Installing 1 Cable per Metal Conduit - Problem?
Installing 1 Cable per Metal Conduit - Problem?
(OP)
I've heard talk that pulling urd cable into metal conduit with one phase per conduit is a bad idea due to induction. We currently do so at our risers and then the cable runs into pvc conduit underground.
Does anyone know where I can find documentation on this subject or can explain to me the details?
This hasn't been an issue for us until we started getting larger loads and worried that the induction will cause us future problems.
Thanks
Does anyone know where I can find documentation on this subject or can explain to me the details?
This hasn't been an issue for us until we started getting larger loads and worried that the induction will cause us future problems.
Thanks






RE: Installing 1 Cable per Metal Conduit - Problem?
RE: Installing 1 Cable per Metal Conduit - Problem?
RE: Installing 1 Cable per Metal Conduit - Problem?
RE: Installing 1 Cable per Metal Conduit - Problem?
Would a shielded cable help?
RE: Installing 1 Cable per Metal Conduit - Problem?
If you circle any conduit ( PVC, PE, aluminium or stainless steel ) with a magnetic clamp or rebar in a duct bank your going to heat it up.
I have engineered jobs with single conductor 15 KKV URD cable in PE and PVC conduit and it works. We grouped the conduits close together and made sure there was no magnetic loops around any one conduit.
RE: Installing 1 Cable per Metal Conduit - Problem?
RE: Installing 1 Cable per Metal Conduit - Problem?
A solution I have seen in switchgear is to only make 1 side of the box out of a non-ferrous material - The others can still be metal - elimantes path for inductive heating. I don't know if conduit can be purchased in this manner...
Another thing I have seen is when single conducters are run through a metal wall 4 slits are placed around the cutout- once again to eliminate inductive heating...
RE: Installing 1 Cable per Metal Conduit - Problem?
RE: Installing 1 Cable per Metal Conduit - Problem?
Sounds logical in theory, but I still haven't found any documentation on the subject and haven't experienced it on any of our metal conduit.
RE: Installing 1 Cable per Metal Conduit - Problem?
Don
RE: Installing 1 Cable per Metal Conduit - Problem?
I'm thinking of going to a high scheduled pvc, though, instead of putting all the phases in one conduit. That way if we fault a phase we won't loose all three.
RE: Installing 1 Cable per Metal Conduit - Problem?
You need to correct these installations.
Talk with any cable supplier - they can provide you with documentation.
RE: Installing 1 Cable per Metal Conduit - Problem?
o “Cables in ac circuits should not be installed with each phase in separate magnetic conduits under any circumstances due to the high inductance under such conditions."
o "Cables in a-c circuits should not be installed with each phase in separate metallic non-magnetic conduit when their size exceeds 4/0 unless the conduit is insulated to prevent circulating currents."
o "Three conductors in magnetic conduit will have a somewhat higher reactance than cables in non-magnetic conduit."
o "Single conductors should not be installed in individual magnetic conduit because of the excessive reactance.”