Practical Arc Flash Protection for Electrical Safety Professionals

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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

Text of Practical Arc Flash Protection for Electrical Safety Professionals

  • 1. Practical Arc Flash Protection for Electrical Safety Professionals www.idc-online.com/slideshare TecThenchonloogloyg Ty rtaraininiinngg tthhaatt wWoorkrkss
  • 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 Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare 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) Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare Arc Flash Protection
  • 11. Battery Hazards Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare 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) Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare Arc Flash Protection Loads Motive, Heating, Lighting Uninterrupted power supplies with battery
  • 15. Potential Hazards-1 Generation equipment: Electric shock, flash-over, mechanical hazards Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare 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) Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare Arc Flash Protection
  • 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 Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare 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 Technology Training that Works www.idc-online.com/slideshare Arc Flash Protection
  • 22. DO YOU WANT TO KNOW MORE? If you are interested in further training or information, please visit: http://idc-online.com/sl