bobelectric

Reviewed a utility high voltage line upgrade proposal for a xfmr upgrade on our facility,today. 25kv lines. What I noticed was from substation to substation phase rotation was flipped about every 1/4 mile.abc,acb,cba. Was this planned or just random?

nick

balance of your point to ground over long distance lines to ground plane , the arrangement of those conductors in space ,usually by need to avoid sparkover between adjacent conductors but phasing mutiple circuits in length or distance runs of three phase high voltage circuits are arranged abc top to bottom and to avoid that old increase in magnetic field in that space , mainly to ground plane to earth path , to avoid this high magnetic effect or non cancel effect problem maybe to cross existing lines above or below these . cba abc bca is used to give it a spiral effect or mixing balance over distance in length of a run , i think it may also effect or help in the high energy of a lighting near arc in the area of conductors which would be a increase if they where abc or stacked in long length. like twisting 400 cycle conductors for high freq work, but do not listen to me , this is just what i think is the only possible reason unless the power company just screwed up your area , think of this lets look at rotation our power co. has bca downtown orlando not abc ,but when you test with your roto meter it reads clockwise , only problem is when we have a tie breaker connection condition you must then know that its real important to know what the power co. has from the start , thanks for the question its got me thinking about what the people we get our power from are doing at the plant and why .

powerlineman78

ABC-BCA-CAB will always give you a clockwise rotation, because in phasing a leads b leads and c leads a. There could be several different reasons the phases were flopped, most likely cause is they rolled into a vertical pole abc and probably rolled out cba or something of that matter.

bobelectric

Thanks to both of you for your answers.

nick

thank you also for that question , and thank you for the solution most of our work is commercial but on some work we do industrial work or we are the subs for the high voltage work so we get a little bit into that . most of the stuff is going underground now in florida we get a little wind and rain down here .and the phases must be stacked in trenches like a above c ,b above a and c above b underground to cancel out magnetic effects . yes i agree incoming to out going is a problem so your correct you solved that one . always interested in what other parts of the usa are doing and you learn that everyday . didnt know if it was overhead or underground i read to fast sometimes and go back and well you know .

bobelectric

Nick,this is overhead,25kv pole mounted 556 AA bare conductor,mostly horizontal,sometimes rolling to vertical,to underground 35kv,750mcm Lotsa watts