advise on ze

[Farmelectrics]

carrying out 5 year perodic testing on commercial buildings having trouble locating ze value searched for hour on end looking in o&m manuals and no value on any of the original test sheets the buildings are all tns systems i phoned up the supplier and the only values they gave me were the max value of 0.8 is this ok to put on test sheet. but surely this is not the measured value which you should be recording we have no acceess into the sub station to measure ourselves all advise welcome.

 

[Electricalserv]

carrying out 5 year perodic testing on commercial buildings having trouble locating ze value searched for hour on end looking in o&m manuals and no value on any of the original test sheets the buildings are all tns systems i phoned up the supplier and the only values they gave me were the max value of 0.8 is this ok to put on test sheet. but surely this is not the measured value which you should be recording we have no acceess into the sub station to measure ourselves all advise welcome.

Why can't you take a measurement? Or are buildings in use?

Ze from supplier is fine. Better takeing a reading though. Last time I spoke to suppliers told 0.8ohms when I took measurement it was 0.02ohms...sub station 20 yards down the road

 

[RWJ]

max value of 0.8 is this ok to put on test sheet.

Depends on the PIR form your using but you can put Ze value by enquiry...
But I still can't see why you can't get a Ze reading???

 

[malcolmsanford]

You will have to mark it down as a limitation. By the sounds of things even if you could get access you would not be able to isoalte the entire installation to remove the main earthing condutor.
http://www.cablejoints.co.uk/sub-product-details/earth-bars-copper
What you'll most likely find is a MET with one of these that will have a disconnection point, but it will not really help if you can't get permision to disconnect, but it will show you where to take a Ze from

http://www.cablejoints.co.uk/sub-product-details/earth-bars-copper

All you can really do is at each DB board throughtout the installation is take a Zdb or Zs of each board.

You can get Ze by either measurement, calculation or enquiry. You can not measure it, I doubt if you can calculate it, so you got yours through enquiry then that is what you enter and mark it down on your PIR as done.

 

[Farmelectrics]

the buildings are in use plus no access to sub supplier has keys we can only get into are lv sub ill put the 0.8 value in but previous experience tells me it would be much lower thanks for advise

 

[RWJ]

Just take Zs at the board and put it down as a limitation