I'm going through the 1584 course and I'm confused as to what constitutes as a "barrier," because during module 7 there is an example of a threaded wire being terminated at a lug and it is a VCB. In the lab experiments the difference is the the VCB just kind of hang there and the VCBB have that block that they terminate in. My question is in a practical setting, because a conductor must be terminated somewhere (such as a lug) where is the line drawn to say this is a barrier or no this is not a barrier.

Thanks

No trying to be smart but try googling examples of arc flash ieee 1584 vcbb barrier and read away. Also on YouTube. Both are more explanatory than I can type here on my phone.

I will take you back to a little history first.

VCB was the original configuration from the 2002 Edition of IEEE 1584. This was simply three solid copper rods either in a metal enclosure (VCB) or in open air (VOA). Those terms did not exist back then as we just referred to it as arc flash "in a box" or "in air"
It did not represent any particular equipment. The industry loved it and the arc flash study industry was off and running.

Shortly after 2002, a few people were jumping ahead and began asking "what about x" "what about y" etc. The 2002 model was the greatest thing the industry had seen but a few decided to make a name for themselves by focusing on the "what abouts" rather than what was done.

VCBB was the result of a few colleagues terminating the electrodes into a sheet of fiberglass instead of air. I was there for some of the early tests. The sheet of fiberglass captured the plasma and allowed sustaining arcs to lower fault currents. It also made the incident energy worse the arc hit the barrier and shot out more aggressively.

A person in Australia, found that if the three electrodes were pointed out of the box horizontally (HCB), the incident energy could also be much worse.

As the next step, a project team was assembled to address the next edition of IEEE 1584 including the "what abouts" I would later be part of the steering committee for the second edition as well being vice-chair of IEEE 1584. The project cost would be around 6.5 million USD with many corporate contributors - until the 2008 economic meltdown when fundraising abruptly ended and only around 3 million USD raised. So the list was prioritized and many subjects wound up on the wrong side of the budget i.e. left out.

The second edition included the original configuration now listed as VCB. The barrier was included as VCBB and the horizontal configuration was listed as HCB. This is what IEEE 1584 second edition is based on.

A few examples are provided in IEEE 1584 2nd Ed. A few photos were from my collection. Much judgement is necessary in deciding. I look at everything is VCB unless proven otherwise. Some look at incoming circuit breakers with conductors terminating in the top as VCBB. That's a tricky one because the testing used a single sheet of insulating material but the incoming circuit breaker will likely have phase barriers between the incoming lugs.

HCB gives me heartburn. Unless there are electrodes that are pointed directly at the worker, it may not be the best option. Although some like to say, it's worst case - so we will use it - placing people in 40 cal suits or greater rather than perhaps being able to use 8 cal. In Arizona where I live, that's a big deal when temperatures regularly reach 110 to 115 degrees in the summer. A few times reaching 120. I know we are not the only HOT location.

As a possible example of HCB might be the stabs where circuit breakers connect in switchgear but WHY would someone be working with equipment energized with breaker removed? The only time I heard this being a case with using a phase rotation meter. Again, no equipment testing.

So, the 2018 edition provided more options and more complexity but judgement and interpretation is needed.

A question that I continue to ask: Has anyone used the 2002 or 2018 edition of IEEE 1584, properly select PPE and there was a severe injury? I have not heard of such a case so it tells me, this is working.

Disclaimer: This is a personal view and is not any official representation of any standards committee.

[quote="Jim Phillips (brainfiller)"]
"A few examples are provided in IEEE 1584 2nd Ed. A few photos were from my collection. Much judgement is necessary in deciding. I look at everything is VCB unless proven otherwise. Some look at incoming circuit breakers with conductors terminating in the top as VCBB. That's a tricky one because the testing used a single sheet of insulating material but the incoming circuit breaker will likely have phase barriers between the incoming lugs"

Would it be fair to say that if you are between VCB and VCBB you should choose VCB unless abundantly obvious that it is VCBB. One of the examples they give in 1584 is an arc that would occur in or behind a circuit breaker which they say VCBB would be a better solution. I think in that example it is pretty obvious there is some sort of barrier for the plasma, but in a case where that barrier is not so obvious it would be better to say VCB.

Thanks

That is an ongoing debate. Many would say use the worst case. I'm not always in agreement and tend to be more pragmatic. The early years of the 2018 edition, many people were quick to jump right to HCB without any reason other than "worst case" I don't believe there is a single right or wrong answer, it is up to opinion and interpretation. One thing to consider, comparing results using VCB and VCBB, does the PPE requirement change? If it does not change, then this does not affect the final result - PPE arc rating. If it does change, then more scrutiny is required. Not a good answer, I know but this is open to judgment and interpretation.

Thank you for the history!

As my kids like to say "I've lived through a lot of history"