1. McGranaghan US Session 2 Block 4 Question 12 Barcelona 12-15 May 2003 1 Statistical Framework for Establishing Target Reliability Levels and Classifying Major Event Days Mark McGranaghan EPRI PEAC Corporation mmcgranaghan@epri-peac.com

2. McGranaghan US Session 2 Block 4 Question 12 Barcelona 12-15 May 2003 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. McGranaghan US Session 2 Block 4 Question 12 Barcelona 12-15 May 2003 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. McGranaghan US Session 2 Block 4 Question 12 Barcelona 12-15 May 2003 4 Statistical Methods Characterize variability of reliability indices Establish control regions Performance-based rates

5. McGranaghan US Session 2 Block 4 Question 12 Barcelona 12-15 May 2003 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. McGranaghan US Session 2 Block 4 Question 12 Barcelona 12-15 May 2003 6 Impact of Major Events on SAIDI

7. McGranaghan US Session 2 Block 4 Question 12 Barcelona 12-15 May 2003 7 Impact of Major Events on SAIFI

8. McGranaghan US Session 2 Block 4 Question 12 Barcelona 12-15 May 2003 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. McGranaghan US Session 2 Block 4 Question 12 Barcelona 12-15 May 2003 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