Dielectric strength and spacings are different requirements.
Dielectric strength is an ageing test for solid insulation, such as on wiring, in transformers and optocouplers.
Spacings are for two other reasons: one (clearance) for short term spikes in the order of 1000-3000V that occasionally appear on the mains, the other (creepage) is to have enough space to protect against long term dust/pollution accumulation.
So you really need to assess all three separately.
Current limit for dielectric strength: IEC 60601-1 does not specify a current limit for the HV tester, however other standards specify 100mA. This high current is theoretically important due to the effect of partial breakdown, but in practice modern insulating materials have dielectric strength well above the needs so it rarely has an impact.
Otherwise, because of EMC capacitors, you may need a HV current capacity of around 5mA.
The current pulled during a HV test is about 6 times the "neutral open" earth leakage current, e.g. if your equipment has 300uA @ 264V earth leakage in SFC (neutral open), you will see ~1.8mA leakage in the basic insulation test (@ 1,500V). It's a nice confirmation of your test set up to confirm this value. Double insulation test current is usually much lower (if not, something is wrong with your set up).
Yoroshiku,
(= regards in Japanese)
Peter
