[jrref]

There was a question a while back in other surge protection posts here on TOTV about surge protectors that use both common MOV devices AND also Gas Discharge Tubes and why they may be better than a traditional surge protector that only uses MOV devices. I finally found an answer that everyone can understand.

When a large power surge occurs in your electrical system with a surge protector that uses both MOVs and Gas Discharge Tubes:

A) The leading edge of the transient is clamped by the MOV to a value just above the normal operating voltage of your electrical system in your home.

B) As the surge increases, the current through the MOV increases and a voltage is developed across it which causes the gas discharge tube to fire. The energy of the transient is now quickly shunted through the gas discharge tube surge arrester and away from the protected circuit i.e. the MOV before the MOV reaches its maximum power and fails.

C) The gas discharge tube surge arrester remains in full conduction for the duration of the transient.

D) When the transient has passed, the gas discharge tube surge arrester opens—ready for the next transient thus saving the MOV.

So, what does this mean?
When you get a very large power surge, in a typical surge protector that only uses MOV devices to absorb the surge and clamp the over voltage, the surge voltage and duration can exceed the capacity of the MOV and destroy it. While this is not common if you are using a surge protector that has a very high capacity, it's one possibility of failure.

When you have a surge protector with hybrid protection, meaning both MOV and gas discharge tube devices, when you get a very large surge, the gas discharge tube will trigger and "crow-bar" or short circuit the surge before the power absorption of the MOV has reached its limit and burns out.

Since the Gas Discharge Tube protects the MOV from reaching its maximum capacity, is why a surge protector with hybrid circuitry should last longer and be able to survive more large events than the typical surge protector using only MOV devices for protection.

Again, while the probability of overwhelming a capable surge protector is not common, I have seen several Ditek surge protectors installed here in the Villages that have burned up while protecting the home from a very large power surges.