I did a project where we predicted transformer failure (they blow up!) from changes in the oil that they have in them (its insulative properties suddenly change). This was 30 years ago so it's all a bit fuzzy, but the one thing that really stuck with me was the story that the SME that we were working with had about the UK grid teetering on the edge of failure during the "great storm" of 1987. His telling was that they really were unsure if they would get it back at all!