Lightning protection circuit specs

I am trying to design a lightning protection circuitry using MOV etc. components. This will be shunt at the output of a relay to protect both load and the relay itself.
Which UL standard/or other standards I should use to review about the required qualification based on the product/environment I am designing for. I need to know this to find the required specifications to chose proper MOV/TVS etc.

To research the UL standard for your application, you can check on for possible help.