RCD tripping in Consumer Unit

[EFLImpudence]

Hence, for, say, 50m of cable that would be 5,000 pF (5 nF) - so, about 640 kΩ at 50 Hz, resulting in an L-E 'leakage' current of about 0.36mA at 230V. Since the N-E potential difference will usually be fairly negligible, the N-E leakage current (which will reduce the L-N imbalance) is also likely to be fairly negligible but, in any event, the maximum L-N imbalance would be about 0.36 mA for 50m of T+E.

If I understand correctly that is not correct; the N-E leakage will add to the total leakage.

 

[JohnW2]

If I understand correctly that is not correct; the N-E leakage will add to the total leakage.

Yes, you're right - my apologies. The L-E leakage (through cable capacitance) will add to the L current (as seen by the RCD), whereas the N-E leakage (through cable capacitance) will subtract from the N current (as seen by RCD), so the L-N imbalance seen by the RCD will be the sum of those two leakages.

However, that makes very little difference to the bottom line of what I said - since, as I said (and as Mr Ohm would confirm), the N-E leakage (current) will be 'fairly negligible', since the N-E potential difference will also usually be 'fairly negligible' - so the L-N imbalance seen by the RCD will primarily be that due to the (much larger) L-E leakage.

Kind Regards, John

 

[Harry Bloomfield]

I obviously can't speak for others but, probably because all of my meters (including the 'fairly expensive' ones) are pretty (in some cases very!) old, I don't have any which can measure AC currents in the mA range.

Even my older ones (I am pretty sure) will cover that range.

 

[Harry Bloomfield]

If I understand correctly that is not correct; the N-E leakage will add to the total leakage.

L-E leakage will add to the total, N-E will subtract from that total...

[EDIT] As your were - it is a duplicate of John's post, sorry..

 

[JohnW2]

Even my older ones (I am pretty sure) will cover that range.

Fair enough. A good few of mine don't do AC current at all, and those which do generally to not have mA resolution.

Kind Regards, John

 

[ericmark]

My AVO Mk8 will measure mA, but would not measure the difference between two power cables, need a clamp on meter for that.

As to measuring actually mA to earth, this is why the ELCB-v was a failure, there are likely many paths to true earth.