Webinar - Electrical Arc Flash Hazards - Is your company in compliance?


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This course is designed to equip the electrical consultant, system designer or any other professional responsible for designing or modernizing commercial and industrial electrical power distribution systems with the fundamentals of the Arc Flash Energy phenomenon.

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Webinar - Electrical Arc Flash Hazards - Is your company in compliance?

  1. 1. Industrial Service Solutions Electrical Arc Flash Hazards Is your company in compliance?
  2. 2. Discussion HighlightsThe Bigger Picture of Electrical SafetyArc Flash Risks and EffectsArc Flash Approach BoundariesArc Flash Hazard Calculations NFPA 70E Tables IEEE Standard 1584-2002Arc Flash RemediationArc Flash Categories & Protective ClothingArc Flash Labels and Permits 2 May 2011
  3. 3. Worker safety is importantWhy?• In addition to being the right thing to do it is intrinsically connected to productivity, worker morale and liability costs• Machinery, processes & facilities usually designed with worker & machine safety as key consideration from start...• However, electrical safety often handled differently… Late, after base system design is finished, sometimes after equipment is purchased . . .It should not be !• Electrical safety can best be optimized by being part of the initially defined mission for the facility’s power distribution system and being considered at every decision point in the design, purchasing and installation process. 3 May 2011
  4. 4. Safety, a bigger pictureSee IEEE article by H. Landis Floyd II, “Potential Impact of ANSI Z10 AND CSA Z1000 on Reducing Electric Shock and Arc Flash Hazard Injuries”, PCIC 2009 conference record. Next few slides borrow heavily from this presentationNew standards for implementing safety programs in facilitiesFrom ANSI Z10 Scope:“… The purpose of the standard is to provide organizations an effective tool for continual improvement of their occupational health and safety performance. An OHSMS implemented in conformance with this standard can help organizations minimize workplace risks and reduce the occurrence and cost of occupational injuries, illnesses and fatalities. …” 4 May 2011
  5. 5. Hierarchy of Hazard Control MeasuresFrom ANSI Z10 1. Elimination of the hazard Thinking through this Substitution for less hazardous equipment, 2. table allows assigning materials or process 3. Engineering control for less hazardous value to different exposure or severity potential solutions to arc 4. Warnings, signs, and other communications flash & shock hazards Administrative controls including safe work 5. practices 6. Personal protective equipmentFor example:A temporary setting such as a maintenance switch is an administrative procedure (5) …Not as good as good as permanently making protection safer which would be asubstitution (2) or Engineering (3) 5 May 2011
  6. 6. Higher level solutions easier at system planning timeElimination of the hazard 1. Elimination of the hazard • The only true way for an 2. Substitution for less hazardous equipment, electrical system to be safe materials or process is for it to be de-energized… Engineering control for less hazardous 3. exposure or severity • But when a process is critical that is difficult to do unless 4. Warnings, signs, and other communications system includes redundant ways to get power to loads… Administrative controls including safe work 5. practicesSubstitution of less hazardous 6. Personal protective equipment equipment • Different types of equipment pose different levels of risk – individually mounted vs. group mounted, draw-out vs. stationary, arc resistant vs. standard, indoor vs. outdoor, etc.3. Design controls, instrumentation, monitoring to minimize hazard • Do everything than can be done remotely, remotely. Use modern diagnostics to minimize exposure and optimize reliability 6 May 2011
  7. 7. Hazards Involved in Working On or Near EnergizedElectrical EquipmentDangers associated with working on or around exposedenergized conductors or parts:Electrical shock - Becoming part of the circuit.Arc Flash - The violent release of superheated gases causedby an electric arc.Arc Blast - The blast effects from the pressure waveassociated with an arc flash occurrence.Shrapnel - Ejection of projectiles or bits of metal.Noise - From initial explosive expansion of air. 7 May 2011
  8. 8. NEC and OSHA References to NFPA 70E• NEC Article 110.16 requires that Electrical equipment such as switchboards, panelboards, industrial control panels, meter socket enclosures, and motor control centers shall be field marked to warn qualified persons of potential electric arc flash hazards.• NEC Article 100, Definitions: Qualified Persons has NFPA 70E referenced for electrical safety training requirements.• OSHA regulation 29 CFR 1910 Subpart S (Electrical Safety) Appendix A: Reference Documents, also references NFPA 70E. 8 May 2011
  9. 9. OSHA Interpretations of NFPA 70EOSHA can, and has enforced lack of arc flash protection under the"general duty clause". Here are some excerpts from a standardsinterpretation letter written by OSHA in 2003:“All your questions involve the NFPA 70E standard, which is one of many industryconsensus standards developed by the National Fire Protection Association. NFPA 70E, which is titled ‘Electrical Safety Requirements for Employee Workplaces,’is the NFPA’s consensus standard for workplace electrical safety. It covers employeeprotection from electrical hazards including shock, arc blasts, explosions initiated byelectricity, outside conductors, etc.“With respect to the General Duty Clause, industry consensus standards may beevidence that a hazard is ‘recognized’ and that there is a feasible means ofcorrecting such a hazard.“These provisions (1910.132(a) personal protective equipment) are written in generalterms, requiring, for example, that personal protective equipment be provided ‘wherenecessary by reason of hazards…’ and requiring the employer to select equipment‘that will protect the affected employee from the hazards…’.“Industry consensus standards, such as NFPA 70E, can be used by employers asguides to making the assessments and equipment selections required by thestandard. Similarly, in OSHA enforcement actions, they (70E) can be used as evidenceof whether the employer acted reasonably. 9 May 2011
  10. 10. OSHA 1910 Subpart S Revisions Effective Aug 13th, 2007 OSHA ADOPTING NFPA 70ENFPA 70E-2000 is the basis for most of the final rule. However, there aresome parts based upon the 2002 NEC and even some selected parts ofNFPA 70E 2004 Edition.“(The final rule) reflects the Agency’s commitment to update its electricalstandards, keep them consistent with NFPA standards, and ensure thatthey appropriately protect employees. The Agency intends to extend thecommitment by using NFPA 70E as a basis for future revisions to itselectrical safety-related work practice requirements and new requirementsfor electrical maintenance and special equipment.” ---Preamble of the Final Rule document 10 May 2011
  11. 11. Arc-Flashover IncidentDescription: A routine voltage check at a 480V terminalboard inside the GAC resulted in an arc flash burning thehand of the person checking the voltage. The checkconsisting of placing one meter lead on a single phase andmeasuring the other 2 phases with the second meter lead.The employee was treated and released to return to work.Direct Cause: The terminal board was delivered withincorrect long terminal lugs that were also not insulated. Broken Insulator and extra long terminalThe terminal points of the meter were exposed clamps too lugslarge for this small equipment.Root Cause: The equipment being used and the equipmentbeing checked was not carefully evaluated prior toconducting the voltage check.Contributing Factors: Terminal board delivered withincorrect terminal lugs that were also not insulated.Corrective Actions:• Use of a different style leads, the use of pointed leads instead of clip leads Clips across• Replace the terminal board with a new component two phases 11 May 2011
  12. 12. What May Happen with aSlow Protective Device 12 May 2011
  13. 13. Worker’s Flame-Resistant Shirt and Insulating Gloves 13 May 2011
  14. 14. Arc Flash Effects• Temperature of the arc can reach 35,000 deg F – about 4 times the temperature of the sun!• In US, 5-10 arc flash incidents requiring hospitalization per day.• 1 – 2 deaths per day from electrical events, (shock, flash & blast).• More than 2,000 workers treated in burn centers per year with severe arc flash injuries. (This does not include injuries in other hospitals and clinics which go unreported.) 14 May 2011
  15. 15. Examples of Activities which Involve Arc Flash Risks• Racking in or out of draw-out circuit breakers.• Removing or installing circuit breakers or fuses.• Working on control circuits with exposed energized primary parts.• Applying safety grounds.• Removing panel covers for inspections or other activities.• Low voltage testing and diagnostics. 15 May 2011
  16. 16. Arc Flash StandardsSimplified Tabular method presented in:• NFPA-70E-2009, “Standard for Electrical Safety Requirements for Employee Workplaces.”• NFPA-70E-2012 to be released later in 2011• In Canada Z462-08, “Workplace Electrical Safety”More sophisticated calculated methods suitable for lowvoltage and higher voltages developed in:• IEEE Std 1584-2002, “IEEE Guide for Performing Arc-Flash Hazard Calculations.”• Amendment 1 issued in 2004 as IEEE Std 1584a-2004, (changes were relatively minor.)• Sometimes combination of these two documents referred to as Std 1584-2004. 16 May 2011
  17. 17. NFPA 70E Approach Boundary Fig. C.1.2.4 17 May 2011
  18. 18. Shock Protection Approach BoundariesLimited Approach Boundary – Distance from an exposed live part within which a shock hazard exists.Restricted Approach Boundary – Distance from an exposed live part within which there is an increased risk of shock, due to electrical arc over combined with inadvertent movement, for personnel working in close proximity to the live part.Prohibited Approach Boundary – Distance from an exposed live part within which work is considered the same as making contact with the live part. Fixed Live Prohibited Restricted Limited Part Approach Approach Approach Distance Distance Distance @480 Volts 0, 1" 1 ft, 0 in 3 ft, 6 in @15,000 Volts 0, 7" 2 ft, 2 in 5 ft, 0 in 18 May 2011
  19. 19. Arc Flash Protection Approach BoundariesFlash Protection Boundary – Distance from an exposed live part within which a person could receive a second-degree burn if an electrical arc flash were to occur. This second-degree burn results from the minimum arc flash energy of 1.2 cal/cm2, ( = 5 joules/cm2). This boundary is determined by calculating the distance at which an arc flash energy of 1.2 cal/cm2 exists.Working Distance - Dimension between the possible arc point and the head and body of the worker positioned in place to perform the assigned task. Value selected for the application – minimum 18”. Fixed Live Working Flash Part Distance Protection Boundary @480 Volts 18" (Typical) (Must be calculated) @15,000 Volts 36" (Typical) (Must be calculated) 19 May 2011
  20. 20. Combined Shock & Arc Flash Boundaries Usually > than the Limited Approach Distance but not always Fixed Live Prohibited Restricted (Arc Flash) Limited Flash Part Approach Approach Working Approach Protection Distance Distance Distance Distance Boundary @480 Volts 0, 1" 1 ft, 0 in 18" (Typical) 3 ft, 6 in (Must be calculated)@15,000 Volts 0, 7" 2 ft, 2 in 36" (Typical) 5 ft, 0 in (Must be calculated) 20 May 2011
  21. 21. Safe Approach DistancesUnqualified persons – Safe when maintaining a distance from exposed energizedparts equal to the Limited Approach Boundary or the Flash Protection Boundary,whichever is greater.Qualified personsAppropriate arc flash protection shall be utilized if flash protection boundary crossed.>>> To cross the Restricted Approach Boundary, the qualified person must:•Have a documented work plan approved by management.•Use appropriate protective equipment for work near exposed conductors and ratedfor voltage and energy level.•Be certain no part of body enters prohibited space.•Keep as much as body as possible out of restricted space. 21 May 2011
  22. 22. Safe Approach DistancesQualified personsAppropriate arc flash protection shall be utilized if flash protection boundarycrossed.>>> To cross the Prohibited Approach Boundary, which is considered thesame as making contact with exposed energized conductors or parts, thequalified person must:•Have specific training for working on energized parts•Have a documented plan justifying the need to work that close approved bymanagement.•Perform a risk analysis approved by management.•Use appropriate protective equipment for work on exposed conductors andrated for voltage and energy level. 22 May 2011
  23. 23. Other Key Arc Flash DefinitionsIncident Energy – The amount of energy impressed on a surface, acertain distance from the source, generated during an electrical arcevent. Measured in joules/cm2 or cal/cm2. (1 joule/cm2 = 0.24 cal/cm2).Flash Hazard Analysis – A method to determine the risk of personalinjury as a result of exposure to incident energy from an electrical arcflash.Arcing Fault Current – A fault current flowing through an electrical arcplasma, also called arc fault current and arc current.Bolted Fault Current – Resulting from a short circuit or electrical contactbetween two conductors at different potentials in which the impedanceor resistance between the conductors is essentially zero.Arc Duration – The total time it takes system protective devices to detectand interrupt a fault current. 23 May 2011
  24. 24. Operating Company Responsibilities1. Conduct an arc flash analysis of the power system.2. Establish shock & protection boundaries and determine incident energy levels at working distances.3. Put warning labels on equipment.4. Implement qualified and general worker training.5. Provide necessary personal protective equipment, (PPE)6. Require outside engineering consulting firms involved in upgrades/expansions to provide 1, 2 and 3.7. Require outside contractors to meet 4 & 5. 24 May 2011
  25. 25. Steps in Performing an Arc Flash Hazard Analysis1. Collect power system data.2. Determine the system modes of operation.3. Determine the bolted fault currents.4. Determine the arcing fault currents.5. Find protective device characteristics and arc durations.6. Document system voltage levels and equipment classes.7. Select the working distances.8. Determine the incident energies for all equipment9. Determine the flash protection boundary for all equipment. 25 May 2011
  26. 26. Performing an Arc Flash Hazard Analysis• Methods o NFPA 70E Table 130.7 (C)(9) o Spreadsheets o Power System Analysis Software• Arc Flash calculation modules can be obtained with commercially available comprehensive power system modeling software.• Short-Circuit Study• Protective Device Coordination Analysis• Arc Flash analysis (Per NFPA 70E or IEEE 1584) 26 May 2011
  27. 27. Potential product based solutionsKeep people away from the equipment as much as possible • Remote diagnostics, metering and controls • Advanced diagnostics to implement condition based maintenanceProtect as fast as possible & as sensitive as possible without giving up selectivity • Use zone selective interlocking and/or bus differential • Use faster electronics and/or faster circuit breakers, or small fuses • Use better instantaneous algorithms that allow low pick up settings • Use light sensing for controlling CBs as an alternative sensitive instantaneousUse arc resistant enclosures and/or equipment • Passive Arc Resistant equipment – Only if doors and panels closed & does not protect equipment • Active Arc Resistant equipment - crowbars or similar driven by light sensingUse temporary sensitive instantaneous protection (maintenance setting)Use local “off” switching 27 May 2011
  28. 28. DistanceKeep people away from the equipment as much as possible •Remote controls – on/off/switching •Remote metering – basic, advanced, condition •Remote diagnostics – troubleshooting equipment condition and process •Advanced diagnostics to implement condition based maintenance –Use information acquired to minimize need to touch equipment •Remote operated racking 28 May 2011
  29. 29. Use fast & sensitive protection- protection withoutgiving up selectivitySeveral strategiesZone selective interlocking (ZSI)/MV Instantaneous Blocking – all manufacturer’s can do it. Essentially allows layered curves over some fault range. Improves system reliability. • Newer generation trips and circuit breakers have faster protection providing ZSI even in the instantaneous range.Bus Differential Protection – Can be done with Relays by all manufacturer’s. Improves system reliability. • Single Processor concept 87B & ZSI simultaneously in LV equipmentOptimized instantaneous selectivity – All manufacturers have tables, some provide improved selectivity over CL devices. Improve system reliability & safety at the same time.Newer LV trip algorithms perform waveform recognition with < cycle of information allowing very low instantaneous settings to remain selective.Arc Flash (light sensitive) relays . . . Careful with LV implementations 29 May 2011
  30. 30. Remote Racking, RemoteControls, Remote MeteringDo not do locally, on live equipment, whatcan be done remotely outside arc flashboundary. 30 May 2011
  31. 31. Containment method – passive arc resistance • Common in MV systems • Moving into LV systems in US • Contains arc safely • Barrier between person & arc • Must be fully assembled • Plenum needed to exhaust May be solution for operators, but not for maintenance 31 May 2011 MEV
  32. 32. Alternative to arc resistance via containment -diversion Transfer energy to alternate current path MV 52 Breaker Common implementation - Crowbar • Remove arcing fault via bolted fault XFMR • Energy goes to lowest impedance path • Protection provided even if equipment doors are open However A Main LV B • Maximum bolted fault current C Breaker • Electrical equipment damage possible • How to test? • Reusable? Feeders ..... 32 May 2011 MEV
  33. 33. 33May 2011
  34. 34. Other arc flash protectionTemporary Instantaneous for reduced energy let-through • Faster protection when desired or most needed. • But needs good “procedures” to makes sure its used when needed • And good procedures to make sure it is off when not needed and undesirable • Need good indication/signaling for reliability • Needs to be set as fast and sensitive as application will allow • Nuisance trip may also have consequences 34 May 2011
  35. 35. Arc Flash Categories & Protective Clothing ATPV Hazard Risk Weight 2 2 cal/cm Category Description of Clothing Oz/yd 0–2 Class 0 Untreated Cotton 4.5 - 7.0 >2 – 4 Class 1 AR Shirt & AR Pants or AR coverall 4.5 - 8.0 + AR Face Shield or Hood >4 – 8 Class 2 Cotton Underwear + AR Shirt & AR 9 - 12 Pants + AR Face Shield or Hood >4 – 8 Class 2* Cotton Underwear + AR Shirt & AR 9 - 12 Pants + AR Hood or AR Face Shield & Balaclava >8 – 25 Class 3 Cotton Underwear + AR Shirt & AR 16 - 20 Pants + FR Coverall + AR Face Shield or Hood >25 – 40 Class 4 Cotton Underwear + AR Shirt & AR 24 - 30 Pants + Multi-layer Flash Suit + AR Hood > 40 Extreme Danger No PPE class applies - 35 Class 2* introduced in NFPA 70E 2009. In 2012, 2 may become 2*. May 2011
  36. 36. Arc Flash PPEHRC 1 HRC 2 HRC 2* HRC 3&4 36 May 2011
  37. 37. Typical Arc Flash & Shock Equipment Signs 37 May 2011
  38. 38. Typical Shock & Arc Flash Work Permit 38 May 2011
  39. 39. Thank you!Any questions? 39 May 2011