These high currents can readily couple into sensitive circuits. Most manufacturers recognize this and provide only minimal internal protection. My equipment has a dedicated powerline. A dedicated line can minimize internal surge damage, but provides a direct pipeline for the more dangerous external surges. Unfortunately some manufacturers state the time for their suppressor to start coming on as opposed to being completely on, giving a misleading view of actual performance.
Some surge suppressors fail in thermal runaway, can overheat and cause fires.
Before buying a suppressor, compare rated service life for various surge levels . Do not purchase a surge suppressor unless it has a stated service life that is reasonable for your application. According to the industry guide IEEE 587, a medium exposure location could have, on average, one 6,000 volt surge per year. The joule rating is a limitation of the product. Shunt suppressors should not be subjected to surges larger than their joule rating or they will likely fail.