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Doan Method (Ref: NFPA 70E Informative Annex D), for Calculation Arc Power and Incident Energy:

Where, R1 (RBattery) = 2.67 mΩ; R2 (Rconductor)= 50 uΩ; R3 (Rarc) = TBD; Battery = 53.8 Vdc

Using the “Complete Guide to Arc Flash Hazard Calculation Studies,” by Jim Phillips; Ch.12 – “DC Arc Flash Calculations,” based on Daniel R. Doan’s Technical Paper, “Arc Flash Calculations for Exposures to DC Systems,” the following was determined:

Idc bolted = Vdc/Rdc, where Rdc = RBattery + Rconductor, and Rconductor was determined by the volume of the Cu Buss plate involved in this incident.

= 53.8V/ (2.67 mΩ +50 uΩ) = 53.8V/ (2.72 mΩ)

= 19.781X103 A

Then Idc arc = .5* Idc bolted, so:

Idc arc = .5*19.781X103 A = 9.89 X103 A

Calculating for DC Arc Resistance (Rarc):

1)G*.534, where G = gap in mm. So for a ¼” gap or G=6.35mm

G*6.35mm = 3.391mm

2)Step 1) + 20 = 23.391

3)Idc arc.88 = (9.89 X103).88 = 3,279.3

4)Rarc = Step2) / Step3) = 23.391/3,279.3 = 7.1328 mΩ

Then re-solving for Idc arc:

Idc arc = Vdc /(Rdc + Rarc) = 53.8V/ (2.72 mΩ + 7.1328 mΩ)

= 5.4604 X103 A

Note: Both Rarc & Idc arc, were re-solved for 5 more iterations, until these values did not change significantly from the previous values and converged to the final answers of:

Idc arc = 2.149 X103 A & 27.331 mΩ

Using the calculated Rarc & Idc arc, the Power and Energy in the Arc was determined as follows:

Parc = Idc arc2 * Rarc

= (2.149X103 )2 *(27.331X10-3)

= 126.22KW

Earc = Parc*tarc, again assuming tarc = .1s, then:

= (126.22KW)* (.1) = 12.622KJ

Incident Energy is determined by-

Ei = Earc/(4∏D2)

Ei, whereby D = 1”or 25.4mm, then: 12.622KJ /(4*∏*25.42) = 1.5577 J/mm2

For calories/cm2; take J/mm2*(23.39), then:

As you'll notice, I referenced Chapter 12, of Jim's “Complete Guide to Arc Flash Hazard Calculation Studies.” So, you may want to consider purchasing said doc if you don't have it already. I've realized it's well worth the price vs. beating your head against a wall trying to calculate such, especially w/ DC systems. Yes, I realize the math models (Arc flash S/W packages) are now realizing this arena, But....

Statistics: Posted by 321Liftoff — Mon Nov 01, 2021 8:32 am

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Wilkins posted it on an IEEE bulletin board.

Does anyone know if Wilkins post is still available today?

Statistics: Posted by w5m — Wed Oct 13, 2021 4:22 am

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Hi ,

Can you kindly share the picture of the Sequence viewer? (the one with a magnifier in the toolbar). Please note the time of each breaker. Since they are all in the instantaneous region, the tripping time of all the devices may be the same. Since the time may be same, the animation is following the alphanumeric order of the device ID.

Thank you

here is the pic of the sequence of events

https://ibb.co/xJTSjbH

DP1-MCB & CB-DP2 show the exact same T1 & T2 but notice DP1-MCB If (kA) is lower

So this indicates to me that DP1-MCB would indeed trip last? (if If was to be the same)

I did manage to get them to trip in the right sequence (by tweaking with the breaker settings) and this is still with the instantaneous region all overlapping

https://ibb.co/DwfrW0x

Statistics: Posted by Designer82 — Mon Aug 02, 2021 8:57 pm

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https://ibb.co/61RTXD9

Or...

Ugly like this but with instantaneous all enabled:

https://ibb.co/hFNrmfZ

Statistics: Posted by Designer82 — Mon Aug 02, 2021 8:45 pm

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Can you kindly share the picture of the Sequence viewer? (the one with a magnifier in the toolbar). Please note the time of each breaker. Since they are all in the instantaneous region, the tripping time of all the devices may be the same. Since the time may be same, the animation is following the alphanumeric order of the device ID.

Thank you

Statistics: Posted by Raghu — Mon Aug 02, 2021 2:07 am

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If anyone can figure this out, you are a god

https://ibb.co/j8C1GZD

Statistics: Posted by Designer82 — Fri Jul 30, 2021 10:43 am

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does PV that is loadside connected impact short circuit, selective coordination & arc flash calculations? I received a short circuit, selective coordination & arc flash study for an assisted living facility. The building is now installing a 289kw PV system with about 300 amps of AC inverter output that is connected to a loadside breaker at the service equipment switchboard. The PV system is being installed while construction is ongoing but after the study was released, the PV was not part of the released study. Thanks in advance for any info

I worked with photovoltalic grid tie inverters. The DC voltage generated by the photo cells does need to be factored into the arc flash calculations. In the case of the inverters I worked with, that DC voltage could be as high as 1000 VDC.

Statistics: Posted by Larry Stutts — Mon Jul 05, 2021 5:56 am

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Is Anyone out there familiar with the NENS 09 Australian AF Calculation method?

This method was published in the "ENA NENS 09-2014 National Guideline PPE Arc" Guideline that's used in Australia. (See equations in attached image)

They list the methodology and equations but I don't see a breakdown of the method limitations.

For example, in IEEE 1584 there is a disclaimer saying the applicable voltage, fault currents, etc that the method is valid for.

Based on the citings this method may have originated from the following document but I can't seem to find it anywhere online.

EESA Electrical Arcing Hazards - A paper by Dr. David Sweeting (Sweeting Consulting) and Professor Tony Stokes (Electrical Engineering University of Sydney) presented at the EESA Conference in Sydney on 12 August 2004;

If anyone can shed some light on this or point out the limitations of the method that would be appreciated!

I realize the method is older in comparison to IEEE 1584 but I'm interested to see how the assumptions of this method compare to the updated IEEE 1584 model.

Statistics: Posted by wfg42438 — Mon May 17, 2021 9:25 am

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