Gas discharge tube datasheet impulse sparkover specification
What does the Impulse Sparkover at 100 V/us and 1000 V/us mean?


What it tells you is that if you applied a fast rising surge changing at a rate of 100 volts per microsecond then the GDT would sparkover when the surge waveform reached 250 volts absolute. That's a time delay of 2.5 us.

However, if the surge was rising at 1000 volts per microsecond then sparkover wouldn't occur until the waveform reached 525 volts - that's a time delay of 0.525 us.

In other words, GDTs cannot be used (on their own) for some fast applications because they have an inherent time delay. A lot can happen to a circuit in 0.525 us!


  How does the impulse help us decide with which GDT to choose?


This is sometimes why GDTs are used in parallel with MOVs. MOVs are fast but don't like being overloaded excessively. The MOV takes the initial brunt and then the GDT takes over and handles the remaining bulk energy of the surge.