TN-C-S to TN-S !!!

[Bamfus]

I'm scraching my head with this one...! Street lighting circuits, the supply comes in as TN-C-S Board supply, gose to a small two way circuit board which has a single pole and nuetral and two HRC fuse outputs. 1 which goes up to the lamp column, the other goes to another colume with a simla fuse protection via a swa cable. Now here is the Question ! I'm shown by the company spark the way they do there Test Sheets, Sheet One you wright the incoming supply which is TN-C-S for the first colume.
And on Sheet Two Underground Cables, you wright the incoming supply as TN-S I thought if it comes in as TN-C-S it stays as tn-c-s maybe i need to go back to collage.!!

 

[sparkwright]

Without looking anything up, I would think that's reasonable, as I presume the second column is fed by a separate neutral/separate earth.

 

[JohnW2]

Without looking anything up, I would think that's reasonable, as I presume the second column is fed by a separate neutral/separate earth.

It's really a 'bureacratic question', but I thought the whole point (definition) of a TN-C-S supply was that it starts out with neutral and PE combined and then, at some point (usually entry to a building for indoor installations), they separate (hence "-C-S"). That doesn't stop one calling the 'installation' a TN-C-S one throughout, even though the neutral and PE remain separate throughout the actual interesting.

I guess the underlying bureaucratic question relates to what is considered to be 'an installation' when one is talking about street lighting!

Kind REgards, John

 

[westie101]

From memory we are not allowed to install a combined neutral/earth cable into a street lamp.

 

[RF Lighting]

I'm sure I've worked on Leeds city council streetlighs with a PME feeder. It's a few years ago now, so I might be wrong.

 

[ChrisRogers]

I've worked on lots of PME fed street lighting columns. Even had one with a broken PEN conductor over christmas......

 

[westie101]

Oh I know there are a lot of PME fed columns but ......................
(I'll have a read through the relevant documents on Monday)

 

[RF Lighting]

I've worked on lots of PME fed street lighting columns. Even had one with a broken PEN conductor over christmas......

I'd like to see a dog have a pee against that column

 

[westie101]

I'd like to see a dog have a pee against that column

That's quite often how we find out

 

[streetlighter]

now here is my input as someone whom works on streetlighting currently as a sparky!

most newly installed columns with a DNO Supply, have TNCS Earting Arrangement, on the test sheets any colums that are supplied from a private network say outgoing ccts in a feeder pillar are noted down as being a TNS service even if the DNO Supply to a feeder pillar is in fact a TNCS.

 

[rickyp333]

hi don't no if i can be any help to any of these threads but im a electrician with 20 years experience now working as a overhead lines man for the last 2 years and would just like to state that there is no such a thing as a tns system at some point in the line they are combined as earth is neutral be it at the substation or at the nearest transformer neutral originates from the ground

 

[RF Lighting]

Maybe you ought to do a bit of reading up on electrical supplies and earthing systems...

 

[ricicle]

PME is PME. It doesn't become TNS just because you are running a sub main with separate N/E[/i][/code]

 

[ban-all-sheds]

hi don't no if i can be any help to any of these threads

Not so far.

 

[Spark123]

Yep, if the supply is TN-CS then you cannot have a directly connected system becoming TN-S downstream, it is still TN-CS.

Always made me wonder though if the DNO ever gives us what is TN-CS upstream in a split concentric or PILC, making the normal sparky think it is TN-S