NFPA 70E-2009
ARC FLASH PROTECTION
What is an Electric
Arc?
• Electric Arc –The passage
of a substantial electric
current through a gas, such
as air or vaporized metal.
– An electric arc...
• Typically lasts less than one
second
• Has an extremely high
percentage of radiant energy
• Is explosive in nature
• Can ignite and/or melt most
things in its path.
The Arc
1
2
Electrical Hazards
• ARC FLASH – A dangerous condition associated
with the release of energy caused by an electric
arc due to either a phase to ground or phase to
phase fault.
– Note that this explosive condition includes a broad
spectrum of electromagnetic energy, vaporized metal
(plasma), heat, pressure wave, fragments and a spray
of molten metal projectiles.
• PLASMA - Superheated gas that is created by
the arc flash and expands rapidly from the Arc
location.
C
Arc Flash
• This phase to ground or
phase to phase fault can
result from many factors,
including dropped tools,
accidental contact with
electrical systems, build
up of conductive dust,
corrosion, and improper
work procedures.
Example of an arc flash
C
Electrical Hazards
• Arc Blast –Pressure wave caused by the
expansion of gases and conducting materials with
flying molten materials. (Arc temperature can
reach 35,000°F - this is four times hotter than the
surface of the sun. Fatal burns can occur at
distances over 10 ft.).
Serious injuries and damage can result
an arc flash/blast.
What Determines the
Intensity of an Electric
Arc Exposure?
•
•
•
•
The electric arc itself
Its fault current
Its duration
Its configuration or
enclosure
– Also known as “Arc-in-aBox”
C
What Determines the Intensity
of an Electric Arc Exposure?
• The number of phases
involved.
• The system you’re working
on
– Its electrode gap
– Its available voltage
• Your location
– How close or far you are from
the electric arc when it occurs
What Risks are
Possible with Electric
Arc Exposures?
• Electrocution.
• Physical injury resulting from
explosive forces.
• Burn injuries (without
electrical contact) resulting
from:
– Intense radiant energy
– Molten metal splatter
– Secondary fires (e.g., from
transformer oils)
• The ignition or melting of
clothing.
Why Are Burn Injuries a Major
Concern?
• The most severe
burns are caused by
ignited clothing, not
by the original flash
fire or electric arc
exposure.
C
Electric Arc Flash
81 Cal Incident
Inner
Layer
Outer Layer
Survival Chances from
Burn Injuries (recap)
100
90
80
70
60
50
40
30
20
10
0
25%
50%
75%
% of body
burn
20-29
30-39
40-49
American Burn Association Study
50-59
Are You in Compliance?
• Industry standards and
regulations:
– OSHA 29 CFR 1910 Subpart S
– NEC
– NFPA 70E-2009 Edition
– Various ASTM Requirements
OSHA Regulations
• OSHA 29CFR 1910, Sub-part SElectrical.
– Design safety standards for electrical
systems. These regulations are contained in
1910.301 through 1910.399.
Hazardous Locations
OSHA Regulations
• 29CFR 1910.335(a)(1)(i)
– “Employees working in areas
where there are potential
electrical hazards shall be
provided with, and shall use,
electrical protective equipment
that is appropriate for the
specific parts of the body to be
protected and for the work to be
performed”.
What is the NFPA 70E-2009?
• NFPA 70E is:
– National consensus standard and a
“Standard for Electrical Safety in the
Workplace”.
– and is a part of the National Electrical
Code and has been adopted by OSHA
as an enforcement standard.
NFPA 70E – 2009 Edition
Standard
– Addresses hazards:
• Shock
• Arc Flash
– Requirements for
shock and arc flash
boundaries.
– Requirements for
personal protective
equipment.
C
Content of NFPA 70E, Standard for
Electrical Safety in the Workplace
NFPA 70E 2009
• Chapter 1 addresses safe installations,
procedures for avoiding injury during electrical
work, proper tools, and PPE.
• Chapter 2 addresses maintenance requirements.
• Chapter 3 addresses special equipment, i.e.
battery rooms, electrolytic cells, lasers, and
electronics.
• Chapter 4 addresses installation requirements
similar to OSHA Subpart S.
Electrical Installations
NFPA vs. OSHA
OSHA
NFPA
1910.301 .308
70E, Chap.
4
Markings & Identification
X
X
Work Space 3’
X
X
Reference
Impedance Requirements
Polarity & Grounding
X
X
GFCI for Restrooms &
Rooftops
Hazardous Locations
X
X
Class I
“Divisions”
Class I
“Zones”
Safety Related Work Practices
NFPA vs. OSHA
OSHA
NFPA
1910.331-.360
NFPA 70E
Working on Live Parts
X
X
Qualified Employees
Training
Approach Boundaries
X
X
Reference
PPE
Electrical Safety Program
X
Some
X
X
Scope of Standard
• Covers electrical safety requirements for
employee workplaces that are necessary for the
protection of employees in their pursuit of gainful
employment.
– Includes:
•
•
•
•
•
•
•
Public & Private premises
Mobile Homes, Recreational vehicles
Floating Buildings
Yards, Lots, Parking Lots
Carnivals
Industrial Substations
Electrical Utility Installations
What Job Tasks are Covered
Under NFPA 70E*?
• Installing conductors and
other electrical
equipment on industrial
substations or buildings,
residential or
commercial.
• Connecting the
installations to a supply
of electricity.
• Installing other outside
conductors.
*Examples Only
What Job Tasks are NOT
Covered under NFPA 70E?
Installations...
• In ships, watercraft, railway rolling stock,
aircraft, or automotive vehicles other than
mobile homes and RVs.
• In underground mines.
• Of railways for operation of rolling stock.
• Communication equip. under control of
communication utilities.
• Under the control of electric utilities.
Electrical Safety Program
Principles
• Inspect/evaluate electrical equipment.
• Maintain equipment insulation and
enclosures.
• Plan every job.
• Document first time procedures.
• Deenergize, if possible.
Electrical Safety Program
Principles
• Anticipate unexpected events.
• Identify and minimize the hazard.
• Protect from shock, burn, blast, and
other hazards.
• Use the right tools for the job.
• Assess employee’s ability.
• Audit these principles.
Electrical Safety Program
• Components
– Employee Training
– Procedures
• Working on or near live parts at 50V or greater
– Hazard Evaluation and Assessment
– Job Briefing
– Energized Electrical Work Permit System
– Inspection of Portable Cord & Plug
Equipment and Flexible Cord Sets
Electrical Safety Program
Controls
• Every conductor or circuit is considered live until
proven otherwise.
• No bare-hand contact with exposed energized
parts above 50V, unless using the “bare handed
method” properly.
• Deenergizing electrical to make it safe is
considered a potentially hazardous task.
Electrical Safety Program
Controls
• Employer develops the programs and the
employees apply them.
• Train employees to make them qualified.
• Identify & categorize tasks to be performed on or
near exposed electrical.
• Identify & use precautions appropriate to the
working environment.
Lockout/Tagout
• Individual LOTO
– Used when only one person is working and
circuit is under that persons control and
observation and only on one shift.
• Simple LOTO
– Used when only one person is working and
it involves deenergizing one set of
conductors or circuit part.
C
Lockout/Tagout
• Complex LOTO
– Used when there is:
•
•
•
•
Multiple energy sources  Multiple crews
Multiple crafts

Multiple employers
Multiple shifts

Particular Sequences
Different disconnecting means
– One person in charge
• Can install locks on behalf of other employees
C
Lockout/Tagout
– Requires written procedures
– Requires written plan
– Testing requirement
– Personnel accountability system
– Formal lock removal process
– Installation of temporary grounds
Temporary Grounding
• Prevent employees from being exposed to
hazardous differences of electrical potential.
• Capable of conducting the maximum fault
current that could flow.
• Must meet requirements of ASTM on Temporary
Grounds.
• Impedance low enough to cause immediate
operation of protective devices.
Definitions
• Flash Protection Boundary – An
approach limit at a distance from exposed
live parts within which a person could
receive a second degree burn if an
electrical arc flash were to occur.
Definitions
• Limited Approach Boundary – An
approach limit at a distance from an
exposed live part within which a shock
hazard exists.
• Restricted Approach Boundary – An
approach limit at a distance from an
exposed live part where there is an
increased risk of shock due to electrical
arc for employees working in close
proximity to the live part.
Definitions
• Prohibited Approach Boundary – An
approach limit at a distance from an
exposed live part which work is considered
to be the same as making contact with the
live part.
Definitions
• Working near (live parts) – Any activity
inside of a Limited Approach Boundary.
• Working on (live parts) – Coming into
contact with live parts with the hands, feet,
or other body parts with tools, probes, or
test equipment regardless of the PPE a
person is wearing.
Definitions
Qualified Person:
• One who has skills and knowledge
related to the construction and
operation of the electrical equipment
and installations and has received
safety training on the hazards involved.
•Who would be a qualified person?
•Are you a qualified person?
•If your not a qualified person, what is
your role around electricity?
Approach Limits
• Principles
– Increase the distance between the person
and decrease the potential for an accident.
– Unqualified employees should not cross the
Flash Protection Boundary.
– Qualified personnel shall not cross the Flash
Protection Boundary unless appropriate PPE
is used.
Approach Limits
• Qualified personnel shall not approach or
take any conductive objects closer than
the Restricted Approach Boundary unless
they or the electrical equipment is
protected AND
– They have a plan
– Are using the appropriate PPE for the energy
level involved
Approach Limits
Flash Protection
Boundary
Limited Approach
Boundary
Exposed
Energized
Part
Prohibited Space
Restricted Space
Limited Space
Prohibited
Approach Boundary
Restricted
Approach
Boundary
Approach Limits
Nominal
Voltage
Range
Flash
Limited A. B. Limited A. B.
Protection Exposed
Exposed
Boundary Movable C.
Fixed C.
50-300KA
Restricted Prohibited
Approach Boundary
Boundary
50 –
300V
4 ft.
10 ft.
3.5 ft.
Avoid
Contact
Avoid
Contact
301 –
600V
4 ft.
10 ft.
3.5 ft.
1 ft.
1 in.
600 –
750V
Based on
Cal’s.
10 ft.
3.5 ft.
1 ft.
1 in.
751 –
15 KV
Based on
Cal’s.
10 ft.
5 ft.
2 ft. 2 in.
7 in.
Exposed Energized Parts
• Only qualified persons are allowed to
work on live exposed parts.
• Spaces and areas with live parts must be
well lighted.
• Don’t reach into blind areas.
• When working in confined spaces with
live parts, protective shields, barriers, or
insulating materials shall be used on the
live circuits, etc.
Exposed Energized Parts
• Ladders must be of nonconductive
materials.
• Conductive clothing and jewelry should
not be worn.
• Nonconductive cleaning materials and or
precautions should be used around live
parts.
• Control hazards to prevent ignition of
flammable & combustible materials.
Overhead Lines
• Should be deenergized and grounded
when working around.
• Employees should be aware of the
approach distances.
• Mechanical and vehicular equipment
should be kept at least 10’ away, in transit
4’.
• Blanketing may also be used as an added
precaution.
• Watch overhead when working with long,
conductive objects.
Electrical Power and
Lighting Circuits
• Circuit breakers must be used to open
circuits under load conditions.
• Safety of the circuits must be checked
before reenergization.
• Over-current protection cannot be
modified.
• Only qualified employees can test
electrical parts or circuits operating at 50V
or more.
Use of Equipment
70 E & 1910.334
• Cords must have proper grounding.
• Check the cord for defects.
• Do not lift or lower equipment by the
cord.
• Do not unplug equipment by pulling on
the cord.
• Do not tack or staple cords in place.
• Cords must be approved for the
location.
Flexible Cords
• Visually check for defects such as:
– Loose Parts
– Deformed or missing prongs
– Damaged jackets or insulation
– Conduct on a daily basis
Safeguards for Personal
Protection - 1910.335
• Employers must provide personal
protective equipment.
• Employees must wear it.
• Must be maintained in a safe condition
and inspected.
• Non-conductive head protection must
be worn.
• Appropriate tools should be used.
Who’s Required To Do
What?
• NFPA 70E 130.6 (C)
General: employees working in areas
where there are electrical hazards shall be
provided with, and shall use, protective
equipment that is designed and constructed
for the specific part of the body to be
protected and for the work to be performed.
PPE Clothing Not Permitted
– Clothing made from Synthetic materials
such as acetate, nylon, polyester, rayon,
either alone or in blends with cotton, shall
not be worn.
• The most severe burns are caused by
ignited clothing, not by the original Flash
Fire or Electrical Arc Exposure.
• Clothed areas can be burned more
severely than exposed skin.
Personal Protective
Equipment
• 70E 2009, Table 130.7(C)(9)(a)Hazard Risk
Category Classifications,pages 29 thru 31.
– Based on task, voltage, type of equipment and
notes (fault current and clearing time) the table
shows:
• hazard / risk category
• if V-rated gloves are required
• if V-rated tools are required
– For any task, voltage, fault current or clearing
times not listed in the table, do the calculation
outlined in 70E, 130.3(A),page 25.
Protective Clothing
• For most low-energy work (240 volts or below),
natural-fiber, non-melting clothing is adequate; some
higher risk tasks require FR clothing.
• Most work on or near systems rated 480 volts and
above requires at least one layer of flame-resistant
(FR) clothing worn over natural-fiber clothing.
• High-energy tasks require FR flash suits and flash
hoods worn over FR clothing.
Underlayers
• Meltable synthetic fibers
shall be avoided in fabric
underlayers (underwear)
next to the skin.
– When the FR clothing
system has been
appropriately assessed to
the hazard, then a cotton
undergarment will provide
additional protection.
Personal Protective Equipment
(PPE) Requirements
Required PPE includes:
• Flame-resistant clothing
•
•
•
•
Flash suits (for high-energy arc exposure)
Flash suit or Balaclava hoods
Natural Fiber Clothing
Fire Retardant Coveralls
• Insulating gloves
• Insulated tools
• This is in addition to normally used hard hat,
safety shoes, safety glasses, and hearing
protection.
NFPA 70E Provides Two Choices
for Selecting the Appropriate
PPE:
• Conduct an arc flash hazard analysis, and
document the incident energy exposure.
– Duke Flux Software (Freeware)
– ArcPro II Software
– IEEE 1584 Standard
• As an alternate, use the “Hazard Risk
Category Classifications” table to choose the
PPE level required for the task.
Hazard Risk Category Tables
ASTM F-1959 Electric Arc Panel
Test Results
ATPV - Arc Thermal Performance Value
Total incident energy (cal/cm2) on the surface of a
fabric that would be expected to just cause a second
degree burn on skin behind and in contact with the
fabric.
HAF - Heat Attenuation Factor
Percent of the Incident Energy Blocked By the Fabric.
Ebt - BreakOpen Threshold Energy
Average of the five highest incident energy values
(cal/cm2) which did not cause breakopen of the fabric
(and are below the Stoll Curve).
Simulated Electric Arc Blast –
Untreated Cotton Shirt ( 5.7 oz/yd2
)
Before Electric Arc Blast
During Electric Arc Blast
After Electric Arc Blast
Simulated Electric Arc Blast:
NOMEX® Workwear (4.5 oz/yd2 )
Before Electric Arc Blast
During Electric Arc Blast
After Electric Arc Blast
Personal Protective Equipment
Protective Clothing (non-melting)
Hazard/Risk category
70E, page 34
ATPV=arc
thermal
performance
value
Cal/cm2
(Calories per Sq.
Centimeter)
Protective Clothing
ATPV/ Cal/cm2
0
Untreated Cotton
ATPV n/a
1
FR shirt and FR pants
ATPV 4 cal/cm2
2
Cotton underwear plus
FR shirt and FR
pants
ATPV 8 cal/cm2
3
Cotton underwear plus
FR shirt and FR
pants plus FR
coverall
ATPV 25 cal/cm2
4
Cotton underwear plus
FR shirt and FR
pants plus double
layer switching coat
and pants
ATPV 40 cal/cm2.
NFPA 70E – Hazard Risk 0
Hazard/Risk
category
Protective Clothing
ATPV/ Cal/cm2
0
Untreated Cotton
ATPV n/a
This hazard risk category poses minimal risk.
Some examples of tasks in this category are tasks that
involve:
• Circuit breaker or fused switch operation with covers on when
working with Panel boards rated 240 V and below.
• Contactor operation with enclosure doors closed when working
with NEMA E2 (fused contactor) Motor Starters, 2.3 kV through
7.2 kV.
NFPA 70E – Hazard Risk 1
Hazard/Risk
category
1
Protective Clothing
ATPV/ Cal/cm2
FR shirt and FR
pants
ATPV 4 cal/cm2
This hazard risk category poses some risk. Some
examples of tasks in this category are tasks that involve:
• Circuit breaker or fused switch operation with covers off when
working with Panel boards rated 240 V and below.
• Opening hinged covers (to expose bare,
energized parts) when working with
"Other 600 V Class (277 V through
600 V, nominal) Equipment.
NFPA 70E – Hazard Risk 2
Hazard/Risk
category
2
Protective Clothing
Cotton underwear plus
FR shirt and FR pants
ATPV/ Cal/cm2
ATPV 8 cal/cm2
This hazard risk category involves tasks that pose a
moderate risk. Some examples of tasks in this
category are tasks that involve:
• Circuit breaker or fused switch operation with enclosure doors
closed when working with 600 V Class Motor Control Centers
(MCCs).
• Work on control circuits with energized parts 120 V or below,
exposed when working on Metal Clad Switchgear, 1 kV and
above.
NFPA 70E – Hazard Risk 3
Hazard/Risk
category
3
Protective Clothing
Cotton underwear plus
FR shirt and FR pants
plus FR coverall
ATPV/ Cal/cm2
ATPV 25 cal/cm2
This hazard risk category involves tasks that pose a high
risk. Some examples of tasks in this category are tasks that
involve:
• Insertion or removal of circuit breakers from cubicles, doors open,
when working with 600 V Class Switchgear (with power circuit
breakers or fused switches).
• Opening hinged covers (to expose bare, energized parts) when
working with "Metal Clad Switchgear, 1 kV and above.
NFPA 70 E – Hazard Risk 4
Hazard/Risk
category
Protective Clothing
ATPV/ Cal/cm2
4
Cotton underwear plus FR
shirt and FR pants plus
double layer switching coat
and pants
ATPV 40 cal/cm2.
This hazard risk category represents tasks that pose the
greatest risk. Some examples of tasks in this category
are tasks that involve:
• Removal of bolted covers (to expose bare, energized parts)
when working with NEMA E2 (fused contactor) Motor Starters,
2.3 kV through 7.2 kV.
• Opening voltage transformer or control power transformer
compartments when working with Metal Clad Switchgear, 1kV
and above.
Care and
Maintenance
• All personal protective
equipment shall be
maintained in a sanitary
and reliable condition.
• Oil and other stains should
be cleaned to eliminate a
fuel source.
• FR clothing shall be
inspected before each use.
What Products are Available to
Accomplish these Requirements?
• Voltage rated gloves and
protectors.
• Insulated/Insulating tools.
• Insulating blankets.
• Insulating protective
shielding.
• Insulating sleeves.
• Dielectric footwear.
Additional Equipment
Insulating Blanket
Arc & Flame
Resistant
Raingear
Dielectric Footwear
Insulating Shielding
Insulating Gloves
OSHA 1910.333(a)(1)
• Rubber insulating
gloves are among the
most important
articles of personal
protective equipment
for electrical workers.
• They are the first line
of defense for contact
with any energized
components or lines.
Leather Protector Gloves
Leather Protector
Gloves should
always be worn over
TYPE I or II
electrical insulating
gloves to provide
needed mechanical
protection against
abrasion or cuts.
Gloves & Shoes
• Gloves rated by voltage
»
»
»
»
Class 00 = 500 volts max
Class 0 = 1000 volts max
Class 1 = 10 kV max
Class 2 = 20 kV max
• Shoes - Heavy-duty leather work shoes
shall be used for all tasks when ATPV is
5 cal/cm2 and above.
• insulating soles are recommended.
• overshoes or dielectric boots are
recommended.
Portable Glove Inflation
Tester
• All insulating gloves must be
electrically tested every six
months to be in accordance
with OSHA 29 CFR
1910.137.
• In addition, gloves must be
visually inspected to check for
tears, rips and punctures.
– Salisbury G-99 glove inflator
will simplify visual
inspection.
Hard Hats
Z89.1-1997, Type 1, Class C,E,G - This is the
ANSI stamp of approval that specifies the hard hat
meets all safety requirements.
Classifications under old and new standards:
Z89.1 – 1986
Z89.1 – 1997
Application Test Voltage
(Old Standard) (New Standard)
A
G
General
2,200
B
E
Electrical
20,000
C
C
Conductive
Not Tested
Additional Protective
Equipment
• Face shields are available that are listed with
ATPV ratings from many manufacturers... Do not
use general duty face shields.
– Always wear safety glasses under face
shields (no metal frames).
– Always wear a hard hat.
– Hearing protection is recommended.
– Protective hoods or parkas should be worn in
conjunction with shields and hard hats.
Insulated Tools
• Insulated tools that
meet ASTM F1505
and OSHA
1910.333 (c)(2).
• The tools are rated
1000V to be used
on working with
energized
equipment.