There are two types of electrical surges that can be produced by lightning: directly injected and indirectly induced. Directly injected is that which enters on the power line and will cause a surge potector at the service entrance to fire. Indirectly induced is caused by the elecromagnetic radiation produced in the atmosphere by the lightning stroke. This electromagnetic radiation can couple to the house wiring and cause damage eventhough the primary surge protector across the service entrance does not fire. For this reason it is wise also to use MOVs or other protection devices at your equipment. If you have a large surge enter on the elecrical service, only having protection at the equipment itself may not be enough. So, to be really safe both are needed.
This is essentially what Bob_bundus has done in his house--primary protection at the service entrance and secondary protection at the equipment.
This is essentially what Bob_bundus has done in his house--primary protection at the service entrance and secondary protection at the equipment.