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IEEE 1584 circuits less than 240V

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  1. bec51392 is offline NETA Level II Pro Subscriber
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    IEEE 1584 circuits less than 240V

    According to IEEE 1584, Circuits less than 240V supplied from transformers less than 125kVA may be omitted from an Arc Flash Hazard Analysis and will be assumed to have a hazard risk category 0.
    Your Answer: False
    Correct Answer: True

    1584 2002 4.2 states "Equipment below 240 V need not be considered unless it involves at least one 125 kVA or larger low impedance transformer in its immediate power supply."

    BUT 1584 2018 removed that statement and gives direction for 208v and above

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  3. TestingProToBe is offline Junior Member Pro Subscriber
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    Can you site the passage?

    Quote Originally Posted by bec51392 View Post
    According to IEEE 1584, Circuits less than 240V supplied from transformers less than 125kVA may be omitted from an Arc Flash Hazard Analysis and will be assumed to have a hazard risk category 0.
    Your Answer: False
    Correct Answer: True

    1584 2002 4.2 states "Equipment below 240 V need not be considered unless it involves at least one 125 kVA or larger low impedance transformer in its immediate power supply."

    BUT 1584 2018 removed that statement and gives direction for 208v and above
    I’m a little confused. So they removed the mention on excluding 240 v , 125kva and below. And replaced it by only addressing 208v and above?

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  5. bec51392 is offline NETA Level II Pro Subscriber
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    Quote Originally Posted by TestingProToBe View Post
    I’m a little confused. So they removed the mention on excluding 240 v , 125kva and below. And replaced it by only addressing 208v and above?
    Sorry I could have worded it better. I submitted it to the report a problem thread and then it was moved here.

    Correct. So the true or false question is no longer accurate since it is no longer true 100% of the time.

    IEEE 1584 2002 section 4.2 end of paragraph 5
    "Equipment below 240 V need not be considered unless it involves at least one 125 kVA or larger lowimpedance
    transformer in its immediate power supply."

    1584 2018 that is completely removed. non existent.
    but 4.2 does state
    "4.2 Range of model
    The following empirically derived model, based upon statistical analysis and curve-fitting programs as well as
    an understanding of electrical arc physics, is applicable for systems with the following parameter range:
    — Voltages in the range of 208 V to 15 000 V, three-phase (line-to-line)"

    and 4.3 states

    "Sustainable arcs are possible but less likely in three-phase systems operating at 240 V nominal or less
    with an available short-circuit current less than 2000 A."
    Last edited by bec51392; 4 Weeks Ago at 01:52 PM. Reason: add ref

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  7. bec51392 is offline NETA Level II Pro Subscriber
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    Quote Originally Posted by Wiche1971 View Post
    Sustainable arcs are possible but less likely in three-phase systems operating at 240 V nominal or less with an available short-circuit current less than 2000 A.
    right.... but now they still have to be included in the arc flash study? so the true false question on the practice exam is no longer valid?

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  9. anonymous is offline Junior Member Pro Subscriber
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    Quote Originally Posted by bec51392 View Post
    right.... but now they still have to be included in the arc flash study? so the true false question on the practice exam is no longer valid?
    I think this question is just no longer a good question. IEEE 1584-2018 models arc flash hazards based on extensive testing using four different three phase voltage ranges: 208 V to 600 V, 2.7 kV, 4 kV, and 12 kV to 15 kV. Importantly, this is not an update to the model shown in IEEE 1584-2002, instead it's an entirely new model based on entirely new laboratory testing. It applies to all equipment in the voltage ranges shown in the scope, but obviously it's hard to produce a sustained arcing fault at low voltage.

    My view is that if you're conducting an arc flash survey, you should collect information on all three phase equipment likely to require service or inspection while energized, including anything rated 208 V or higher.

    IEEE 1584.1-2013 3.1 Scope of the arc-flash study:
    ...As a minimum, the arc-flash study should encompass all equipment likely to require service or inspection while energized from the customer-owned service entrance equipment down through end user equipment rated 208 V nominal. IEEE Std 1584™ should be consulted for requirements for equipment rated less than 240 V (line-to-line).
    NOTE—Consult the latest edition of IEEE Std 1584™ for guidance.
    IEEE 1584-2018 1.1 Scope:
    ...Applications include electrical equipment and conductors for three-phase alternating current (ac) voltages from 208 V to 15 kV.
    What the new arc flash model actually looks like is just a curve fit to their calorimeter readings for the tests they used to make the model. You can read about the methodology in Annex F & G, which also have some cool pictures. IEEE 1584-2018 G.1 Summary:
    The new model was developed based on over 1860 tests performed by the project at different voltage levels. The model performance was also evaluated against the existing IEEE Std 1584-2002 test results (approximately 300 tests). The new model performance was evaluated against 932 tests between 0.208 kV to 0.6 kV, 325 tests at 2.7 kV, 202 tests at 4 kV, and over 400 tests between 12 kV and 15 kV.
    The new IEEE 1584 arc-flash model is an empirically derived model, and just like the 2002 model, is considered to yield consistent results when applied within the recommended range of its parameters. The model was evaluated as a whole, and its performance was observed using a holistic approach. It is the conclusion that this model produces results that are more accurate than those of its predecessor for configurations common in both models. Further, the new model provides a method to evaluate the incident energy for other configurations not previously considered, such as vertical conductors in a box with a barrier and horizontal conductors in a box and without a box.

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