3. Electrical Safety
ARC-FLASH
• As much as 80% of all electrical injuries are
burns resulting from an arc-flash and ignition
of flammable clothing.
• 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.
4. Electrical Safety
ARC EXPOSURE ENERGY BASICS
• Exposure Energy is Expressed in cal/cm2
• 1 cal/cm2
Equals the Exposure on the tip of a finger
by a Cigarette Lighter in One Second
• An Exposure Energy of Only One or Two cal/cm2
Will Cause a 2nd Degree Burn on Human Skin
5. Electrical Safety
Industry Standards and Regulations
• OSHA 29 CFR 1910 Subpart S
• OSHA Enforces NEC2002 110.16 & NFPA70E
• NFPA 70E-2000
• Requirements for shock and arc flash boundaries
• Requirements for personal protective equipment
• NEC 110.16-2002
6. Electrical Safety
NEC 2002
110.16 Flash Protection. Switchboards, panel boards, industrial control
panels, and motor control centers in other than dwelling occupancies,
that are likely to require examination, adjustment, servicing, or
maintenance while energized, shall be field marked to warn qualified
persons of potential electric arc flash hazards. The marking shall be
located so as to be clearly visible to qualified persons before
examination, adjustment, servicing, or maintenance of the equipment.
FPN No. 1: NFPA 70E-2000, Electrical Safety Requirements for
Employee Workplaces, provides assistance in determining severity of
potential exposure, planning safe work practices, and selecting personal
protective equipment.
FPN No. 2: ANSI Z535.4-1998, Product Safety Signs and Labels,
provides guidelines for the design of safety signs and labels for
application to products.
7. Electrical Safety
Sample NEC Warning Article 110.16
!
WARNING
Arc Flash and Shock Hazard
Appropriate PPE Required
8. Electrical Safety
ARC Flash Analysis
• OSHA 1910.132(d) Where work will be performed within the
flash protection boundary, the flash hazard analysis shall
determine, and the employer shall document, the incident energy
exposure to the worker (in cal/cm2
)
• OSHA 1910.269(I)(6) Flame resistant (FR) clothing and PPE
shall be used by the employee based upon the incident energy
exposure associated with the specific task.
• As an alternative, PPE requirements of NFPA 70E Part II 3-3.9
may be used in lieu of a detailed flash hazard analysis.
11. Electrical Safety
Approach Boundaries
Nominal System
Voltage Range
Limited Approach Boundary Restricted Approach
Boundary
Prohibited Approach
Boundary
Phase-to-Phase Exposed Moveable
Conductor
Exposed Fixed Circuit
Part
Includes Inadvertent
Movement Adder
0 - 50 Not specified Not specified Not specified Not specified
51 - 300 10 ft. 0 in. 3 ft.6 in. Avoid contact Avoid contact
301 - 750 10 ft. 0 in. 3 ft.6 in. 1 ft. 0 in. 0 ft. 1 in.
751V - 15 kV 10 ft. 0 in. 5 ft.0 in. 2 ft. 2 in. 0 ft. 7 in.
15.1 – 36 kV 10 ft. 0 in. 6 ft.0 in. 2 ft. 7 in. 0 ft. 10 in.
36.1 – 46 kV 10 ft. 0 in. 8 ft.0 in. 2 ft. 10 in. 1 ft. 5 in.
46.1 – 72.5 kV 10 ft. 0 in. 8 ft.0 in. 3 ft. 3 in. 2 ft. 1 in.
72.6 – 121 kV 10 ft. 8 in. 8 ft.0 in. 3 ft. 3 in. 2 ft. 8 in.
138 – 145 kV 11 ft. 0 in. 10 ft.0 in. 3 ft. 7 in. 3 ft. 1 in.
12. Electrical Safety
NFPA 70E provides two choices for PPE
selection:
• Do an arc flash hazard analysis, and document
the incident energy exposure
– IEEE 1584
– SKM (Arc Flash Evaluation Module)
– ArcPro Software
– Duke Power Cal/Flux Software
• As an alternate, use the “Hazard Risk Category
Classifications” table to choose the PPE level
required for the task
14. Electrical Safety
Hazard Risk Category Classification
• NFPA 70E – Hazard Risk 0
– This hazard risk category poses minimal risk.
• NFPA 70E – Hazard Risk 1
– This hazard risk category poses some risk.
• NFPA 70E – Hazard Risk 2
– This hazard risk category involves tasks that pose a
moderate risk.
• NFPA 70E – Hazard Risk 3
– This hazard risk category involves tasks that pose a
high risk.
• NFPA 70E – Hazard Risk 4
– This hazard risk category represents tasks that pose
the greatest risk.
15. Electrical Safety
Methods of Reducing Hazard Risk
• Specifying Current Limiting Fuses on Low Voltage
Switchgear Breakers
• Specifying ARC Resistance Medium Voltage
Switchgear
• Remote Control of Switchgear Breakers
• High Resistance Grounding on Low Voltage and
Medium Voltage (15kV and below) Systems
16. Electrical Safety
What We Offer Our Clients
• Design of safer power systems while insuring compliance
with OSHA NFPA 70E standards and IEEE 1584
• Save time with the fully integrated Short Circuit, Time
Current Coordination, Equipment Evaluation and Arc
Flash Evaluation
• Offer alternatives to reduce exposure to ARC Flash
Energy.
