What do you mean by circuit failure? Speak in a popular way.

Breakdown refers to the place where there should be no current, because the voltage across it is too high, so there is current, and the current is very large. This situation is called collapse.

We can often see, for example, that an object is not close to the high-voltage line, but a discharge arc is generated between the wire and the object. This kind of clock phenomenon is the most common "fault". The decomposed medium is air.

I hope you are satisfied with this answer.