Greg, I have to disagree, your example is not a dual power system.
All a UPS does, as you quite correctly point out is hold the load whilst back-up power kicks in, read the generator fires up and stabalises, that doesn't make it redundant. It still requires, as I mentioned a change over switch to switch the input to the UPS between mains and generator.
Everything from the change over switch onwards is therefore not part of a redundant power circuit, normally it would be called an essential power circuit. Clearly any fault from the changeover switch to outlet will therefore cause a back-out on that circuit. Also a problem with the generator will also cause a blackout once the UPS has run dry.
The only truley redundant systems is where the circuits are completely separate to the outlet and where the equipment has dual power supplies. Data centre servers and network hardware etc generally being where you would see this set-up.
PS I studied electrical engineering at TAFE back in the day and still work in the bizz in the area of data centres, comms and PABX systems.
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