how to identify a pme system help

[lucus]

hi all
i am just wondering how can i identify if a properly that used to be TT has been upgraded to TNCS (pme) one i recently done a job in used to be feed from a pole but now has been upgraded to underground concentric cable would you say this is pme?

 

[acat]

Have youb done a Ze test also do a PEFC & PSCC if you get the same result on both its PME.

Hope that helps


Chris

 

[lucus]

so im looking for a different result on pefc and pscc there usually very simular in my experiance what am i looking for on the ze, a higher reading for live and earth compared to live and neutral as the earth is smaller than the neutral?
regards

 

[Guest123]

On a PME system the PEFC and PSCC will be the same.

Your Ze reading should be lower tham 0.35ohms. If it is still a TT then the Ze wll be much higher than this and the fault currents will be different.

 

[lucus]

Thanks I know this is for a instalation with a main earth cable in place already I'm wondering if there's a test to see if there is pme available, as in when doing the ze I'm not just testing the neutral path, the supply company update the cut out but don't seem to put a new main earth cable.

 

[Spudnik]

Disconnect all bonding and test at 20ohm setting with line test lead on L and and neutral & earth leads together on the N in the CU.

If no PME you will get no reading.

 

[lucus]

sorry but what am i testing here ze? also is this the no trip setting so it uses the neurtal? so im connecting both the neutral and earth leads together on the neutral of the cut out.
thanks allot lads just trying to get my head around this.

 

[Spudnik]

Yep spot on and yes sorry, you are testing Ze.

And do the test at the tails in the CU, not the cut out.

 

[Deleted member 9648]

Thanks I know this is for a instalation with a main earth cable in place already I'm wondering if there's a test to see if there is pme available, as in when doing the ze I'm not just testing the neutral path, the supply company update the cut out but don't seem to put a new main earth cable.

You cant do a test to see if pme is available if there is not an earth already connected.....you will have to contact the DNO for this info.

 

[aptsys]

Disconnect all bonding and test at 20ohm setting with line test lead on L and and neutral & earth leads together on the N in the CU.

If no PME you will get no reading.

Surely for Ze test you're testing between the incoming phase terminal and the supply earth? Between Phase and Neutral would be for calculating PFC.

 

[ezzzekiel]

Cant understand the problem is there no earth visible? if its been upgraded by dno then an earth will be in place its there responsabilty so if theres not and your sure its been upgraded ring them and they can confirm for you.
You cant carry out a test to find out with no main earth in place between cut out and equipment.

 

[pushrod]

Would this work to identify a pme? - Do a Ze test across L and E and then do a Ze across L and N. If the readings are identical then it is a tn-c-s. [not at all experienced on this sort of thing yet ]

 

[Risteard]

Would this work to identify a pme? - Do a Ze test across L and E and then do a Ze across L and N. If the readings are identical then it is a tn-c-s. [not at all experienced on this sort of thing yet ]

Don't mean to be pedantic (do you believe me?) but a "Ze test across L and N" wouldn't be a Ze test.

 

[ezzzekiel]

Would this work to identify a pme? - Do a Ze test across L and E ]

not really possible if there is no earth

am i missing something here?

 

[lucus]

sorry for the confusion what i am asking is if there is a way to test the neutral for a pme, what has happened is a house ive been doing work at used to be fed from a pole but has recently been upgraded to underground concentric but the supply company didnt fit any earth cable from the cut out and i am wondering if i can test to see if pme is available.
regards