Insulation resistance on a live DC cable?

[mikemack00]

Hi

Was wondering if you could clear up a few things I on't quite understand, I've been told it is possible to do an insulation resistance test on a live DC cable (Solar pv) by testing to ground. Is this right, and what voltage rating should I set the megger to?

Also on a domestic solar pv installation would you test to earth on the consumer unit?

Also how is the voltage given out by the megger affected by the voltage in the circuit? and vice versa.

Confusion reigns:mad2:

 

[yellowvanman]

Hi

Was wondering if you could clear up a few things I on't quite understand, I've been told it is possible to do an insulation resistance test on a live DC cable (Solar pv) by testing to ground. Is this right, and what voltage rating should I set the megger to?

Yes, and voltage set should be in line with Table 61 of BGB

Also on a domestic solar pv installation would you test to earth on the consumer unit?

Yes, that could be the same as the 'ground' mentioned above, you should also test to the array metalwork.

Also how is the voltage given out by the megger affected by the voltage in the circuit? and vice versa.

If you connect the megger to one side (+ or -) only and to earth it doesn't see the PV voltage (or shouldn't) as you are not completing the circuit!