Solution Reliability Evaluation Of Engineering Systems By Roy Billinton And =link= -

| Index Category | Specific Index | Definition (Billinton’s phrasing) | | :--- | :--- | :--- | | | LOLP | Probability that the load will exceed available capacity at a given time. | | Frequency | LOLE | Expected number of days (or hours) per year that a deficiency exists. | | Duration | LOLD | Average duration of each deficiency event. | | Energy | EENS | Expected Energy Not Supplied (in MWh). Used for economic costing of failures. | | Customer | SAIFI | System Average Interruption Frequency Index (customer-centric). | | Customer | CAIDI | Customer Average Interruption Duration Index (restoration speed). |

Below is a comprehensive, long-form article exploring the concepts, methodologies, and legacy of Billinton’s approach to reliability evaluation. Introduction: The Shift from Certainty to Probability For most of the 20th century, engineers designed systems using the "deterministic criterion." A power system, for example, was deemed reliable if it could withstand the sudden loss of the largest generating unit or a single transmission line (the infamous N-1 criterion ). While simple, this approach ignores two fundamental truths: components fail randomly, and not all failures have the same consequence. | Index Category | Specific Index | Definition

System passes (one turbine fails, remaining 20 MW < 25 MW? Actually, that fails. So deterministic says "Unreliable – add a third turbine." Cost: $10M. | | Energy | EENS | Expected Energy Not Supplied (in MWh)