They are wound on modern winding machines:
Distribution Transformers Windings: Low voltage winding conductor is copper. Layer insulation in sheet windings is provided with thermally improved resin paper (DPP).
High Voltage winding conductor is copper. Windings are enameled round copper wire, insulation paper covered flat copper wire. Layer windings are wound with computer controlled fully automatic machines, layer insulation is formed in the form of a wedge with strip-shaped electrical insulation papers (electrical kraft, thermally improved kraft and resin thermal paper). This layer insulation structure increases the resistance of the winding against excessive voltage impacts; this method allows the obtaining of void-free, solid, excellent-featured coils.
Power Transformers Windings:
Low voltage and high voltage winding conductors are copper. Windings are wound using copper wire covered with insulation paper as layer winding, continuous disc winding, helical winding or screw winding depending on the transformer power.
