It is worth noting that Equation 6 (for calculating intermediate incident energy at Voc = 600 V) on page 25 uses 2 different arcing current values (Iarc & Iarc_600), so it would be worth checking that you are doing the same - as this is easy to miss.

Statistics: Posted by w5m — Tue Jan 07, 2020 1:02 am

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Yes, I've obtained the same values as in the sample calc's.

A little tip; check the Iarc current that is used in the formulae. For voltages < 600 V there is something special going on for the arcing current. Took me a while to figure out.

Good luck figuring out the error

Thanks.

Statistics: Posted by electrical-bbq — Tue Dec 24, 2019 6:09 am

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Hello all,

I trust you are all well.Going through the sample calculations provided in this new standard.While I'm waiting for the new software to be purchased by our firm ,I'm currently using excel spreadsheets (which is more laborious of course) for now.

For those of you who went through the sample calculations provided within the IEEE 1584-2018, whether you used software or manual methods (excell etc), are your values coming out matching those provided in the standard ?

Most of my values are coming out quite correct , except they are a bit higher towards the end i.e the stage of recalculating the arc flash boundary and incident energy based on the reduced arcing current.I'm referring to the example of the 480V system , where my incident energy is around 65 J/mm instead of 53 J/mm as shown on the standard.

Have any of you gone through those sample examples on your own and obtained similar values as ones in the stanmdard? Just want to know whether I am wrong or not, although I have double checked numerous times.

Regards

Ashford

yes the values are coming out matching those provided in the standard.

Statistics: Posted by arcad — Sun Dec 22, 2019 8:59 am

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I trust you are all well.Going through the sample calculations provided in this new standard.While I'm waiting for the new software to be purchased by our firm ,I'm currently using excel spreadsheets (which is more laborious of course) for now.

For those of you who went through the sample calculations provided within the IEEE 1584-2018, whether you used software or manual methods (excell etc), are your values coming out matching those provided in the standard ?

Most of my values are coming out quite correct , except they are a bit higher towards the end i.e the stage of recalculating the arc flash boundary and incident energy based on the reduced arcing current.I'm referring to the example of the 480V system , where my incident energy is around 65 J/mm instead of 53 J/mm as shown on the standard.

Have any of you gone through those sample examples on your own and obtained similar values as ones in the stanmdard? Just want to know whether I am wrong or not, although I have double checked numerous times.

Regards

Ashford

Statistics: Posted by Ashdgee — Sat Dec 21, 2019 9:39 am

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However, in the new 1584-2018 there is a very important aspect of AF calculations that is clear...

So, my advice it to use the largest gap in the space that "could" host the arc. That will give you the lowest arcing current and the most energy per unit time. I.e. it is conservative for both! If you guess to long but set the protection appropriately for it you may have over-calculated Ei by a calorie or two. If you guess to low for the arc gap, you may get a lower arcing current in the real event, then have your protection may not operate as fast as expected and your calculated Ei could be under-calculated by tens of calories!

Any value you use may be incorrect... the key is to bias it so the resultant error is more acceptable... For gap bias to a larger gap, for Ibf bias to a range of both low and high, for a box... if it is way too large, you may want to calculate Iarc as open and set protection accordingly, then recalculate as enclosed to get Ei. Generally do not use 24" unless you "know" that is the working distance, rarely is. Etc. a lot of human inputs into this calculation and it is not exact to the 3rd decimal palce, bound to be errors... they just need to be acceptable errors!

Statistics: Posted by MarceloEValdes — Mon Dec 02, 2019 8:55 am

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Thank you for feedback.

yes, i am also considering the protective device tripping time.

This project follows IEC construction and starting to see some big differences between IEC and the North American standard for the switchboard construction. I am measuring very small working distances and big electrodes gaps (for several reasons here)

What standard does the North American industry follows for the Switchboard construction?

Once again, thanks for you support.

Fluffy Bunny Feet

Statistics: Posted by FlufflyBunnyFeet — Sun Dec 01, 2019 11:30 pm

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Since the bus gap affects the arcing short circuit current, it will also require close evaluation of the protective device's time-current characteristic.

Hope this helps.

Statistics: Posted by Jim Phillips (brainfiller) — Fri Nov 29, 2019 8:03 am

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thanks for the reply.

Please check the attached picture.

In this situation i have a busbar along all SWB with a GAp of 111 mm between buses and also have electrodes with gap of 50mm in the connection to the protection unit, in this case the incomer from the source.

All the cubicles can be open in all the switchboard with live bus.

In this situation what should be the Gap to be used, 111 mm or 50 mm? With this question i am considering that a arc can exist anywhere in the SWB, in the main bus or in the electrodes that go to theprotection unit.

Thanks,

Statistics: Posted by FlufflyBunnyFeet — Thu Nov 28, 2019 1:46 am

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The gap would be related to the point where the arcing is.

In a switchboard there could be an extremely large number of possible arcing points, each with their own gap and electrode configuration.

I don't know of anyone that puts lots of effort into fine tuning their calculations. I believe most people simply use the default gaps and 2 or 3 electrode configurations, in an effort to determine a worst case condition.

JBD Sums it up quite well. I attached a photo from a test set up in the lab. The gap (from the lab) is the distance between the conductors (copper rods in this case).

As JBD stated, there can be many different gaps for a single piece of equipment so most use the IEEE 1584 (software) defaults based on equipment type/class.

If you want to change the gap in the calculations you can do that as long as it is within the range of applicability of IEEE 1584.

Statistics: Posted by Jim Phillips (brainfiller) — Wed Nov 27, 2019 1:22 pm

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can you please help me in this question?

I can have all the measurements, gaps, distances in a specific switchboard, no problem.

I just want to understand this GAP issue, Is my understanding correct, can you please give me some guidance?

Thanks

Statistics: Posted by FlufflyBunnyFeet — Tue Nov 26, 2019 2:48 pm

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Some of the reasons:

Is someone really going to measure the equipment

There are multiple gaps for any give piece of equipment

This ties into the 2018 Edition. Back in the first year or 2 of the 2002 Edition, people were second guessing everything as there was only minimal guidance. Similar to what we have today with the 2018 Edition. But, just like 2002, it is slowly getting sorted out.

Statistics: Posted by Jim Phillips (brainfiller) — Tue Nov 26, 2019 1:44 pm

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Should not be related with the protection unit? Since the incident energy depends on T ( tripping time), the gap between the electrodes should not be the Gap in Iarc calculation?

I don't understand why we should relate with the busbar between the cubicles if there is no protection to clear the fault...

What is your opinion?

Statistics: Posted by FlufflyBunnyFeet — Tue Nov 26, 2019 10:03 am

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In a switchboard there could be an extremely large number of possible arcing points, each with their own gap and electrode configuration.

I don't know of anyone that puts lots of effort into fine tuning their calculations. I believe most people simply use the default gaps and 2 or 3 electrode configurations, in an effort to determine a worst case condition.

Statistics: Posted by JBD — Tue Nov 26, 2019 8:29 am

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I have a question regarding the the Gap between the conductor.

As you know, in a switchboard the main bus will have a bigger distance between electrodes if compared with the electrodes that connected to the protection unit.

Is this Gap related to the electrode configuration, VCB, VCBB, etc?

Or is this Gap related to the main bus of the swithboard?

Thanks,

Fluffy Bunny Feet

Statistics: Posted by FlufflyBunnyFeet — Tue Nov 26, 2019 6:43 am

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Statistics: Posted by electrical-bbq — Sat Nov 09, 2019 8:04 am

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