300 MW SOLAR PHOTOVOLTAIC PLANT, GENERATOR INTERCONNECTION FEASIBILITY STUDY

Transcription

1 300 MW SOLAR PHOTOVOLTAIC PLANT, GENERATOR INTERCONNECTION FEASIBILITY STUDY El Paso Electric Company System Planning August 2006

2 TABLE OF CONTENTS 1.0 EXECUTIVE SUMMARY...Page PURPOSE...Page INTRODUCTION...Page Performance Criteria...Page Voltage Violation Criteria...Page Voltage Drop Violation Criteria...Page PNM s additions and exceptions to the NERC/WECC Criteria - Voltages...Page Tri-State s additions and exceptions to the NERC/WECC Criteria - Voltages...Page Loading Violation Criteria...Page Reactive Margin (Q-V) Criteria...Page Arroyo Phase Shifting Transformer (PST) Maximum Angle Requirement...Page Criteria Violations...Page METHODOLOGY...Page Assumptions...Page Procedure...Page Base Case Development and Description of Cases without the XXX Project: Benchmark Cases...Page Base Case Development and Description with the XXX Project Modeled...Page Modeling of the XXX Project in the Cases...Page Sensitivity Cases with the XXX Project Modeled...Page Powerflow Analysis Methodology...Page List of Contingencies...Page Short Circuit Analysis...Page 20 Generator Interconnection Feasibility Study i El Paso Electric Company

3 5.0 POWERFLOW ANALYSIS RESULTS...Page All-Lines-in-Service (ALIS) Analysis Results for Overloaded Elements Benchmark Cases (without the XXX Project)...Page Single-Contingency (N-1) Analysis Results for Overloaded Elements Benchmark Cases (without the XXX Project)...Page Double-Contingency (N-2) Analysis Results for Overloaded Elements Benchmark Cases (without the XXX Project)...Page All-Lines-in-Service (ALIS) Analysis Results for Overloaded Elements in All Cases with the XXX Project Modeled...Page Single-Contingency (N-1) Analysis Results for Overloaded Elements in All Cases with the XXX Project Modeled......Page Sensitivity Case Modeling Only Two Diablo 345/115 kv Autotransformers......Page Double-Contingency (N-2) Analysis Results for Overloaded Elements in All Cases with the XXX Project Modeled......Page Non-Converging Contingencies...Page Results of Voltage Violations...Page Sensitivity Involving No Third Party Generation Online (All Third Party Generation Offline...Page Sensitivity Involving New Alamogordo-Holloman 115 kv Line Voltage Effects...Page Arroyo PST Phase Angle Values Analysis...Page Q-V REACTIVE MARGIN ANALYSIS RESULTS...Page SHORT CIRCUIT ANALYSIS...Page Short Circuit Analysis Modeling......Page Results of the Short Circuit Analysis... Page Short Circuit Analysis Conclusions..... Page COSTS ESTIMATES...Page XXX Generator Interconnection Cost....Page SNM Facility Additions/Modifications Assumed to be in place prior to the XXX Project Page System Upgrade Costs Due to the XXX project...page Total Costs Page DISCLAIMER...Page CERTIFICATION...Page 59 Generator Interconnection Feasibility Study ii El Paso Electric Company

4 APPENDICES Generator Interconnection Feasibility Study: Study Scope...Appendix 1 EPE s FERC Form 715 Filing...Appendix 2 Powerflow Maps One-Line Diagrams...Appendix 3 List of Contingencies...Appendix 4 Base Case & Contingency Results Detailed Tables...Appendix 5 Base Case & Contingency Results Detailed Tables No Third Party Generation Cases - Sensitivity...Appendix 6 Q-V Plots...Appendix 7 Generator Interconnection Feasibility Study iii El Paso Electric Company

5 1.0 EXECUTIVE SUMMARY In February 2006, XXXXXXXXXXXXXX (XXX) signed an Interconnection Feasibility Study Agreement to study the interconnection of a 300 MW Solar photovoltaic plant (the XXX project) to the Luna 345 kv Switching Station in Deming, NM ( the XXX Generator Interconnection ). El Paso Electric Company (EPE) has performed this 300 MW Solar Photovoltaic Plant, Generator Interconnection Feasibility Study for XXXXXXXXXXXXXXX (XXX) pursuant to this study agreement. The purpose of this Feasibility Study (FS) is to evaluate the feasibility of the proposed interconnection to the New Mexico (NM) transmission system, determine any violations of criteria due to the XXX project, recommend facilities needed to accommodate the XXX project, and provide associated non-binding good faith cost estimate for those facilities and a nonbinding good-faith construction timing estimate. The XXX project was studied at two net MW output levels. The cases modeled the net MW output from the XXX project as the following: 180 MW and 300 MW for the years 2009 and 2011, respectively, with the study period analyzed as the Heavy Summer (HS) season. The output was scheduled to WECC. Each case was studied using the criteria and methodologies described in subsequent sections of this study report. The proposed interconnection point, Luna 345 kv Substation, is jointly owned by El Paso Electric Company (EPE), Public Service Company of New Mexico (PNM), and Texas-New Mexico Power Company (TNMP). This Study analyzed powerflow, Q-V reactive margin, and short circuit analyses. Two (2) Western Electricity Coordinating Council (WECC) GE format base case powerflow cases called the benchmark cases (i.e. cases without the XXX project) were jointly developed by EPE and PNM for this analysis. These benchmark cases reflect load forecast, transmission configuration upgrades in southern New Mexico (SNM) and northern New Mexico (NNM), and facilities associated with each of the prior requestors interconnection projects for the years 2009 and These cases represent the boundaries in which the SNM and NNM system may operate with and without the XXX project. Generator Interconnection Feasibility Study 1 El Paso Electric Company

6 These cases consist of the following, Case 1 and Case 2: 2009 HS and 2011 benchmark cases consist of the base case with all third party generation ahead of the XXX project in the study queue. The third party generation included the following: a. 570 MW of generation interconnected at the Luna 345 kv Substation (scheduled to WECC). b. 141 MW of generation interconnected at Afton 345 kv Substation (scheduled through the Arroyo Phase Shifting Transformer (PST) south-to-north to PNM and reducing San Juan generation). c. 160 MW of generation interconnected at TNMP s Hidalgo 115 kv substation (scheduled to WECC). d. 80 MW of generation interconnected at TNMP s Lordsburg 115 kv substation (scheduled to WECC). e. 94 MW of generation interconnected at Afton 345 kv Substation (scheduled to WECC). In addition to the third party generation above, the study assumes that all EPE local generators are online, the schedule at the Eddy County dc-tie in 200 MW east-to-west (133.3 MW for EPE, 66.7 MW to TNMP), and that EPE s Newman 5 generation is interconnected at the Newman 115 kv bus. In the 2009 HS benchmark case (Case 1), this new generator is modeled as a gas turbine generator with a net MW output of 70 MW. In the 2011 HS benchmark case (Case 2), this new generator is modeled as a gas turbine generator with a net MW output of 123 MW and a steam turbine generator with a net MW output of 90 MW (in a combined cycle arrangement). The additions and modifications assumed to be associated with the above Newman 5 modeling are the following: 1. Add 2nd Arroyo 115/345 kv auto transformer (modeled in the 2009 and 2011 HS benchmark cases). 2. Add 3rd Caliente 115/345 kv auto transformer (modeled in the 2009 and 2011 HS benchmark cases). 3. Reconductor Newman-Shearman 115 kv line from ACSR to 795 ACSR conductor (modeled in the 2011 HS benchmark case). 4. Reconductor Newman-FB2-GR-Vista 115 kv line from ACSR to 795 ACSR conductor (modeled in the 2011 HS benchmark case). 5. Add a 2nd Milagro 115/69 kv autotransformer (modeled in the 2011 HS benchmark case). Generator Interconnection Feasibility Study 2 El Paso Electric Company

7 There were two additional system additions modeled in the benchmark cases: 6. Reconductor Austin-Dyer 69 kv line from 4/0 CU to ACSR conductor (modeled in the 2011 HS benchmark case). 7. Add 3rd Diablo 115/345 kv auto transformer (modeled in the 2009 and 2011 HS benchmark cases). Because Item 7 is not associated with the additions and modifications assumed with Newman 5, the need for a third Diablo 345/115 kv autotransformer was examined as a sensitivity case. It was found that a third Diablo 345/115 kv autotransformer is needed prior to the XXX project. The additions and modifications above are needed prior to the XXX project modeled as on in any case. Because these additions and modifications are needed before the XXX project is modeled, these will be considered an exception to the criteria, will not have a penalizing effect when evaluating the XXX project, and the cost to correct them will not be charged to the XXX project. All cases were evaluated with the Arroyo PST in-service. All cases included 141 MW of generation interconnected at Afton 345 kv Substation (scheduled through the Arroyo PST south-to-north). Given that the Arroyo PST schedule is usually 201 MW without Afton generation on, the cases modeled an Arroyo PST schedule of 201 MW -141 MW = 60 MW north-to-south reflecting PNM s previous transmission purchase from Afton-to- Westmesa. With the benchmark cases developed the XXX project was added to the benchmark cases and two (2) additional WECC GE format base case powerflow cases were developed in order to determine which impacts resulted from this generator interconnection. The XXX project was modeled in powerflow using data supplied by the XXX consultant. Note that the cases with the XXX project are based on the benchmark cases. As such, the facility additions and modifications described in the previous section (items 1-7) appear in the cases with the XXX project modeled. However, the costs of these facility additions and modifications will be separated from the costs of facilities due to the XXX project. Note that all cases modeling the XXX project included the third party generation described in Section These two cases with the XXX project modeled and with the Arroyo PST in-service with a schedule of 60 MW north-to-south consist of the following: Case 3: 2009 Heavy Summer (HS) benchmark case with the XXX project modeled with the net output from the XXX project at 180 MW (as metered at Luna 345 kv). The output is scheduled to WECC in the cases. Generator Interconnection Feasibility Study 3 El Paso Electric Company

8 Case 4: 2011 Heavy Summer (HS) benchmark case with the XXX project modeled with the net output from the XXX project at 300 MW (as metered at Luna 345 kv). The output is scheduled to WECC in the cases. It should be noted that this Study was not meant to analyze every scenario that could occur on the NM and AZ systems with the XXX Project. The Study analyzed the primary boundaries around which the NM and AZ systems may operate, under the scenarios agreed to by EPE, XXX, and PNM. Utilizing engineering judgment, proposed system modifications to correct the criteria violations found in the analyses and estimated costs for those proposed modifications are included in this Study. However, this feasibility study does not include additional studies to validate the effectiveness of any proposed remediations. Results of the powerflow analyses show that various criteria violations occur on the existing AZ and NM systems with the XXX project. Powerflow analysis results show that the Green-AE 345/230 kv transformer owned by SWTC (Southwest Transmission Cooperative, Inc) is overloaded during a singlecontingency of the PYoung-Winchester 345 kv line in the 2011 HS case with the XXX project modeled. This overload is not present prior to the addition of the XXX project. Therefore, for this study, it will be assumed that adding a second Green-AE 345/230 kv autotransformer will alleviate this overload that will be assigned as a direct consequence of the XXX project for the net MW output studied in the applicable study year identified in Section 5.5. This is noted for this report. EPE did coordinate through XXX to address the overloading of the Green-AE 345/230 kv under the above N-1 condition. This overload will be examined in any follow up study for the XXX project. The results in Section 5.11 indicate that with the XXX project net MW of 300 MW at the Luna 345 kv bus), the angle range of the Arroyo PST is affected. Specifically, with a schedule of 201 MW N-S on the Arroyo PST an angle of degrees is required. This is near the angle range limit (of 34 degrees at one end) of the Arroyo PST. There were also some voltage violations caused by the XXX project. There were some undervoltage voltage violations at PNM buses in SNM in which PNM has planned system additions that would mitigate the low voltages caused by the XXX project. Generator Interconnection Feasibility Study 4 El Paso Electric Company

9 Some post-xxx project post-contingency thermal violations were observed on some SNM lines and transformers for some double contingencies (see Table 7, Section 5.7). However, in this report, it is assumed that the thermal violations during double contingencies will be used to help identify which elements get overloaded as a result of the XXX project. In this study, it will be assumed that XXX will not be required to build, add or modify elements showing a thermal violation for a double contingency (such as the ones showing up in Table 7) as a result of the XXX project; rather, these overload violations will help the owners of the these facilities identify what procedures or new automatic or manual operating procedures need to be in place as a result of the XXX project. In order to study the XXX project further, there were some cases developed in which cases 1-4 were examined without the third party generation labeled a-e previously. The results of the analysis on these cases revealed minor voltage violations caused by the XXX project and no overloading violations as a result of the XXX project. There are some future system additions in SNM that may help with the voltage violations observed. Total Costs Due to the XXX Project The total costs of the XXX project are the sum of the interconnection costs plus the costs of the NM system modifications to alleviate the impacts to the NM system because of the XXX project. These total costs are shown on Table A. Table A Estimated Total Costs: XXX Project Costs and Costs of SNM Facility Additions/Modifications Needed due to the XXX Project SYSTEM MODIFICATION COSTS YEAR ESTIMATED COST (2006$) XXX Generator Interconnection costs to the Luna 345 kv Bus 2009 $ 2,500,000 Total Costs to Interconnect the XXX Project $ 2,500,000 Note that is the report, the costs associated with adding a second Green-AE 345/230 kv transformer to relieve an overload caused by the XXX project in 2011 were not included in the costs assigned to the XXX project. Therefore, any equipment and related costs associated with and including a second Green-AE 345/230 kv transformer does not appear on Table A. However, this violation is noted for this report and may be included as a cost in the next XXX study. Generator Interconnection Feasibility Study 5 El Paso Electric Company

10 Note that a Static Var Compensator (SVC) device, described in Section 4.2.3, is a critical component that was modeled in this study as part of the XXX end of the XXX project and XXX costs. This SVC must be in place as part of the XXX project prior to the project s interconnection. It was assumed that this SVC was connected to the XXX 115 kv bus at the XXX substation. This MVAR SVC and associated equipment are estimated to cost $ 50,000-$ 100,000/MVAR for a total of $6,500,000 to $ 13,000,000. As an alternative to the SVC, if the inverters within the photovoltaic system are proven to be capable of producing reactive load (VARs) as designed, the SVC may be supplanted by inverters for the purpose of supplying VARs to the grid. The inverters are designed to produce 1 VAR for every 3-kW generated. Facilities determined to be needed to accommodate the XXX project net output of 180 MW will be required for 1 MW to 179 MW of net output from the XXX project. Facilities determined to be needed to accommodate the XXX project net output of 300 MW will be required for 181 MW to 299 MW of net output from the XXX project. Generator Interconnection Feasibility Study 6 El Paso Electric Company

11 2.0 PURPOSE The purpose of this Feasibility Study (FS) is to provide a fatal flaw feasibility analysis of the New Mexico (NM) and Arizona (AZ) transmission systems, determine any violations of criteria due to the XXX project described in the next section, recommend facilities needed to accommodate the XXX project, and provide associated non-binding good faith cost estimate for those facilities. As such, this Study will to identify potential major impacts associated with the XXX project. Generator Interconnection Feasibility Study 7 El Paso Electric Company

12 3.0 INTRODUCTION XXXXXXXXXXXXXXXXXX (XXX) has submitted a valid request for a generator interconnection to the EPE system. Therefore, as per the requirements of the Federal Energy Regulatory Commission (FERC) Large Generator Interconnection Procedures (LGIP), EPE is initiating a Feasibility Study (FS) to study the interconnection of a 300 MW Solar photovoltaic plant (the XXX project) to the Luna 345 kv Switching Station in Deming, NM ( the XXX Generator Interconnection ). This FS was performed in response to XXX s request to determine any impacts on the New Mexico (NM) and Arizona (AZ) systems including the El Paso Electric (EPE) system due to the interconnection of the XXX project that was studied at two net MW output levels. The cases modeled the net MW output from the XXX project as the following: 180 MW and 300 MW for the years 2009 and 2011, respectively. The output from the plant was scheduled to WECC. The XXX project was connected through a 115/345 kv, 340/360 MVA step-up transformer. Each case was studied using the criteria and methodologies described in subsequent sections of this study report. The study was performed as a joint analysis by EPE and Public Service Company of New Mexico (PNM). EPE, XXX, and PNM developed a Study Scope for this study (Appendix 1). This scope included the examination of different Scenarios for the XXX Generator Interconnection (see Base Case Development under Methodology). The study periods analyzed in this study were the 2009 Heavy Summer (HS) and 2011 HS load seasons. EPE and PNM did not analyze any other seasons with different import levels, load levels, and/or generation patterns in this FS. This Study was performed in order to identify potential major impacts associated with the XXX Generator Interconnection, to provide a preliminary view of the efforts, identify the facility additions and modifications to the NM system that will mitigate those impacts (remediations) that are a result of the XXX project for the scenarios outlined in the Study Scope (Appendix 1), and to provide good faith estimates of the costs that would be needed to achieve the XXX project with a good-faith estimate of the construction time. As part of the evaluation process in studying the impact of the XXX generation on the NM and AZ transmission systems, this FS included powerflow, Q-V reactive margin, and short circuit analyses. The study results were evaluated using contingency voltage and loading requirements and criteria under All-Lines-in-Service (ALIS), single contingency (N-1) conditions, double contingency (N-2) conditions, in addition to the reactive margin criteria identified in the sections that follow. However, this feasibility study does not include additional studies to validate the effectiveness of any proposed remediations. The impacts of the XXX project on the southern New Mexico (SNM) system were noted and included for the purposes of remediations and associated costs. Generator Interconnection Feasibility Study 8 El Paso Electric Company

13 The proposed interconnection point, Luna 345 kv Substation, is jointly owned by EPE, PNM, and TNMP. However, any proposed generation interconnection may affect any owner of the NM or AZ systems. As such, the impacts on the owners of the SNM system were focused on in this study. Besides EPE and PNM, the other owner of the SNM system is Tri-State Generation and Transmission Association, Inc. (TSGT). TNMP is owned by PNM. The criteria used for the AZ and NM systems appear in Table 1. It must be noted that this study was not meant to analyze every scenario that could occur on the SNM system with the XXX project since that approach would require more time. The study does not include transient stability analysis, economic evaluations for the reinforcement alternatives, detailed facility design, or equipment specification. This study was meant to analyze the primary boundaries around which the SNM system can operate, under the scenarios agreed to by EPE, XXX, and PNM. The modifications called for will allow the XXX project to interconnect to the NM system. 3.1 Performance Criteria This study shall adhere to the following minimum criteria as described below or as referenced in specified documents that are accessible through WECC. 1. The North American Electric Reliability Council (NERC)/WECC Planning Standards, December WECC Reliability Criteria for Transmission System Planning 3. WECC Voltage Stability Criteria, Undervoltage Load Shedding Strategy, and Reactive Power Reserve Monitoring Methodology. The reliability criteria standards used in performing this study are readily acceptable standards are listed in this report and in EPE s latest FERC Form 715 filing (Appendix 2). The XXX project in this analysis will not decrease the performance level beyond what is stated as acceptable in FERC Form 715. Any exception determined in the benchmark case, however, will not have a penalizing effect when evaluating the XXX project. This analysis was performed using the GE PSLF program. Pre-contingency flows on lines and transformers must remain at or below the normal rating of the element, and post-contingency flows on network elements must remain at or below the emergency rating. Flows above 100% of an element s rating are considered violations. If only one rating was given for an element, it was used as both the normal and emergency rating. The minimum and maximum voltages are specified in the appropriate FERC Form 715. Any voltage that does not meet criteria in the benchmark cases (without the XXX project) was considered an exception to the criteria for that specific bus and did not have a penalizing effect when evaluating the XXX project. Generator Interconnection Feasibility Study 9 El Paso Electric Company

14 The performance criteria utilized in monitoring the SNM and northern New Mexico (NNM) area are shown in Table 1. Table 1: Performance Criteria. AREA EPE LOS ALAMOS TSGT PNM TNMP AZ CONDITIONS LOADING LIMIT VOLTAGE (P.U.) VOLTAGE DROP COMMENTS kV and above Artesia 345 kv Normal < Normal Rating Arroyo 345 kv PS source side Alamo, Farmer, Rgc Lobo, Sierra Blanca and Van Horn 69kV kv to 115 kv % Artesia 345kV Contingency Arroyo 345kV PS source % side < Emergency Rating Alamo, Farmer, Rgc Lobo, Sierra Blanca and Van Horn 69kV % Hidalgo, Luna, or other 345 kv buses Normal < Normal Rating kV and above Contingency < Emergency Rating 6% 60kV and above Normal < Normal Rating kV and above Contingency < Emergency Rating kV and above Normal < Normal Rating kV and above 6 % 60kV and above Contingency < Emergency Luna, Mimbres, Hermanas, Rating 7 % Hondale, and Deming 115kV Normal < Normal Rating kV and above Contingency < Emergency Rating % 60kV and above Normal < Normal Rating kV and above Contingency < Emergency Rating % 100kV and above Voltage Violation Criteria The voltage criteria used in this study is shown in Table 1. All voltages 69 kv or above in cases with ALIS must have per unit voltages between 0.95 and 1.05 pu. Under contingency conditions, voltage drops cannot exceed the voltage drop criteria. For all cases during contingencies the per unit voltages cannot exceed 1.05 pu. Generator Interconnection Feasibility Study 10 El Paso Electric Company

15 3.1.2 Voltage Drop Violation Criteria The voltage drop criteria used in this study is shown in Table 1. It should be noted that the voltage drop criteria is specified as a percentage of the precontingency voltage. For example, if the pre-contingency voltage at the Luna 345kV bus is pu, and the voltage drops to pu during the contingency, the voltage drop would be 7%, calculated as: dv = (Vpre-Vpost) / Vpre = ( ) / = /1.030 = 7.0% Bus voltage drop (i.e. changes in bus voltages from pre- to post-contingency) must be less than defined on Table 1 for single contingencies and less than 10% for double contingencies PNM s additions and exceptions to the NERC/WECC criteria - Voltages For voltage levels above 1 kv, the minimum and maximum range is 0.95 p.u. and 1.05 p.u., respectively for N-1 contingencies. For N-2 and breaker failures the minimum voltage level is 0.90 p.u. The 46 kv system voltages are not monitored since the distribution primary voltages are monitored. Changes in bus voltages from pre- to post-contingency must be less than 6% with the exception of the Deming area, which is held to the southern New Mexico criterion of 7% voltage drop for N-1 outages. PNM allows no greater than a 10% voltage drop for N-2 and breaker failures outages TSGT s additions and exceptions to the NERC/WECC criteria - Voltages All voltages will be maintained between 0.95 and 1.05 pu for all lines in service. All voltages will be maintained between 0.90 and 1.10 pu for outage conditions. Changes in bus voltages from pre- to post-contingency must be no greater than 6% for Tri-State buses served from the PNM system for N-1 contingencies and no greater than 10% for N-2 contingencies. For TSGT buses served from the TSGT system, changes in bus voltages from preto post-contingency must be no greater than 8% for N-1 contingencies and no greater than 10% for N-2 contingencies. Generator Interconnection Feasibility Study 11 El Paso Electric Company

16 3.1.5 Loading Violation Criteria The loading criteria used in this Study were the WECC loading criteria. An element (transmission line, transformer) cannot be loaded to over 100% of its continuous/normal rating for an ALIS condition. During single or double contingency conditions, the element many not exceed 100 % of its emergency rating. All violations will be monitored and noted for the benchmark case (without the XXX project). Any flow which does not meet the criteria in that case will be considered an exception to the criteria for that specific element and will not have a penalizing effect when evaluating the XXX project. For elements outside of the EPE system, the loading criteria will be 100% of the capacity as listed in the powerflow basecase data Reactive Margin (Q-V) Criteria The load increase methodology, for determining reactive margins, outlined in the WECC Voltage Stability Criteria, Undervoltage Load Shedding Strategy, and Reactive Power Reserve Monitoring Methodology report was used to determine as the basis for the reactive margin criteria in this study. Using this methodology, EPE load was increased by 5% and the worst contingency was analyzed to determine the reactive margin on the system. The margin is determined by identifying the critical (weakest) bus on the system during the worst contingency. The critical bus is the most reactive deficient bus. Q-V curves are developed and the minimum point on the curve is defined as the critical point for this study. If the critical point of the Q-V curve is positive, the system is reactive power deficient. If it is negative, then the system has sufficient reactive power margin and meets the WECC criteria. For reactive capability analysis, only N-1 analysis was performed Arroyo Phase Shifting Transformer (PST) Maximum Angle Requirement The Arroyo PST maximum angle range shall not be exceeded in any case with the XXX project Criteria Violations Criteria violations will be identified and summarized in tabular form. All comparisons will be made on a relative performance basis (e.g. the change in line loading from the benchmark system cases to that those cases modeling the XXX project, stated in terms of percent of line rating) as well as an absolute basis (i.e., the percentage of overload or outside of voltage criteria). Results will be presented to show which, if any, thermal or voltage violations are caused or significantly exacerbated by the XXX project. Generator Interconnection Feasibility Study 12 El Paso Electric Company

17 4.0 METHODOLOGY 4.1 Assumptions The following assumptions are consistent for all study scenarios unless otherwise noted. Project dollar amounts shown are in 2006 U.S. dollars. The cost of the XXX Generator and associated equipment is separate and not included in this study. This study assumes that substation space is available for the system recommended modifications or will note assumptions taken in this regard. The cost estimates provided here include material, labor, and overhead costs for installing new equipment. There was no accounting for using spare equipment but it should strongly be considered. The practicality of the solutions and space limitations at each substation was of secondary concern in this study but should be examined in any further studies. 4.2 Procedure As previously mentioned, the analyses in this study include powerflow, Q-V, and short circuit analyses. Detailed discussions for each topic have been included in this report (for quick reference of any topic, refer to the Table of Contents). The following is a description of the procedures used to complete the analyses Base Case Development and Description of Cases without the XXX Project: Benchmark Cases Two (2) WECC GE format base case powerflow cases called the benchmark cases (i.e. cases without the XXX project) were jointly developed by EPE and PNM for this analysis. These benchmark cases reflect load forecast, transmission configuration upgrades in SNM and NNM, and facilities associated with each of the prior requestors interconnection projects for the years 2009 and Previous studies have shown that the summer season is most limiting for the SNM transmission system; as such, the study cases will be based on the latest WECC Heavy Summer cases for each of these years. These cases represent the boundaries in which the SNM and NNM system may operate with and without the XXX project. Generator Interconnection Feasibility Study 13 El Paso Electric Company

18 These cases consist of the following, Case 1 and Case 2: 2009 HS and 2011 benchmark cases consist of the base case with all third party generation ahead of the XXX project in the study queue. The third party generation included the following: a. 570 MW of generation interconnected at the Luna 345 kv Substation (scheduled to WECC). b. 141 MW of generation interconnected at Afton 345 kv Substation (scheduled through the Arroyo Phase Shifting Transformer (PST) south-to-north to PNM and reducing San Juan generation). c. 160 MW of generation interconnected at TNMP s Hidalgo 115 kv substation (scheduled to WECC). d. 80 MW of generation interconnected at TNMP s Lordsburg 115 kv substation (scheduled to WECC). e. 94 MW of generation interconnected at Afton 345 kv Substation (scheduled to WECC). In addition to the third party generation above, the study assumes that all EPE local generators are online, the schedule at the Eddy County dc-tie in 200 MW east-to-west (133.3 MW for EPE, 66.7 MW to TNMP), and that EPE s Newman 5 generation is interconnected at the Newman 115 kv bus.. In the 2009 HS benchmark case (Case 1), this new generator is modeled as a gas turbine generator with a net MW output of 70 MW. In the 2011 HS benchmark case (Case 2), this new generator is modeled as a gas turbine generator with a net MW output of 123 MW and a steam turbine generator with a net MW output of 90 MW (in a combined cycle arrangement). The additions and modifications assumed to be associated with the above Newman 5 modeling are the following: 1. Add 2nd Arroyo 115/345 kv auto transformer (modeled in the 2009 and 2011 HS benchmark cases). 2. Add 3rd Caliente 115/345 kv auto transformer (modeled in the 2009 and 2011 HS benchmark cases). 3. Reconductor Newman-Shearman 115 kv line from ACSR to 795 ACSR conductor (modeled in the 2011 HS benchmark case). 4. Reconductor Newman-FB2-GR-Vista 115 kv line from ACSR to 795 ACSR conductor (modeled in the 2011 HS benchmark case). 5. Add a 2nd Milagro 115/69 kv autotransformer (modeled in the 2011 HS benchmark case). There were two additional system additions modeled in the benchmark cases: Generator Interconnection Feasibility Study 14 El Paso Electric Company

19 6. Reconductor Austin-Dyer 69 kv line from 4/0 CU to ACSR conductor (modeled in the 2011 HS benchmark case). 7. Add 3rd Diablo 115/345 kv auto transformer (modeled in the 2009 and 2011 HS benchmark cases). Because Item 7 is not associated with the additions and modifications assumed with Newman 5, the need for a third Diablo 345/115 kv autotransformer was examined as a sensitivity case in Section 5.6. The additions and modifications above are needed prior to the XXX project modeled as on in any case. Because these additions and modifications are needed before the XXX project is modeled, these will be considered an exception to the criteria, will not have a penalizing effect when evaluating the XXX project, and the cost to correct them will not be charged to the XXX project. All cases were evaluated with the Arroyo PST in-service. All cases included 141 MW of generation interconnected at Afton 345 kv Substation (scheduled through the Arroyo PST south-to-north). Given that the Arroyo PST schedule is usually 201 MW without Afton generation on, the cases modeled an Arroyo PST schedule of 201 MW -141 MW = 60 MW north-to-south reflecting PNM s previous transmission purchase from Afton-to- Westmesa (see Table 2, next, for schedule details). Table 2. Arroyo PST Schedule* SCHEDULING ENTITY 60 MW N-S (WESTMESA TO ARROYO) ARROYO PST SCHEDULE 201 MW N-S (WESTMESA TO ARROYO) ARROYO PST SCHEDULE EPE (OATT) EPE (SSI) TSGT PNM PNM (AFTON GENERATION THROUGH ARROYO PST TO PNM) WAPA -2-2 * Negative denotes Westmesa to Arroyo schedule. Positive denotes Arroyo to Westmesa schedule. The Arroyo PST angle setting in each case is included in this report in Section 5.12 in order to document that Arroyo PST maximum angle criteria was not exceeded. Generator Interconnection Feasibility Study 15 El Paso Electric Company

20 4.2.2 Base Case Development and Description of Cases with the XXX Project Modeled With the benchmark cases developed the XXX project was added to the benchmark cases and two (2) additional WECC GE format base case powerflow cases were developed in order to determine which impacts resulted from this generator interconnection. The XXX project was modeled in powerflow using data supplied by the XXX consultant. Note that the cases with the XXX project are based on the benchmark cases. As such, the facility additions and modifications described in the previous section (items 1-7) appear in the cases with the XXX project modeled. However, the costs of these facility additions and modifications will be separated from the costs of facilities due to the XXX project. Note that all cases modeling the XXX project included the third party generation described in Section These two cases with the XXX project modeled and with the Arroyo PST in-service with a schedule of 60 MW north-to-south consist of the following: Case 3: 2009 Heavy Summer (HS) benchmark case with the XXX project modeled with the net output from the XXX project at 180 MW (as metered at Luna 345 kv). The output is scheduled to WECC in the cases. Case 4: 2011 Heavy Summer (HS) benchmark case with the XXX project modeled with the net output from the XXX project at 300 MW (as metered at Luna 345 kv). The output is scheduled to WECC in the cases. Generator Interconnection Feasibility Study 16 El Paso Electric Company

21 4.2.3 Modeling of the XXX Project in the Cases The XXX model was further refined and the model was agreed to by EPE, XXX, and PNM. According to the Study Scope the Project was to provide for real and reactive power losses up to the point of interconnection to 345 kv grid. This was interpreted to mean that for ALIS, the powerflow model for the XXX project would output the net MW amounts described next for their respective year and zero MVAR at the Luna 345 kv bus). In addition, the ability of the XXX project to have the capability to achieve the delivery of 97.8 % power factor requirement to the system (during outages) was placed on the XXX project powerflow model. This requirement was agreed to by EPE and XXX in a Scoping Meeting for the XXX generator Interconnection that took place in late February During this meeting, it was felt that the XXX project should have no impact on the SNM and NNM systems and the way to achieve this was to place a power factor requirement on the XXX project so that it can contribute MVAR to the system. A Static VAR Compensator (SVC) was modeled at the original XXX plant. The size of the SVC was determined by calculating the MVAR component from the 300 MW net output in order to achieve a 97.8 % power factor (64 MVAR) and adding the MVAR requirement when the XXX output was 300 MW to achieve 0 MVAR at the Luna 345 kv bus (66 MVAR, from the powerflow under ALIS). This resulted in a SVC size of 130 MVAR lagging (64 MVAR + 66 MVAR) and with a minimum reactive capability limit of 0 MVAR (based on preliminary study work). The model provided by XXX included modeling of loads at the XXX plant. To provide for the XXX loads and losses from the XXX 115 kv bus to the Luna 345 kv bus, the output of the XXX project was set to a gross MW output consisting of the net MW output needed at the Luna 345 kv bus plus auxiliary loads plus any other losses occurring between the XXX 115 kv bus and the Luna 345 kv bus such that the net MW output at the Luna 345 kv bus from the XXX project was 180 MW and 300 MW for the years 2009 and 2011, respectively. The complete model for the XXX project consisted of a generator connected to a XXX 115 kv bus with a gross output of MW and 21.1 MVAR in the 2009 case and with a gross output of MW and 66 MVAR in the 2011 case. The generator had a QMAX limit of 135 MVAR reflecting the SVC previously described. The XXX plant loads were modeled on the XXX 115 kv bus as 18.5 MW and 7.3 MVAR in 2009 and 31.5 MW and 20.9 MVAR in The generator and the loads were connected through a 115/345 kv step-up transformer with a normal rating of 340 MVA and emergency rating of 360 MVA. From here the XXX 345 kv bus was connected to the Luna 345 kv interconnection point through a short line (this line is called the Luna-XXX 345 kv line in this study). Appendix B of the Study Scope (Appendix 1) contains preliminary data supplied by XXX. The SVC device described above and its cost will be discussed in Section 8.1, as it is a critical component of the XXX project. Generator Interconnection Feasibility Study 17 El Paso Electric Company

22 4.2.4 Sensitivity Cases with XXX Project Modeled There were other cases (sensitivity cases) developed as part of this study in order to examine other system conditions that merit study and also in order to perform an analysis of the reactive margin at selected buses for a set of system conditions. Because there was a need to examine the addition of a third 345/115 kv autotransformer at EPE s Diablo Substation (as assumed in the 2009 and 2011 cases used in this study, see Section 4.2.1), there was a sensitivity case examined in which this third autotransformer is not in the case. The results of this sensitivity are covered in Section 5.6. Another set of sensitivity cases had the Arroyo PST angle setting in each case at different Arroyo PST schedules and is included in this report in Section 5.12 in order to document that Arroyo PST maximum angle criteria was not exceeded. Also examined, is a sensitivity in which all third party generation specified in Section is turned off and the effects of the XXX project are examined. This sensitivity was examined with two Diablo 345/115 kv autotransformers modeled. This analysis is included in Section Powerflow Analysis Methodology A relative approach was used in the powerflow analysis in order to determine the impact of the XXX project on the performance of the SNM transmission system. First, performance of the benchmark system, without the XXX project, was evaluated in order to establish the baseline. The cases without the XXX project were evaluated with alllines-in-service (ALIS) for both loading and voltage criteria violations. Next, single and double contingency powerflow analysis was performed on these benchmark cases by taking single and double contingencies on most lines and transformers with base voltages of 100 kv and above in the SNM area and 69 kv and above in the EPE area as determined by engineering judgment (see Section 4.2.6). All bus, lines, and transformers with base voltages greater than or equal to 60 kv in the New Mexico area including the EPE control area were monitored in all study cases. All generators were modeled with regard to self-regulating or remote bus regulating as they are modeled in the submitted WECC GE format powerflow data. All generators which control a high side remote bus will be set at the pre-disturbance voltage at the terminal bus. The single and double contingencies were taken one at a time. When modeling a single or double contingency involving an autotransformer or line that is connected to the Luna 345 kv bus (e.g. any 345 kv line connected to the Luna 345 kv bus: Springerville-Luna, Luna-Arroyo, Luna- Hidalgo, Luna-Newman, and/or the Luna 345/115 kv autotransformer), the XXX unit was modeled in two separate ways: 1) as tripped, outage takes out the XXX project simultaneously, and 2) as not tripped, outage does not take out the XXX project. Engineering judgment was used to determine if the XXX project unit was also tripped for a single or double contingency involving any other element(s) in the system. Generator Interconnection Feasibility Study 18 El Paso Electric Company

23 For pre-contingency solutions, transformer tap phase-shifting transformer angle movement and static VAR device switching was allowed, as was tap changing under load (TCUL) tap changing ratio adjustment and area interchange control. For each contingency studied, the contingency was studied with all regulating equipment being fixed at pre-contingency positions (transformer controls and switched shunts). This was achieved by setting all solve options to zero (up to 50 solution iterations were allowed with 3 iterations before VAR limits). For the cases with the XXX project included, the performance analysis, described for the benchmark cases, was repeated. Next, for the sensitivity cases (with the XXX project included) the analysis procedure described in the section covering each sensitivity was used. The results for the cases with the XXX project were evaluated against the baseline to determine criteria violations in the NM systems that resulted from the XXX project List of Contingencies The same contingencies were evaluated for all cases and are identified in Appendix 4. Note that the list contains both single (N-1) and double (N-2) contingencies. Most of the double contingencies were breaker failure contingencies. For these breaker failure contingencies, if a power circuit breaker at a substation fails to open during a fault, secondary zone relay protection and breaker operation comes into play taking out the two transmission elements on each side of the failing (stuck) circuit breaker so as to remove the fault from the bus affected. Based on engineering judgment, all contingencies taken were selected because they are the ones most likely to stress the SNM system. After an additional evaluation of the Arizona system representation, there were some single-contingencies involving lines in southeastern Arizona added to the analysis. These are included in Appendix 4. There were three single contingencies involving PNM/TNMP 115 kv lines in SNM executed as part of the study that required the modeling of an automatic operating procedure called a remedial action scheme (RAS) that is used to relieve certain voltage and/or overloading that may occur on elements affected by the specific single contingency. In this study the following RAS procedures were assumed. 1. For the outage of the Hidalgo-Lordsburg 115 kv line with the Lordsburg generation operating, the Lordsburg 115/69 kv transformer is tripped when the transformer loading is greater than 33.5 MVA. 2. For the outage of the Hidalgo-Turquoise 115 kv line, the industrial load at Turquoise is tripped. This involves tripping the Turquoise-PDTyrone 115 kv line. Generator Interconnection Feasibility Study 19 El Paso Electric Company

24 3. For the N-2 (breaker failure or otherwise) outage of the Central-Hurley-Luna 115 kv line and the Central-Turquoise 115 kv line, the industrial load served from Central 115 kv along with the shunt capacitor at Central 115 kv will be tripped. This involves tripping the Hurley-Chino and Central-Ivanhoe 115 kv lines and the Central 115 kv capacitor Short Circuit Analysis Short circuit studies were performed with and without the XXX project. These consisted of substation three phase and single phase-to-ground bus fault simulations at the Luna 345 and 115 kv Substations as well as those substations with direct 345 kv or 115 kv transmission line connections into it. The objective was to make certain that the existing substation breakers would safely accommodate fault currents for either scenario. The analysis identified all breakers whose ratings were exceeded. The short circuit analysis results are covered in Section 7. Generator Interconnection Feasibility Study 20 El Paso Electric Company

25 5.0 POWERFLOW ANALYSIS RESULTS 5.1 All-Lines-in-Service (ALIS) Analysis Results for Overloaded Elements Benchmark Cases (without the XXX Project) Each of the cases with system benchmark conditions (without the XXX project) as described in Section was examined with all lines in service (ALIS). Table 3 shows the base case overloads present in the cases without the XXX project. Table 3. Pre-Contingency Thermal Violations, Benchmark Conditions Element Case Owner Rating(MVA) % Loading Blythe-Buckblvd 161 kv Line 2011 HS AZ Blk Mesa 230 kv/bma.3wp3 100 kv Transformer 2011 HS AZ Blk Mesa 230 kv/bma.4wp3 100 kv Transformer 2011 HS AZ Cholla 345 kv/ Cholla kv Transformer 2011 HS AZ Cholla 230 kv/ Cholla kv Transformer 2011 HS AZ N.Havasu 230 kv/n.hav3wp 100 kv Transformer 2011 HS AZ Tucson 138 kv/tuc.3wp 100 kv Transformer 2011 HS AZ Blythe-Buckblvd 161 kv Line 2011 HS AZ Blk Mesa 230 kv/bma.3wp3 100 kv Transformer 2011 HS AZ Table 3 shows the overloaded element, element owner, and element rating and the benchmark case in which the thermal overload occurred. The percent loading on the element, based on the element rating, is indicated in the rightmost column and includes the range of overloading without the XXX project. There were some Arizona elements loaded above their normal and/or emergency rating. These overloads included one line and five transformers. Since the violations listed in Table 3 were found to occur in the case before the XXX project was modeled, they will be considered an exception to the criteria, will not have a penalizing effect when evaluating the XXX project, and the cost to correct them will not be charged to the XXX project. 5.2 Single-Contingency (N-1) Analysis Results for Overloaded Elements Benchmark Cases (without the XXX Project) The benchmark cases as described in Section were examined under single contingency conditions. Table 4 shows the base case post-contingency overloaded SNM elements present in the cases without the XXX project under N-1 conditions. If an element (line or transformer) was overloaded under pre-contingency (ALIS) conditions, it was considered a pre-contingency overload and was not included in Table 4. Generator Interconnection Feasibility Study 21 El Paso Electric Company

26 Table 4 shows the overloaded element and element rating. The percent loading range on the element, based on the element rating, is listed next, and the contingency condition is indicated in the rightmost column. Table 4. Post-Contingency (N-1) Thermal Violations, Benchmark Cases, SNM Elements Element Case Owner Lordsbrg 115/69 Kv Transformer 2009 HS PNM/ TNMP Lordsbrg 115/69 Kv Transformer 2011 HS PNM/ TNMP Central-Silver 69 kv Line 2011 HS PNM/TN MP Rating (MVA) Leo-Milagro 69 kv Line 2009 HS EPE % Loading Contingency Description Hidalgo-Turquoise 115 kv Line (RAS) Hidalgo-Turquoise 115 kv Line (RAS) Turquois 115/69 kv Transformer Milagro-Newman 115 kv Line As shown in Table 4, some pre-xxx project post-contingency thermal violations were observed on some SNM lines and transformers. These contingency criteria violations listed in Table 4 will not have a penalizing effect on the evaluation of the XXX project. 5.3 Double-Contingency (N-2) Analysis Results for Overloaded Elements Benchmark Cases (without the XXX Project) The benchmark cases as described in Section were examined under double contingency conditions. Table 5 shows the base case post-contingency overloaded SNM elements present in the cases without the XXX project under N-2 conditions. If an element (line or transformer) was overloaded under pre-contingency (ALIS) conditions, it was considered a pre-contingency overload and was not included in Table 5. Table 5 shows the overloaded element and element rating. The percent loading range on the element, based on the element rating, is listed next, and the contingency condition is indicated in the rightmost column. As shown in Table 5, some pre-xxx project post-contingency thermal violations were observed on some SNM lines and transformers. These contingency criteria violations listed in Table 5 will not have a penalizing effect on the evaluation of the XXX project. EPE did coordinate through XXX to make arrangements with AZ for the study of the overloading of these elements under the above N-1 conditions to verify if these elements are overloaded. These overloads will be examined in any follow up study for the XXX project. Generator Interconnection Feasibility Study 22 El Paso Electric Company