TNC earthing system

[lyledunn]

The TNC system is rare in the UK. It is a system where the source star point is earthed through an impedance and the function of neutral and earth is combined througout the system.
I would like to find out more about the use of this system, advantages and disadvantages etc. Could anyone advise from where such info might be sought? Regards,

Lyledunn

 

[busbar]

Lyle—

You might look over/post here… “pauluk” is the moderator there.

http://electrical-contractor.net/cgi-bin/forumdisplay.cgi?action=topics&number=9

http://electrical-contractor.net/ubb/Forum9/HTML/000001.html

http://electrical-contractor.net/ubb/Forum15/HTML/000044.html

PaulCoxwell@aol.com PaulCoxwell@aol.com

 

[lyledunn]

Thanks Busbar.
Interesting site but I am afraid no mention of the system I was looking for. I have a feeling that this system may have a use say in production lines etc where security of supply is paramount. It may be used with earth monitoring devices.
I am really looking for someone who has used the system. As it is a rarity in the UK,I have no direct experience. Regards,

Lyledunn

 

[powrgen]

Are you sure you mean TN-C? This system does not usually use an impedance to to earth. The system that does is IT and is used where supplies are critical -operating theatres spring to mind.

 

[jbartos]

Suggestion: Visit

http://www.efinet.com/images/pdfs/wi_sgap.pdf

http://www.efinet.com/images/pdfs/wi_din.pdf

etc. for more info.

 

[busbar]

Lyle, I have experience with high-resistance grounded systems in the western US, based on ANSI standards; not in the UK. Don’t know if that’s of any use to you. tmp173@@nikola.com

 

[lyledunn]

Powrgn,

Yes, I do mean TNC, Re; Geofrey Stokes commentary on the IEE wiring regulations. However, you may be right, I really have no experience of this system. I am assuming that because phase will in effect be connected to exposed conductive parts through the winding or element of the piece of equipment concerned then it would be sensible to have some kind of limiting impedance at the connection with earth at source.

Many thanks busbar, I need to get this out of my hair first. (whats left of it!!)
Regards,

Lyledunn