I was driving along Manitoba highway 6, between Grand Rapids and Nowhere and one of the major lines from the hydroelectric generating stations down to the south runs alongside the road.
At two points (that I saw) the three big conductors change places with an elaborate jumper setup on the tower.
Location:
Google Maps
a) Why?
b) Does one change the wire-order to another config and the other location where I saw this change it back?
It’s the same basic idea of having twisted pairs for data cables. It helps reduce crosstalk and interference.
Called Transposition (wikipedia).
I knew about twisted pairs in Cat5 & up. Had no idea powerlines needed to be flipped occasionally. Thanks!
I thought twisted pair used the right hand rule to cancel noise.
That was so cool.
Never heard of that before.
Thank you for sharing.
I wonder if this swapping would change anything at the consumer end ?
A three phase motor for example wired for RYB.
As long as they rotate rather than swap two elements, the behavior will be the same. You could reverse the direction of a three-phase motor if they swapped two cables and left the third as a pass-thru. It’ll work as a rotation as long as every input wire gets permuted to a different output wire.
Thank you.
Direction of rotation was what I was thinking about.
Hmm… so what phenomena induces extra NORMAL MODE ( difference between the phases) voltages on high voltage tranmission lines ?
Earths Magnetic field ? Nope. thats common mode ( look at the sum of the three or four instantaneous voltages… voltages compared to ground… )
background EM noise ? the white noise ? nope, its going to sum to zero.
Radio transmissions ? thats it. the high power in SW, MW bands… (such as regular AM radio , eg around 1 MHz., ) transmissions using broadcast carrier (rather than suppressed carrier ) such as AM systems can induce a bit of voltage and the first/outside phase can tend to get it more than the hidden phases… so I guess thats mostly the reason that that the voltage differences might be add up if the phases aren’t swapped.
Transposition is used to keep the capacitance between phases balanced. Without transposition the center wire would couple to two phases (the two outer wires) but the outer wires would only couple to one.