Transposition in transmission line is a technique use to restore some sore of “electrical voltage drop” and current balance of the transmission line system. It is only applicable though in three phase system. It us done by literally, and physically exchanging the conductor position along the line.
When the conductors of a three phase line are not spaced equilaterally, which is case often, the flux linkage and inductance of each phase are not the same. This difference in each phase results in an unbalanced circuit.
Balance of these phases can be restored by exchanging the positions of the conductors at regular intervals along the line so that each conductors occupies the original position of every other conductor over an equal distance.
A complete transposition cycle is shown below:
Transposition results in each conductor having the same average inductance over the whole cycle.
Modern power lines are usually not transposed at regular intervals, although interchange in the positions of the conductors may be made at switching stations, in order to balance the phases more closely.
More transposition tutorial and pdf download links below:
TRANSMISSION LINE TRANSPOSITION
According to existing concept the transposition of transmission line phases is intended for reducing the unbalance of current and voltage in normal operation mode of electric system and for limiting the obstructive influence of transmission lines to low-frequency transmission channel. Read more...
RESONANCE EFFECT DUE TO CONDUCTOR TRANSPOSITION IN THREE PHASE POWER LINES
This paper is concerned with the effects produced by conductor transposition in long overhead three phase power lines. Consideration of these resonance phenomena is of major importance and should be taken into account in a variety of situations. Read more...