Ze again

[buttonmoon]

Ok I've got 2 supplies with continuity between the various earthing arrangements on both sides but I can only find 1 MET. one side is 3 phase and the other is single phase. the MET is on the single phase side which has a TN-s earthing system. the other side has a TN-C-S earthing system. on the single phase TN-S side with the MET I am getting a reading of .54 for Ze which is acceptable for TN-S but not TNC-S. There is a piece of fixed furniture in front of the TNC-S CU which is preventing me from taking a direct measuement of Ze on that side but the client is desperate to keep his seating arrangement as is. I could take an r1 + r2 and subtract from Zs (Zs-(r1+r2)=Ze).

Any ideas???

 

[WayneL]

Does anybody else's head hurt?

 

[Sintra]

Does anybody else's head hurt?

Sure does very confused.

 

[Sintra]

On the supply that you state is TNC-S you say that the Ze is 0.54.
Take an external impedance reading between L - N on this supply and compare this to the Ze reading both should be approximately equal if it is a TNC-S.
The reason i am saying this is that a reading of 0.54 L - N seems very high for any type of system.
Point is are you sure it is TNC-S.

 

[brucelee]

nice one sintra i was getting confused didnt read properly so deleted my other thread as didnt want to give incorrect advice

 

[buttonmoon]

Let me start by apologising for the way I have explained this.

OK sintra its the TN-S side that I have managed to measure the Ze on which is why .54 is considered acceptable ( less than 0.8). The reason I say its TNC-S on the other(3Phase) side is that it says either PME or PEN either way that makes it TNC-S no?

 

[buttonmoon]

Just a thought perhaps the continuity between the earthing systems is being achieved through external paths which would mean that there could be no earthing on the 3 phase side???