Some questions about a terminal block voltage and maximum ratings
The voltage rating for a terminal block is generally the RMS or DC voltage rating. The breakdown voltage would generally be higher for both consequent terminals and terminals a to steel mounting surface. I believe the terminal block may need to pass a test for something like twice the rated voltage plus 1000 volts. For a 1000 volt terminal block that would be a 3000 volt test if I am recalling the standard accurately.
I believe transient voltage is included in the breakdown voltage test.
You can increase the terminal to terminal rating by using every other terminal, but the terminal block may then need to have additional mounting surface insulation. Both of those could cause difficulty with testing laboratory listing. You would need to have the specific use examined rather than relying on the listing for the terminal block.


I don't have any reference to verify the above. If is is correct for USA standards it may not be correct elsewhere.