Arc Flash MV Switchgear

[Modula2]

For 5 kV switchgear, main or feeder breakers, I expected enclosure type to be Box. However, I am looking at a study where Open type was used, which gives a lower calculated incident energy. Has anyone seen something on this?

 

[Zogzog]

What do you mean seen anything on this? Thats a pretty broad question. Who did this study? What method was used? If this study was done using open air for MV switchgear, I would be questioning everything that was done.

 

[jraef]

Does anyone even make open air MV switchgear? If so, I cannot for the life of me understand how something open like that can have a lower incident energy rating for arc flash than an enclosed piece of gear. If so, someone is probably exploiting a loophole. The entire Arc Flash issue is about limiting the exposure for personnel to the dangers of arcs. How can you do that with open exposed equipment no matter how "low" the incident energy is? Being exposed to the arc of a 2000A switch even at 12V would be potentially dangerous if you were standing right in front of it IMHO.

Keep in mind, I am not meaning utility switch yard equipment; you said "switchgear" which I interpret as being distribution equipment in a facility. Utility switch yards already have access restrictions and safeguards in place to limit exposure.

 

[Modula2]

ZogZog, that is what I think also. It's by a Consultant, directed by multi-facility owner. Latest IEEE 1584. I'm an independent reviewer. None of them can form basic sequence networks, but they all have software.

 

[Modula2]

jraef, the box is higher by the physics. In Open, the energy radiates outward, so you mainly get the direct. In the box, you get the direct, but also, reflections off the sides of the box. In IEEE 1584, eqn (4), the constant K1 is the difference in calculating incident energy; higher energy for arc-in-box.

 

[dpc]

If it is truly metal-clad switchgear, it must be considered "in-box" for IEEE 1584 arc-flash calcs. There is no room for debate on this. This will have a significant impact on the arc-flash levels.

However, some older facilities may have outdoor 5 kV breakers with exposed bus, etc. These could be considered "in air".

 

[Zogzog]

I would ask for some references and qualifications of this consultant. Just buying the software dosent mean you know how to do an analysis. We have done hundreds of studies and are still learning every day, as are the software people. How many updates has SKM had over the last year? Several, because they (Adn the users) keep finding senarios that no one ever thought of.