Running Substation UG Conductors in One Conuit or Three
Running Substation UG Conductors in One Conuit or Three
(OP)
I have been asked a question by a coworker at a utility about whether it better to install each phase of conductors from a distribution substation transformer in its own separate PVC conduit or to put all three phases in one conduit. Generally, we always see each phase plus the neutral in conduits served by our own customer site distribution transformers. 5 sets of cable, 5 conduits. However, this is in a substation application and our operations group wants to utilize three separate conduits )PVC with rigid (ferromagnetic) elbow outside of the substation fence to the UG riser. They want to do this for eas of pulling since it is 1000 mcm cable. They would pull in a ground wire with each conduit. Each conductor has a concentric neutral (1/3rd or 1/9th of phase, not sure). My thought was there could be a problem with heating the elbows since there would be little cancelation of magnetic field for each phase because the other phases would be in conduit 6" and 12" away depending on which phases you are referencing. There would be about 300-400 amps of line current which is about half the peak of the substation transformer. Any comments and references would be welcomed.
thanks
j
thanks
j






RE: Running Substation UG Conductors in One Conuit or Three
RE: Running Substation UG Conductors in One Conuit or Three
In UG distribution circuits, three separate conduits, one for each phase, is a common practice, since there will be single-phase loads and taps. Generally a fourth empty conduit is installed in case a cable failure damages the conduit to the extent that a new conductor cannot be pulled. But this all has to be PVC, or non-magnetic conduit.
Within a substation, I don't see a reason for this, and would run all three phases in each conduit. Then steel conduit can be used.
RE: Running Substation UG Conductors in One Conuit or Three
RE: Running Substation UG Conductors in One Conuit or Three
RE: Running Substation UG Conductors in One Conuit or Three
RE: Running Substation UG Conductors in One Conuit or Three
RE: Running Substation UG Conductors in One Conuit or Three
Here is a link from the UK.
http://www.roltesting.com/UserFiles/File/eddy.pdf