Electrical safety is an important issue for those working on electrical facilities in utility networks and large industrial installations. A number of serious accidents including fatalities occur every year due to accidents involving electricity resulting in huge financial losses and wasted man-hours. Arc flashes in electrical equipment are now considered one of the major causes of electrical accidents even surpassing the well known hazards of electric shock. Avoiding arc flash incidents and the resulting injuries is one of major challenges today facing electrical workers and requires adequate attention in the stages of system planning, design, installation, operation and maintenance. Injuries due to arc flash can depend on many factors, one of which is the incident thermal energy on a worker exposed to a flash. Today, a considerable body of knowledge exists as a result of research efforts and is available to designers and maintenance engineers in the form of standards such as IEEE 1584 and NFPA 70E. This workshop will detail the basis of this approach and also about the major advances that have been made in the area of PPE made of FR fabrics and rated for different levels of thermal exposure. Prevention however still remains the best form of protection and switchgear manufacturers have made considerable design advances to ensure that the effect of arc flash incidents is contained within the enclosure of switchgear (often called arc flash resistant switchgear) and methods of testing such switchgear have also evolved simultaneously. Another important factor is the approach to avoid arc incidents within the switchgear by proper design and maintenance and techniques to reduce the severity of the flash should such incidents occur. These would form the key focus areas of this workshop. MORE INFORMATION: http://www.idc-online.com/content/practical-arc-flash-protection-electrical-safety-professionals-22

1. Practical Arc Flash Protection
for Electrical Safety
Professionals
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2. Overview
• Hazards of general nature in industrial installations
• Electrical hazards
– Direct and Indirect electric shock
– The deadly combination of heights and electric shock
– Hazards due to arcing/flashover
– Hazards from use of electrical equipment in explosive environment
– Hazards due to high temperature in electrical equipment
– Need for periodic inspection and maintenance for safe operation of
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Arc Flash Protection
electrical equipment

3. Electrical Hazards
• Electric shock and associated effects
• Injuries by electric shock combined
with fall
• Arc flash causing external burns
• Explosion caused by electrical
sparks
• Other thermal effects
• Hazards from electrical battery
installations
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Arc Flash Protection

4. Electric Shock-Reasons
• An electric shock can happen
– Due to exposure to live parts
(Direct contact)
– Due to exposure to parts that
accidentally become live
(Indirect contact)
• Due to potential difference in the
ground under certain conditions
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Arc Flash Protection

5. Electric Shock: Effects
• Causes current flow through body
• Causes muscular contraction
• Can cause stoppage of heart/breathing
• A shock is often accompanied by a fall
– A non-fatal shock can result in a fatal fall
– While working on electrical systems at heights, adopt
preventive measures to avoid a fall
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Arc Flash Protection

6. Burns
• An electrical short circuit is accompanied by arcing
• Extent of arcing depends on
– Fault energy level of the system (VA)
– Time of fault clearance
• High energy faults can cause melting of components
– Copper/aluminium conductors
– Steel parts of enclosure
– Results in deposition of toxic copper salts on the skin
• Skin burns can also be caused at the point of contact (without overt arcing)
• Internal damage due to passage of electricity
(Example: Lightning current through a human body)
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Arc Flash Protection

7. Temperature Hazards
• External surfaces of electrical
equipment often attain elevated
temperature
– Example: Bus ducts can often attain
surface temperatures of over 60 Deg C
• Exposed conducting parts can attain
even higher temperatures
– Example: Bus bars often run at
temperatures in excess of 100 Deg C
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Arc Flash Protection

8. Temperature Hazards
• Electrical joints/mating surfaces can have temperatures
exceeding the conductor temperature
• This is because of increased localised resistance
• High surface temperature can cause ignition if
flammable vapors are present in the environment
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Arc Flash Protection

9. Fire Hazard
• An external fire can often result from an electrical
fault
– Example: A wiring short circuit and presence of
combustible substances in the vicinity
• Certain electrical equipment contain inflammable
substances and improper handling can result in fire
– Example: Large transformers with mineral oil for
cooling
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Arc Flash Protection

10. Explosion Hazard
• Special care for electrical equipment in hazardous atmosphere
• Many electrical equipment produce arcing or sparking in normal
operation
– Example: Contactors, Carbon brushes, Push buttons/switches
• Some equipment may generate arcs during abnormal conditions
– Example: A terminal short circuit in a motor
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Arc Flash Protection

11. Battery Hazards
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Arc Flash Protection
• Electric shock
• Lead dust toxicity
• Acid fumes
• Explosion

12. Structure of an Electrical System
• Incoming circuit
• Step-down transformer
• Primary distribution
• In-plant generation (Primary)
• Step down transformer
• Secondary distribution
• In-plant generation (Localised/secondary)
• Local distribution centers (MCC/DBs)
• Uninterrupted power supplies to specific critical loads
• Loads on primary and secondary distribution system
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Arc Flash Protection

13. Main Components-1
• Generation equipment-(Captive generation in
industry)
• Step-up/step-down Transformers
• Transmission lines (long distances)
• Cables (Medium distances)
• Bus ducts (Short distances)
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Arc Flash Protection

14. Main Components-2
• Distribution equipment
– Isolation equipment (for safety purposes)
– Bus bars
– Switching equipment (circuit breakers/contactors)
– Instrument transformers
– Protection equipment
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Arc Flash Protection
• Loads
– Motive, Heating, Lighting
• Uninterrupted power supplies with battery

15. Potential Hazards-1
• Generation equipment:
– Electric shock, flash-over, mechanical hazards
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Arc Flash Protection
• Transformers:
– Electric shock, flash-over, fire hazard
• Overhead Transmission/distribution lines:
– Electric shock, flash-over, fall from heights
• Cables:
– Electric shock, flash-over, fire hazard
• Battery Installations:
– Electric shock, toxicity, explosion/fire

16. Potential Hazards-2
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Arc Flash Protection
• Bus ducts
– Electric shock, flash-over, thermal hazard
• Distribution equipment
– Electric shock, flash-over, thermal hazard, fire hazard
• Motive equipment
– Electric shock, flash-over, thermal hazard, mechanical hazards
• Heating equipment
– Electric shock, flash-over, thermal hazard

17. Potential Hazards-3
• Lighting equipment
– Electric shock, flash-over, thermal hazard, fall from
heights
• Uninterrupted power supplies with battery
– Electric shock, flash-over, hazards from corrosive
liquids and explosive gases, toxicity (lead, cadmium)
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Arc Flash Protection

18. Reasons for Electrical Accidents
• Failure to isolate or inadequate or insecure
isolation (60%)
• Poor maintenance and faulty equipment (30%)
• Insufficient information about the system being
worked on
• Carelessness and lack of safe procedures
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19. Summary of Safety Measures-Technical
• Safe design/installation of plant and equipment
• Safe operating and maintenance practices
• Appropriate knowledge on the part of workers
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Arc Flash Protection
– Training
– Certification
• Warning signs at points of hazard
• Use of equipment/sensors to warn incipient
problem

20. Summary of Safety Measures-Procedural
• Documented procedures and instructions
• Proper periodic inspection and prompt repairs
• Use of personal safety equipment
• Avoiding live/hot work except where mandated by
the relevant procedures
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Arc Flash Protection

21. Summary of Safety Measures-
Organisational
• Creating an organisational safety structure to
handle safety issues, lapses and accidents
• Updating documentation to reflect latest regulatory
changes
• Employee training
• Competence testing and certification
• Create safety awareness by frequent safety
campaigns and rewarding accident-free operation
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22. DO YOU WANT TO KNOW MORE?
If you are interested in further training or information, please
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Arc Flash Protection