Good few years back, house near us took a direct lightning strike, which blew most of their sockets off the wall, and put the chimney throught the roof into the room below.
Here, about 100 yards away, the Fax/Phone intelligent splitter box fried, as did the modem in the PC, though the fax escaped.
Every TV in the house was damaged to a greater or lesser extent, and we also ended up having to install a new switchboard. One TV was beyond economic repair, which was a pain, as it was a nice set in those days.
It was clear that the most serious spikes and damage came in on the phone and Cable TV lines rather than on the main electricity supply.
All the cables locally were underground, so it wasn't a case of induced spikes in overhead wiring, I suspect that the problem was more related to the lack of local earthing on the "other" services, at least with the main power system, there are connections to ground all over the thing, so any spike can be discharged more readily.
Even with a UPS, there are risks to equipment from surges, it depends on how the UPS works, and it's quality, in that if it "supports" the mains, rather than converting incoming mains to DC, and then producing "new" AC from the DC or battery as appropriate, there is a risk that a high surge can get past the internals of the UPS, with the potential (arrghh
) to do damage to whatever is downstream.
So, to disconnect or not. I suppose the safest path is yes, if there's significant weather about, then disconnect, but do make sure that you know what the settings are for any box that's going to be powered off. Also, remove both the mains lead AND the incoming line. A spike on either can do damage even if the box itself is powered down.
Some of the more expensive and complex protector devices for power and lines can help, as they have the internal components to provide the protection to the equipment that's connected. Be warned, in some cases, if they do provide protection against a strike, it may be necessary to have some of the internal components replaced, as they are designed to fry and protect the connected equipment, and once fried, they ain't going to work any more.
OK, that's enough for this session, hope it helps
Cheers