Catenary wire

[D Skelton]

Where? If the regs classify catenery wire as extraneous then they're wrong! You're right in the catenery wire is neither exposed or extraneous in 99% of circumstances however if there is a risk that it could become live due to a faliure in basic insulation then it would be an exposed, not an extraneous conductive part, therefore it would require earthing, not bonding.

 

[Silly Sausage]

I'd take what OS says sometimes, with a pinch of salt.
I vaguely remember, from his introductory speech, he likes to be 'controversial', hence his name (his words)!!!!


Or he's making some really basic mistakes!?!?!

 

[D Skelton]

I don't mind controversy at all, if anything I relish it! But it has to be reasoned!

 

[Outspoken]

I'd take what OS says sometimes, with a pinch of salt.
I vaguely remember, from his introductory speech, he likes to be 'controversial', hence his name (his words)!!!!


Or he's making some really basic mistakes!?!?!

Actually I know the definitions..

Let me quote if I may, and you can take with a pinch, shovel or bucket of salt all you like.

Exposed-Conductive-Part. Conductive part of equipment which can be touched and which is not normally live, but which may become live under fault conditions.

Extraneous-Conductive-Part. A conductive part liable to introduce a potential, generally Earth potential, and not forming part of the Electrical Installation

You will find the above on page 27 and page 28 respectively.

Now catenary wire is not part of the equipment, it is a conductive part that is likely to introduce a potential, namely an Earth potential, but which, under fault conditions may be at a different potential to the general mass of Earth, thus introducing a potential shock hazard.

Now I would wholly agree that neither definition is exact in covering catenary wire, but then we have to fall back on good understanding and experience, the catenary wire is never an exposed conductive part as it is not part of the electrical installation, no more so than the the steel sections of a dry lined wall are or the radiators in a wet central heating system, and as such the definition of Extraneous Conductive Part is correct.

Now perhaps you wish to write a more accurate definition, be my guest, it is needed to be honest, but I really can't see the IET and the BSI rewriting anything for the 1/1 billion chance that the catenary will become live in the literal sense.