Hello cuky2000,
it really depends mainly on your negotiating power with respect to the transformer manufacturer. The minimum technical time could be on the 9 to 15 months, depending on the availability of bushings, tap changers etc...
In European and North American markets, as mentioned in previous posts, in the absence of bargaining power you can expect even times of 24 to 30 months. Turning to Asian markets you may have significantly shorter lead times, to which you will have to add the higher transportation times.
Si duri puer ingeni videtur,
preconem facias vel architectum.