This is armoured cables.

HV might be a bit different from LV, but in broad principles, as long as the armour is adequately Earthed, then the tray won't be an exposed-conductive-part, so won't need Earthing on that score. If they tray supports are fixed into the ground in such a way that they could introduce an potential (Earth potential) that could be different from the Generator's Earthing, then it probably should be bonded (as distinct from Earthed) as an extraneous-conductive-part.

Just out of curiosity, what's that green(?)/yellow looking cable going up from the top left corner of the tray doing?

   -  Andy.

Hi Andy, 

Are you saying that for an LV installation the traywork would be an exposed or extraneous conductive part if the armouring of a SWA wasn't earthed?

Hi Andy, 

Are you saying that for an LV installation the traywork would be an exposed or extraneous conductive part if the armouring of a SWA wasn't earthed?

Are you saying that for an LV installation the traywork would be an exposed or extraneous conductive part if the armouring of a SWA wasn't earthed?

I'm suggesting that for something to be an exposed-conductive-part the tray would have to be liable to become and remain live if there was a fault in the basic insulation - interposing an earthed armour (with ADS operational) is one way to to prevent that - but I'm not saying that's the only way - another, for example, would be the use of insulated and sheathed cables (if the installation conditions were suitable). Using an armoured cable with the armour unearthed opens several cans of worms - neither the bedding nor the outer sheath are normally required to have the properties of an insulating sheath of an unarmoured cable, so you comply with neither the requirements for ADS nor the requirements for double or reinforced insulation (using a sheathed insulated cable) - so the cable itself would usually have to be considered a shock hazard even before you get to thinking about contact with the traywork. I suppose you could try and construct some kind of enclosure using tray, but that's really not what tray should be used for (use trunking instead).

Extraneous-conductive-parts are a different (if related) kettle of fish - If the tray could introduce a potential into the installation (or sometimes the location) - e.g. by some independent connection to the general mass of the earth - then it would be extraneous, and the cable mostly wouldn't affect that. If you had an armoured cable with the armour in contact with the tray (perhaps like the old lead covered cables) and the cable was earthed from a different installation, then they tray might in that  case be an extraneous-conductive-part as far as your installation was concerned (but then so would the armour). So there might be the odd corner case where a cable without a plastic sheath from another installation, carried on a tray, would make the tray an extraneous-conductive-part, but not that common I would have thought.

  - Andy.