Twisting scheme
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
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
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 |
swell
- Prof. Oswald: Lecture Electrical Energy Supply I. (PDF; 708 kB) (No longer available online.) University of Hanover, 2005, p. 55ff , archived from the original on July 19, 2007 ; Retrieved December 29, 2008 .