Switchboard and MCC Arc Fault containment

[kitosepa]

Morning gents/ladies
I am looking for a good explanation or a source that can explain what is meant by Limited and also Unlimited arc fault containment in Switchboards and MCC's (magnitude, time, flying objects etc), and what the advantages of one above the other is. I have fragmented information, and lots of references to standards that does not adequately answer my question. Also, I am trying to determine if there are switchgear with removable motor starters that conforms to Unlimited Arc fault containment
Any help?

 

[alehman]

I am not familiar with the terms "limited" and "unlimited" as pertains to arc fault containment. Can you consult your local equipment vendor/sales engineer?

 

[Zogzog]

I have never heard those terms either. Either switchgear is arc resistant or it is not. ANSI has standards on what this entails.

 

[kitosepa]

I searched further as I found reference to these words "umlimited and limited arcing fault" in more than one place. An ABB website gave a description:
"Testing AS/NZS 3439.1;2002
In the "Standard" arc fault containment tests set out in LV standard AS/NZS 3439.1, the arc is initiated on the load side of the functional unit protection device. This was called a "Limited" arcing fault under the old AS 1136 standard. The protection device limits the let through energy. Typically on small motor starters protected by HRC Fuses the arc duration is around 2 milliseconds and the resultant damage is minimal. Typically on Larger motor starters, protected by conventional circuit breakers, the arc duration can be in excess of 40 milliseconds and here the damage is quite substantial. The longer the arcing time the greater risk of the arc developing into a line side fault or secondary arcing on the distribution busbars. Under AS1136 this was called "Unlimited" arcing fault. In AS/NZS 3439.1 these unlimited tests are called "Special Tests".
This seems to be a good answer.

 

[Zogzog]

Right, those terms are refering to the arcing event itself, not containment of the arc flash.

Arc rated switchgear needs to comply to IEEE Std C37.20.7

Go look at this thread

http://www.eng-tips.com/viewthread.cfm?qid=212085&page=13