Twisting scheme

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A Verdrillschema is a scheme by which the twist of transmission lines by means Verdrillmasten occurs. In order to ensure an even capacitive coating of the overhead line operated with three-phase alternating current , each of the three conductors must hang once at a place on the overhead line. Depending on the type of line, the so-called α, β or γ twists are thus obtained.

α-twist

Different types of twist.

Single-circuit three-phase cables are twisted at 1/3 and 2/3 of the cable length (α1). Since this leads to a different sequence of phases, the α2 scheme is often used, in which the 1/3 twist is divided into two 1/6 and the phase sequence is the same at the beginning and end of the line.

β twist

In the case of two-circuit three-phase cables, the twisting occurs when both cables are operated asynchronously, with one circuit the twisting takes place at 1/3 and 2/3 of the cable length and with the other circuit at 1/9, 2/9, 3/9, 4/9 , 5/9, 6/9, 7/9 and 8/9 of the cable length.

γ-twist

In the case of two-circuit three-phase cables, if both cables are operated synchronously, the twisting takes place at 1/3 and 2/3 of the cable length, whereby the direction of rotation is always opposite to one another (γ1 twist). If the phase sequence is to be the same again, a third of the twist is divided and the line twisted according to the scheme 1/6, 1/3, 1/3, 1/6 (γ2 twist).

particularities

At this twisting mast, two phases are swapped on the left, all three rotated on the right.

Since with multi-circuit three-phase cables the asymmetry caused by the mutual influence of the circuits is often greater than that caused by the structure of the cable, twists can also be found that do not correspond to the twisting scheme, whereby with three-phase cables it is also not uncommon that the twisting point is twisted only takes place between two phases.

example

Twisting diagram of the Hoheneck-Herbertingen high-voltage line completed in 1929 (length: 123.5 kilometers). Until 1964 this line carried two 220 kV three-phase circuits, since 1964 this line has been a 380 kV / 220 kV line. Originally there were nine twisting points, as both circuits were operated asynchronously. In the meantime, the last two twisting masts at Rommelsbach and Gomadingen have also been dismantled to normal guy masts.

mast Distance to the starting point (Hoheneck substation) Status
Mast 48 12.3 km abandoned
Mast 90 24.4 km abandoned
Mast 174 47.6 km abandoned
Mast 206 57.7 km abandoned
Mast 260 72.7 km abandoned
Mast 288 80.8 km abandoned
Mast 316 88.6 km abandoned
Mast 366 101.8 km abandoned
Mast 413 114.6 km abandoned

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