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Big Stone II Study Update

Big Stone II Study Update

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Big Stone II Study Update

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  1. Big Stone II Study Update SPG Meeting October 19, 2006

  2. Presentation Overview • Summary of September 18 MAPP DRS Mtg. • Interconnection Study • Delivery Service Study • Phase 5 Summer Off-peak Analysis • Model Assumptions • Results • Upcoming Schedule

  3. Recap of Sept. 18 DRS Mtg. • Interconnection Study • Presentation given to MAPP DRS • Discussion led to conditional approval of the IC study with 4 follow-up items: • Verify ND Load Levels in Stability Models • Arrowhead-Weston 345 kV Stability Sensitivity • Resolution of local stability issues • Update DRS once transmission option selected by the MN PUC

  4. Recap of Sept. 18 DRS Mtg. • Delivery Service Study • Presentation given to MAPP DRS • Discussion led to identification of 4 follow-up items before DRS will take action on study. • Finish Phase 5 analysis (Summer off-peak study) • Prior outage analysis of Phase 3 models • Deeper explanation of flowgate analysis • Identify fixes for delivery related issues (revise motion)

  5. Phase 5 – Summer off-peak High Simultaneous transfer case • Phase 5 only for DRS review. Submitted to the DRS on Sept 29th for review at the November 2nd meeting • Not part of MISO submittals

  6. Technical Scope • This phase is steady state only • Base case is 2006 summer off-peak case from the NMORWG package with: • MHEX South = 2175 MW • NDEX = 1950 is base case – raised with Big Stone II • MWSI = 1480 MW prior to Arrowhead – Weston in service. Maintained at such level prior to Arrowhead – Weston throughout study. • Since this case has maxed out interfaces, the model does not reflect existing firm commitments. • Baseloads within NDEX @ URGE • Load within NDEX approx @ 70% • NMORWG TITLE: URG-S7006AA.UZVV424.SAV

  7. Powerflow model additions • Added some new topology: • Split Rock – Nobles Co. – Lakefield 345 kV • Lakefield – Fox Lake 161 kV #2 • Arrowhead – Stone Lake – Gardner Park 345 kV • Series Compensation of Lakefield – Wilmarth 345 kV • Upgrades associated with Council Bluffs 4 and Nebraska City 2 • Other miscellaneous model changes in addition to this

  8. Study • BSP II output sunk to generation similar to that of Phase 3 and 4 of the Delivery Study • One scenario for each of the two interconnection alternatives studied.

  9. Results • Thermal overloads observed, and impacted above 2% DF: • Big Stone – Blair 230 kV. Loaded between normal and emergency rating • Granite Falls 230/115 kV xmfrs • Aurora – Brookings 115 kV • Arlington – Watertown 115 kV • Brookings – Watertown 115 kV • McLeod 230/115 kV xfmr • Granite Falls – Morris 230 kV • Morris 230/115 kV xfmr • Watertown 345/230 kV xfmr • Johnson Jct. – Ortonville 115 kV • Grant County – Hoot Lake 115 kV

  10. Results - continued • Part of this study is to identify if TTC of interfaces would be reduced because of this project. Note that the model is not reflective of firm commitments. • Two of the thermal issues seen is part of the current NDEX interface definition: • Big Stone – Blair 230 kV • Morris – Granite Falls 230 kV • No new steady state voltage concerns observed. • Discussion on what the constraints that will have to be mitigated will be held at the DRS meeting.

  11. Upcoming Schedule • November 2 DRS Mtg. • Discuss Phase 5 Analysis • December 7 DRS Mtg. • Discuss Remaining Follow-Up Items • December 31 Draft IA • MISO Approval of IC Study • January 2007 Begin Phase 6 Analysis • Sensitivity to EHV line and other regional transmission projects