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Joined: Oct 2000
Posts: 2,721
Scott35 Online Happy OP
Broom Pusher and
Lineworkers: What's the correct term for this Animal?

[Linked Image]

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!


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Joined: May 2003
Posts: 26
Transposition? Old open wire telephone circuits have 'em too.

Joined: Oct 2001
Posts: 597
I agree. Transposition. And balancing reactance is exactly what it is for.

Al Hildenbrand
Joined: Apr 2002
Posts: 2,527
Mee too.

Balances phase-to-ground characterstics.

Joined: Apr 2002
Posts: 2,527
Moderator 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 ;-)

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

Joined: Apr 2002
Posts: 558

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


Curt Swartz
Joined: Oct 2001
Posts: 135
Very interesting links Bjarney.
Thanks for posting them.

Joined: Aug 2001
Posts: 7,520
Old open wire telephone circuits have 'em too.
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.

Joined: Jul 2002
Posts: 8,407
What sort of thing is that?.
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?. [Linked Image]

Joined: Apr 2002
Posts: 2,527
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.

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