Northern Tier Transmission Group Report to Columbia Grid Planning Committee February 9, 2012 “To ensure efficient, effective, coordinated use & expansion of the members’ transmission systems in the Western Interconnection to best meet the needs of customers & stakeholders.”

NTTG Biennial Planning Cycle We are here Q1 Q2 Q3 Q4 Q5 Q1 Q6 Q2 Q7 Q3 Q8 Q4 Gather Information Develop Study Plan, Assumptions Perform Draft Plan Analysis Prepare & Review Draft Report Process Econ. Studies, CostAlloc. Prepare & Review Final Report Obtain Final Plan Approval Economic Study Requests Perform Economic Studies Report and Review Economic Study Requests Perform Economic Studies Report and Review NTTG Economic Study Cycle NTTG Biennial Planning Cycle

NTTG Biennial Planning Report & Summary

Just finished Quarter 8 of Cycle –Finalized and Approved Report and Exec Summary –Available at Quarter 1 of Biennial Planning Process –Stakeholder Requests: Planning needs and data –Request window open for Economic Study Requests No WECC Wide requests received this year Expecting several “Regional” ESRs before NTTG window closes March 31, 2012 –Data and Modeling Improving Round Trip base case process Working on TEPPC 2010 and 2022 Cases Other Activities –FERC Order 1000 Regional compliance NTTG Planning Committee

Final Planning Report for Cycle Core Case Reliability Study: –Five hours of stress test cases for NTTG’s footprint were exported from production cost studies for power flow reliability analysis –Cases were solved and passed high level N-1 contingency analysis within study criteria Existing System will not be able to reliably serve network load growth requirements in 2020 and transmission additions are required The NTTG projects on the Foundation list (either under construction and/or meeting other SCG Criteria) are sufficient to meet reliability requirements for 2020 network loads

System Scenarios Additional renewable generation scenario cases were performed in response to stakeholder requests - generation but no specific receiving customers. Delivery points calculated from Production Cost Model –Since no agreements in receiving area –Scenario resource additions were offset by generation reductions in California & Arizona Reliability studies for the same five hours as for Core Case (so 20 cases performed) –All required additional transmission above the Foundation List Looked for limited transmission additions that would allow all five stress test hours to pass an N-1 contingency study –HVAC and HVDC additions considered –Generic additions so as not to pick specific sponsor 6

Scenario 1 Results Scenario 1 – 6,000 Megawatts in Wyoming –Adding 3,000 MW transfer capability Clover-Crystal line was inadequate 2,100 MW over limit on COI, 433 criteria violations –Also adding 3,000 MW transfer capability Aeolus-Crystal still left problems COI was 760 MW over its limit 147 criteria violations –Further addition of 1,500 MW transfer capability Midpoint-Robinson left fewer problems COI still 200 MW over limit 119 remaining criteria violations –Addition of phase shifting transformers or substituting two kV DC lines would likely further reduce problems 7 Midpoint Aeolus Clover Crystal Robinson

Scenario 2 Results Scenario 2 – 3,000 MW in Montana, 3,000 in Wyoming –Adding Townsend-Midpoint and Clover-Crystal was inadequate 1,700 MW over limit on COI, 1,600 MW over Montana-Northwest limit –Tested combined Scenario 3 and Scenario 4 transmission additions 3,000 MW capability from Townsend via Midpoint and Robinson to Harry Allen plus 1,500 MW from Aeolus to Crystal plus 1,500 MW from Clover to Crystal 29% over limit on Victorville-Lugo 350 MW over COI limit of 4,800 MW 98 criteria violations –Appears adequate, violations can be resolved with local controls –Other hours have not been tested, given previous dominance of March hour 8 Townsend Midpoint Aeolus Clover Crystal Robinson

Results of Scenario 3 Analysis Scenario 3 – 3,000 MW in Montana –Significant problems again occurred on the high export hours –Problems with Montana to Northwest, COI paths Generic Solution: Add Transfer Capability 1)Added 1,500 MW from Townsend (Central MT) to Midpoint (Central ID) Montana-Northwest over by 400 MW Still 1,700 MW over on COI 2)Tested 3,000 MW transfer capability from Townsend via Midpoint and Robinson to Harry Allen Fixed problems on Montana-Northwest COI just 325 MW over limit 77 violations 2) appears adequate, violations can be resolved with local controls –Other hours studied again have fewer issues 9 Townsend Midpoint Harry Allen Robinson

Midpoint Aeolus Clover Crystal Robinson Results of Scenario 4 Analysis 10 Scenario 4 – 3,000 MW in Wyoming –Significant problems occurred on the high export hours (March noted here) –Problems with paths TOT2A, COI Generic Solution: Add Transfer Capability 1)1,500 MW capacity from Clover (Central UT) to Crystal (Southern NV) Still 900 MW over COI limit 2)1) + 1,500 MW capacity Midpoint-Robinson COI less than 100 MW over, 200 violations 3)1) + 1,500 MW capacity Aeolus-Crystal COI 104 MW over limit, 132 violations 3) appears adequate, violations can can be resolved by local controls Other hours studied have fewer issues

Scenario Conclusions  Adding 3,000 MW of generation in either Montana or Wyoming appears to require 3,000 MW of additional transfer capability through a partial double-circuit 500 kV AC or DC circuit to deliver via Southern Nevada to Arizona and California  Delivery via Northwest would require upgrades MT-NW and to COI  Adding 3,000 MW in both Montana and Wyoming works relatively well with double-circuit 500 from Townsend to Harry Allen via Midpoint and Robinson, a 500 kV line from Aeolus to Crystal and another from Clover to Crystal or DC tie lines  With 6,000 MW in Wyoming, double-circuit from Aeolus to Crystal plus double-circuit from Clover to Crystal still needs Midpoint- Robinson to get reasonable results or DC tie lines 11

Annual Economic Studies 2010 Economic Study Requests – 25 Received –21 Interregional sent up to TEPPC –3 NTTG Sub-Regional Amps 230 kV upgrade to 401 MW MSTI Colstrip 500 kV system upgrade –1 NWE Local 1500 MW 230 kV radial collector lines into Townsend 500 kV & MSTI 2011 Economic Study Requests – 24 Received –None Sub-Regional –All Interregional and directed up to TEPPC 2012 NTTG ESR Window will Open Jan 1 – Mar 31 –Note WECC window closes Jan 20 next year (instead of 1-31)

Economic Studies NTTG Cluster Study - Added 1500 MW wind at Townsend. Performed economic studies with expansion : 1. Increase capacity of the AMPS line (Path 18) from 337 to 401 MW 2. Increase rating of Montana-Northwest path (Path 8) by 600 MW 3. Add Mountain States Transmission Intertie (MSTI) project Results –Large congestion and coal cycling without additions Some wind spill –Moderate congestions and cycling with Path 8 and 18 –Acceptable performance with all 3 upgrades