8.26
Arc Flash Detection 0.88 1.97 3.35 5.91
98. E (cal/cm2) versus Distance
Normal Coordination (5 cycle)
100
90
PPE
E
80 FC = 25ka (cal/cm2) Cat
FC = 40ka
1.2 0
Incident Energy (cal/cm2)
70
FC = 50ka
60 FC = 63ka 4 1
50 PPE 8 2
Cat
40 25 3
4
30 40 4
20 >40 N/A
3
10
2
0 1
0 6 12 18 24 30 36
Distance to Arcing Point (inches)
99. E (cal/cm2) versus Distance
PPE
Normal Coordination (5 cycle) Cat
40
PPE
35
FC = 25ka
E
FC = 40ka 4 (cal/cm2) Cat
FC = 50ka
30
1.2 0
Incident Energy (cal/cm2)
FC = 63ka
25
4 1
20
3 8 2
15
25 3
10
2 40 4
5
1 >40 N/A
0
0 12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216
Distance to Arcing Point (inches)
(216” = 18’)
100. E (cal/cm2) versus Distance
PPE
Bus Differential + Arc Flash (3 cycle) Cat
40
FC = 25ka
35
FC = 40ka 4 PPE
E
30
FC = 50ka
(cal/cm2) Cat
Incident Energy (cal/cm2)
FC = 63ka
1.2 0
25
4 1
20 8 2
3 25 3
15
40 4
10
>40 N/A
2
5
1
0 0
0 6 12 18 24 30 36
Distance to Arcing Point (inches)
101. Remote Racking/Control Advantages
Normal Coordination (800ms clearing time)
Standard 5 cycle Breakers
Fault Operation at Front Operation at 20 Feet E PPE
Current of Cubicle Door from Cubicle Door
(cal/cm Cat
2)
2
25kA 8.31 cal/cm 0.51 cal/cm2 1.2 0
40kA 18.58 cal/cm2 1.13 cal/cm2
4 1
50kA 31.56 cal/cm2 1.93 cal/cm2
63kA 55.79 cal/cm2 3.40 cal/cm2 8 2
25 3
Bus Differential Protection (107ms interrupt) 40 4
Standard 5 cycle Breakers >40 N/A
Fault Operation at Front Operation at 20 Feet
Current of Cubicle Door from Cubicle Door
2
25kA 1.78 cal/cm 0.11 cal/cm2
40kA 3.98 cal/cm2 0.24 cal/cm2
50kA 6.76 cal/cm2 0.41 cal/cm2
63kA 11.94 cal/cm2 0.73 cal/cm2
102. Recommended Scheme
Transformer Differential Protection
Bus Differential Protection
Arc Flash Detection
To CT’s at
Transformer
87T Zone
87B Zone
Arc Flash
Detection
Zones