“LARGE POWER TRANSFORMERS AND THE U.S. ELECTRIC GRID”
https://energy.gov/sites/prod/files/Large%20Power%20Transformer%20Study%20-%20June%202012_0.pdf
Infrastructure Security and Energy Restoration
Office of Electricity Delivery and Energy Reliability
U.S. Department of Energy
“this lead time could extend beyond 20 months and up to five years in extreme cases if the manufacturer has difficulties obtaining any key inputs, such as bushings and other key raw materials, or if considerable new engineering is needed.”