2008 Annual Report of the Western Electricity Coordinating Council’s Transmission Expansion Planning Policy Committee ___________________ Part 3 Western Interconnection Transmission Path Utilization Study An analysis of Path Flows and Schedules on the WECC Transmission System during 2007 Historical Analysis Work Group April 2009 TABLE OF CONTENTS I. INTRODUCTION ------------------------------------------------------------------------------------ 1 II. OBJECTIVE OF STUDY -------------------------------------------------------------------------- 2 III. ANALYSIS METHODOLOGY ------------------------------------------------------------------ 2 Nomenclature ------------------------------------------------------------------------------------ 2 WECC Paths Analyzed ------------------------------------------------------------------------ 3 Methodology --------------------------------------------------------------------------------------- 6 Historical Actual Flow Data -------------------------------------------------------------------- 7 Historical Schedule Data ----------------------------------------------------------------------- 7 POR POD Mapping Process ------------------------------------------------------------------ 8 Other Historical Data ---------------------------------------------------------------------------- 9 Congestion Indices ----------------------------------------------------------------------------- 10 OTC/TTC Assumptions ------------------------------------------------------------------------ 10 WECC Scheduling and OASIS Posting Process ---------------------------------------- 10 IV. RESULTS ------------------------------------------------------------------------------------------- 11 Path by Path Analysis and Congestion Indices Calculations ---------------------------- 11 Path Usage Rankings ---------------------------------------------------------------------------- 20 Related Transmission Projects ----------------------------------------------------------------- 22 Unscheduled (Loop) Flow ----------------------------------------------------------------------- 23 WECC Unscheduled Flow Curtailments in 2007 ------------------------------------------- 23 California Import ----------------------------------------------------------------------------------- 24 Regional flow analysis ---------------------------------------------------------------------------- 24 V. TREND ANALYSIS ------------------------------------------------------------------------------- 26 1998 through 2007 -------------------------------------------------------------------------------- 26 VI. LIMITATIONS ON APPLICATION OF STUDY RESULTS --------------------------- 27 VII. CONCLUSIONS ---------------------------------------------------------------------------------- 27 VIII. FIGURES ------------------------------------------------------------------------------------------ 31 Figures 4 – 7 Typical Path Chronology & Duration plots for Path 66 (COI) ----- 31 Figures 8 – 11 U75 bar charts & peak flow chart ---------------------------------------- 35 Figures 12 - 14 Usage Ranking Charts ----------------------------------------------------- 39 Figures 15 Major Loop Flow 2007 ----------------------------------------------------- 42 Figures 16 California Import ------------------------------------------------------------- 43 Figure 17 Trend Analysis --------------------------------------------------------------- 44 XI. APPENDICES ------------------------------------------------------------------------------------ 45 I. Path-by-Path Observations ---------------------------------------------------------------- 45 II. Individual Path Performance Appendix IIa – NW Paths (Paths 3, 8, 14, 17, 18, 19, 20) ------------------------------- 55 Appendix IIb – SW Paths (Paths 22, 23, 47, 48, 49, 50, 51) ---------------------------- 85 Appendix IIc - RM Paths (Paths 30, 31, 34, 35, 36) ------------------------------------- 113 Appendix IId – CA Paths (Paths 45, 46, 65, 66, CA Import)--------------------------- 134 Appendix IIe – Regional Analysis (PNW, CA, DSW, RM) ----------------------------- 152 III. Metric Calculations -U75, U90, U99 All Hour, Seasonal and Heavy/Light Load ------------------------------------------------------------------------------------------------------- 156 IV. Path Usage Ranking Charts ------------------------------------------------------------ 173 TEPPC Annual Report - Part 3 I. INTRODUCTION The analysis of historical power flow and schedule data for the Western Interconnection transmission system provides an indication of how marketers and load serving entities have utilized the transmission system to market energy and serve load. This information is also useful in the analysis and identification of potential future areas of congestion and for verifying model representation for power flow and production costing analysis. Previous studies have analyzed only actual MW flow data. For the first time, this study gathered and analyzed historical path schedule data for 23 Western Electricity Coordinating Council (WECC) paths. Schedule data was obtained by OATI from archived electronic scheduling tags (e-Tags) by mapping POR POD segments to WECC paths, searching the OATI archived e-Tag database and converting the individual e-Tag schedules to WECC path schedules. Together with actual flow data from the WECC PI database, the study was able to evaluate usage of the transmission system considering both actual flows and transaction schedules. This work is the latest in a continuing effort to analyze utilization of the Western Interconnection transmission system that started in 1999. The WECC Transmission Expansion Planning Policy Committee’s (TEPPC) Historical WG (HWG) performed the analysis in this report. Similar analysis was performed previously by the three western Regional Transmission Associations (RTAs) as documented in their Biennial Transmission Plan dated July 2000 and by the Seams Steering Group – Western Interconnection (SSG_WI), in their report dated February 2003. A previous analysis by TEPPC was documented in the report “Western Interconnection Transmission Path Flow Study” dated September 2007. The analysis in this report was performed for 23 Western Interconnection transmission paths, representing the major transmission paths in the western interconnection. The analysis utilized real time hourly power flow and operating transfer capability data archived in the WECC PI database. Schedule data was obtained by OATI from archived e-Tags. An attempt was made to utilize ATC and Reservation data from the WestTrans OASIS. However, this data was found to be incomplete and could not be used in this study. Actual flow and schedule data was also obtained from the Bonneville Power Administration, El Paso Electric Company and PacifiCorp. To facilitate performance comparison among the paths, utilization metrics were calculated. These metrics represent the percentage of time the path flow or schedule exceeds 75%, 90% and 99% of its operating transfer capability. The 75% utilization level was chosen as an indicator of a path that may be considered heavily utilized. The 90% utilization level is an indicator of very heavy path loading. The 99% utilization indicator is representative of the time a path is operating at its full capacity. The magnitudes of the metrics by themselves are not necessarily an indication that there is congestion (an inability to meet the needs of transmission users on the path) or that Final - 06Apr2009 Page 1 of 177 TEPPC Annual Report - Part 3 there is a reliability concern. In the Western Interconnection, paths are designed to be loaded to 100% of their operating transfer capability and withstand credible outages without violating WECC and NERC reliability standards. Some paths are designed to operate at very high capacity factors such as those dedicated to integrating specific generating plants. II. OBJECTIVE OF STUDY The purpose of the study was to measure the historical utilization of the major transmission paths in the Western Interconnection during 2007 and to provide insight into where transmission congestion might be occurring. It should not be concluded from this analysis that it is necessary or economical to take corrective actions for the loading levels reported. The results may, however, provide information for identifying paths for further study regarding the potential benefits and costs of increasing their transfer capacity. Additional information may be needed to help identify where heavy loadings and heavy schedules on the transmission system are a bottleneck to the operation of a more efficient resource market. A portion of this study effort was funded by Lawrence Berkeley National Laboratory. The information in this report is being provided to the US Department of Energy for use in their 2009 transmission congestion report of the nation’s transmission infrastructure. III. ANALYSIS METHODOLOGY 1. Nomenclature Following is a definition of some of the acronyms and terms used in this report (These may be abbreviated definitions and not the official WECC definitions for these terms): 1. OTC – Operating Transfer Capability - the MW capacity limitation of a path which can vary hourly with changing operating conditions 2. TTC – Total Transfer Capability - the WECC Path Rating as defined in the 2008 WECC Path Rating Catalog 3. WECC Path Number – a unique number assigned to each path described in the WECC Path Rating Catalog 4. TP – Transmission Provider 5. U75, U90, U99 – congestion metrics defined as the % of