Arc Flash Training

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This training presentation covers the basic on arc flash and other electrical hazards, including the effects of an arc flash incident and how to determine shock and flash protection boundaries for a safe workplace

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Arc Flash Training

  1. 1. Arc Flash Basics TRAINING SM
  2. 2. Electrical Hazards • Shock (A) Touch Potential (B) Step Potential (C and D) Touch / Step Potential • Arc Flash • Arc Blast SM
  3. 3. Arc Flash & Arc Blast • Arc Flash – Heat – Fire • Arc Blast – Pressure – Shrapnel – Sound SM Example of an arcing fault
  4. 4. 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 • Over 2000 people are admitted into burn centers each year with severe electrical burns SM
  5. 5. Arc Blast • An arc fault develops a “pressure wave” • Sources of this blast include: – Copper expands 67,000 times its original volume when vaporized – Heat from the arc, causes rapid air expansion • This may result in a violent explosion of circuit components and thrown shrapnel • The blast can destroy structures, knock workers from ladders, or across the room SM
  6. 6. Arcing Fault - Effects Molten Metal 35,000 F Pressure Waves Sound Waves Shrapnel Copper Vapor: Solid to Vapor Hot Air-Rapid Expansion Expands by 67,000 times SM Intense Light
  7. 7. Arc Flash Hazard • Energy of Arc Flash determined by: – Arcing fault duration or time to clear • Speed of the overcurrent protective device – Arcing fault current magnitude • Available fault current • Current-limitation can reduce – Distance to Arcing Fault SM
  8. 8. Test 4 Still Photo Before SM
  9. 9. Test 4 Still Photo INITIAL SM
  10. 10. Test 4 Still Photo DURING SM
  11. 11. Test 4 Still Photo FINAL SM
  12. 12. Test 4 RESULTS • Burns – 3rd Degree at Neck and Hands – Shirt did not ignite and reduced to below 2nd degree burn • Sound – 141.5 db • Pressure – Collapsed Lungs SM
  13. 13. NFPA70E - Electrical Hazard Analysis NFPA 70E 110.8(B)(1) – Requires an electrical hazard analysis if working on or near exposed conductors or circuit parts • Shock Hazard Analysis – “Approach Boundaries” • Flash Hazard Analysis – Flash Protection Boundary – Incident Energy / PPE SM
  14. 14. Shock Hazard Analysis • NFPA 70E 130.2(A) • A shock hazard analysis shall determine: – The voltage to which exposed – The boundary requirements – The personal protective equipment necessary in order to minimize the possibility of electric shock to personnel SM
  15. 15. Shock Protection Boundaries • NFPA 70E 130.2(B) • The shock protection boundaries identified – Limited Approach: Qualified persons and unqualified if accompanied by qualified person – Restricted Approach: Qualified persons only – Prohibited Approach: Qualified persons only – PPE as if in direct contact with live part SM
  16. 16. Shock Protection Boundaries NFPA 70E Table 130.2(C) Column Number (1) (2) (3) (4) (5) Limited approach Boundary Restricted Prohibited Nominal System Approach Approach Voltage Range Boundary Boundary Includes Includes Exposed Exposed Inadvertent Reduced Movable Fixed Movement Inadvertent Phase-to-Phase Conductor Circuit Part Adder Movement Adder Energized Part to Employee - Distance in feet - Inches Less than 50 V Not Specified Not Specified Not Specified Not Specified 50 V to 300 V 10 ft. 0 in. 3 ft. 6 in. Avoid Contact Avoid Contact 301V to 750 V 10 ft. 0 in. 3 ft. 6 in. 1 ft. 0 in. 0 ft. 1 in. 751 V to 15 kV 10 ft. 0 in. 5 ft. 0 in. 2 ft. 2 in. 0 ft. 7 in. 15.1 kV to 36 kV 10 ft. 0 in. 6 ft. 0 in. 2 ft. 7 in. 0 ft. 10 in. SM
  17. 17. Flash Hazard Analysis • NFPA 70E 130.3 Flash Hazard Analysis: Flash hazard analysis shall be done in order to protect personnel from the possibility of being injured by an arc flash. …” • What is required? – Determine Flash Protection Boundary – Determine the personnel protective equipment (incident energy determination) SM
  18. 18. Flash Protection Boundary Linear distance from exposed live parts within which a person could receive second degree burns (1.2 cal/cm2) resulting from an arc flash 480V MCC SM
  19. 19. Flash Hazard Analysis Three common methods (600V or less): 1) Default FPB and task-hazard/ PPE tables • Qualifiers and limitations 2) Utilize NFPA 70E equations • Incident energy – select PPE • FPB 3) IEEE1584: equations or calculator • Incident energy – select PPE SM
  20. 20. Flash Hazard Analysis • NFPA 70E 130.7(C)(10) Protective Clothing and Personal Protective Equipment Matrix – Determine after calculating the incident energy of the arc – Hazard Risk Category • HRC 0: 0-1.2 cal/cm² • HRC 1: 1.2-4 cal/cm² • HRC 2: 4-8 cal/cm² • HRC 3: 8-25 cal/cm² • HRC 4: 25-40 cal/cm² • DANGEROUS: > 40 cal/cm² SM
  21. 21. NFPA70E - Electrical Hazard Analysis Flash Protection Boundary (FPB) Equipment Must wear appropriate PPE PROHIBITED RESTRICTED LIMITED Q Q Q Q Q U U U U U Arc Flash PPE Q U Shock PPE + SM

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