surge / spike protection

[andyes]

Hi Guys hoping you can help here I am an electrician and fit digital clock like the one below. However recently I have been called back to 2 clocks where I suspect have been blown by a suspected surge or spike.
So is there anything I can fit on the clock mains supply that would give it some protection

[andyes]

Hi guys being doing some more research and would using 3 MOVs give protection ie 1 across L-N then 1 across L and N to earth .

Would that work ? and what MOV rating would you use ?

Any help would be appreciated

Andy