When flooded with too much electricity, the sudden surge can cause a transformer explosion. As transformers detect an energy spike, they’re programmed to turn off, but it can take up to 60 milliseconds for the shutdown. However fast those milliseconds may seem, they still may be too slow to stop the electrical overload.
A chamber full of several gallons of mineral oil keeps the circuits cool, but given too much electricity, the circuits fry and melt, failing in a shower of sparks and setting the mineral oil aflame. Mineral oil, in turn, combusts explosively and rockets transformer scything into the air.
All it takes is a trigger, a corroded or faulty wire, and the circuits surge will get ahead of the breaker.
Salt from sea water, for example, can create hazardous conditions for underground electrical systems since it acts as a corrosive agent. Old transformers can explode when their insulating materials begin to fail, too.