There are other sources of power line transients but lightning is our heavy hitter here. It is not usually a direct strike, just the spike induced by a near miss. That can also show up as a ground shift where different grounding electrode systems have different potentials. That is probably the most destructive. Manufacturers try to avoid using the word lightning since a true lightning protection system goes beyond surge protection. For that matter, surge protection goes beyond simply having point of entry protection too but it is the starting point. Be sure all of your inputs (power, phone TV and data) have protectors bonded to the same grounding point. The NEC addressed this several cycles ago when they required the inter system ground bus. True lightning protection also requires air terminals and fat braided ground wires for the most part. As counter intuitive as it sounds, that should be bonded to the GES. You should also have protection on any sensitive equipment you want to save tying all input protection together. That is more about locally produced transients.
The switcher power supplies are a good news bad news joke. They tend to insert high frequency noise on the power line but those supplies themselves are somewhat immune to that noise.
IBM had a big war on power line noise, all the time not admitting that it was our own power supplies doing it. Once all of our power supplies were switchers, the problem went away, at least for our stuff. These days that is the power supply most people are using so the scary term "sensitive electronic equipment" is somewhat obsolete. If your power supply says 100-250v 50 or 60 hz, it is not going to see most transients if they put in a 10 cent MOV but you still need to worry about transients from different inputs.
