Transposition (telecommunications)

Twist is the Gegeneinanderverwinden and the helical Umeinanderwickeln of fibers or wires. The twisting of wires and in telecommunications is also called stranding. Typical applications for electrical conductors, the twisted-pair cable, such as is used in the range of Ethernet.

In a twisted replace the individual conductors within a circuit either in their whole course (with cables), or at specific points ( overhead lines ) to each other their place. By twisting the mutual influence of electrical conductors is reduced. The twist is an effective measure to reduce inductively coupled- mode interference.

Communication technology

In telecommunications, the stranding is used to reduce the crosstalk coupling. The essential measure in the stranding is the twist - also called twist length, twist pitch or pitch length. The twist is the pitch or pitch of the helix, resulting in the twisting of the wires and has influence on the management coverings. By stranding the individual wires are longer than the cable itself The Verseilungsfaktor is the ratio single wire length to cable length; he is at telecommunication cables about 1.02 to 1.04.

Verseilungsarten

In practice, the following Verseilungsarten occur more often:

Twisted pairs

Two individual wires are twisted to a pair of wires ( twisted pair ). Typical applications of twisted pairs are, for example,

• Network cable with 4 pairs.
• Telephone installation cable JY (St ) Y ( from 3 pairs, 2 pairs is Quads )
• G51 (from 1 pair, Switzerland )
• F- YAY (from 1 pair, Austria )

Dreierverseilung

Three individual wires are twisted into a triple. Shift cable in Dreierverseilung were, for example, earlier used in analog telephone exchanges.

Viererverseilung

Typical applications are found in the article Viererverseilung.

• Sternverseilung (star -quad) Four individual cores have at any point of stranding each other in the same position, with the wires of a pair ( dual core) facing each other diagonally. In the star-quad cables have stranded opposite pairs stranded cables following advantages: Higher packing density and lower attenuation due to reduced operating capacity of the couples.
• Diesel Horst -Martin- stranding (DM) A special, for decades outdated nature of the quartet in remote telephone cables ( see Article Viererverseilung ).

Both the star and the DM- four the additional transmission of a third speaking circuit by means of phantom circuit is possible. This technique is now hardly significant.

Suppression by twisting

The twisting causes a noise voltage induced by a magnetic field is reduced. By twisting include spanned between the wires subareas alternating negative and positive. By integrating a magnetic flux density over all sub- areas, the effective magnetic flux from which follows the induced voltage is very low or ideally to zero, so that the induced noise voltage is greatly reduced. For the river applies:

For the induced voltage is:

Energy Technology

For longer lines without branches, the twisting is usually fixed by Verdrillschemen. By the twist is the asymmetry of the line which can result in different capacitive surfaces with respect to ground in three-phase systems are reduced. This balancing of earth capacitance is essential for the application of earth fault. The twist is usually done with overhead lines at so-called Verdrillmasten.

In closely branched networks and parallel guide several circuits - especially with multiple voltage levels - to the same masts often outweighs the external unbalanced line from the parallel run circuits. In these cases we find large deviations from the Verdrillschemen, for example by twists are realized, in which only two of the three phase change place on the masts. Also, in such plants Verdrillstellen found to poles immediately before introduction into the switchgear to the best possible arrangement of the feeding system, the outer conductor ( L1/L2/L3 ) to allow within the substation (crossing Freedom of the Ladder).

The twist occurs either in the field or on chip Verdrillmasten.

Since the mutual influence of electric circuits may change in the context of restructuring of the grid, it is possible that certain Verdrillstellen disappear or get worse after construction on the grid.

Engineering Mechanics

The twisting is the rotation of the cross section of a torsion rod as claimed in length based on ( rotation angle / probe length ). It is also referred to as a relative angle of twist.