I think that the "100-240V" is used so that Kemper doesn't need to change the back panels for different markets. The KPAs for the American market are configured to run on 120V, and as they are digital devices you really don't want to subject them to excessive voltage spikes.
From what I know KPA has SMPS that can handle Input voltages from 100 - 240V.
Of course the best is to avoid high spikes - but KPA should work with this range of AC voltages.
This. The Profiler is self-adaptative to mains voltage.
Having said that, I am not sure that a spike within the boundaries can be managed as if there had been none. Someone expert in transformers will easily answer this I think 
A power conditioner may be overkill - using a powerstrip with a Surge Protector has served me well for hundreds of gigs since I got my KPA.
I use a small UPS with 2 puffered and 2 unpuffered Plugs including surge protection.
In case of power fault the Kemper has enough Power for shut down.
I have read that a rebooting after powerdrop can make problems.
This. The Profiler is self-adaptative to mains voltage.
Having said that, I am not sure that a spike within the boundaries can be managed as if there had been none. Someone expert in transformers will easily answer this I think
I stand corrected!
I have read that a rebooting after powerdrop can make problems.
What kind of problems Harry?
What kind of problems Harry?
2 times in a thread (I dont remember when and where) it was reported, that after a suddenly powerfault the rebooting of the KPA tooks quite longer than normal. In a live situation even a normal reboot time (> 30 sec) would be unconfortable.
I did not proof the longer rebooting time , but for me it sounds possible. KPA is like a computer.
The price of my UPS was about 65,- EUR. The capacity of the battery is enough for several minutes maybe hours. (I did not test the max. time)
Yep, maybe some system file or table would need to be rebuilt in some cases.
I agree with you, even tho I can't remember the thread nor this has happened to me even after an accidental reboot.
As someone that has worked on microprocessor based equipment in the field for decades now, IMHO it is essential to have a power conditioning UPS on any equipment like the Kemper if you are using it on a stage. Many stages have notoriously bad power; I sometimes play on a stage that routinely has 99VAC at the outlets (we have a voltmeter in the monitor rack). If you end up having to plug into an outlet at the end of a 100' drop cord, and there are power amps plugged into the same outlet, you are going to drop some volts. And many outdoor stages use generators, and those can be notorious for noisy power.
None of this takes into account noise injected into the power lines by equipment in a building such as HVAC.
All that being said, my Kemper has been rock solid and I have had no issues with power, but I haven't used it in any unknown environments yet. Since the Kemper ends up being the totality of your tone, and it takes a significant amount of time to boot up, spending $60 or so on a small battery backup UPS is money well spent.
In my day job we often place equipment with a power supply similar to the Kemper's in the field for demonstrations, and without fail we always buy a new UPS the day prior to the installation and charge its batteries overnight. We then install it with the equipment. When the equipment is returned, we simply leave the UPS at the customer site as someone always wants a new UPS for free. $60 for a UPS is a lot cheaper than disappointing a customer and losing a sale or blowing up a $30K piece of equipment.
I had once a problem that the kemper did not start up after someone accidently cut the fuse...
It happened just before a gig... and it took at least 5 minutes before I could start the Kemper...
KPAs different reaction to power blackout! Why do some KPAs do better than others?
As someone that has worked on microprocessor based equipment in the field for decades now,
Ähäm, me too, but this was in another live 
All that being said, my Kemper has been rock solid and I have had no issues with power, but I haven't used it in any unknown environments yet. Since the Kemper ends up being the totality of your tone, and it takes a significant amount of time to boot up, spending $60 or so on a small battery backup UPS is money well spent.
I spent more than 200 Euro for mechanical Protection. (Thon Case) The approx.65 Euro for electrical protection are really peanuts and I have plugs for additional equipment. (Monitor , extern delay and reverb)
Here in Austria we have a very stabile net, but the installation of some places I play are not always in a perfect state.
Its really a very usefull investment, even that I believe that the kemper is built very stabil regarding electrical influences.
