[Thesis Title Goes Here]

MANAGING ENVIRONMENTALLY STRESSED AGING ASSETS IN ELECTRIC POWER UTILITIES A Dissertation Presented to The Academic Faculty by Urenna Onyewuchi In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Electrical & Computer Engineering Georgia Institute of Technology December 2012 Copyright 2012 by Urenna Onyewuchi MANAGING ENVIRONMENTALLY STRESSED AGING ASSETS IN ELECTRIC POWER UTILITIES Approved by: Dr. Miroslav Begovic, Advisor Dr. Ronald Harley School of Electrical and Computer School of Electrical and Computer Engineering Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Reginald DesRoches Dr. Saibal Mukhopadhyay School of Civil and Environmental School of Electrical and Computer Engineering Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Thomas Habetler School of Electrical and Computer Engineering Georgia Institute of Technology Date Approved: November 12, 2012 To my family and loved ones ACKNOWLEDGEMENTS My decision to pursue a PhD began with my advisor, Prof. Begovic, when an opportunity opened up with the National Electric Energy Testing Research and Applications Center (NEETRAC). I appreciate the opportunity he gave me to stretch my mental capacity and learn several unique things only possible through a PhD path. He taught me how one can reach near-perfection by working towards it in patience rather than hurriedly. I have learned to look at problems from multiple perspectives. I have developed a new kind of resilience and strength through this academic refinement. I thank him for my maturity and growth over the past few years. It is imperative that I acknowledge Dr. Okorie of Fair Lakes Urgent Care Center, VA and the faith he had in me from the first day we met. He, to this day, believes I am some kind of genius. Whenever I had doubts and fears about the conclusion of my research, his belief in me strengthened me. I am grateful for family and friends I made in Virginia while at George Mason University, especially Tim, Gbenga, Chinedu and Preye. I appreciate the advice and encouragement of Profs. Zietsman (who is now at Virginia Tech), Beale (now retired) and Gertler (my Signals and Systems professor) to pursue a PhD degree. I also appreciate the friends I made in Georgia. I am grateful my path crossed that of Mrs. Milliner in the ECE Development Department, who introduced me to Ms. Pittman (Ms. P. as she is fondly called). These women provided me with probably the only social “life” I had at Georgia Tech. They believed in me, encouraged me, and could see a very bright future for me even when I couldn’t. They connected me with people they felt would provide me with guidance in my career. I have grown, just knowing them. Because of my friendship with them, Mrs. ii Milliner thought of me in a meeting with Corning. That meeting changed my life, with regards to research and my career, and has presented me with a new chapter in my life. Doyin Oyelaran and Ian Jefferson found my resume interesting. Doyin did everything possible to get me an interview with Corning Inc., which is a great company, and stay connected with the company. He advised me about how to succeed in corporate America and stayed in touch with me during my career decision process. Because of my interest in electric power, I was matched with Gerard Cliteur, a multi-talented and open- minded Corning employee, whom I respect, look up to, and admire. Gerard and Doyin have from the start, inculcated in me, the importance of staying true to myself. Gerard believes in me and is excellent about making time to listen to questions or ideas concerning my research or Corning work. His belief greatly increased my confidence in my latter semesters. Sometime in there, I became a new person (for the better). So, I can say I am indebted to Gerard and to Doyin. I hope I make them proud at Corning. I would not be the woman I am today without the influence of my mother. I have had the honor of living with her the past five or so years as an adult, and many years as a child of course. She bore the brunt of my frustrations and took them well. She provided food for me; so I didn’t have to spend time cooking but could focus on research instead. She ensured I did not leave my apartment looking haggard. She prayed for me constantly and told me I would do great. She labeled me as a “PhD” before I had even proposed. I could write about her for days but would like to summarize by saying that I hope I can be as great a mother as she is to me and my siblings. My siblings have always encouraged me, and never doubted that would excel. Every time I share with them that I excelled in some exam, test or interview, they make it iii a point to say “What’s new?” I am grateful to have them as my best friends: to chat with them at any time. I am also grateful for Osa’s friendship for almost two years now. He helped me review my PhD proposal, listened to and critiqued my presentation. Whenever he was not pleased with my delivery of my work, he said so and told me to remember why my research is important to the world: for public safety and management of key assets that drive the American lifestyle (and those of other nations). Keeping this point in mind gave me passion during my presentations. The discipline I have shown during my entire academic life can be attributed partly to that instilled in my siblings and me by my father. I am grateful for his lessons. My uncle Morris and his wife have always been proud of me and my work. They have kept an open door for me while I was in Atlanta and I appreciate them tremendously. In conclusion, saving the best for last, I give all glory to God and my Christian faith. Somehow, God has kept me away from taking the wrong paths all these years. He guided me through this PhD and let me know that I was not alone. If, as I mentioned previously, my family, my advisor, Gerard and everyone believed in me, then God Himself has been my confidence, my pillar, and has heard every single prayer. I hope this dissertation is to His liking because I would not have been able to do it without Him. I am grateful to Georgia Tech as a whole for this great opportunity. I also thank Ms. Doria Moore, Siri, Chris, Ms. Mycko, Dr. Ferri and Tasha for lots of help; also, Dr. Gary May for signing my first teaching assistantship. I was opportune to attend school without need for a loan. There is no greater blessing than that, where school is concerned. I consider myself blessed to have met everyone I mentioned in this journey of life, and so many more that who have been close to me. iv TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ii LIST OF TABLES ix LIST OF FIGURES xiii SUMMARY xxii 1 Introduction 1 1.1 Problem Statement 3 1.2 Literature review 5 1.2.1 Failure prediction 5 1.2.2 Diagnostics 9 1.2.3 Economics of Management of Power Utility Components 11 1.3 A new approach to component management 14 1.3.1 Failure prediction 14 1.3.2 Diagnostics and preventive replacements 15 1.3.3 Economics 16 1.4 Navigating the dissertation 18 1.5 Summary 18 1.6 REFERENCES 20 2 Reliability-type Modeling of Components in Electric Power Utilities Using Preventive Replacement Data 24 Introduction 24 2.1 Reliability-Type Analysis of Preventive Replacements of Components from Utility Inspection Databases 25 2.1.1 Applying the Kaplan-Meier Method to Preventive Replacement Data 26 v 2.2 Comparing Reliability Models Generated from Power Utility Inspection Databases to Models from Failure Databases 32 2.2.1 Metric for Quantifying Difference in Reliability Estimates of Components using Corrective or Preventive Replacement Data 34 2.3 An Ideal Failure Database for Components in an Electric Power Utility 39 2.4 Summary 40 3 Modeling Failure Rates 41 Introduction 41 3.1 Age-Based Failure Estimation and Prediction 42 3.1.1 Exponential Case 43 3.1.2 Non-Exponential Case 59 3.2 Stress-Based Failure Estimation and Prediction 80 3.2.1 Fragility Assessment of Wind-Stressed Components 82 3.2.2 A Second Predictor of Stress-Based Failure Risk: Age 90 3.2.3 A Strategy for Prioritizing the Geographic Scheduling of Component Inspections using Environmental and Fragility Risk: Development of the Inspect Index 97 3.2.4 Economic Effects of Component Replacements 101 Sample Results: Wood Poles 103 3.3 Summary 107 3.4 REFERENCES 110 4 Predictive Maintenance: Diagnostics and Preventive Replacement of High-Risk Components 112 Introduction 112 Navigating this Chapter 113 4.1 Analyzing the Accuracy of Individual Diagnostic Tests 114 4.1.1 Measures of Diagnostic Accuracy 115 vi 4.1.2 Sampling Power System Components for Destructive Tests 118 4.1.3 Ranking Accuracies of Diagnostic Tests using Statistical Tools and Economics of Diagnostic Decisions 134 4.2 Improving Diagnostic Accuracy and Validity by Combining Diagnostic Test Results 143 4.3 Analyzing the Accuracy of Combined Diagnostic Tests 149 4.3.1 Applying Logistic Regression Analysis to Multiple Diagnostic Test Predictions 149 4.3.2 Applying Receiver Operating Characteristics (ROC) Analysis to Multiple Diagnostic Test Predictions 155 4.3.3 Applying Combinatorial Logic Rules 156 4.4 Effects of Cost-Relationships on Decisions of Preventive Replacements from Multiple Diagnostic Testing 166 4.5 Summary 170 4.6 REFERENCES 173 5 Stochastic Optimization of Preventive Maintenance Programs for Power System Components 174 Introduction 174 5.1 Optimizing the Component-Management Process 176 5.1.1 Costs that affect Decision-Making in Management of Environmentally Stressed Aging Components 178 5.1.2

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