120 MW SOLAR-THERMAL PLANT GENERATOR INTERCONNECTION FEASIBILITY STUDY. May 2008 Prepared by: EL PASO ELECTRIC COMPANY

Transcription

1 . 120 MW SOLAR-THERMAL PLANT GENERATOR INTERCONNECTION May 2008 Prepared by: EL PASO ELECTRIC COMPANY

2 Foreword This report was prepared for XXXXXXXXXXXXXXXXXXX by System Planning at El Paso Electric Company. Any correspondence concerning this document, including technical and commercial questions should be referred to: Dennis Malone Manager System Planning Department El Paso Electric Company P.O. Box 982 El Paso, Texas Phone: (915) Fax: (915) Study Performed by: Joaquin Aguilar Principal Engineer GENERATOR INTERCONNECTION i MAY 2008

3 TABLE OF CONTENTS 1.0 Executive Summary...Page Introduction...Page Performance Criteria...Page Methodology...Page Assumptions...Page Procedure...Page Base Case Development and Description of Cases...Page List of Contingencies...Page Q-V Analysis...Page Short-Circuit Analysis...Page Powerflow Analysis Results...Page Sensitivity Studies...Page A Ft. Craig PST Schedule at 201 MW...Page B Ft. Craig PST Schedule at -30 MW...Page Voltage Analysis Results...Page Q-V Analysis Results...Page Short-Circuit Analysis Results...Page Cost Estimates...Page Disclaimer...Page Certification...Page 31 GENERATOR INTERCONNECTION ii MAY 2008

4 APPENDICIES Generation Interconnection Feasibility Study Scope...Appendix 1 Overload Tables...Appendix 2 EPE s FERC Form 715 Filing...Appendix 3 List of Contingencies...Appendix 4 Q-V Plots...Appendix 5 XXXXX Powerflow and Short-Circuit Modeling Data...Appendix 6 One-Line Maps...Appendix 7 Burns & McDonnell Cost Estimates...Appendix 8 GENERATOR INTERCONNECTION iii MAY 2008

5 1.0 EXECUTIVE SUMMARY The XXXXXXXXXXXXXXXXXXX (XXXXX) submitted a request for a generator interconnection to the El Paso Electric Company (EPE) transmission system. Therefore, as per the requirements of the Federal Energy Regulatory Commission (FERC) Large Generator Interconnection Procedures (LGIP), EPE initiated a Generator Interconnection Feasibility Study (GIFS) to study the impact of the interconnection. A Study Scope Agreement (Appendix 1) between XXXX and EPE was signed on January 14, 2008 defining what the GIFS would encompass. The concentrated solar power plant consisting of two steam driven generators of 67 MW each will be connected to EPE s Luna 345 kv Substation in Deming, NM. A two mile, 2156 kcmil ACSR, 345 kv transmission line will connect the generation site to the Luna Substation 345 kv bus. Each generator will employ a 345/13.8 kv, 51/67.83/84.78 MVA, step-up transformer. The interconnection generators are planned to be in service on December 1, XXXX (Lunasol) Generation Site GENERATOR INTERCONNECTION 1 MAY 2008

6 GENERATOR INTERCONNECTION 2 MAY 2008

7 In April 2008, EPE completed the GIFS for XXXX which determined all impacts to the EPE system and southern New Mexico area and to a lesser degree the Arizona area. A 2012 powerflow case was developed for powerflow analysis that included two generation interconnection projects ahead of the XXXX Project. One of those generation interconnection projects was in the System Impact Study Phase (500 MW) and the other one was in the Feasibility Study Phase (990 MW). System improvements necessary to accommodate the 990 MW generation interconnection project had not been fully defined when the XXXX Study commenced. Consequently, preliminary estimated system improvements for the 990 MW project were modeled in the study case. As an Affected System under the LGIP, Public Service Company (PNM) of New Mexico assisted in reviewing the case data and results. The two generation interconnection projects ahead of the XXXX Project as well the XXXX Project have been modeled in this study such that the generation from these projects is sold to all entities (and no specific one) in the Western Electricity Coordinating Council (WECC) system. Consequently, no specific transmission path for energy sales has been defined nor does this study guarantee a transmission path will be available when the generator is constructed. Powerflow results showed that overload and voltage criteria violations occur in the southern New Mexico and Arizona systems without the addition of the XXXX Project. The addition of the XXXX project aggravates the situation slightly in most cases but is not the cause of the criteria violations. The criteria violations in the southern New Mexico system can be attributable to the generation interconnection projects ahead of the XXXX Project and these projects are expected to make the necessary system improvements to rectify the violations. It is expected that the added system improvements by the interconnection projects ahead of XXXX will include enough remaining capacity to absorb the impacts from the XXXX Project. If the XXXX Project should continue to the System Impact Study Phase, this expectation will be further investigated. Overloads in the Arizona area are also not attributable to the XXXX Project but for the most part are a result of inadequate system modeling by Arizona utilities in the Western Electricity Coordinating Council beginning powerflow case. Fault study results showed that several substation circuit breakers exceeded their capabilities without the XXXX Project in service. The XXXX Project adds to the available fault currents but is not the cause for exceeding the short circuit capabilities of the breakers. Circuit breaker upgrades are expected to be supplied by the two generation interconnection projects ahead of the XXXX Project and not by XXXX. The estimated powerflow system improvements used in the study case for the 990 MW generation interconnection project included significant VAR support. As such, the XXXX Project benefited from it. Q-V VAR margin study results showed that with the XXXX Project in service there is more than adequate VAR margin on all buses monitored under all lines in service and contingency conditions. The overall study results for this Feasibility Study Phase of the XXXX Project showed that the only system improvement that XXXX will be responsible for (other than their generation site and transmission line) is the expansion of the Luna 345 kv Substation to accommodate the termination of their 345 kv transmission line. This is based on the assumption that the two GENERATOR INTERCONNECTION 3 MAY 2008

8 generation interconnection projects ahead of the XXXX Project will be implemented and projected system representations by all utilities in the 2012 powerflow case are implemented as planned. Consequently, this study satisfied the request for Energy Resource and Network Resource Interconnection Services. According to the FERC LGIP, a restudy of the XXXX Project (at XXXX s expense) will need to be conducted if either of the two generation interconnection projects ahead of the XXXX Project should drop out. Burns & McDonnell cost estimate for the expansion of the Luna 345 kv bus to accommodate the line termination for the XXXX interconnection is $2,837,000 in 2008 dollars. The Project completion will take 15 months after authorization to begin work. Cost estimate details are included in Appendix 8. No cost estimates were provided for the generation site and associated transmission interconnection line to the Luna 345 kv Substation in this Feasibility Study Phase as requested by XXXX. GENERATOR INTERCONNECTION 4 MAY 2008

9 2.0 INTRODUCTION The XXXX XXXXXXXXXXXXXXXXXX (XXXX) of XXXXXXXXXXXXX is proposing to interconnect to the southern New Mexico transmission system at EPE s Luna 345 kv Substation. The generation interconnection will consist of a solar-thermal generation plant with an in-service date of December 1, The concentrated solar power plant, consisting of two steam driven generators of 67 MW each, will be connected to EPE s Luna 345 kv Substation in Deming, NM. A two mile, 2156 kcmil ACSR, 345 kv transmission line will connect the generation site to the Luna Substation 345 kv bus. Each generator will employ a 345/13.8 kv, 51/67.83/84.78 MVA, step-up transformer. As per the requirements of the Federal Energy Regulatory Commission (FERC) Large Generator Interconnection Procedures (LGIP), EPE initiated a Generator Interconnection Feasibility Study (GIFS) to study the impact of the interconnection. EPE conducted powerflow, VAR margin and short-circuit analyses. PNM contributed by reviewing the system modeling and study results. In April 2008, El Paso Electric Company (EPE) completed the GIFS for XXXX which determined all impacts to the EPE system and southern New Mexico area and to a lesser degree the Arizona area. A 2012 powerflow case was developed for powerflow analysis that included two generation interconnection projects ahead of the XXXX Project. One of those generation interconnection projects was in the System Impact Study Phase (500 MW) and the other one was in the Feasibility Study Phase (990 MW). System improvements necessary to accommodate the 990 MW generation interconnection project had not been fully defined in the XXXX Study case because the 990 MW generation interconnection study had just begun. Consequently, preliminary system improvements for the 990 MW project were estimated. The two proposed 345 kv lines from Ft. Craig to BA in the 990 MW generation interconnection project will be reevaluated in the System Impact Study Phase using an alternative configuration developed by PNM (if the project continues to the next phase). Also, as previously noted, a re-study of this XXXX Project would need to be conducted if any of the generation interconnection projects ahead of the XXXX project decide not to pursue their projects any further. 2.1 PERFORMANCE CRITERIA The reliability criteria standards used by EPE in performing this Study are readily acceptable standards and are listed in Section 4 of EPE s FERC Form 715 (Appendix 3). The powerflow analysis was performed using the GE PSLF program. For pre-contingency solutions, transformer tap phase-shifting transformer angle movement and static VAR device switching was allowed. For each contingency studied, all regulating equipment (transformer controls and switched shunts) was fixed at pre-contingency positions. All buses, lines, and transformers in the El Paso and surrounding New Mexico control areas with base voltages of 69 kv and above were monitored. 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. The minimum and maximum voltages are specified in EPE s FERC Form 715. Voltages that did not GENERATOR INTERCONNECTION 5 MAY 2008

10 meet criteria in the benchmark cases were considered an exception to the criteria for that specific bus and did not have a penalizing effect when evaluating the XXXX generation interconnection. The performance criteria utilized in monitoring the EPE and New Mexico areas are shown in Table 2-1. The voltage drop criteria are specified as a percentage of the pre-contingency 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% Area EPE PNM TSGT Conditions Normal Contingency Normal Contingency Normal Contingency Table 2.1: Performance Criteria. Loading Limit < Normal Rating < Emergency Rating < Normal Rating < Emergency Rating < Normal Rating < Emergency Rating Voltage Voltage (p.u.) Drop Comments kV and above Artesia 345 kv Arroyo 345 kv PST source side Alamo, Sierra Blanca and Van Horn 69kV % 60 kv to 115 kv % Artesia 345kV % Arroyo 345kV PST source side Alamo, Sierra Blanca and Van Horn 69kV % Hidalgo, Luna, or other 345 kv buses * Above 1 kv with ALIS 46 kv buses not monitored * 6% Above 1 kv 7% for Deming area only All voltages with ALIS % All voltages for N-1 contingency conditions * Voltage limits are 0.95 p.u. to 1.10 p.u. at Guadalupe and Taibanmesa 345 kv stations. GENERATOR INTERCONNECTION 6 MAY 2008

11 3.0 METHODOLOGY 3.1 Assumptions The following assumptions are consistent for all study scenarios unless otherwise noted. System improvement dollar amounts shown are in 2008 U.S. dollars. The cost of the XXXX generators, associated equipment, and transmission line interconnection is separate and not included in this study. This study assumes that space is available in the EPE substations where the system upgrades are recommended to be installed. This study did not analyze any transmission service from the interconnection point to any specific point on the grid. It determined system upgrades necessary to deliver the proposed XXXX output uniformly into the entire WECC transmission grid. 3.2 Procedure The analyses in this study included Powerflow, Q-V, and Short-Circuit. Detailed discussions for each topic are included in this report. A description of the procedures used to complete the analyses is shown below Base Case Development and Description of Cases A heavy summer load 2012 WECC powerflow case was used with the below modifications to establish a benchmark case without the XXXX Project. Benchmark Case: The 2012 benchmark case included the following third party generation: MW of generation (Luna Energy Facility) interconnected at the Luna 345 kv bus and scheduled to the WECC grid MW of generation (Afton CT) interconnected at the Afton 345 kv Substation and scheduled to the PNM area through the Arroyo PST in a South-to-North direction MW of generation (Pyramid) interconnected at PNM s Hidalgo 115 kv Substation and scheduled to the WECC grid MW of generation (Lordsburg) interconnected at PNM s Lordsburg 115 kv Substation and scheduled to the WECC grid MW of generation (Afton ST) interconnected at the Afton 345 kv Substation and scheduled to the WECC grid MW of generation interconnected at EPE s Artesia-Amrad 345 kv line MW of generation interconnected to the EPE and PNM systems in southern New Mexico. GENERATOR INTERCONNECTION 7 MAY 2008

12 Generation Interconnection Case: The XXXX Generation Interconnection case modeled the benchmark case described above with the proposed XXXX generation in service. The XXXX generation output was modeled at 134 MW with 14 MW dedicated to station service List of Contingencies The list of contingencies has been included in Appendix 4. Based on engineering judgment, these contingencies were selected because they represent a good cross section of potential contingencies that would stress the EPE system and PNM s southern New Mexico system. Double contingencies were also analyzed but only for informational purposes to identify potential problem areas QV Analysis Q-V analyses were performed to verify that the WECC criteria for reactive power margin will be met under the worst contingencies on the EPE system. A procedure developed by WECC was used to determine the reactive power margin. As outlined in this procedure, 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. 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. Prior experience has shown that the worst contingencies impacting reactive power margin are the Springerville-Luna, Luna-Diablo, and Greenlee-Hidalgo 345 kv lines and the buses most impacted are the 345 kv buses at Arroyo, Newman, Caliente, Diablo, Luna, and Hidalgo. All these contingencies and more were analyzed for Q-V margin. The Q-V results are shown on page 24 and the plots for these analyses can be seen in Appendix Short-Circuit Analysis Short-circuit analyses were performed with and without the XXXX generation interconnected into the EPE control area. These consisted of substation three phase to ground, two phase to ground, phase to ground, and phase to phase faults. Fault simulations were conducted at several 345 kv and 115 kv buses as shown in the short-circuit analysis table starting on page 27. The objective of these analyses was to determine the incremental fault current contribution from the XXXX generation interconnection and determine if the existing substation breakers in the surrounding area will safely accommodate this additional fault current without exceeding their interruption ratings. The Short-Circuit Analysis report can be found on page 27. GENERATOR INTERCONNECTION 8 MAY 2008

13 4.0 POWER FLOW ANALYSIS RESULTS Powerflow study results for the EPE load area showed that the EPE Arroyo-Las Cruces 115 kv line overloads to 104.4% of normal rating without the XXXX Project being modeled in the system and with all lines in service. However, when the XXXX Project was modeled in the system, the overloading of the line dropped to 103.2% of normal rating. Consequently, reconductoring of this line will not be assigned to the XXXX Project but rather to one of the generation interconnection projects ahead of the XXXX Project. With all lines in service, the southern New Mexico transmission system showed no overloads. In the Arizona area with all lines in service, overloading (101.2% of normal rating) of the Shiprock 345/230 kv transformer occurs with the addition of the XXXX Project. However, in the case without the XXXX Project the Shiprock transformer overloads (115% of emergency) under the Springerville-Coronado 345 kv line outage. Consequently, the remedial solution to this overload will not be assigned to the XXXX Project. Also, there were a number of other overloaded elements in the Arizona transmission system. All of these Arizona overloaded elements can be tracked to being caused as a result of the 990 MW generation interconnection project, the 500 MW generation interconnection project or as existing in the 2012 WECC beginning powerflow case. The Arizona area overloads occur without the XXXX Project in service and are very slightly aggravated (less than 1% increase) in the majority of cases when the XXXX Project is added in the powerflow case. In the cases where the % delta overloads impact of the XXXX Project exceeded 1%, a summary of these impacts is shown in the table below that compares the benchmark case (no XXXX Project) with the case that includes the XXXX Project. ARIZONA AREA - ALL LINES IN SERVICE OVERLOADS 2012 BENCHMARK CASE - NO XXXX 2012 CASE WITH XXXX % OF % OF % FROM TO NORMAL FROM TO NORMAL OVERLOADS BUS KV BUS KV RATING AREA/S BUS KV BUS KV RATING AREA/S DELTA GREEN-SW 230 GREEN-SW AZ GREEN-SW 230 GREEN-SW AZ 1.7 CHOLLA 500 SAGUARO AZ CHOLLA 500 SAGUARO AZ 1.1 CHOLLA 345 PRECHCYN AZ CHOLLA 345 PRECHCYN AZ 1.3 COPPERVR 345 COPPERVR AZ COPPERVR 345 COPPERVR AZ 1.4 SHIPROCK 230 SHIPROCK AZ SHIPROCK 230 SHIPROCK AZ 2.2 If the generation interconnection projects ahead of the XXXX Project provide for system improvements to relieve the overloading with enough capacity to absorb the delta overloads shown in the above table, XXXX will not be expected to provide additional system improvements. However, if the added improvements are barely enough to address the overloads, XXXX will be responsible for any necessary added improvements. If this should happen, the issue of overloads in the Arizona system will have to be addressed by XXXX directly with the GENERATOR INTERCONNECTION 9 MAY 2008

14 appropriate Arizona entity if the project should move forward. No cost figures for any remedies in the Arizona system have been provided in this study. Powerflow results for contingency scenarios (see Appendix 4 for list of contingencies) also exhibited similar results as in the all lines in service case. That is, in many of the scenarios, overloads existed prior to the addition of the XXXX Project. The impact of adding the XXXX Project in many of the contingency scenarios was to aggravate the overloading by less than 1%. In some contingencies, there were some transmission element overloads that were aggravated over 1% because of the XXXX Project and are shown in the following tables BENCHMARK CASE - NO XXXX - CONTINGENCY SET # CASE WITH XXXX - CONTINGENCY SET #1 % OF % OF % OVER- FROM TO EMERG. FROM TO EMERG. LOADS BUS KV BUS KV RATING AREA/S BUS KV BUS KV RATING AREA/S DELTA GREENLEE 345 HIDALGO EPE/NM GREENLEE 345 HIDALGO EPE/NM 5.2 LUNA 115 HURLEY_# EPE/NM LUNA 115 HURLEY_# EPE/NM 8.4 LUNA 345 LUNA EPE/NM LUNA 345 LUNA EPE/NM 6.6 MD 115 HURLEY_# EPE/NM MD 115 HURLEY_# EPE/NM 7.6 BLK MESA 230 BMA.3WP AZ BLK MESA 230 BMA.3WP AZ 5.5 COPPERVR 345 COPPERVR AZ COPPERVR 345 COPPERVR AZ 2.1 GREEN-SW 230 GREEN-SW AZ GREEN-SW 230 GREEN-SW AZ 1.8 GREENLEE 345 HIDALGO AZ GREENLEE 345 HIDALGO AZ 5.2 SHIPROCK 230 SHIPROCK AZ SHIPROCK 230 SHIPROCK AZ BENCHMARK CASE - NO XXXX - CONTINGENCY SET # CASE WITH XXXX - CONTINGENCY SET #2 % OF % OF % OVER- FROM TO EMERG. FROM TO EMERG. LOADS BUS KV BUS KV RATING AREA/S BUS KV BUS KV RATING AREA/S DELTA GREEN-SW 230 GREEN-SW AZ GREEN-SW 230 GREEN-SW AZ BENCHMARK CASE - NO XXXX - CONTINGENCY SET # CASE WITH XXXX - CONTINGENCY SET #3 % OF % OF % OVER- FROM TO EMERG. FROM TO EMERG. LOADS BUS KV BUS KV RATING AREA/S BUS KV BUS KV RATING AREA/S DELTA GREENLEE 345 HIDALGO EPE/NM GREENLEE 345 HIDALGO EPE/NM 8.3 GENERATOR INTERCONNECTION 10 MAY 2008

15 2012 BENCHMARK CASE - NO XXXX - CONTINGENCY SET # CASE WITH XXXX - CONTINGENCY SET #4 DOUBLE CONTINGENCIES DOUBLE CONTINGENCIES % OF % OF % OVER- FROM TO EMERG. FROM TO EMERG. LOADS BUS KV BUS KV RATING AREA /S BUS KV BUS KV RATING AREA/S DELTA ARROYO 115 LAS_CRUC EPE/NM ARROYO 115 LAS_CRUC EPE/NM 1.5 DONA_ANA 115 PICACHO EPE/NM DONA_ANA 115 PICACHO EPE/NM 5 EL_BUTTE 115 PICACHO EPE/NM EL_BUTTE 115 PICACHO EPE/NM 7.8 LAS_CRUC 115 DONA_ANA EPE/NM LAS_CRUC 115 DONA_ANA EPE/NM 4.2 LUNA 115 HURLEY_# EPE/NM LUNA 115 HURLEY_# EPE/NM 8.5 LUNA 345 LUNA EPE/NM LUNA 345 LUNA EPE/NM 7.1 MD 115 HURLEY_# EPE/NM MD 115 HURLEY_# EPE/NM 7.8 PICACHO 115 AIRPOR_T EPE/NM PICACHO 115 AIRPOR_T EPE/NM 4.1 GREEN-SW 230 GREEN-SW AZ GREEN-SW 230 GREEN-SW AZ 1.5 SHIPROCK 230 SHIPROCK AZ SHIPROCK 230 SHIPROCK AZ BENCHMARK CASE - NO XXXX - CONTINGENCY SET # CASE WITH XXXX - CONTINGENCY SET #5 % OF % OF SHIPROCK 230 SHIPROCK AZ SHIPROCK 230 SHIPROCK AZ 2 Note: 1. PNM plans to implement an under-voltage load shedding scheme that would trip the PD/Ivanhoe load at MD based on low voltage at MD and overload of the Luna transformer. 2. EPE/NM overloaded transmission elements & owners: ARROYO-LAS_CRUC 115 KV EPE DONA_ANA-PICACHO 115 KV TRI (Tri-State Gas & Transmis sion) EL_BUTTE-PICACHO 115 KV TRI LAS_CRUC-DONA_ANA 115 KV TRI LUNA-HURLEY_# 115 KV PNM LUNA 345/115 KV PNM MD-HURLEY_# 115 KV PNM PICACHO-AIRPOR_T 115 KV PNM GREENLEE-HIDALGO 345 KV EPE & PNM Engineering judgment suggests that even though the overload delta contributions of the XXXX Project are over 1%, the system upgrades that would be required to be put in place by either of the two generation interconnection projects ahead of the XXXX Project would probably contain enough capacity margins to absorb the impacts of the XXXX Project. Note, due to space constraints on this page, the contingency showing the overloads have been omitted but can be found in the more comprehensive tables starting on page 12 (also included as Appendix 2). Additionally, the overloads shown in the table for double contingencies are for informational purposes only and no system improvements were evaluated to address these overloads. % OVER- FROM TO EMERG. FROM TO EMERG. LOADS BUS KV BUS KV RATING AREA/S BUS KV BUS KV RATING AREA/S DELTA GREEN-SW 230 GREEN-SW AZ GREEN-SW 230 GREEN-SW AZ 1.5 GENERATOR INTERCONNECTION 11 MAY 2008

16 GENERATOR INTERCONNECTION 12 MAY 2008

17 GENERATOR INTERCONNECTION 13 MAY 2008

18 GENERATOR INTERCONNECTION 14 MAY 2008

19 GENERATOR INTERCONNECTION 15 MAY 2008

20 DOUBLE CONTINGENCIES GENERATOR INTERCONNECTION 16 MAY 2008

21 GENERATOR INTERCONNECTION 17 MAY 2008

22 As can be seen from the table results, in all cases the XXXX Project adds to existing overloads but is not the cause of the overloads. EPE System One-Line Diagrams with and without the XXXX Project with all lines in service can be found in Appendix 7. Note in the diagrams that in the EPE area the Arroyo-Las Cruces line thickness is much greater than adjacent lines indicating an overloading condition for both the scenario with and without the XXXX Project in service. System improvements necessary in the EPE/PNM areas due to the impact of the XXXX Project in this Feasibility Study Phase consists of expanding the Luna 345 kv bus to accommodate the 345 kv line from the XXXX generation site. Burns & McDonnell Engineering Company, Inc. prepared the cost estimate (page 29) and construction schedule (Appendix 8) for this system improvement. As requested by XXXX, no cost estimates were provided for the generation site and associated transmission interconnection line to the Luna 345 kv Substation in this Feasibility Study Phase. 4.1 Sensitivity Studies 4.1A Ft. Craig PST Schedule at 201 MW - The powerflow studies discussed above were based on north to south scheduled flows of 60 MW over the Ft. Craig Phase Shifting Transformer (PST). This scenario is the most likely operating scenario but in the event that the PST is scheduled at its maximum contract flow of 201 MW north to south, a sensitivity analysis on transmission loading was conducted using contingency set #1. As can be seen from the table below, a comparison of the 60 MW vs. 201 MW PST schedule shows that transmission overloading in most cases increases slightly. However, as previously mentioned the overloads are not because of the XXXX project and are expected to be resolved by the generation interconnection projects ahead of the XXXX Project. GENERATOR INTERCONNECTION 18 MAY 2008

23 2012 CASE WITH XXXX - CONTINGENCY SET #1 - FT. CRAIG PST AT 60 MW NORTH TO SOUTH 2012 CASE WITH XXXX - CONTINGENCY SET #1 - FT. CRAIG PST AT 201 MW NORTH TO SOUTH % OF % OF FROM TO EMERGENCY FROM TO EMERGENCY OVERLOADS BUS KV BUS KV RATING CONTINGENCY AREA/S BUS KV BUS KV RATING CONTINGENCY AREA/S DELTA GREENLEE 345 HIDALGO SPRINGERVILLE-GREENLEE 345 KV EPE/NM GREENLEE 345 HIDALGO SPRINGERVILLE-GREENLEE 345 KV EPE/NM 2.2 ARROYO 115 LAS CUCES LUNA-MIMBRES 115 KV EPE/NM ARROYO 115 LAS CUCES LUNA-MIMBRES 115 KV EPE/NM 1.6 LANE # 115 LANE SCOTSDALE-VISTA 115 KV EPE/NM LANE # 115 LANE SCOTSDALE-VISTA 115 KV EPE/NM 0 LUNA 115 HURLEY_# LUNA-HIDALGO 345 KV EPE/NM LUNA 115 HURLEY_# LUNA-HIDALGO 345 KV EPE/NM 3.9 LUNA 345 LUNA LUNA-HIDALGO 345 KV EPE/NM LUNA 345 LUNA LUNA-HIDALGO 345 KV EPE/NM 2.4 MD 115 HURLEY_# LUNA-HIDALGO 345 KV EPE/NM MD 115 HURLEY_# LUNA-HIDALGO 345 KV EPE/NM 3.6 BLK MESA 230 BMA.3WP MANY CONTINGENCIES AZ BLK MESA 230 BMA.3WP MANY CONTINGENCIES AZ -5.4 BLK MESA 230 BMA.3WP MANY CONTINGENCIES AZ BLK MESA 230 BMA.3WP MANY CONTINGENCIES AZ 0 BMA.3WP3 100 BLKMSA MANY CONTINGENCIES AZ BMA.3WP3 100 BLKMSA MANY CONTINGENCIES AZ 0 COPPERVR 345 COPPERVR GREEN-SW 230/345 KV AZ COPPERVR 345 COPPERVR GREEN-SW 230/345 KV AZ 0.8 CYPRUS 138 CYPRS SM MANY CONTINGENCIES AZ CYPRUS 138 CYPRS SM MANY CONTINGENCIES AZ 0.1 DINOSAUR 230 DINOSAUR MANY CONTINGENCIES AZ DINOSAUR 230 DINOSAUR MANY CONTINGENCIES AZ 0.1 GREEN-SW 230 GREEN-SW SPRINGERVILLE-CORONADO 345 KV AZ GREEN-SW 230 GREEN-SW SPRINGERVILLE-CORONADO 345 KV AZ 0.8 GREENLEE 345 HIDALGO MANY CONTINGENCIES AZ GREENLEE 345 HIDALGO MANY CONTINGENCIES AZ 2.2 GRIFFITH 230 GRIFFITH MANY CONTINGENCIES AZ GRIFFITH 230 GRIFFITH MANY CONTINGENCIES AZ 0 HILLTOP 230 HLT.3WP MANY CONTINGENCIES AZ HILLTOP 230 HLT.3WP MANY CONTINGENCIES AZ 0 HILLTOP 230 HLT.3WP MANY CONTINGENCIES AZ HILLTOP 230 HLT.3WP MANY CONTINGENCIES AZ 0 HLT.3WP1 100 HILLTOP MANY CONTINGENCIES AZ HLT.3WP1 100 HILLTOP MANY CONTINGENCIES AZ 0 HLT.3WP2 100 HILLTOP MANY CONTINGENCIES AZ HLT.3WP2 100 HILLTOP MANY CONTINGENCIES AZ 0 LAGUNA 69 LAGUNATP SPRINGERVILLE-VAIL 345 KV AZ LAGUNA 69 LAGUNATP SPRINGERVILLE-VAIL 345 KV AZ 0 LINCSTRT 230 WPHXAPSN GREENLEE-HIDALGO 345 KV AZ LINCSTRT 230 WPHXAPSN GREENLEE-HIDALGO 345 KV AZ 0 LINCSTRT 230 WPHXAPSN SPRINGERVILLE-VAIL 345 KV AZ LINCSTRT 230 WPHXAPSN SPRINGERVILLE-VAIL 345 KV AZ 0 LINCSTRT 230 WPHXAPSN SPRINGERVILLE-CORONADO 345 KV AZ LINCSTRT 230 WPHXAPSN SPRINGERVILLE-CORONADO 345 KV AZ 0 N.HAVASU 230 N.HAV3WP MANY CONTINGENCIES AZ N.HAVASU 230 N.HAV3WP MANY CONTINGENCIES AZ 0 OCOTILLO 230 OCOTILLO MANY CONTINGENCIES AZ OCOTILLO 230 OCOTILLO MANY CONTINGENCIES AZ 0 SHIPROCK 230 SHIPROCK SPRINGERVILLE-CORONADO 345 KV AZ SHIPROCK 230 SHIPROCK SPRINGERVILLE-CORONADO 345 KV AZ -0.4 N.HAV3WP 100 N.HAVASU MANY CONTINGENCIES AZ N.HAV3WP 100 N.HAVASU MANY CONTINGENCIES AZ 0 BMA.3WP4 100 BLKMSA MANY CONTINGENCIES AZ BMA.3WP4 100 BLKMSA MANY CONTINGENCIES AZ 0 GENERATOR INTERCONNECTION 19 MAY 2008

24 4.1B FT. Craig PST Schedule at -30 MW As previously mentioned, most of this study was conducted based on a north to south scheduled flow over the Ft. Craig Phase Shifting Transformer (PST) of 60 MW. A powerflow sensitivity study was done with the PST scheduled at one extreme (201 MW) as shown above and now this sensitivity study looked at the other extreme of -30 MW. The -30 MW limit has been established assuming that Afton generation is off. (If Afton generation is on, the PST limit increases to -50 MW.) The table below compared the transmission loading results in the EPE/New Mexico area using Contingency Set #1 with and without the 990 MW Generation Interconnection Project but with the XXXX project in service. As can be seen in the table, loading on the lines shown is reduced as the PST flow is reversed when comparing sensitivity case 4.1A with 4.1B. For example, with the PST schedule at 201 MW (see 4.1A), the Greenlee- Hidalgo 345 kv line is at 115% of emergency under the Springerville-Greenlee 345 kv line outage but is only at 105.3% of emergency for the same circumstances when the PST schedule is at -30 MW. The table also shows that the overloading on the lines shown is eliminated if the 990 MW Project is not in service but the XXXX Project is. If the XXXX Project should continue into the next study stage, these sensitivity studies will be further investigated. GENERATOR INTERCONNECTION 20 MAY 2008

25 2012 CASE WITH XXXX & 990 MW PROJECTS (AFTON GENERATION "OFF") 2012 CASE WITH XXXX & NO 990 MW PROJECT (AFTON GENERATION "OFF") CONTINGENCY SET #1 - FT. CRAIG PST AT -30 MW NORTH TO SOUTH CONTINGENCY SET #1 - ARROYO PST AT -30 MW NORTH TO SOUTH % OF % OF FROM TO EMERGENCY FROM TO EMERGENCY OVERLOADS BUS KV BUS KV RATING CONTINGENCY AREA/S BUS KV BUS KV RATING CONTINGENCY AREA/S DELTA GREENLEE 345 HIDALGO SPRINGERVILLE-GREENLEE 345 KV EPE/NM GREENLEE 345 HIDALGO SPRINGERVILLE-GREENLEE 345 KV EPE/NM ARROYO 115 LAS CUCES LUNA-MIMBRES 115 KV EPE/NM ARROYO 115 LAS CUCES LUNA-MIMBRES 115 KV EPE/NM LANE # 115 LANE SCOTSDALE-VISTA 115 KV EPE/NM LANE # 115 LANE SCOTSDALE-VISTA 115 KV EPE/NM -4.8 LUNA 115 HURLEY_# LUNA-HIDALGO 345 KV EPE/NM LUNA 115 HURLEY_# LUNA-HIDALGO 345 KV EPE/NM -34 LUNA 345 LUNA LUNA-HIDALGO 345 KV EPE/NM LUNA 345 LUNA LUNA-HIDALGO 345 KV EPE/NM MD 115 HURLEY_# LUNA-HIDALGO 345 KV EPE/NM MD 115 HURLEY_# LUNA-HIDALGO 345 KV EPE/NM -31 GENERATOR INTERCONNECTION 21 MAY 2008

26 5.0 VOLTAGE ANALYSIS RESULTS Transmission bus voltage profiles were monitored in the EPE, southern New Mexico and Arizona areas for the powerflow cases with and without the XXXX Project. Bus voltage comparison (with and without XXXX) tables were created for ALIS and select worst contingency conditions to evaluate the impact of bus voltages due to the XXXX Project. The reason this was done was because it was noted that in the case without the XXXX Project there were some bus voltages (especially in Arizona) that were not meeting voltage criteria. After further review of the Arizona system it was concluded that the low bus voltage profiles in Arizona were primarily due to inadequate system modeling by Arizona utilities in the beginning powerflow case. Another reason for the comparison analysis was because as previously mentioned, the 990 MW Generation Interconnection Project (ahead in the study queue of the XXXX Project) was also in the feasibility study stage and system improvements necessary to accommodate this project had not been fully defined but were consequently estimated. It is assumed that once the 990 MW Study Project is finalized and the necessary system improvements defined and implemented that voltage profiles in the EPE/NM area will meet criteria. As can be seen from the tables below, the bus voltage impacts due to the XXXX project are minimal. Engineering judgment strongly favors that once final system improvements are made due to impacts from the 500 MW and 990 MW projects that voltage profiles will also be met after the XXXX Project is added. However, as previously mentioned, a restudy of the XXXX Project will be needed if either of the two generation interconnection projects ahead of the XXXX Project decide not to continue with their planned projects. EPE AND NEW MEXICO AREAS - ALL LINES IN SERVICE - WORST BUS VOLTAGES 2012 CASE WITH NO XXXX 2012 CASE WITH XXXX NOMINAL ACTUAL NOMINAL ACTUAL P.U. KV BUS PER UNIT KV BUS PER UNIT VOLTAGE BUS VOLTAGE VOLTAGE BUS VOLTAGE VOLTAGE DELTA VANBUREN VANBUREN CLAYTON CLAYTON AMISTAD AMISTAD DURAN DURAN TORRANCE TORRANCE GAVILAN GAVILAN RUIDOSO RUIDOSO HOLLYWO# HOLLYWO# ESTANCIA ESTANCIA WILLARD WILLARD GENERATOR INTERCONNECTION 22 MAY 2008

27 EPE AND NEW MEXICO AREAS - LUNA-HIDALGO 345 KV OUTAGE - WORST BUS VOLTAGES 2012 CASE WITH NO XXXX 2012 CASE WITH XXXX NOMINAL ACTUAL NOMINAL ACTUAL P.U. KV BUS PER UNIT KV BUS PER UNIT VOLTAGE BUS VOLTAGE VOLTAGE BUS VOLTAGE VOLTAGE DELTA VANBUREN VANBUREN CLAYTON CLAYTON IVANHOE IVANHOE AMISTAD AMISTAD DURAN DURAN TORRANCE TORRANCE MD MD CHINO CHINO HURLEY_# HURLEY_# GAVILAN GAVILAN ARIZONA AREA - ALL LINES IN SERVICE - WORST BUS VOLTAGES 2012 CASE WITH NO XXXX 2012 CASE WITH XXXX NOMINAL ACTUAL NOMINAL ACTUAL P.U. KV BUS PER UNIT KV BUS PER UNIT VOLTAGE BUS VOLTAGE VOLTAGE BUS VOLTAGE VOLTAGE DELTA N.HAV3WP N.HAV3WP SAN LUIS SAN LUIS N.HAVASU N.HAVASU HLT.3WP HLT.3WP DINOSAUR DINOSAUR HILLTOP HILLTOP HLT.3WP HLT.3WP LAGUNA LAGUNA HILLTOP HILLTOP N.GILA N.GILA N.GILA N.GILA THUNDRS THUNDRS DINOSAUR DINOSAUR GRIFFITH GRIFFITH GENERATOR INTERCONNECTION 23 MAY 2008

28 ARIZONA AREA - GREEN-SW 230/345 KV OUTAGE - WORST BUS VOLTAGES 2012 CASE WITH NO XXXX 2012 CASE WITH XXXX NOMINAL ACTUAL NOMINAL ACTUAL P.U. KV BUS PER UNIT KV BUS PER UNIT VOLTAGE BUS VOLTAGE VOLTAGE BUS VOLTAGE VOLTAGE DELTA N.HAV3WP N.HAV3WP SAN LUIS SAN LUIS N.HAVASU N.HAVASU HLT.3WP HLT.3WP DINOSAUR DINOSAUR HILLTOP HILLTOP HLT.3WP HLT.3WP LAGUNA LAGUNA HILLTOP HILLTOP N.GILA N.GILA N.GILA N.GILA THUNDRS THUNDRS DINOSAUR DINOSAUR GRIFFITH GRIFFITH CARREL CARREL Q-V ANALYSIS RESULTS Q-V analyses were conducted in order to verify that the scenarios modeled in this Study comply with the WECC Voltage Stability Criteria. The analysis provides a way to investigate the potential for voltage collapse during the post-transient period within 3 minutes after the disturbance. Analyses were performed on the benchmark and XXXX powerflow cases. A procedure developed by WECC was used to determine the reactive power margin. As outlined in the procedure, load is increased by 5% and the worst contingency is 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 the critical point. If the minimum point of the Q-V curve is positive, i.e., above the x-axis, the system is reactive power deficient. If it is negative, i.e., below the x-axis, then the system has some reactive power margin and meets the WECC criteria. From experience, it has been established that the worst contingency impacting reactive power margin on the EPE system is an outage of the Luna-Diablo 345 kv line. This single contingency along with single contingencies of the Springerville-VLTap 345 kv, VLTap-Luna 345 kv, Westmesa-Ft. Craig PST 345 kv, Greenlee-Hidalgo 345 kv, Ft. Craig-VLTap 345 kv, Ft. Craig- Arroyo 345 kv, and Newman-Afton 345 kv lines were simulated and analyzed for Q-V margin. The Arroyo, Luna, Caliente, Newman, and Diablo 345 kv buses were monitored for Q-V margins (as shown in the tables below) to verify that EPE reactive power margins are in GENERATOR INTERCONNECTION 24 MAY 2008

29 compliance with the WECC criteria. As can be seen, there is more than enough VAR margin to meet criteria. Resulting plots can be found in Appendix 5. Note that a negative number indicates that there is sufficient reactive power to meet WECC criteria and a positive number indicates that the system is deficient in reactive power and does not meet the criteria Heavy Summer Load Case Q-V Margin (MVAR) Springerville-VLTap 345 kv Line Outage Without With Bus XXXX XXXX Arroyo 345 kv Luna 345 kv Caliente 345 kv Newman 345 kv Diablo 345 kv Luna-Diablo 345 kv Line Outage Without With Bus XXXX XXXX Arroyo 345 kv Luna 345 kv Caliente 345 kv Newman 345 kv Diablo 345 kv VLTap-Luna 345 kv Line Outage Without With Bus XXXX XXXX Arroyo 345 kv Luna 345 kv Caliente 345 kv Newman 345 kv Diablo 345 kv Westmesa -Ft. Craig PST 345 kv Line Outage Without With Bus XXXX XXXX Arroyo 345 kv Luna 345 kv Caliente 345 kv Newman 345 kv Diablo 345 kv GENERATOR INTERCONNECTION 25 MAY 2008

30 Greenlee-Hidalgo 345 kv Line Outage Without With Bus XXXX XXXX Arroyo 345 kv Luna 345 kv Caliente 345 kv Newman 345 kv Diablo 345 kv Ft. Craig-VLTap 345 kv Line Outage Without With Bus XXXX XXXX Arroyo 345 kv Luna 345 kv Caliente 345 kv Newman 345 kv Diablo 345 kv Ft. Craig-Arroyo 345 kv Line Outage Without With Bus XXXX XXXX Arroyo 345 kv Luna 345 kv Caliente 345 kv Newman 345 kv Diablo 345 kv Newman-Afton 345 kv Line Outage Without With Bus XXXX XXXX Arroyo 345 kv Luna 345 kv Caliente 345 kv Newman 345 kv Diablo 345 kv GENERATOR INTERCONNECTION 26 MAY 2008

31 7.0 SHORT-CIRCUIT RESULTS Short-circuit (fault) analyses were performed with and without the XXXX generation interconnected into the EPE system. These consisted of substation three phase to ground, two phase to ground, single phase to ground and phase to phase fault simulations. The objective of this analysis was to determine the incremental fault current contribution from the XXXX generation interconnection and determine if the existing substation circuit breakers can safely accommodate this additional fault current without exceeding their interruption ratings. Study results are shown in the tables below and show that in the benchmark case (no XXXX generation interconnection) that certain circuit breaker short-circuit capabilities are exceeded and are further aggravated when XXXX is added to the system. Consequently, XXXX will not be assigned circuit breaker upgrade responsibilities but are expected to be resolved by either the 500 MW or 990 MW generation interconnection projects that are ahead of the XXXX Project in the study queue. The powerflow and short-circuit modeling data supplied by XXXX and used in the modeling of the XXXX Project are shown in Appendix 6. Fault Current (in Amperes) Without XXXX Generation Lowest Rating (Amperes) Substation 3Ø-g 2Ø-g 1Ø-g L-L of Any Breaker at Substation Bus Amrad 345 kv ,000 Amrad 115 kv ,000 Caliente 345 kv ,000 Caliente 115 kv ,000 Afton 345 kv ,000 Arroyo 345 kv ,000 Arroyo 115 kv ,000 Diablo 345 kv ,000 Diablo 115 kv ,000 LEF 345 kv ,000 Luna 345 kv ,000 Luna 115 kv ,000 Newman 345 kv ,000 Newman 115 kv ,000 Ascarate 115 kv ,000 Ft. Craig 345 kv to be engineered VLTap 345 kv to be engineered Z345 kv to be engineered Lunasol 345 kv n/a n/a n/a n/a to be engineered B-A 345 kv ,000 Springerville 345 kv ,000 Westmesa 345 kv ,000 Picante 345 kv to be engineered Picante 115 kv to be engineered Rio Grande 115 kv ,000 Rio Grande 69 kv ,000 GENERATOR INTERCONNECTION 27 MAY 2008

32 Fault Current (in Amperes) With XXXX Generation Lowest Rating (Amperes) Substation 3Ø-g 2Ø-g 1Ø-g L-L of Any Breaker at Substation Bus Amrad 345 kv ,000 Amrad 115 kv ,000 Caliente 345 kv ,000 Caliente 115 kv ,000 Afton 345 kv ,000 Arroyo 345 kv ,000 Arroyo 115 kv ,000 Diablo 345 kv ,000 Diablo 115 kv ,000 LEF 345 kv ,000 Luna 345 kv ,000 Luna 115 kv ,000 Newman 345 kv ,000 Newman 115 kv ,000 Ascarate 115 kv ,000 Ft. Craig 345 kv to be engineered VLTap 345 kv to be engineered Z345 kv to be engineered Lunasol 345 kv to be engineered B-A 345 kv ,000 Springerville 345 kv ,000 Westmesa 345 kv ,000 Picante 345 kv to be engineered Picante 115 kv to be engineered Rio Grande 115 kv ,000 Rio Grande 69 kv ,000 GENERATOR INTERCONNECTION 28 MAY 2008

33 8.0 COST ESTIMATES A good faith cost estimate (in 2008 dollars) of $2,837,000 and construction schedule for the generation interconnection 345 kv line termination at Luna Substation was prepared by Burns & McDonnell Engineering Company, Inc. (estimate details shown in Appendix 8). Also, as requested by XXXX, no cost estimates were provided for the generation site and associated transmission interconnection line to the Luna 345 kv Substation in this Feasibility Study Phase. In recent years, equipment and material costs have fluctuated on a monthly basis. As a result, the costs will be applicable only at the date of the report from Burns & McDonnell. These costs may change in the future depending on market forces. GENERATOR INTERCONNECTION 29 MAY 2008

34 9.0 DISCLAIMER This study assumes that transmission service has not been obtained by XXXX to deliver its generation output. Therefore, this Study modeled the XXXX power output as being distributed evenly across the entire WECC electrical grid. Whenever XXXX determines where it will deliver its generation output to, XXXX will have to purchase the required transmission service from the appropriate entity and a Transmission Service Study will be performed to determine the impacts of the XXXX generation interconnection and transmission path of the XXXX generation on the EPE and surrounding transmission systems. This study makes no warranties as to the existence or availability of any transmission service XXXX will need in order to deliver its generation output. Also, the transfer capacities of certain transmission lines and paths within the southern New Mexico transmission system are limited by contracts between the New Mexico transmission owners and any use of the transfer capacities above the contractual limits will require approval by the contractual parties and renegotiation of the applicable contract(s). If any of the project data used in this study and provided by XXXX varies significantly from the actual data once the XXXX equipment is installed, the results from this study will need to be verified with the actual data at the Project developer's expense. Additionally, any major change to the southern New Mexico system will require a re-evaluation of this Study. GENERATOR INTERCONNECTION 30 MAY 2008

35 10.0 CERTIFICATION El Paso Electric Company (EPE) performed a Generation Interconnection Feasibility Study (GIFS) for XXXXXXXXXXXXXXXXXXX (XXXX) pursuant to XXXX s letter requesting to interconnect its solar-thermal generating plant to EPE s Luna 345 kv Substation. The Study determined the impacts to the EPE and surrounding transmission systems due to the interconnection of the XXXX generation planned for December 1, This study recommends system upgrades required to correct impacts due to the addition of the proposed XXXX generation and estimated costs for installing those required system upgrades. Cost estimates at the generation site and the interconnecting transmission line were not provided in this Feasibility Study Phase as requested by XXXX. The powerflow and short-circuit data used to model the XXXX generation was supplied by XXXX. EPE performed power flow, Q-V reactive margin, and short-circuit analyses in this study. Name: Title: Dennis H. Malone Manager, System Planning Signature: Date: Investigating Engineer: Joaquin Aguilar GENERATOR INTERCONNECTION 31 MAY 2008