rcbo functional earth

[tank]

hello, does the functional earth of a rcbo have value of loop impedance that has to be met in order for it to work as designed?

 

[Richard Burns]

I do not believe so it is just an earth reference cable it is not a CPC. Anyway how would you test this there is no access to the FE at the RCBO.

 

[tank]

i was curious as to whether having a ze of say 156 Ω on a tt system as opposed to say 0.2 Ω on a tncs would have any effect on the operation of the fe on a rcbo

 

[Engineer54]

None, ...it's purely for reference purposes...

 

[MarkieSparkie]

None! The functional earth is used by the RCBO as reference for the internal electronics necessary to increase the sensitivity and speed of operation needed to miniaturise the earth fault functionality and package it in a one module unit not much bigger than MCB. It also allows the device to detect an earth fault, even if in a rare event of the neutral becoming disconnected.