R&D doesn't means you exactly know the concept of insulation design, I taught lots of R&D for insulation safety concept in past years, even famous IT manufacturer located worldwide.
I means no offense but are you sure "市電中並沒有危機的" ? Are you able to tell category I to IV? The hazard will not only be the "surge cause by lightning" but also the "transient voltage caused by unstable load". If you're R&D, you must know it's possible to have unstable power quality if your electricity system wasn't built according to local electrical regulation, and surge suppressor will not be the only solution in your design.