Paper Continuously Transposed Conductor (CTC) is the most used for windings on power transformers, which consists of a number of rectangular, film insulated conductors made into an assembly and usually over-wrapped with layers of insulating material. The number of conductors is usually an odd number (from 5 to 81), arranged side by side in two stacks. A special tool alternately pushes the upper left and lower right wires onto the respective neighboring stack so that each wire takes on every possible position within one cycle in the continuously transposed cable. The length of the continuously transposed cable for one complete cycle depends on the smallest diameter of the transformer winding, the number and size of the single strip.

Paper insulated copper conductor technical parameters:

Transposition number	5 – 81 (odd or even optional)
Maximum dimension	height 120 mm, width 26 mm (tolerance ± 0.05 mm)
Single conductor size	thickness a: 0.90 – 3.15 mm, width B: 2.50 – 13.00 mm (tolerance ± 0.01 mm)
The recommended width thickness ratio of a single conductor	2.0 < B / a < 9.0
The recommended coating thickness of enameled wire	0.08-0.12mm
The thickness of adhesive layer	0.03-0.05mm

Continuously transposed cable ctc Advantages
• Transformers against unstable electrical network and the risks of shorts.
• PVA‑EPOXY enamelled rectangular wires used in transposed conductors provide exceptionally strong bond strength in the winding.
• Conductors in the winding become like a solid beam and can withstand strong electrodynamic stresses created during short circuit event.
• No special treatment is needed by the user.

CTC PVA-EPOXY CPR is characterised by the following properties:
• Copper with high mechanical characteristics (generally CPR with a proof stress 0.1% of 140 ÷ 250 MPa) – in order to withstand the electrodynamic stresses in case of short circuits.
• Rectangular wires enamelled with polyvinylacetal enamels resistant to transformer oils.
• Epoxy coating over the enamelled rectangular wires (PVA‑EPOXY) – a thin layer of tack-free cresol-free epoxy B-stage that bond the strands together after the thermal treatment of the winding, getting a solid monolithic winding in order to withstand the electrodynamic stresses in case of short circuits.
• Wrapping the transposed conductors with special insulation papers (thermally upgraded, calendered, crepe) internally in contact with the strands and externally, in order to give the best geometry (well defined oil ducts) allowing good cooling performance of transformers.

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