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Improving Safety Through Arc Flash Technology

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  • 200,000 Pascal = 29 PSIARC FLASH VERSUS ARC BLAST
  • Injury from the pressure wave is minimal in contrast because the human body can survive up to 2 bar (30 psi) while most buildings can only withstand a 0.8 bar (12 psi) blast.The air around us already puts pressure on us to the tune of 14 pounds per square inchSurface areas or men 1.9m²For women 1.6m²1.9 square meter = 2,945 square inch/ 1.6 square meter = 2,480 square inchAnywhere from 20 to 40 added pounds per square inch can be fatal, depending on the time it takes to wash over the body.A wave of pressure that lasts less than .3 milliseconds leaves the eardrum no time to adjust to changes in pressure, and simply tears it. This can happen with pressure change as small as 5 psi.Pressure changes of 5 psi can cause 160 mile-per-hour winds. Changes of twenty psi can cause winds of 470 miles per hour.
  • There are MANY Global arc resistant testing guides and standards including:EEMAC G14-1IEC 62271-200 (Annex A)IEEE C37.20.7 (2007)IEC 61641 for LV manufactured in according to IEC 60439-1CSA C22.2 no. 22-11For global vendors, like Rockwell Automation, this creates a significant issue!IEEE C37.20.7, the most common used in North America, now includes internal arcing fault testing guidelines for equipment 38 kV and lowerLV MCC s - IEC 60439-1, IEC 60529, IEC/TR 61641:2008 for arcing durations up to 300 ms, KEMA certified (TTA), GOST-R certified (Russia), ASTA 61439 (Australia), CE conformance marked, CCC conformance marked (China), ABS Certification
  • First, the accessibility types in the various documents differ, and the working group wanted to make it clear that an accessibility type in one document might not be identical in performance to that in another document. In addition, the IEC identified types A, B and C, but types A and B concerned personnel safety whereas type C related to the amount of damage to the equipment during the test. Type C was thus considered as irrelevant to personnel safetySuffix C specifies that arcing does not cause holes in the freely accessible front, sides, and rear of the enclosure or in the walls separating the compartment in which the arc is initiated from all adjacent compartments. Suffix D: A modification of type 1 in which one or more of the enclosure surfaces is excluded from the arc resistant category. For example, type 1D-SR would indicate a design with arc-resistant functionality on the front and the right side only, with the rear and the left side considered inaccessible to personnel
  • NOTE THE DATE ON THE PICTURE 7 years ago!!!!
  • During arc-fault design tests, the energy release by an arcing fault is monitored by mounting racks of a black cotton material in panels covering the surface of the switchgear. This material is similar to 4.5oz/yd untreated t-shirt material identified as Hazard/Risk Category 0 per NFPA 70E Table 130.7(c) (11).The panels are mounted at 3.9 inches from all possible seams and one of the many acceptance criteria of ANSI C37.20.7 is that none of the cotton indicators ignites during or following a test. While the focus of NFPA 70E is the heat from the arc in medium-voltage switchgear, it is the pressure wave associated with the arc fault that dictates the design of the switchgear. The switchgear designed for arc-resistant protection requires heavy reinforcing of the entire structure.In conclusion, arc-resistant switchgear designs the hazard out of the tasks and reduces the level of risk for normal tasks to a zone 0 category. The result is a reduced need for PPE. The design focus of arc-resistant equipment is to provide the necessary enhanced safety features while requiring no addition maintenance, calibration, or final element tests to assure functionality
  • NFPA 70E 400.11 (also NEC 110.16 )
  • A new Section 110.6(D)(1)(f) has been added to the NFPA-2012 editionThis new section reads: “The employer shall determine through regular supervision and through inspections conducted on at least an annual basis that each employee is complying with the safety-related work practices required by this standard.” This mirrors similar language in OSHA 29 CFR 1910.269(a)(2)(iii).
  • The purpose of arc-resistant equipment certified to ANSI C37.20.7 is to eliminate the risk from the arc blast and the by-products (heat, pressure, shrapnel, and molten copper) during normal tasks performed on the equipment.
  • Rockwell Automaton does provide one of the broadest arc resistant product offerings in the marketplace.From NEMA and IEC 600V MCCs to full 7.2 kV and 15kV arc resistant control products
  • 7% -None existent9% -Site written but just general2% -Direct quotes from OHSA, not specific to sites14% -Direct quotes from OHSA & NFPA-70E, not specific to sites26% -General Corporate ESP with site specifics42% -Site specific with specific instructions
  • Transcript

    • 1. Educational Session A: Improving Safety Through Arc Flash Technology John A. Kay, CET Senior Product Specialist, Medium Voltage TechnologiesCopyright © 2011 Rockwell Automation, Inc. All rights reserved. V11.7.1 1
    • 2. Agenda1. Arc Dynamics2. What is arc resistance equipment all about?3. Global arc resistant testing guides and standards4. How these guides and standards affect what you specify5. What are the key aspects to arc resistant product specs6. How are arc resistant equipment designs tested7. The role arc resistant products play in your safety program8. Compliance to current NFPA-70E requirements9. What’s on the horizon? Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 2
    • 3. NFPA 70E Defines an Arc Flash Hazard as….“..a dangerous condition associated with therelease of energy caused by an electric arc.” Flash Facts Surface of the sun- 9,032F Arc Flash core- 35,000F Source- NASA, NOISH Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 3
    • 4. Faults Exhibited in Electrical Circuits Bolted Fault – current flowing through bolted bus bars or other electrical conductors. • A bolted fault test is standard for all MCCs, Switchgear and most electrical designs • It is an electro-mechanical test, i.e. bus/cable bracing Arcing Fault – current flowing through air • Always lower current than bolted fault current • Voltage drop across the arc due to resistance within the arc plasmaSpecify bolted fault & arcing fault currents levels separately!THEY ARE NOT THE SAME! IBF is always more than IAF Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 4
    • 5. Arc Flash/Blast Dynamics 35,000° FShrapnel Molten Metals Sound & Intense Heat Pressure Expelled Waves Copper VaporsIntense Light (Expansion rate 67,000 times) Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 5
    • 6. Characteristics of an Arc Flash• A conductive plasma, which has a much lower impedance and much higher conductivity than air• Melts and vaporizes components - flooding the air with more conductive particles• A large pressure wave is created by the expansion of the super heated air and the vaporized materials• The flash occurs virtually instantaneously, releasing a huge amount of energy in a very short period of time• The available short circuit current has a major influences on the energy released in the arc* *-other factors also must be considered! Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 6
    • 7. Dynamics Stages of Arc in an Enclosure1 2 3 4 1 • Compression Pressure 2 • Expansion Current 3 • Emission 4 • Thermal Arc Voltage Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 7
    • 8. Typical Arc Pressure & Temperature Profile Total clearing time Opening time of a 5 cycle with coordinated breaker (83 ms) NOT overcurrent including relaying latency protection (up to 225 ms ) typical T&P Temperature [C] >12,700 C(>23,000 F) 2·105 Pa Steel fire I²t, kA² s (~1550°C)(~29 PSI) Pressure [Pa] calories Copper fire (~1100°C) Cable fire (~600°C) 10 20 30 100 200 ms t Extensive damage to equipment and critical injury to personnel >250 ms Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 8
    • 9. How Long Can Arcing Occur?• The arc will continue as long as, – The voltage available is high enough to sustain it – Current continues to flowing in the arc plasma – There is fuel to „feed‟ the arc – materials that can provide the ions necessary to sustain current flow within an air mixture Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 10
    • 10. Arc Resistant Equipment• Arc Resistant is a term used to describe how a piece of equipment resists the effects of an internal arc fault (relates to arc flash exposure)• The level of arc flash protection is defined by the level to which an arc flash/blast is: – Extinguished or Controlled – Channeled away from personnel – Prevented from propagating• Testing must be performed to validate a level of resistance (protection) – Defined as the “Arc Resistant Accessibility Rating”• The equipment manufacturer is responsible to test to a given standard or guide to validate a given accessibility rating. The Accessibility Rating defines one of the performance characteristics for arc resistant equipment…. Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 11
    • 11. Common Arc Testing Guides & Standards• EEMAC G14-1-1987 “Procedure for Testing the Resistance of Metal-Clad Switchgear under Conditions of Arcing Due to an Internal Fault”• IEC 62271-200 “AC Metal-Enclosed Switchgear and Controlgear for Rated Voltages Above 1 kV and up to and Including 52 kV”, Annex A - Internal Fault• IEC 61641-2008 “Enclosed low-voltage switchgear and controlgear assemblies – Guide for testing under conditions of arcing due to internal fault”• IEEE C37.20.7-2007 "IEEE Guide for Testing Metal-Enclosed Switchgear Rated Up to 38 kV for Internal Arcing Faults”• CSA C22.2 NO. 0.22-11 “Evaluation Methods for Arc Resistance Ratings of Enclosed Electrical Equipment” Many global guides and standards for AR equipment ….. Compliance to one does not mean compliance to the others! Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 12
    • 12. Global Accessibility Types Type A-Accessible to authorized PersonnelIEC Type B-Accessible to general public Type C-Pole top equipment Type A-Front onlyEEMAC Type B-Front, back, sides Type C-Front, back, sides, & compartmental Type 1-Front onlyIEEE, Type 2-Front, back, sidesCSA Suffix A-Used if no other suffix applies Suffix B-Control compartment* (new in 2007) † Suffix C -Adjacent Compartments protection Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 13
    • 13. IEEE Accessibility Type 1 Illustrative graphic only. Additional PPE may be required. Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 14
    • 14. IEEE Accessibility Type 2 Illustrative graphic only. Additional PPE may be required Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 15
    • 15. IEEE Accessibility Type 2BLV ControlCompartment Illustrative graphic only. Additional PPE may be required. Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 16
    • 16. Other Arc Resistant Specifications• Arc Fault Current Level – The tested level of arcing current • Varies by equipment type, system voltage, manufacturer and global region • Typical values are 10kA, 25kA, 31.5kA, 40kA, 50kA, 60kA • Testing guides permit any level• Arc Duration – The time the arc was sustained for the test • Nominal is 0.10, 0.25, 0.5, 1 or 3 second ratings • Typically 0.5 seconds is used (suggested max. by IEEE) • Varies by vendor • Testing guides permit any time period Testing guides permit any levels Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 17
    • 17. Other Arc Resistant Specifications, con’t• Mechanical Considerations – Top & Bottom exit/entry- don‟t assume both are available • Not all arc resistant controller suppliers can provide top exit! – Footprint could be bigger than non-arc resistant designs • Important for room layouts – You‟ll need more ceiling height – Gas plenums or chimneys? • Where are they located? There are more things to take into account when installing arc resistant equipment! Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 18
    • 18. Plenum & Chimney Installation Considerations• Where should the energy from an arc flash be directed? – Within the building assumes an area can be made inaccessible to personnel and no flammable materials are present – Externally is generally preferred, implying that a barrier be used to restrict the entry of weather or vermin• If the arc gases are going to be released into a small control room or building that houses the arc resistant equipment, it must be designed to withstand: – Overpressure, up to 15-20 psi, on a transient basis – The effects of hot gases and flames as they are released into the room (i.e. non-flammable construction materials are required) – Special ventilation may be required Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 19
    • 19. Other Aspects to Consider• NEMA based Testing Guides don‟t fully cover LV MCCs! – IEEE C37.20.7-2007 now includes consideration for metal-enclosed Low Voltage power circuit breaker switchgear – Standard is under review and revision currently – Difficult to find a consensus due to various manufacturers designs• Rockwell Automation has always used IEEE C37.20.7 as a guide for testing both their LV & MV MCC – IEC products are tested to the appropriate IEC guide • Bulletin 2500 IEC LV MCC tested to IEC 61641-2008 • Bulletin 7700 IEC MV MCC tested to IEC 62271-200 Flash Facts OSHA Lockout/Tagout standard, which outlines the MINIMUM requirements to control hazardous energy, was the 5th most frequent cited violation from fiscal year 2005 to 2009 Source- OHSA Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 20
    • 20. How Are The Tests Completed? LV MCC Prototype tests! Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 21
    • 21. Test Setups Vary by Global Testing GuidesGenerally• Flammable cotton indicators are placed vertically around the test unit as follows: – Vertical indicators are placed 100 mm from the enclosure walls • From the floor to a height of 2 m (79”) • Facing areas thought to be likely to emit gases• Indicators cover the area being evaluated, seams etc.• Horizontal indicators are placed at a height of 2 m (79”) above the mounting surface and parallel to the floor – Indicators extend beyond the switchgear by at – least 300mm, 1000 mm typical• Each testing guide has slight changes to the electrical configurations Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 22
    • 22. Typical Test Setup Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 23
    • 23. Horizontal Indicators Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 24
    • 24. MV Unit Under Test Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 25
    • 25. A Successful MV Arc Test Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 26
    • 26. Passing an Arc Test Generally Means:• Doors and covers do not open (bowing allowed)• No parts are ejected from the equipment• The arc does not burn any holes in the exterior of the tested structure (in the applicable planes for the accessibility level)• 150 mm2 (6 in2 ) – 150 g/m2 Cotton test indicators at a distance of 100 mm (4 in) must not ignited or be perforated, (approximates typical industrial work clothes)• The grounding connections remain effective Performance criteria varies by testing guide Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 27
    • 27. Arc Resistant Equipment Considerations• Arc resistant equipment should been tested to a relevant testing guide or standard• Certification Letter or Letter of Attestation should be available to corroborate the claimed results• Not included in the existing Nationally recognized testing standards for LV and MV motor controls – UL 845 – “Standard for Motor Control Centers” does not address arc fault performance • Specific performance criteria is mandated under bolted fault, short circuit conditions for electric shock and fire hazards – UL 347, for MV MCCs, also does not include content related to arcing faults Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 28
    • 28. Keeping it “Arc-Resistant” When I Use itThis requires that,• The equipment is properly installed in accordance with only the manufacturer‟s instructions• All* doors and covers be properly secured (*- for type 1B or 2B the LV controls compartment door can be open) – If any door or cover is open to a medium voltage compartment, the equipment is not in its “arc-resistant” condition and the level of protection to personnel will be compromised!• Any exhaust vents must be free of obstructions• Extra care in cable installation Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 29
    • 29. Where are These Standards Taking Us? Enhanced Safety CSA Z-462-2012 NFPA-70E-2012 NFPA-70E-2009 CSA Z-462-2008 NFPA-70E-2003 IEEE 1584-2001 NFPA-70E-2000 Arc resistant Switchgear-1990’s Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 30
    • 30. So Now What?NFPA-70E is your guide…• To understand your risk areas, you need to perform and maintain an arc flash hazard study within your facility, – If you don‟t, you must adhere to the data and guidelines provided within NFPA-70E regarding PPE, boundaries, etc.• Label electrical equipment, based on the study, to indicate, – The level of the arc flash hazard (incident energy) – The PPE requirements – The boundaries defined by NFPA-70E• Obtain and maintain the appropriate Personal Protective Equipment (PPE)Rockwell Automation can perform complete arc flash hazardstudies and provide risk mitigation solutions Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 31
    • 31. So Now What?• You need to determine the extent of the risk- you may not require AR equipment! – Your arc flash study will give you the facts!!!• It is the electrical system designer, constructor, and user/owner who are responsible to define, manage and mitigate risks to a tolerable level• Develop, implement and train proper work place safety policies, procedures and methods• Train the workers (both internal and contract)• You must actively update and audit the safety program in your facility Rockwell Automation can assist you with these tasks! Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 32
    • 32. So What is OHSAs Position on All of This• “…Industry consensus standards can be evidence that there is a hazard for which that PPE is "necessary." While the NFPA 70E consensus standard has not been adopted as an OSHA standard, it is relevant as evidence that arc flash is a recognized hazard and that PPE is necessary to protect against that hazard….”• “…An flash hazard analysis shall be done in order to protect personnel from the possibility of being injured by an arc flash. The analysis shall determine the Flash Protection Boundary and the personal protective equipment that people within the Flash Protection Boundary shall use…” Failure to protect workers will result in OHSA prosecuting to the fullest extent of the law, based on these premises Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 33
    • 33. So What is OHSA’s Position on All of This• Complacency is a major danger to anyone working around electrical energy• Appropriate PPE should ALWAYS be used• Not only should OHSA and like standards be followed, but all employers must adhere to the consensus standards- like NFPA-70E Flash Facts Electrical hazards are one of the top causes of workplace deaths and violations of electrical standards routinely top OSHA’s list of cited violations. Source- OHSA Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 34
    • 34. How can AR Equipment Help?• Can be a part of the overall protection strategy• MV arc resistant equipment can reduces the hazard/risk category to Level 0 – The lowest level defined by NFPA-70E! – For LV MCCs see Article 130.7/(C)(15)(a)- no reduction at this point• May simplify your safety program• Select an accessibility type that best suits you requirements – e.g. Type 2B• Always refer to NFPA-70E for details!Arc resistant equipment reduces the hazard/risk categoryto Level 0- the lowest level defined by NFPA-70E Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 35
    • 35. How Can Rockwell Automation Help? 7.2kV NEMA & IEC MCCs15kV IEC MCCs LV NEMA MCC LV IEC MCC ArcShield & ONEGear Arc resistant LV and MV MCCs Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 36
    • 36. What Else is on the Horizon• Light/current based arc detection systems- available now!• Personal arc detection sensors- available now!• Arc clamping devices- available now!• Pre-emptive arc detection technologies – In develop stages – Predicts immanent failures – Still doesn‟t address the human factor….but..• Human-Machine Interaction Bioengineering • Safety in Design • Understanding, more thoroughly, the interaction of humans Future Technologies For the Future Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 37
    • 37. Other Ways We Can Help……• On Site Training including Arc Flash Training• On site data collection, Arc Flash Analysis, Protective Device Coordination Studies, Short Circuit Analysis and Arc Flash Labeling• Category Mitigation Services (Design and Engineering)• Written Program Services• Electrical Work Permit Services• Ongoing support for the updating of site electrical diagrams and the labeling of new panels• Reporting using industry recognized software tools Rockwell Automation is your partner in machine safety! Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 38
    • 38. Key Points and Take Aways!!!!• You must have a up to date and maintained safety program• You should have a maintained arc flash study of your facilities• You must have your equipment properly labeled• You must have the necessary PPE available based on your study• Arc resistant equipment can be a critical part of your overall safety program• Arc resistant equipment can vary dramatically between vendors• Certification guides and standards continue to evolve• Guides and standards are behind the technological improvementsRockwell Automation is your partner in creating a comprehensivesafety program compliant to NFPA-70E! Copyright © 2011 Rockwell Automation, Inc. All rights reserved. 39
    • 39. QuestionsCopyright © 2011 Rockwell Automation, Inc. All rights reserved. 40