Intro to Arc Flash

Embed Size (px)

Citation preview

  • 8/16/2019 Intro to Arc Flash

    1/22

    Introduction to Arc FlashGuest Lecturer: Jon Leman, P.E.

    University of Idaho: BSEE 2001, MSEE 2010

    U.S. Navy – Physics/Electrical Engineering Instructor (4 years)

    POWER Engineers, Inc. – Electrical System Studies (10 years)

  • 8/16/2019 Intro to Arc Flash

    2/22

     Arc Flash - Description

    Arc Flash = Short Circuit Through the Air

    Temp. can reach 5000° F Hot Gassing

    Molten Metal

    Severe Pressure Wave

  • 8/16/2019 Intro to Arc Flash

    3/22

     Arc Flash - Description

    Arc Flash = Short Circuit Through the Air

    Temp. can reach 5000° F Hot Gassing

    Molten Metal

    Severe Pressure Wave

    Shrapnel

    http://www.youtube.com/watch?v=Hp1JdVwbN_U

    http://www.youtube.com/watch?v=hA-w0QAaxRU

    http://www.youtube.com/watch?v=FDy6fixKVxc&list=UUa8eW

    ErXv1OSBLpQemGEkog

  • 8/16/2019 Intro to Arc Flash

    4/22

     Arc Flash - Description

  • 8/16/2019 Intro to Arc Flash

    5/22

     Arc Flash - Theory  Thermal aspects of arc flash were first described

    mathematically by Ralph Lee in a 1982 paper called

     “The Other Electrical Hazard: Electric Arc Blast Burns”.His approach made use of the maximum power transferTheorem.

  • 8/16/2019 Intro to Arc Flash

    6/22

     Arc Flash - Theory  Ralph Lee Method (significant limitations)

  • 8/16/2019 Intro to Arc Flash

    7/22

     Arc Flash – Calculations (Energy) (Power ⋅ Time) (Voltage ⋅ Current ⋅ Time)

    Energy on a surface at a distance d from the source is inverselyproportional to the distance squared

    Energy (Voltage ⋅ Current ⋅ Time)

    Distance2

    =>Easily seen in the Lee equations – Not easily seen inIEEE equations.

    Incident Energy is reported in Joules per cm2 or Calories per cm2

  • 8/16/2019 Intro to Arc Flash

    8/22

     Arc Flash - Theory  IEEE 1584 Method: Empirical Equations

  • 8/16/2019 Intro to Arc Flash

    9/22

     Arc Flash – Industry Standards National Electrical Code (NFPA-70, Revised 2014)

    OSHA 29 CFR 1910 (Revised in 2014)

    IEEE 1584 (Revised in 2002, revision pending)

    NFPA 70E (Revised 2015)

    Software Most programs use the IEEE 1584 approach Non IEEE 1584 methods:

    Duke Heat Flux ArcPro (by Kinectrics)

  • 8/16/2019 Intro to Arc Flash

    10/22

     Arc Flash - Description PPE = Personal Protective

    Equipment

  • 8/16/2019 Intro to Arc Flash

    11/22

     Arc Flash – Calculations1. Gather System Data

    2. Identify Voltages and Equipment Types3. Select Working Distances

    4. Relate computer model to physical equipment

    5. Determine Modes of Operation (Worst)

    6. Determine Bolted Fault Currents

    7. Determine Arcing Fault Currents

    8. Determine Duration of Arcs

    9. Calculate Incident Energies

    10. Calculate Flash Protection Boundaries

  • 8/16/2019 Intro to Arc Flash

    12/22

     Arc Flash – Calculations

  • 8/16/2019 Intro to Arc Flash

    13/22

    Note: relays are inserted below breaker they

    control. This not typical and was done to get

    around a software limitation.

  • 8/16/2019 Intro to Arc Flash

    14/22

    http://www.apt-power.com/wp-content/uploads/Medium-Voltage-Switchgear-Distribution-Switchgear-APT.pdf Used with permission 

  • 8/16/2019 Intro to Arc Flash

    15/22

  • 8/16/2019 Intro to Arc Flash

    16/22

  • 8/16/2019 Intro to Arc Flash

    17/22

  • 8/16/2019 Intro to Arc Flash

    18/22

  • 8/16/2019 Intro to Arc Flash

    19/22

  • 8/16/2019 Intro to Arc Flash

    20/22

     Arc Flash – Considerations Always relate electrical models to the actual physical

    system.

    Pick the right location for worst case analysis

    Be aware of available evacuation space or lack thereof 

    Higher fault currents and longer clearing times compete forworst case arc flash conditions

    Be aware of interrupting device ratings. If fault currentsare too high, it may not be safe to assume the device clears

    the fault. Poorly maintained equipment can also fail tointerrupt a fault.

    Remember that it takes breakers a finite time to clear a

    fault (typical 3-5 cycles).

  • 8/16/2019 Intro to Arc Flash

    21/22

     Arc Flash – Mitigation Arc resistant gear

    More PPE Administrative constraints such as prohibiting energized

    work or other procedures that eliminate or reduce

    exposure.

    Faster clearing times

    Reduce pickup/time dial (may need to be temporary and include a

    lock-out procedure)

    Cubicle flash detecting instantaneous element (arc flash/optical relays)

    Remote operation

    Reduce fault currents (series reactors).

  • 8/16/2019 Intro to Arc Flash

    22/22

    Questions?