Solution Reliability Evaluation Of Engineering Systems By Roy Billinton And [patched] -

Naïve view = 0.01% annual outage. Actual = Loss of both feeds simultaneously = 1/2000 chance per year, but when switch fails → 10-hour outage.

The Bathtub Curve (infant mortality → useful life → wear-out). Most engineers ignore the early "break-in" period. Billinton shows that’s where 40% of system failures hide. Naïve view = 0