Hi Everyone,
I am writing to ask if anybody can signpost me to a document that explains the reasoning behind the requirements of 560.6.12, particularly point (i).
The reason I ask is, that based on my current understanding, this requirement - "[a UPS shall be able to] operate distribution circuit protective devices" would mean that a UPS used on a safety service supply would have to sized to blow all of the fuses that it feeds when on battery backup.
However, almost all of the UPSes I have encountered only directly feed one board. This means the UPS has to be sized to be capable of blowing that one single fuse.
But why would that matter? I can see why there could be a problem if the UPS tries to lower the inverter output voltage during a fault, but on battery backup, what would be the difference between trying to blow that single fuse that cuts off the power to the distribution board, and just letting the inverter turn off and try to switch back to maintenance bypass?
Hope that all makes sense! Thanks in advance.