Lineworkers: What's the correct term for this Animal?



Hello all;

Whaddaheck is the correct term for these Line Position changing setups, used with M.V. and H.V. distribution?

I know what it is for (at least I think so...) - Capacitive Reactance corrective measures for long circuits.
Just never knew what it should be called - or better yet, what the trade slang term is.

Seen it on many circuits strung on steel towers - and see it done on 12 to 66 KV circuits strung on wood poles;
just not as elaborate as what are seen on steel towers.

Any info is appreciated!

Scott35

Transposition? Old open wire telephone circuits have 'em too.

I agree. Transposition. And balancing reactance is exactly what it is for.

Mee too.

Balances phase-to-ground characterstics.

www.emfs.info/Source_transmission.asp The field also depends on the relative phasing of the two circuits (see the figure below). A few lines have "untransposed" phasing, with the phases in the same order from top to bottom on the two sides of the towers. This produces a field which falls as the inverse square of distance from the line. However most lines have "transposed" phasing, with the opposite order of the phases on one side to the other. This introduces an extra degree of symmetry and extra cancellation between the fields from equal currents on the two sides; the resultant field falls more nearly as the inverse cube of distance, producing a much lower field at large distances from the line.

And if you’re really bored ;-)
eent1.tamu.edu/elen459/documents/Transmission_Line_Parameter_Calculation_edit.pdf www.ee.uidaho.edu/ee/power/EE524/lectures/L22/session22.pdf www.dromeydesign.com/articles/conductor_and_transformer_modeling.htm




[This message has been edited by Bjarney (edited 02-18-2004).]

Scott

Are you reading my mind????
I was planning on posting a picture and ask the same question this week.

Curt

Very interesting links Bjarney.
Thanks for posting them.

Yep. The telephone version is to cater for the reverse process of the lines being affected by external fields.

The transposition every so often results in better balancing of the line and minimizes crosstalk and noise pick-up.

Scott35,
Foof,
What sort of thing is that?.
Bjarney,
Is this sort of thing peculiar to the US?, as I have never seen a thing like this before in NZ or in Australia?.
Also Bjarn, how is this thing operated?.

Trumpy — Transpositions would be more likely found on longer lines, which are by default transmission voltages.

Another way of looking at it would be to imagine ‘phase rolling,’ and that a dual-circuit line may have one set of 3 conductors twisted clockwise and one twisted counter-clockwise at a transposition point. In Scott35’s pic, though, it looks like both circuits roll in the same direction.

The purpose is to balance phase-to-ground and limit circuit-to-circuit reactances, which helps in voltage balance, makes it easier to sense line-to-ground faults and less susceptible to mutual coupling, which can cause sympathetic line tripping—where two adjacent circuits both trip with one circuit faulted and one healthy.

Just wanted to thank everyone for the replies!
Had seen this on many H.V. Transmission circuits over the years, and finally I know what to call it!


What's odd is the only Transposition method I have seen is with the two circuits "turning" in the same direction -
i.e.:
"A", "B" & "C"
transpose to:
"C", "A" & "B"
on both circuits on the same pole
(like shown in the image).
After reading Bjarney's message, it's funny that the rotation does not spin different between the two circuits. Makes sense to me having them spin in opposing directions.

The image I posted here is a two circuit 3Ø 3W setup, and judging from the size of the Insulators, the Voltage must be 66KV.
It runs through an easement - along with another 66KV 2 circuit setup and a two circuit 138KV setup; from an SCE yard, through the City of Anaheim's yard, to another SCE yard.
This image was taken apx. 1.5 miles Northwest of Disneyland.

Anyhow, thanks again everyone for the replies!

Scott35

Scott,
I have been waiting to reply to this because there is a slang term for this. I just can't remember what it is! My lineman Friend told it to me years ago but he has moved away and I am haven't heard back from him. I agree it's probably 66KV. It's probably part of the runs that used to run trough Disneyland's parking lot.

I don't want to sound like a know-it-all, but I thought I would add my input. A majority of sub-transmission lines throughout the USA run at 69kV, 46kV, and 34.5kV. By the looks of the tower, that looks like a 69kV tower to me. Alot of 69kV sub-tranmission lines were built on lattice towers. Nowadays, they are being built on wooden structures, steel poles and sometimes maybe concrete poles. Here is an example of AC circuits that run in the USA if you have always wanted to know this. 115kV, 138kV, 161kV, 230kV, 287kV, 345kV, 500kV and 765kV. There is a 1,000kV DC line in Oregon. Hope this helps.
~Nick Ogden

Nick,
That slang wouldn't be "Tramp", would it?

I don't think so. I seem to have lost contact with my friend. I have known him for 20 years and sometimes he disappears for a while.