Which earthing system?

[Hayeso32]

Guys, I'm currently working on a national grid site and have been tasked with checking over some NIC sheets of the subbie. However access to the dno kiosk is not available quickly and the drawings aren't to hand. I have been told that the supply is tnc-s that then goes through a isolating transformer which is tt. So my question is what earthing system would I put on the test sheets?

Thanks in advance for any replies!!

 

[Plonker 3]

Meh....

 

[trev]

Talking cack as per.

 

[Hayeso32]

Typical condescending spark!!!

 

[Clive P]

Hi,
Having worked on dozens of National Grid sites, I would record the Earthing System as TT. All of your testing and circuitry reverts back to the secondary of the 1:1 Transformer, this as you will be aware is where you will get your Ze reading. You can measure the Ze on the primary side to check your TNCS supply to ensure it meets the relevant criteria, but as said TT.
.
Regards.

 

[Amp David]

I'd opt for TNS

 

[Engineer54]

Might be an idea to tell us what this isolating transformer is being used for and what is it supplying?? You say this is a National Grid site your working on and then say, you can't gain access to to a DNO kiosk, so again what is this kiosk supplying??


The Secondary side Neutral at the TX, will be earthed as a matter of course, it's what happens after this connection as to what earthing system is eventually used. It could be any TNC-S, TN-S, or TT!!

 

[Outspoken]

Guys, I'm currently working on a national grid site and have been tasked with checking over some NIC sheets of the subbie. However access to the dno kiosk is not available quickly and the drawings aren't to hand. I have been told that the supply is tnc-s that then goes through a isolating transformer which is tt. So my question is what earthing system would I put on the test sheets?

Thanks in advance for any replies!!

What is this transformer doing, that's a helpful start..

At first look if the secondary side is TT'ed then it should have an earth stake, thus it is TT!! Now there is rocket science for you..

 

[trev]

Typical condescending spark!!!

Don't know who that was directed at but if you look at the reasons for editing both Dillb and I had valid reasons for withdrawing our comments. Mine of "talking cack as per" was actually a criticism of myself.

 

[telectrix]

criticism or praise, trev? :6:

 

[MDJ]

Typical condescending spark!!!

Really? well racists and idiots tar everyone with the same brush due to lack of brain cells, are you suggesting sparks are typically condescending? Now if you would suggest Plumbers are condescending idiots I would agree LOL

 

[Outspoken]

Really? well racists and idiots tar everyone with the same brush due to lack of brain cells, are you suggesting sparks are typically condescending? Now if you would suggest Plumbers are condescending idiots I would agree LOL

Isn't that Tradism?

 

[Engineer54]

What is this transformer doing, that's a helpful start..

At first look if the secondary side is TT'ed then it should have an earth stake, thus it is TT!! Now there is rocket science for you..

Errrr, all TX secondary neutral points are earthed via a TT system, especially at a sub-station or in this case, National Grid site. It depends from that point onward, as to what the actual system earthing is. As i stated it could be any of three usual systems, could even be an IT system!! Without knowing what this TX is doing, it's anyone's guess!!

 

[Hayeso32]

Thanks for all replies so far, to clarify the site is a gas agi and is being worked on as part of the CNI project. The site is unmanned and so falls under the sco1+2 permit to work procedure thus making it difficult to gain access. The isolating transformer supplies all of the essential equipment to do with the gas pumping as far as I am aware.

 

[Outspoken]

Errrr, all TX secondary neutral points are earthed via a TT system, especially at a sub-station or in this case, National Grid site. It depends from that point onward, as to what the actual system earthing is. As i stated it could be any of three usual systems, could even be an IT system!! Without knowing what this TX is doing, it's anyone's guess!!

E54, couple of points, my first comment did actually ask what the Tx was doing..and secondly, IT systems are illegal to install in the UK and have been since the mid 1960's. Tate and Lyle had the last such operational system in the UK, located in what was the Industrial part of London Docklands. That was decommissioned and demolished in the late 1980's and the British Sugar (Formerly Tate and Lyle) site in Bury St Edmunds has it's own 132kV dual feeders incoming and all systems on site are TN-C.

So there is no way the Tx would be IT. It is obvious to anyone in the know that all generator sets and Tx's on the distribution grid are effectively TT systems, as such the enclosure they are in should be treated as such...well according to National Grid anyway..