Neutral cable in ductbank system

[intelsath]

I'm working in a design using a ductbank 3 x 4/0 XLPE with 4" PVC duct, but I can't find information about how I should Size de netral cable and where I shoul put it inside the ductbak.
The load is 3 Mw and the distance of ductbak is 3 miles.
The sistem depend of substation in start configuration with neutral solid grounding.
The voltaje is 13.8 Kv.

I can't see the location of neutral cable in the pictured attached.

 

[Palletjack]

MV cable will have 1/3 or full neutral if you order jacketed concentric neutral cable

Where’s the rest of the drawing that specs the cable out?

 

[7anoter4]

Usually, 13.8 kV System does not supply single phase consumers, so no neutral is needed.
However, the cable shield needs to be grounded. Up to 1-1.2 miles a single point grounding it could be used. Above this length a special bonding is required [See IEEE-575/2014]. A parallel ground continuity conductor it is necessary. See:
6.3.3 Parallel ground continuity conductor
Accordingly, it is recommended that single-point bonded and multiple single-point bonded cable
installations be provided with a parallel GCC that is grounded at both ends of the route as shown in Figure 2. The spacing of this conductor from the cable circuit should be sufficiently close to limit the voltage rise of the shield/sheath to an acceptable level during a single-phase fault. The size of this conductor must be adequate to carry the full, expected fault current for the cable system.

 

[davidbeach]

Why would you say that a 13.8kV system wouldn’t supply single phase loads?

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Palletjack]

Usually, 13.8 kV System does not supply single phase consumers, so no neutral is needed.

??
East coast here. 25kV system. We have lots of single phase consumers..
They all need a neutral

 

[7anoter4]

I apologize. I exaggerated a bit. I meant to say that you don't run 3 miles cables in a duct bank to supply residentials.