Direct Burial MV 25kV cable

[KLinn]

Issue was discussed with the AHJ in reference to Figure 310.60 detail 7 and 8. Is there a more detailed definition of tri-plex cable with-in the NEC? Paralleled cable runs from the mfg. on the reels are similar in look, but not truly tri-plex cable. In the direct burial application, the heat dissipation factors, I assume, are the reasons for the separation of conductors and circuits. We were running in conduit on this particular project, but the AHJ asked us why we ran the tri-plex in the PVC. That is what brought me to this point with other projects coming soon after that are very similar in construction. Thoughts?

 

[JoeStillman]

Closest thing to a definition is in 392.6, Messenger Supported Wiring;

Messenger-Supported Wiring. An exposed wiring support
system using a messenger wire to support insulated conductors
by any one of the following:
(1) A messenger with rings and saddles for conductor support
(2) A messenger with a field-installed lashing material for
conductor support
(3) Factory-assembled aerial cable
(4) Multiplex cables utilizing a bare conductor, factory assembled
and twisted with one or more insulated conductors,
such as duplex, triplex, or quadruplex type of construction

Note that the ampacity tables of 310.60 make a distinction between "Insulated Three-Conductor cable" 310.60(C)(71) and "Triplex" cable 310.60(C)(72).

Not sure what the AHJ meant by the question. Could have been "why in conduit", or "why that kind of cable".

 

[KLinn]

Ok, 396.2(4) great info. for definition.
Let me better clarify. The conduit was underground, with 3-4/0 aluminum 25kV cables, no ground as she approved the concentric neutral as an acceptable replacement . With the available supply of cables now, this cable is listed for direct burial. I think that was her question reference that she would have accepted direct buried. Since it was not purchased as tri-plex, just paralleled, we didn't even consider it.