MILLIGAN SOLAR PROJECT

Transcription

1 February 16, 2009 Page 1 of 18 A subsidiary of Pinnacle West Capital Corporation MILLIGAN SOLAR PROJECT FINAL Feasibility Study Report APS Contract Prepared by: Arizona Public Service Company Transmission & Distribution Asset Management And Transmission Planning February 16, 2009

2 February 16, 2009 Page 2 of 18 Executive Summary CUSTOMER is evaluating the feasibility of interconnecting an 80 MW solar resource to the Arizona Public Service (APS) transmission system. The proposed project, Casa Grande Solar Project, would consist of solar photovoltaic arrays with inverters converting DC to AC electrical power. The planned commercial operation date of the Milligan Solar Project is May 2013 and will be located near the existing Milligan substation, southwest of Eloy, AZ. The solar photovoltaic arrays electrical output will be interconnected to APS Pinal 69 kv system. Additionally, the Customer requested Energy Resource Interconnection Service only. At the Customers request, APS determined the possible transmission paths from the Point of Interconnection plus associated transmission reinforcements required to interconnect the Milligan Solar Project. This Feasibility Study (Milligan Solar Project, APS Contract 52117) evaluated two alternate options for interconnecting the Project. The interconnection options include: Option 1: The Primary Point of Interconnection for the proposed Milligan Solar Project to the APS Pinal 69 kv system is a tap into the Milligan Toltec 69 kv line. Option 2: The Alternate Point of Interconnection for the proposed Milligan Solar Project to the APS Pinal 69 kv system would consist of a direct interconnection to the Milligan 69 kv. APS performed the Feasibility Study modeling the heavy summer coincident peak loads demand power flow base cases in the 2011 and 2012 timeframe. Power flow analysis was performed and the results were used for the evaluation of each of the interconnection options. Short circuit studies were performed to evaluate the system impact of adding the Project to the APS transmission system. High level interconnection costs and timelines were estimated for each of the interconnection options based on the approximate locations. Another utility s planned transmission line in the Pinal area is slated for a 2013 in-service date. With the assumption that the planned transmission line is in-service, the power flow study results concluded that the deliverability of the entire Project output of 80 MW can be achieved without impacting the APS transmission system from the implementation of either of the two interconnection options. Short circuit study results indicate that the existing transmission system breakers would not be overstressed by the interconnection of the Project. However, detail short circuit analysis would be needed to determine breaker sizes for the final interconnection plan.

3 February 16, 2009 Page 3 of 18 Interconnection cost and timeline estimates are listed on the table below: Table 1: Summary of Project Interconnection Costs Option 1 Cost Estimate Option 1 Time Line Option 2 Cost Estimate Option 2 Time Line Equipment $550,000 9 months $750,000 9 months Line Right of Way $484, months $727, months Line Construction $917, months $1,294, months Grand Total $1,952, months $2,772, months

4 February 16, 2009 Page 4 of 18 Contents...Page Introduction...1 Study Objectives...1 Project and Interconnection Information...1 Feasibility Interconnection Options...1 Study Base Cases, Assumptions and Methodology...2 Feasibility Study Results...2 Interconnection Options and Delivery to the Pinal 69 kv System...3 Short Circuit Analysis...3 Interconnection Cost Estimate...4 Appendix A...Power Flow Results Summary.11 Appendix B.. One-Line Diagrams Appendix C..Power Flow Diagrams... 16

5 February 16, 2009 Page 5 of 18 Introduction CUSTOMER has submitted a valid and complete large generator interconnection application Arizona Public Service (APS) for Milligan Solar Project under the APS OATT. The proposed Project consists of solar photovoltaic arrays with inverters to convert DC to AC power. The maximum net output of the Project to the APS controlled grid will be 80 MW. The planned commercial operation date of the Project is May The proposed Project will be located near the existing Milligan substation, and the output will tap into APS Pinal 69 kv system. Customer has requested Energy Resource Interconnection Services for the proposed Project. APS decided that an interconnection Feasibility Study was required to determine the impact of the Customer-requested alternate Points of Interconnection for the proposed Project to the APS transmission system. This report summarizes the results of the Feasibility Study. Study Objectives The main objective of this Study is to evaluate the requested interconnection points and determine any associated transmission reinforcements required to interconnect the Milligan Solar Project. The Study provides high level cost and timeline estimates for the different requested interconnection plans and system additions for the proposed Project. Project and Interconnection Information The general Project and interconnection information is provided below: Project location: Southwest Pinal District Maximum Plant output: 80 MW Step Up transformer: 34.5/0.265 kv, 1 MVA, Z=7.5% Power Factor: Project studied at variable power factor from 0.95 leading to 0.95 lagging Plant Voltage: Voltage regulated at 1.02 per unit at the 34.5kV level Feasibility Interconnection Options The interconnection options evaluated as part of the feasibility study are listed below: Option 1: The Primary Point of Interconnection for the proposed Milligan Solar Project to the APS Pinal 69 kv system is a tap into the Milligan Toltec 69 kv line. Option 2: The Alternate Point of Interconnection for the proposed Milligan Solar Project to the APS Pinal 69 kv system would consist of a direct interconnection to the Milligan 69 kv.

6 February 16, 2009 Page 6 of 18 Study Base Cases, Assumptions and Methodology APS conducted the Feasibility Study using a 2011 and 2012 heavy summer base case. This base case modeled all APS approved transmission projects that will be operational by summer 2011 and Proposed generation projects in APS control area that have an interconnection queue date ahead of this Project and have an online date prior to summer 2011 were modeled. The pre-project base case was tested to ensure that it meets WECC/NERC and APS planning standards. The proposed generating facility was modeled as one 80 MW solar plant for this Feasibility Study. The Milligan Solar Project was studied as in service and generating at 100% capacity (80 MW) for each of the two interconnection alternate options. High level power flow studies were performed to evaluate the impact of the proposed Project on the existing transmission system. Under normal operating conditions (all elements in-service); the continuous rating of any system element should not be exceeded. For single-contingency conditions, the following guidelines were followed: Sub-transmission lines should not exceed 100% of their continuous rating. 230/69 kv transformers should not exceed 120% of their top FOA rating measured at the 69 kv level. 69 kv voltage deviations should be less than 5% at unregulated stations. 69 kv voltage deviations should be less than 10% for regulated substations. Where these guidelines were not met, options were evaluated to find the best solution that would bring the system to within guidelines. Short circuit studies were performed to evaluate the impact of the Project on selected substation breaker duties. High level interconnection cost estimates are provided for the different feasibility interconnection options evaluated. Feasibility Study Results The results of the Feasibility study details the two options that enable the Project to interconnect and be delivered to the Pinal system. The interconnection options and associated system upgrades detailed will be required if the Project proceeds to an Interconnection Agreement.

7 February 16, 2009 Page 7 of 18 Interconnection Options and Delivery to the Pinal 69 kv System Option 1 Milligan Toltec 69 kv Line Tap With the tap into the Milligan Toltec 69 kv line there are no limiting factors during normal (N-0) conditions or single (N-1) conditions. Based on the Study results, there is no plan of service needed for Interconnection Option 1. Option 2 Direct Connection to the Milligan 69 kv With the Milligan CUSTOMER Solar 69 kv line there are no limiting factors during normal (N-0) conditions or single (N-1) conditions. Based on the Study results, there is no plan of service needed for Interconnection Option 2. Short Circuit Analysis Short circuit studies were performed on all the feasibility interconnection options as part of this Study. The study included three-phase and phase-to-ground fault analysis. Provided below are the study results. Table 2: Summary of Short Circuit Study Evaluation Base Case With CUSTOMER Solar Option 1 3 Ph. Ph-G (ka) (ka) With CUSTOMER Solar Option 2 3 Ph. Ph-G (ka) (ka) 3 Ph. (ka) Ph-G (ka) Min. Brkr Rating - ka Milligan 69kV Millgan Solar 69kV As Required Toltec 69kV As can be seen from Table 2, the interconnection of the project does not cause the existing substation breakers to exceed their minimum rating. However, a detailed short circuit study will be needed at the System Impact Study level to determine the breaker sizes for interconnecting the project.

8 February 16, 2009 Page 8 of 18 Interconnection Cost Estimates High level interconnection cost estimates for each of the feasibility interconnection options are tabulated below. The interconnection cost for each option is based solely on the plan of service of that option as provided under section Feasibility Study Results. 69 kv Line Assumptions: No 12 kv underbuild is included in the estimate. Construction estimate based on one 8 person crew. Rebuilds will be rebuilt in existing location. Terrain was not considered when estimating line route. R.O.W. = 40 feet wide. Environmental studies will be required on new and existing lines crossing federal lands. Access and Lay Down Yards are not included in the Estimate. Land Values will fluctuate based on specific location. N.E.P.A. Process estimated at $3,000 per mile. BLM, State or Indian lands acquisition time is typically 18 to 24 Months. Private acquisition could be 18 months if condemnation is required. Equipment Estimates does not include land, communications, access, drainage and grading costs. All Estimates are in 2008 dollars.

9 February 16, 2009 Page 9 of 18 Option 1 Table 3a Option 1 Equipment Cost Estimates Equipment Description Design Time Construction Time Estimated Cost ($) Milligan CUSTOMER Solar Sub: (1) 69kV 6 months 3 months 550,000 Breaker Grand Total 6 months 3 months 550,000 Table 3b Line Section From Bus To Bus New Line Length (mi) Rebuilt Line Length (mi) Option 1 Line Cost Estimates Conductor Type Design time (MO) Construction time (MO) Cost ($) Comments Milligan Solar Milligan Tap 2 795AA ,758 Grand Total ,758 Table 3c Option 1 Right of Way Cost Estimates Line Section Land Type (mi) From Bus To Bus New Line Length (mi) Rebuilt Line Length (mi) ROW Time Mo. Total Estimated Cost ($) Est. Land Value Per Acre Private BLM State Indian Comments Milligan Solar Milligan Tap ,848 $ 50,000 2 Grand Total ,848

10 February 16, 2009 Page 10 of 18 Option 2 Table 4a Option 2 Equipment Cost Estimates Equipment Description Design Time Construction Time Estimated Cost ($) Milligan CUSTOMER Solar Sub: (1) 69kV 6 months 3 months 550,000 Breaker Milligan Sub: (1) 69kV Breaker 3 months 1 month 200,000 Grand Total 6 months 3 months 750,000 Table 4b Line Section From Bus To Bus New Line Length (mi) Rebuilt Line Length (mi) Option 2 Line Cost Estimates Conductor Type Design time (MO) Construction time (MO) Cost ($) Comments Milligan Solar Milligan Sub AA 9 3 1,294,804 Grand Total ,294,804 Table 4c Option 2 Right of Way Cost Estimates Line Section Land Type (mi) From Bus To Bus New Line Length (mi) Rebuilt Line Length (mi) ROW Time Mo. Total Estimated Cost ($) Est. Land Value Per Acre Private BLM State Indian Comments Milligan Solar Milligan Sub ,273 $ 50,000 3 Grand Total ,273

11 February 16, 2009 Page 11 of 18 Appendix A (Power Flow Result Summary)

12 February 16, 2009 Page 12 of 18 CUSTOMER Solar Pinal System Outage Summary 2011 Outage Description From Bus Name Overload Element Base KV To Bus Name Base KV Rating Base case Flow MVA MW MVAR Amps Loading (%) Comments No Overload or Voltage Issues 2012 Outage Description From Bus Name Overload Element Base KV To Bus Name Base KV Rating Base case Flow MVA MW MVAR Amps Loading (%) Comments No Overload or Voltage Issues

13 February 16, 2009 Page 13 of 18 Appendix B (One-Line Diagrams)

14 February 16, 2009 Page 14 of 18 Approximate circuit length (miles) Santa Rosa Vista 15.3 Vista East Gate 4.6 East Gate Casa Grande 6.3 East Gate Toltec 12.0 Toltec Milligan 5.0 Pinal 69kV System 69kV bus 69kV line N.O. 69kV line 69kV breaker Santa Rosa Asarco Vista 108 MVA 108 MVA 230/69kV 167 MVA East Gate Casa Grande SE8 108 MVA 108 MVA 230/69kV 100 MVA Toltec Milligan 108 MVA 230/69kV 187 MVA

15 February 16, 2009 Page 15 of 18 CUSTOMERSolar Milligan Point of Interconnection (POI) 69kV bus 69kV line N.O. 69kV line Primary POI 69kV breaker Approximate circuit length (miles) Milligan Toltec 5.0 Milligan POI 1/4-1 POI CUSTOMERSolar 2.0 Toltec Milligan 108 MVA 230/69kV 100 MVA POI Solar Alternate POI Approximate circuit length (miles) Milligan Toltec 5.0 Milligan CUSTOMERSolar 3.0 Toltec Milligan 108 MVA 108 MVA 230/69kV 100 MVA Solar

16 February 16, 2009 Page 16 of 18 Appendix C (Power Flow Diagrams)

17 February 16, 2009 Page 17 of Base Case 2011 Base Case with CUSTOMER Solar

18 February 16, 2009 Page 18 of Base Case 2012 Base Case with CUSTOMER Solar