1. 1 CATS HV Status Report Presented to the 2008 BTA Workshop May 22, 2008

2. 2 CATS HV Study Area

3. 3 Summary With a 25 MVAR capacitor at Thornton: The Ten-Year Plan exhibits no pre or post outage condition voltage or thermal issues in CATS HV system N-1 performance with additional local load beyond 2016 load level: –voltage violations commence @ +100 MW –thermal violations begin @ + 200 MW

4. 4 Addendum to 2007 Study Thermal Overloads and Voltage Violations identified in 2016 “growth” scenario cases Review Western 115kV upgrades to 230kV construction (poles and wire) but still operated at 115kV Conclusions –Upgrades Mitigate Voltage and Thermal Violations –CATS HV System can accommodate at least 300MW of additional loads beyond 2016 time frame with proposed upgrades Approved by CATS HV participants

5. 5 CATS HV Participants Transmission Owners –Arizona Public Service Tucson Electric Power –Salt River Project Western Area Power Administration –Southwest Transmission Coop. Load Serving Entities –Arizona Public Service Electrical District 2 –Central Arizona Project Electrical District 3 –San Carlos Irrig. Project Electrical District 4 –Trico Distribution Coop. Electrical District 5 Governmental Entities –AZ Attorney General’s Office Arizona Corp. Commission –Arizona Power Authority City of Casa Grande –Town of Eloy Town of Coolidge –Town of Maricopa Pinal County

6. 6 Study Group Participants –Arizona Public Service –Electrical District 2 –Electrical District 3 –Electrical District 4 –Electrical District 5 –Salt River Project –Southwest Transmission Coop. –Tucson Electric Power

7. 7 2008 Study Plan 2018 Transmission Plan for CATS HV detailed system with WestConnect coordinated base case Resource Scenarios based on probable energy zones (500MW increments) Document all findings and conclusions coincident with SWAT/WestConnect Annual Report by October 2008