Arc Flash Hazards and Arc Mitigation Solutions

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  • Arc Flash Hazards and Arc Mitigation Solutions

    Shlomy Allalouf, Shallan Garrett, and Karin Lundbom

  • Arc Flash Hazards and Arc Mitigation Solutions

    Shlomy Allalouf, Shallan Garrett and Karin Lundbom, ABB

  • Content

    Introduction to Arc flash

    Arc flash standards

    Arc protection and arc mitigation solutions

    December 2-3, 2014

  • Electric Arc phenomenon

    The electric arc is a phenomenon that takes place as a consequence of a discharge.

    This occurs when the voltage between two points exceeds the insulating strength limit of the interposed gas

    December 2-3, 2014

  • Dangers associated with Arc flashes

    Flying debris Copper expands by a factor of 67,000:1 when turning

    from solid to vapor Molten metal and shrapnel travel as fast as

    1600km/hour Pressure

    The sound of an arc blast can easily surpass 160dB (OSHA limit is 115dB for max 15 minutes, NIOSH limit is 112dB for max 56 seconds)

    Arc blasts can and have caused death at distances above 10ft (3m)

    Extreme heat Temperature of arc an blast can reach over 21,000

    oC

    (surface of the sun is roughly 5500 oC)

    December 2-3, 2014

  • Arc flash hazards

    December 2-3, 2014

  • Arc Flash Regulating Codes and Industry Standards IEEE Standard 1584 Guide for Performing Arc Flash Hazard

    Calculations NFPA 70E Standard for Electrical Safety Requirements for

    Employee Workplaces OSHA 29 Code of Federal Regulations (CFR) Part 1910

    Subpart S NFPA 70 National Electrical Code (NEC) C37.20.7 IEEE Guide for Testing Medium-Voltage Metal-

    Enclosed Switchgear for Internal Arcing Faults IEC 61641 This technical report applies to enclosed low-

    voltage switchgear and controlgear assemblies manufactured according to IEC 60439-1.

    December 2-3, 2014

    PresenterC37.20.7A procedure for testing, evaluating the performance of medium-voltage metal-enclosed switchgear for internal arcing faults is covered in this guide. A method of identifying the capabilities of this equipment is given. Service conditions, installation, application of equipment are also discussed.

    IEEE Std.1584tm, Guide for Performing Arc-Flash Hazard Calculations, is just that. It provide steps how to analyze potential arcing fault currents (worst case scenarios of course), model the potential arc flash, and calculate the potential arc flash energy. These are not trivial tasks. But, lets go to basics. One has to calculate: 1. the available arc fault current, 2. available arc fault (arc flash) energy of the arc, 3. arc fault energy at a given distance from the source (more correctly it is the energy density).

    NFPA 70E addresses employee workplace electrical safety requirements. The standard focuses on practical safeguards that also allow workers to be productive within their job functions. Specifically, the standard covers the safety requirements for the following:1. Electrical conductors and equipment installed within or on buildings or other structures, including mobile homes, recreational vehicles, and other premise (yards, carnival, parking lots, and industrial substations)2. Conductors that connect installations to a supply of electricity3. Other outside conductors on the premises

    The standard provides a guide to the industry how to treat the electrical arc hazards and what level of PPE (Personal Protection Equipment) is required for workers in the different zones (areas) of potential electrical arc exposure. Examples of PPE are gloves, goggles, special footwear, protective clothing, etc. There is still much confusion about requirement defined in this standard between protection against electrocution and protection against the burn potential associated with arc flash. Arc Thermal Performance Value (ATPV) is a measure [in cal/cm2] how well a given piece of PPE can withstand the arc flash energy. Typical values of ATPV range from 2 cal/cm2 to 40 or more cal/cm2. Different Hazard/Risk Category (HRC) from 0 to 4 require different PPE with different ATPV rating.

  • Different arc protection solutions Passive protection

    December 2-3, 2014

    Active protection

  • Passive protection, PPE suit requirements

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    0 1 2 3 4

  • Time is crucial for active protection

    December 2-3, 2014

    IEEE 1584 final step calculation of incident energy:

    NFPA 70E-2004 calculation of incident energy:

  • Incident energy example

    December 2-3, 2014

  • Without active Arc protection

    December 2-3, 2014

  • With active Arc protection

    December 2-3, 2014

  • Segments that need Arc protection

    December 2-3, 2014

  • Q&A - session

    December 2-3, 2014

    Arc Flash Hazards and Arc Mitigation SolutionsArc Flash Hazards and Arc Mitigation SolutionsContentElectric Arc phenomenonDangers associated with Arc flashesArc flash hazardsArc Flash Regulating Codes and Industry Standards Different arc protection solutionsPassive protection, PPE suit requirementsTime is crucial for active protectionIncident energy exampleWithout active Arc protectionWith active Arc protectionSegments that need Arc protectionQ&A - session