This course is designed to equip the electrical consultant, system designer or any other professional responsible for designing or modernizing commercial and industrial electrical power distribution systems with the fundamentals of the Arc Flash Energy phenomenon.

1. Industrial Service Solutions
Electrical Arc Flash Hazards
Is your company in compliance?

2. Discussion Highlights
The Bigger Picture of Electrical Safety
Arc Flash Risks and Effects
Arc Flash Approach Boundaries
Arc Flash Hazard Calculations
NFPA 70E Tables
IEEE Standard 1584-2002
Arc Flash Remediation
Arc Flash Categories & Protective Clothing
Arc Flash Labels and Permits
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May 2011

3. Worker safety is important
Why?
• In addition to being the right thing to do it is intrinsically connected to
productivity, worker morale and liability costs
• Machinery, processes & facilities usually designed with worker & machine
safety as key consideration from start...
• However, electrical safety often handled differently… Late, after base
system design is finished, sometimes after equipment is purchased . . .
It should not be !
• Electrical safety can best be optimized by being part of the initially defined
mission for the facility’s power distribution system and being considered
at every decision point in the design, purchasing and installation process.
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May 2011

4. Safety, a bigger picture
See IEEE article by H. Landis Floyd II, “Potential Impact of ANSI
Z10 AND CSA Z1000 on Reducing Electric Shock and Arc Flash
Hazard Injuries”, PCIC 2009 conference record. Next few
slides borrow heavily from this presentation
New standards for implementing safety programs in facilities
From ANSI Z10 Scope:
“… The purpose of the standard is to provide organizations an
effective tool for continual improvement of their occupational
health and safety performance. An OHSMS implemented in
conformance with this standard can help organizations
minimize workplace risks and reduce the occurrence and
cost of occupational injuries, illnesses and fatalities. …”
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May 2011

5. Hierarchy of Hazard Control Measures
From ANSI Z10
1. Elimination of the hazard
Thinking through this
Substitution for less hazardous equipment,
2. table allows assigning
materials or process
3.
Engineering control for less hazardous value to different
exposure or severity
potential solutions to arc
4. Warnings, signs, and other communications flash & shock hazards
Administrative controls including safe work
5.
practices
6. Personal protective equipment
For example:
A temporary setting such as a maintenance switch is an administrative procedure (5) …
Not as good as good as permanently making protection safer which would be a
substitution (2) or Engineering (3)
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May 2011

6. Higher level solutions easier at system planning time
Elimination of the hazard 1. Elimination of the hazard
• The only true way for an 2.
Substitution for less hazardous equipment,
electrical system to be safe materials or process
is for it to be de-energized… Engineering control for less hazardous
3.
exposure or severity
• But when a process is critical
that is difficult to do unless 4. Warnings, signs, and other communications
system includes redundant
ways to get power to loads… Administrative controls including safe work
5.
practices
Substitution of less hazardous 6. Personal protective equipment
equipment
• Different types of equipment pose different levels of risk – individually
mounted vs. group mounted, draw-out vs. stationary, arc resistant vs.
standard, indoor vs. outdoor, etc.
3. Design controls, instrumentation, monitoring to minimize hazard
• Do everything than can be done remotely, remotely. Use modern
diagnostics to minimize exposure and optimize reliability
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May 2011

7. Hazards Involved in Working On or Near Energized
Electrical Equipment
Dangers associated with working on or around exposed
energized conductors or parts:
Electrical shock - Becoming part of the circuit.
Arc Flash - The violent release of superheated gases caused
by an electric arc.
Arc Blast - The blast effects from the pressure wave
associated with an arc flash occurrence.
Shrapnel - Ejection of projectiles or bits of metal.
Noise - From initial explosive expansion of air.
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May 2011

8. NEC and OSHA References to NFPA 70E
• NEC Article 110.16 requires that Electrical equipment such as
switchboards, panelboards, industrial control panels, meter socket
enclosures, and motor control centers shall be field marked to warn
qualified persons of potential electric arc flash hazards.
• NEC Article 100, Definitions: Qualified Persons has NFPA 70E referenced for
electrical safety training requirements.
• OSHA regulation 29 CFR 1910 Subpart S (Electrical Safety) Appendix A:
Reference Documents, also references NFPA 70E.
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May 2011

9. OSHA Interpretations of NFPA 70E
OSHA can, and has enforced lack of arc flash protection under the
"general duty clause". Here are some excerpts from a standards
interpretation letter written by OSHA in 2003:
“All your questions involve the NFPA 70E standard, which is one of many industry
consensus standards developed by the National Fire Protection Association.
NFPA 70E, which is titled ‘Electrical Safety Requirements for Employee Workplaces,’
is the NFPA’s consensus standard for workplace electrical safety. It covers employee
protection from electrical hazards including shock, arc blasts, explosions initiated by
electricity, outside conductors, etc.
“With respect to the General Duty Clause, industry consensus standards may be
evidence that a hazard is ‘recognized’ and that there is a feasible means of
correcting such a hazard.
“These provisions (1910.132(a) personal protective equipment) are written in general
terms, requiring, for example, that personal protective equipment be provided ‘where
necessary by reason of hazards…’ and requiring the employer to select equipment
‘that will protect the affected employee from the hazards…’.
“Industry consensus standards, such as NFPA 70E, can be used by employers as
guides to making the assessments and equipment selections required by the
standard. Similarly, in OSHA enforcement actions, they (70E) can be used as evidence
of whether the employer acted reasonably.
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May 2011

10. OSHA 1910 Subpart S Revisions
Effective Aug 13th, 2007
OSHA ADOPTING NFPA 70E
NFPA 70E-2000 is the basis for most of the final rule. However, there are
some parts based upon the 2002 NEC and even some selected parts of
NFPA 70E 2004 Edition.
“(The final rule) reflects the Agency’s commitment to update its electrical
standards, keep them consistent with NFPA standards, and ensure that
they appropriately protect employees. The Agency intends to extend the
commitment by using NFPA 70E as a basis for future revisions to its
electrical safety-related work practice requirements and new requirements
for electrical maintenance and special equipment.”
---Preamble of the Final Rule document
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May 2011

11. Arc-Flashover Incident
Description: A routine voltage check at a 480V terminal
board inside the GAC resulted in an arc flash burning the
hand of the person checking the voltage. The check
consisting of placing one meter lead on a single phase and
measuring the other 2 phases with the second meter lead.
The employee was treated and released to return to work.
Direct Cause: The terminal board was delivered with
incorrect long terminal lugs that were also not insulated. Broken Insulator and extra long terminal
The terminal points of the meter were exposed clamps too lugs
large for this small equipment.
Root Cause: The equipment being used and the equipment
being checked was not carefully evaluated prior to
conducting the voltage check.
Contributing Factors: Terminal board delivered with
incorrect terminal lugs that were also not insulated.
Corrective Actions:
• Use of a different style leads, the use of pointed leads
instead of clip leads
Clips across
• Replace the terminal board with a new component two phases
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May 2011

12. What May Happen with a
Slow Protective Device
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May 2011

13. Worker’s Flame-Resistant Shirt and Insulating
Gloves
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May 2011

14. Arc Flash Effects
• Temperature of the arc can reach 35,000 deg F – about 4
times the temperature of the sun!
• In US, 5-10 arc flash incidents requiring hospitalization per
day.
• 1 – 2 deaths per day from electrical events, (shock, flash &
blast).
• More than 2,000 workers treated in burn centers per year
with severe arc flash injuries. (This does not include injuries
in other hospitals and clinics which go unreported.)
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May 2011

15. Examples of Activities which Involve
Arc Flash Risks
• Racking in or out of draw-out circuit
breakers.
• Removing or installing circuit breakers
or fuses.
• Working on control circuits with
exposed energized primary parts.
• Applying safety grounds.
• Removing panel covers for inspections
or other activities.
• Low voltage testing and diagnostics.
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May 2011

16. Arc Flash Standards
Simplified Tabular method presented in:
• NFPA-70E-2009, “Standard for Electrical Safety Requirements for
Employee Workplaces.”
• NFPA-70E-2012 to be released later in 2011
• In Canada Z462-08, “Workplace Electrical Safety”
More sophisticated calculated methods suitable for low
voltage and higher voltages developed in:
• IEEE Std 1584-2002, “IEEE Guide for Performing Arc-Flash Hazard
Calculations.”
• Amendment 1 issued in 2004 as IEEE Std 1584a-2004, (changes were
relatively minor.)
• Sometimes combination of these two documents referred to as Std
1584-2004.
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May 2011

17. NFPA 70E Approach Boundary Fig. C.1.2.4
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May 2011

18. Shock Protection Approach Boundaries
Limited Approach Boundary – Distance from an exposed live part
within which a shock hazard exists.
Restricted Approach Boundary – Distance from an exposed live
part within which there is an increased risk of shock, due to
electrical arc over combined with inadvertent movement, for
personnel working in close proximity to the live part.
Prohibited Approach Boundary – Distance from an exposed live
part within which work is considered the same as making contact
with the live part.
Fixed Live Prohibited Restricted Limited
Part Approach Approach Approach
Distance Distance Distance
@480 Volts 0', 1" 1 ft, 0 in 3 ft, 6 in
@15,000 Volts 0', 7" 2 ft, 2 in 5 ft, 0 in
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May 2011

19. Arc Flash Protection Approach Boundaries
Flash Protection Boundary – Distance from an exposed live part within which a
person could receive a second-degree burn if an electrical arc flash were to occur.
This second-degree burn results from the minimum arc flash energy of 1.2 cal/cm2,
( = 5 joules/cm2). This boundary is determined by calculating the distance at which
an arc flash energy of 1.2 cal/cm2 exists.
Working Distance - Dimension between the possible arc point and the head and
body of the worker positioned in place to perform the assigned task. Value selected
for the application – minimum 18”.
Fixed Live Working Flash
Part Distance Protection
Boundary
@480 Volts 18" (Typical) (Must be calculated)
@15,000 Volts 36" (Typical) (Must be calculated)
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May 2011

20. Combined Shock & Arc Flash Boundaries
Usually > than the
Limited Approach
Distance but not always
Fixed Live Prohibited Restricted (Arc Flash) Limited Flash
Part Approach Approach Working Approach Protection
Distance Distance Distance Distance Boundary
@480 Volts 0', 1" 1 ft, 0 in 18" (Typical) 3 ft, 6 in (Must be calculated)
@15,000 Volts 0', 7" 2 ft, 2 in 36" (Typical) 5 ft, 0 in (Must be calculated)
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May 2011

21. Safe Approach Distances
Unqualified persons – Safe when maintaining a distance from exposed energized
parts equal to the Limited Approach Boundary or the Flash Protection Boundary,
whichever is greater.
Qualified persons
Appropriate arc flash protection shall be utilized if flash protection boundary crossed.
>>> To cross the Restricted Approach Boundary, the qualified person must:
•Have a documented work plan approved by management.
•Use appropriate protective equipment for work near exposed conductors and rated
for voltage and energy level.
•Be certain no part of body enters prohibited space.
•Keep as much as body as possible out of restricted space.
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May 2011

22. Safe Approach Distances
Qualified persons
Appropriate arc flash protection shall be utilized if flash protection boundary
crossed.
>>> To cross the Prohibited Approach Boundary, which is considered the
same as making contact with exposed energized conductors or parts, the
qualified person must:
•Have specific training for working on energized parts
•Have a documented plan justifying the need to work that close approved by
management.
•Perform a risk analysis approved by management.
•Use appropriate protective equipment for work on exposed conductors and
rated for voltage and energy level.
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May 2011

23. Other Key Arc Flash Definitions
Incident Energy – The amount of energy impressed on a surface, a
certain distance from the source, generated during an electrical arc
event. Measured in joules/cm2 or cal/cm2. (1 joule/cm2 = 0.24 cal/cm2).
Flash Hazard Analysis – A method to determine the risk of personal
injury as a result of exposure to incident energy from an electrical arc
flash.
Arcing Fault Current – A fault current flowing through an electrical arc
plasma, also called arc fault current and arc current.
Bolted Fault Current – Resulting from a short circuit or electrical contact
between two conductors at different potentials in which the impedance
or resistance between the conductors is essentially zero.
Arc Duration – The total time it takes system protective devices to detect
and interrupt a fault current.
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May 2011

24. Operating Company Responsibilities
1. Conduct an arc flash analysis of the power system.
2. Establish shock & protection boundaries and
determine incident energy levels at working distances.
3. Put warning labels on equipment.
4. Implement qualified and general worker training.
5. Provide necessary personal protective equipment,
(PPE)
6. Require outside engineering consulting firms involved
in upgrades/expansions to provide 1, 2 and 3.
7. Require outside contractors to meet 4 & 5.
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May 2011

25. Steps in Performing an Arc Flash Hazard Analysis
1. Collect power system data.
2. Determine the system modes of operation.
3. Determine the bolted fault currents.
4. Determine the arcing fault currents.
5. Find protective device characteristics and arc durations.
6. Document system voltage levels and equipment classes.
7. Select the working distances.
8. Determine the incident energies for all equipment
9. Determine the flash protection boundary for all
equipment.
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May 2011

26. Performing an Arc Flash Hazard Analysis
• Methods
o NFPA 70E Table 130.7 (C)(9)
o Spreadsheets
o Power System Analysis Software
• Arc Flash calculation modules can be obtained with
commercially available comprehensive power system
modeling software.
• Short-Circuit Study
• Protective Device Coordination Analysis
• Arc Flash analysis (Per NFPA 70E or IEEE 1584)
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May 2011

27. Potential product based solutions
Keep people away from the equipment as much as possible
• Remote diagnostics, metering and controls
• Advanced diagnostics to implement condition based maintenance
Protect as fast as possible & as sensitive as possible without giving up selectivity
• Use zone selective interlocking and/or bus differential
• Use faster electronics and/or faster circuit breakers, or small fuses
• Use better instantaneous algorithms that allow low pick up settings
• Use light sensing for controlling CBs as an alternative sensitive
instantaneous
Use arc resistant enclosures and/or equipment
• Passive Arc Resistant equipment – Only if doors and panels closed & does
not protect equipment
• Active Arc Resistant equipment - crowbars or similar driven by light sensing
Use temporary sensitive instantaneous protection (maintenance setting)
Use local “off” switching
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May 2011

28. Distance
Keep people away from the equipment as much as possible
•Remote controls – on/off/switching
•Remote metering – basic, advanced, condition
•Remote diagnostics – troubleshooting equipment condition
and process
•Advanced diagnostics to implement condition based
maintenance
–Use information acquired to minimize
need to touch equipment
•Remote operated racking
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May 2011

29. Use fast & sensitive protection- protection without
giving up selectivity
Several strategies
Zone selective interlocking (ZSI)/MV Instantaneous Blocking – all manufacturer’s can do it.
Essentially allows layered curves over some fault range. Improves system reliability.
• Newer generation trips and circuit breakers have faster protection providing ZSI even
in the instantaneous range.
Bus Differential Protection – Can be done with Relays by all manufacturer’s. Improves system
reliability.
• Single Processor concept 87B & ZSI simultaneously in LV equipment
Optimized instantaneous selectivity – All manufacturers have tables, some provide improved
selectivity over CL devices. Improve system reliability & safety at the same time.
Newer LV trip algorithms perform waveform recognition with < cycle of information allowing
very low instantaneous settings to remain selective.
Arc Flash (light sensitive) relays . . . Careful with LV implementations
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May 2011

30. Remote Racking, Remote
Controls, Remote Metering
Do not do locally, on live equipment, what
can be done remotely outside arc flash
boundary.
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May 2011

31. Containment method – passive arc resistance
• Common in MV systems
• Moving into LV systems in US
• Contains arc safely
• Barrier between person & arc
• Must be fully assembled
• Plenum needed to exhaust
May be solution for operators, but not
for maintenance
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May 2011
MEV

32. Alternative to arc resistance via containment -
diversion
Transfer energy to alternate current path
MV
52 Breaker Common implementation - Crowbar
• Remove arcing fault via bolted fault
XFMR • Energy goes to lowest impedance path
• Protection provided even if equipment
doors are open
However
A
Main LV B • Maximum bolted fault current
C
Breaker
• Electrical equipment damage possible
• How to test?
• Reusable?
Feeders
.....
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May 2011
MEV

33. 33
May 2011

34. Other arc flash protection
Temporary Instantaneous for reduced energy let-through
• Faster protection when desired or most needed.
• But needs good “procedures” to makes sure its used when needed
• And good procedures to make sure it is off when not needed and
undesirable
• Need good indication/signaling for reliability
• Needs to be set as fast and sensitive as application will allow
• Nuisance trip may also have consequences
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May 2011

35. Arc Flash Categories & Protective Clothing
ATPV Hazard Risk Weight
2 2
cal/cm Category Description of Clothing Oz/yd
0–2 Class 0 Untreated Cotton 4.5 - 7.0
>2 – 4 Class 1 AR Shirt & AR Pants or AR coverall 4.5 - 8.0
+ AR Face Shield or Hood
>4 – 8 Class 2 Cotton Underwear + AR Shirt & AR 9 - 12
Pants + AR Face Shield or Hood
>4 – 8 Class 2* Cotton Underwear + AR Shirt & AR 9 - 12
Pants + AR Hood or AR Face
Shield & Balaclava
>8 – 25 Class 3 Cotton Underwear + AR Shirt & AR 16 - 20
Pants + FR Coverall + AR Face
Shield or Hood
>25 – 40 Class 4 Cotton Underwear + AR Shirt & AR 24 - 30
Pants + Multi-layer Flash Suit +
AR Hood
> 40 Extreme Danger No PPE class applies -
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Class 2* introduced in NFPA 70E 2009. In 2012, 2 may become 2*. May 2011

36. Arc Flash PPE
HRC 1 HRC 2 HRC 2* HRC 3&4
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May 2011

37. Typical Arc Flash & Shock Equipment Signs
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38. Typical Shock & Arc Flash Work Permit
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May 2011

39. Thank you!
Any questions?
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May 2011