Hi everyone, hope you and yours are doing great.

I have a question regarding the electrode configuration of one distribution switchboard similar to the picture attached.

There you will find in the upper part of the picture a branch circuit breaker. Also, going down the distribution bus there are connected around 8 branch circuit breakers (4 left + 4 right).

My concern is that the bars connecting the line side of the branch circuit breakers seem to me as an horizontal electrode configuration because the worker would stand practically in front of them.

What do you think? Seems to you also HCB configuration?

Kind Regards to all,


Ivan

Sounds reasonable. You could always calculate worst-case and use that.

Mike

This is a good question. I hope someone who helped author the sections of IEEE 1584 would chime in with their opinion. I think this is one area of the 2018 edition of IEEE 1584 that could have used a lot more explanation or an Industry Applications Magazine article.

This is my interpretation of IEEE 1584-2018: This would be VCB. I base that on the illustration in section 6.6 "Determine the equipment electrode configuration", Table 9 and the explanation in Annex C.2 for MCC's. The busbars running horizontal between switchboard sections would also be VCB. Why not HCB? Because the difference between VCB and HCB is the direction of arc relative to the enclosure sides and open side where you are standing. HCB is for when the end of the electrodes are directed out towards you and VCB is for when the electrodes are directed to a side of the enclosure and not towards the open box end where you are standing. This distinction is important because in one instance, the arc is coming straight out towards you (HCB) and in the other instance the arc is directed to a side of the enclosure and being reflected towards you.

Like I said, this is my interpretation, I'd welcome a disagreeing opinion if there's solid reasoning included.

Thank you for your comment Mike. Totally agree with using worst-case for analyzing the equipment.

Hi Jeff, Thank you for your comments, they are very appreciated and of help.

I actually agree with your point of view. According to IEEE 1584-2018, as you said, HCB applies when the end of the electrodes are directed out towards the person in front of them.
For this particular equipment my concern is that if the arc flash event started in the line side part (where the bus is derived to the branch circuit breakers), and because the connection of these branch circuit breakers is constructed in an arrangement kind of directed to the worker in front of the equipment, the plasma could be projected directly to the worker.

I think VCB seems as a choice as you explained in your comments.

I also hope that authors of IEEE 1584-2018 could help us in clarifying this example.


Kind Regards,

I spoke/emailed with Square D a couple of years ago about electrode orientation for their popular QED style switchboards. They said depending on where you are in the board the orientation varies, so worst case is the way to go.