400V,
I've just been reading AS/NZS 3000:2000
and 6.3.4.2.1, states that the Earth Loop MAY be measured to verify that the circuit protection will operate.....
Note 2 to this clause says this
If an RCD operates during the (ELI) test, the test result is considered satisfactory
Also, did you know 400, that Appendix B to this Standard gives actual values of earth loop impedance opposed to disconnection times and lots of diagrams and other pretty pictures!.