cream coloured conductor

[johnboy6083]

I was on a job a few years ago, in Westfield shopping centre, london and there were large cream coulored cables (unarmoured) running along side the main distribution cables from the switchrooms. Inside the switchrooms, each MET (copper busbar on insualting barrels) had one of these cables to it, along wth the normal G/Y ones. Ive heard them called functional or clean earths. What do they actually do? Are they an extra means to keep all METs at the same potential ie as near to 0v as poss?

We are talking about a massive installation here too.

Cheers lads.

John

 

[Risteard]

Functional earths are cream in colour. This is where an earth connection is required for proper functioning and is not a protective conductor.

 

[Sintra]

One common example of a functional earth is on an RCBO.

 

[johnboy6083]

so would they be used for things like large variable frequency drives ect, where large amounts of current leak to earth?

 

[nickblake]

A functional earth connection serves a purpose other than providing protection against electric shock. In contrast to a protective earth connection, a functional earth connection may carry a current during the normal operation of a device. Functional earth connections may be required by devices such as surge suppresion and electromagnetic interference filters, some types of antennas and various measurement instruments. Generally the protective earth is also used as a functional earth, though this requires care in some situations.

 

[bugsy]

Generally instaaled in cooms rooms data suites and for telecom comms eqpt.