We are very pleased to be asked to co-author this book for a variety of reasons, one of which was that it gave us further opportunity to work together. The scope proposed was very wide with the only significant proviso being that the book should be in a mongraph-style and not a teaching text. This require­ ment has given us the opportunity to compile a wide range of relevant material relating to present-day knowledge and application in power system reliability. As many readers will be aware, we have collaborated in many ways over a relatively long period and have co-authored two other books on reliability evaluation. Both of these previous books were structured as teaching texts. This present book is not a discourse on "how to do reliability evaluation" but a discussion on "why it should be done and what can be done and achieved" and as such does not replace or conflict with the previous books. The three books are complementary and each enhances the others. The material contained in this book is not specifically original since it is based on information which we have published in other forms either jointly or as co­ authors with various other people, particularly our many research students. We sincerely acknowledge the important contributions made by all these students and colleagues. There are too many to mention individually in this preface but their names appear frequently in the references at the end of each chapter.

1 - Basic Power System Reliability Concepts.- Probabilistic Evaluation of Power Systems.- Adequacy And Security.- Need For Power System Reliability Evaluation.- Functional Zones.- Hierarchical Levels.- Adequacy Evaluation.- Reliability Cost/Reliability Worth.- Reliability Data.- Reliability Test Systems.- Conclusions.- References.- 2 - Generation Systems Adequacy Evaluation.- Analysis Of The IEEE Reliability Test System.- Generation Planning Using Energy Based Indicies.- Reliability And Economic Assessment Of Novel Generation.- Monte Carlo Simulation.- References.- 3 - Composite System Adequacy Evaluation.- Historical Developments.- Factors In The Contingency Enumeration Approach.- Alternative Methods.- Conclusions.- References.- 4 - Distribution System Adequacy Assessment.- Historical System Performance Assessment.- Basic Distribution Systems.- Distribution System Reliability Assessment.- Distributional Considerations.- Practical Applications.- Conclusions.- References.- 5 - Assessment of Reliability Worth.- Interruption Costs For Commercial Users.- Interruption Costs For Industrial Users.- Interruption Costs For Residential Users.- Interruption Energy Assessment Rate.- References.- 6 - Conclusions.- References.- Appendix 1 - IEEE Reliability Test System.- Load Model.- Generating System.- Transmission System.- Appendix 2 - Additional Data for Use with the RTS.- Derated States.- Maintenance Schedule.- Additional Generating Units.- Load Forecast Uncertainty.- Terminal Stational Equipment.- References.- Appendix 3 - Dependency Effects in Power System Reliability.- Concepts of Dependencies.- Reliability Modeling.- Evaluation Techniques.- Conclusions.- References.- Appendix 4 - Evaluation of Statistical Distributions.- Notation.- Assumptions.- Number Of Load Point Interruptions.- Step 1 - Moments Of Component Performance Parameters.- Step 2 - Evaluation Of Moments.- Step 3 - Evaluation Of Approximate Percentiles.- References.