[Tangurena2]

After a couple incidents where snipers shot at substations or hackers turned stuff off, there was a burst of worry about the fragility of our electrical grid. Of the large transformers that make up substations, almost all of them are unique. There is no inventory of spare transformers. Each one is custom made and takes months. The small transformers you see on poles are made by the thousand, and stocked at every utility. The small ones are not the problem. The big ones - that are the size of SUVs and houses - are the ones that the grid depends on.

[maxerickson]

There's a difference between made to order and bespoke.

Of course, most of the discourse is hand wavy speculation, vs characterization of the existing stock of transformers, like what standards they are built to and the magnitude of an event that would certainly damage them.

[kwhitefoot]

Most large transformers are actually unique but this has little to do with the characteristics of the transformer. It is mostly to do with optimizing the design to minimize the total lifetime cost. This requires a new design for each transformer because the relative prices of core steel and copper or aluminium varies over time. When copper is cheap the total cost will be lower if you use more copper and less core steel for instance while the opposite will be true if the copper price is high.

If cost is not as important as prompt delivery the manufacturer can often just take an existing design and repeat it.

[dgroshev]

I doubt that it's strictly true seeing how quickly Ukraine was replacing their transformers after Russia deliberately targeted them. As far as I can tell it was a strain on the global supply, but evidently not insurmountable.