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Type 2B Gear
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Author:  vaquero [ Fri Oct 04, 2013 3:34 pm ]
Post subject:  Type 2B Gear
Hello everyone, I'm new here, have a few questions about calculation methodology I guess, rather than number crunching.
So, we have this Type 2B 480V Magnum DS switchgear by Eaton with a main and a few feeder breakers. As you all know Type 2B offers protection around the entire perimeter with all doors closed and latched.
In the event of an arcing fault anywhere in the gear, the barriers between cells may (but not necessarily will) burn through so that theoretically the maximum arc energy, which in this case happens to be at the main incoming compartment due to the upstream device setting, is available anywhere within the gear.
My questions are:
  1. Do you assign this maximum energy to the entire lineup? Or
  2. For feeder breaker labels you take the energy available on the main bus (as protected by the main breaker)?
  3. Do you consider an arcing fault in the main incoming compartment and an open feeder breaker door a double contingency whose probability is remote?
Thanks,
I'd be happy to provide further clarifications if need be.
Author:  PaulEngr [ Sat Oct 05, 2013 3:42 am ]
Post subject: 
. This is a subject of debate. There is some data for 480v from JHU and in NEMA PB2 on burn through. Most practitioners treat isolated sections at least as separate just like switch gear so that incident energy js calculated downstream of the main breaker. If you have a cubicle within the same section as the main breaker, some treat this like a panelboard and some don't. There is no rule because the energy necessary to propagate across the main breaker is quite high and absent test data, not very predictable. Tests have shown that even phase barriers offer some protection against propagation of an arc into 3 phase arcing if the energy is low enough.
Author:  Michael McCravey [ Mon Oct 07, 2013 7:21 am ]
Post subject: 
Vaquero,
Our facility has labeled the main breaker compartment with calculated line side energy and all additional compartments with calculated load side energy.
Author:  vaquero [ Mon Oct 07, 2013 9:32 am ]
Post subject: 
PaulEngr & Michael,
Thanks very much for your feedback
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