I am a software developer currently working on a software implementation of IEEE Std 1584-2018 and, I would very much appreciate clarifications or thoughts from Arc Flash experts in relation to the following items...

1. Table 8 in the standard gives typical bus gaps and enclosure sizes for each equipment class (i.e. switchgear, MCCs, panelboards and cable junction box). What default values should be used for bus gaps and enclosure size for an Open Air equipment class?
   
   
2. Table 8 in the standard gives two alternative enclosure sizes for low-voltage MCCs and panelboards and cable junction box equipment classes which relate to whether the depth of the enclosure is "deep" or "shallow". The depth value for a "deep" enclosure is given as "> 8 in". As the words "deep" and "typical" are used interchangeably elsewhere in the standard, would it be reasonable to default the enclosure depth to "deep"/"typical" rather than "shallow"? Also, what do people feel would be a sensible default for a depth greater than 8 inches? 9 inches? 10 inches? 20 inches?
   
   
3. Table 10 in the standard gives typical working distances for each equipment class (i.e. switchgear, MCC, panelboards and cable junction box). What default values should be used for working distance for an Open Air equipment class?
   
   
4. Is the cable junction box mentioned in Tables 8 & 10 of 1584-2018 equivalent to the cable equipment class given in 1584-2002?

Any pointers would be greatly appreciated.

I believe this table comes from previous IEEE 1584-2002. Note please that Equipment Class has been removed from the new IEEE 1584 standard year 2018 edition. Instead, Electrode Configuration has been introduced. Also, Open Air implies the arc not restricted by equipment / enclosure. Hence I see no reason why the Table 8 dedicated to different classes of equipment would include Open Air.



The table shows same typical gap of 25mm both for deep and shallow equipment so I would consider using this value across the board (min to max depth). Also, I would leave it up to end user to specify enclosure dimensions and gap instead of pushing default values. Just make a placeholder indicating accepted range of values and make an info button or help menu showing typical values the user can consult for the information in case accurate information is not readily available. The place holder values would depend on selected equipment class, electrode configuration etc. See screenshot for the example:





The table implies 18 in for low voltage and 36 in for medium voltage. I think you can follow that approach if you really want to include Equipment Class in your application.



I have a strong feeling it is.

Good luck on your project. Note please that at least one IEEE 1584-2018 web API has already been developed and is powering a universal arc flash hazard analysis and labeling app. You may consider focusing on developing the app front-end and hooking it up to that API instead of reinventing the wheel.

Hi Michael,

Thanks for your swift response.
Equipment Class has not been removed from the new 2018 edition, it is a column within Table 8 (the table that also has columns for typical bus gaps and enclosure sizes) and contains:

• 15 kV switchgear,
• 15 kV MCC,
• 5 kV switchgear,
• 5 kV MCC,
• LV switchgear,
• Shallow LV MCCs and panelboards,
• Deep LV MCCs and panelboards
• Cable junction box

The 2002 edition contained Table 6 which comprised the following columns:

• System voltage
• Equipment type
• Typical gap between conductors
• Distance x factor

...and included these equipment types:

• Open air
• Switchgear
• MCC and panels
• Cable

Therefore, I'd suggest that typical bus gap for Open Air equipment is relevant, hence my question. Obviously, enclosure sizes are irrelevant for Open Air equipment as there is no enclosure.

My 2nd question was related to a default value for enclosure depth (greater than 8 inches, if I go with "Deep"/"Typical" as a default) not bus gap.

Fair point, but defaults are helpful if relevant data is unavailable.

That sounds sensible.

I wasn't aware that a 1584-2018 web API was freely-available. I'm updating an existing Windows desktop application which won't necessarily have internet access, so a web API wouldn't be suitable, but I would be interested to find out more about the web API for possible future web-based projects. I presume it's a REST API?

Many thanks for your input.

what I meant is that in IEEE 1584-2002 Equipment Class was tightly coupled with Distance x factor (IEEE 1584-2002 table 4). This distance factor / exponent was used in incident energy and arc flash boundary calculations but has been abandoned with the arrival IEEE 1584-2018 since new equations were introduced. I agree you can still use the new tables 8 and 10 as a reference for typical bus gap and working distance.



The old table 6 never showed a typical bus gap for Open Air. Instead it offered a fairly wide range from 13 to 153 mm to choose from. I guess you can pick any value within the range. I would still leave it up to end user to make a choice instead of pushing defaults. Of course this is your call and I deeply respect the choice you make. I'd love to see and endorse your program when it is done.



Feel free to contact me regarding backend api once you are finished with your Windows application and I'm sure I can be helpful with your future web app.

Many thanks Michael.