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Statistical Framework for Establishing Target Reliability Levels and Classifying Major Event Days Mark McGranaghan EPRI PEAC Corporation mmcgranaghan@epri-peac.com. Background. Deregulation and, in some instances, re-regulation have caused a renewed interest in distribution reliability

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  1. Statistical Framework for Establishing Target Reliability Levels and Classifying Major Event DaysMark McGranaghanEPRI PEAC Corporationmmcgranaghan@epri-peac.com

  2. Background • Deregulation and, in some instances, re-regulation have caused a renewed interest in distribution reliability • Several issues are leading to increased regulatory scrutiny of distribution reliability: • Emerging trend of decoupling price/revenue from cost of distribution service for a certain period of time (“regulatory period”) which allows regulated entities to earn higher profit by reducing cost • Concern regarding excessive budget cutting in the “wires” business to recover huge losses experienced in the energy trading and other businesses • Perception of decreased reliability during severe weather events • In December 2002, EPRI PDM initiated a project to review the current situation in distribution reliability performance indicators for utilities in United States

  3. Characterizing Reliability • Most common indices (IEEE P1366) – SAIFI, SAIDI • Statistical variations are critical • Target levels must include control ranges based on statistical variation characteristics • Handling of “Major Event Days” is a critical factor

  4. Statistical Methods • Characterize variability of reliability indices • Establish control regions • Performance-based rates

  5. Defining Major Events • “Major Event” is defined as an event (typically weather related) that exceeds reasonable design and or operational limits of the electric power system • Widespread service interruption during a major event can significantly influence the yearly distribution reliability indices • Inconsistencies in the definition of “Major Events” has been a bottleneck in comparing reliability statistics among different utilities • IEEE is proposing a statistically-based definition of “Major Event” as part of IEEE P1366 Draft Full-Use Guide for Electric Power Distribution Reliability Indices

  6. Impact of Major Events on SAIDI

  7. Impact of Major Events on SAIFI

  8. Pitfalls in Comparing Reliability Performance • Definition & Data Classification • Major Events • Planned vs Unplanned Events • Momentary interruptions vs outages • Distribution/Transmission • Service Territory • Geography, weather, vegetation, animals, load density • Data Collection Process • Monitoring vs other methods of data collection • System Design • Overhead vs underground, voltage levels, networks, protection, etc.

  9. Comparing Utility Reliability Indices • Consistency in definition of reliability indices and accountability of major events through standardization will promote uniformity among utilities • Need uniformity on an international basis • Collaborative project to compare methods for characterizing reliability, identify preferred statistical methods, benchmark with actual data

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