I have recently passed by the following transformer. It seems to be placed on rails and might be able to roll forward and backwars by about 0.5m each. There are no guards at the end of the rails though, at least not on the front facing end. What is the reason for the rails? It does look a bit like the red part on the top right might be disconnected when the transformer rolls away, but it was difficult to see from this perspective.
BBC sells these "skid-mounted" transformers as something that can be quickly unloaded from a semi truck. So, the rails are mostly for mounting comfort. Hard for me to put a mass to that picture, but if I had to take a guess, it's 20 t to 30 t; so the process of removing the transformer from a truck (or putting it back on there at its end of life or for maintenance) deserves a bit of thought – and having a bit of freedom to be moved might make it easier than having fixed anchor points.
More interesting is that the rails are on heavy steel beams: I suspect the concrete structure this thing is mounted on is actually a simple "bath" to contain the transformer oil (or whatever thermally convective medium they use within) in the unlikely event the transformer tank fails. But I don't know!
