We recently did an arc flash study on a new Siemens 3000 amp 480 volt system. The switchboard came with Siemens’ new Dynamic Arc Reduction system preinstalled. The sort of thumbnail version of what the DAS does is to reset the main breaker so it trips at a much reduced current and time. I asked Siemens representatives this question: if there’s a short at the line side of the main breaker, what does the DAS do? Here is my concern. An electrician decides to open the cabinet and do some testing with the gear left on. He switches on the DAS and assumes he can now wear very low calorie PPE instead of 100 calorie PPE the line side has. He relies on the DAS to greatly reduce the hazard, but there is a line side fault at the main. I doubt this specific scenario may happen, but it is still possible. I’d appreciate your thoughts on this considering the fact that switchboards have few if any internal barriers to slow or stop an arc.

This is a safety training issue. A qualified person would no the zone of protection of the "DAS".
Additional signage/warning labels may be of help.

Training should also emphasis that PPE is the last level of protection. PPE does not guarantee no injuries, only that the injuries received are not likely to be fatal.

Thank you for your comments. Any thoughts on the question of arc reduction in switchboards verses switchgear?

A device cannot protect itself, it needs to be 'remote' or upstream, especially in switchboard and MCC construction with n0n-compartmentalized bus.

It might work in switchgear where the bus is completely compartmentalized. You would need to perform a risk analysis.

JBD, I agree. Seems to me switchgear would be fine with DAS, but not so sure about switchboards.

My understanding, unless there is a barrier to separate the line side section from the load side, the incident energy is not to be reduced to a lower level within the board even it is equipped with a DAS.

Agreed. A major item here is personnel training, potentially including equipment labeling. First someone must program the DAS to ensure it functions. I have seen ERMS/ARMS systems installed all over because "code requires it" but upon analysis, the feature does not provide any benefit. Once DAS is setup personnel must be trained on when to activate it and what its zone of coverage is. It will not have an impact on the hazards upstream of it...i.e. the line side of the main breaker. If compartmentalized/isolated, DAS at the main breaker may lower the hazard for the rest of the panel. Otherwise, it "may" lower the hazard at downstream equipment. Again, this must be assessed as I have seen multiple units installed that are unable to make any impact on the arc flash hazard.