Usually the ethernet cable is not a problem as long as it stays in the building. Where we used to blow stuff up was when the ethernet ran between buildings. I am not even sure those strips would fix that problem. We made the problem go away with a fat bonding wire that was significantly shorter than the ethernet cable, bonding the machine frames together.
We also clamped ferrite beads on the ethernet cable at each end.
There was some engineering dispute about how that worked, but it worked. The basic idea came from the State Farm data guys in Winter Haven on parallel printer cables but we adapted it to ethernet.
Ethernet between buildings is just asking for trouble. Fiber is the best choice there. But you did take the correct steps to minimize the effects. The ferrite beads would not have stopped a differential mode on the ethernet cable, but if it was getting a surge from the voltage difference between buildings (step potential in earth when lightning makes a nearby hit, especially if it hots a building), this would be common mode on the cable, not differential. So the beads would help by having even more of an inductive effect than the cable by itself. Wrapping the cable through a large toroid a few times would help even more on common mode surges (without effecting the differential voltage since both sides are parallel in the cable).
I'd prefer to run fiber optic and use an ethernet converter on each end. They are cheap enough. Even gigabit ones are showing up.
