What 'rated voltage' means in VDE certificates?
Unlike switch contacts that can break inductive current, without looking up the relevant std. specs. I say both AC &amp; DC.

It's my opinion that the  basic insulation here applies to both AC_rms and DC.  For moving contacts the DC rating can be &lt;1/3 Vac rating which does not apply here.

These tests include lightning impulse AC voltage.  There would be some industrial contamination level provided in the spec.

There is no reason to derate a Terminal block for DC vs AC so the same level applies.  That would be true for 70kVdc as it is for 400Vdc. Beyond this the pollution level is a critical factor design factors for creepage, which does not apply here, just FYI.

If you are doubtful on the pollution or dust levels, add a dust shield.