Bundled single phase conductors serving three phase load.

[11bgrunt]

1) Are these conductors installed under the NESC (POCO standards, used for things such as service drops) or NEC (National Electrical Code, used for building wiring)?

-Jon

The utility is not subject to the NEC.
Any rules from the NESC would apply.

 

[winnie]

The utility is not subject to the NEC.
Any rules from the NESC would apply.

I understand the difference between NEC and NESC, I was asking which rules govern the cables being discussed.

Only a few of us here know the NESC (not me). So I can stand by the physics of the answer I previously gave (that there will be circulating currents but I don't know how much), but I have no clue about the code acceptability.

Jon

 

[11bgrunt]

I have never seen a NESC standard governing how a LV OH service will be connected. The 4/0Q is standard issue on OH 3 phase secondary and the rules, are POCO rules.

 

[mbednarik]

But that grounding conductor in the PVC raceway probably won't have the steel strand the ACSR has, so magnetic effects are going to be different.

The ACSR does not encircle the covered conductors so it will not have an inductive heating effect. There will be some minor inductive coupling, but if the ACSR is bonded it won't be an issue.

 

[kwired]

The ACSR does not encircle the covered conductors so it will not have an inductive heating effect. There will be some minor inductive coupling, but if the ACSR is bonded it won't be an issue.

The conductors encircle it though. This is the basis of how motor, transformer and solenoid windings and cores are designed. It probably produces some heat at the very least even if there is little other significant effects.

 

[winnie]

The point about ferromagnetic conduit _encircling_ the conductors is that the conduit is acting as the magnetic core of a transformer.

The issue is that the magnetic fields can induce parasitic current which can cause unintentional heating on top of the desired load current and its necessary heating.

There are two 'loops' that need to be considered: the loop of electrical conductors which can carry the parasitic current, and the magnetic coupling which can induce this parasitic current.

The encircling ferromagnetic conduit would act as a core to enhance the magnetic coupling.

The system described, with its ACSR cables and isolated phases, is more like an air core transformer. There will be coupling from the phase conductors to the ACSR messenger cables, and there will be circulating current in the closed ACSR loops.

But I repeat that I don't know how significant an issue this would be.

-Jon