I am designing a circuit that can detect if a cable is connected to mains voltage (e.g. via an external relay or switch). The device will be installed in electric cabinets.
The circuit is tested and works, but I want add further protection. I read about the differences between TVS Diodes, MOVs, etc. and decided to use TVS Thyristors because they seem to be the safest option.
But I could not find out how to properly select a TVS Thyristor. As I said I want to protect 230V AC mains voltage.
At Digi-Key the most important stats are "Voltage - Breakover" and "Voltage - Off State" I assume. I suppose this is supposed to be the peak voltage (i.e. \$230V * \sqrt 2 \approx 325V\$) multiplied by some safety margin factor and not the effective voltage (i.e 230V). I don't really want to prevent "small" transients, because my circuit can handle probably at least 400V peak voltage.
Does that mean I have to select as TVS thyristor with a "Voltage - Breakover" of 400V? And what does the "Voltage - Off State" mean which would be between 300V and 320V in that case?
Is this the correct approach anyway or would other protection devices be better suited?
Edit: Added schemtic upon request. The exact ciruit does not really matter, because the question is mainly about the nature of TVS Thyristors in general and not just this specific case.