El Paso Electric Company

Transcription

1 Feasibility Study XXXXXX Solar Generation Prepared for El Paso Electric Company Prepared by TRC Engineers, LLC 249 Eastern Avenues Augusta, ME (207) Project Number: May 2013

2 FOREWORD This report was prepared for the project Interconnection Customer, by System Planning at El Paso Electric Company. Any correspondence concerning this document, including technical and commercial questions should be referred to: Dennis Malone Director System Planning Department El Paso Electric Company 100 North Stanton El Paso, Texas Phone: (915) Fax: (915) Or David Gutierrez Principal Engineer El Paso Electric Company 100 North Stanton El Paso, Texas Phone: (915) Fax: (915) Project i

3 Table of Contents EXECUTIVE SUMMARY INTRODUCTION PERFORMANCE CRITERIA STUDY METHODOLOGY ASSUMPTIONS PROCEDURE Development and Description of Cases XXXXXX Solar PV Generation Modeling Contingency List STEADY STATE POWER FLOW ANALYSIS PRE-PROJECT POWER FLOW EVALUATION Pre-Project N-0 Flow Violations Pre-Project N-1 Flow Violations POST-PROJECT POWER FLOW EVALUATION Post-Project N-0 Power Flow Analysis Post-Project N-1 Power Flow Analysis POWER FLOW ANALYSIS CONCLUSION STEADY STATE VOLTAGE ANALYSIS SHORT CIRCUIT ANALYSIS SHORT CIRCUIT ANALYSIS MODELING SHORT CIRCUIT ANALYSIS PROCEDURE SHORT CIRCUIT ANALYSIS RESULTS SHORT CIRCUIT ANALYSIS CONCLUSIONS DISTRIBUTION ANALYSIS GENERAL REQUIREMENTS IEEE Standards Noise and Harmonics VOLTAGE FLICKER ANALYSIS TRANSIENT STABILITY ANALYSIS Transient Stability Study Case Development Transient Stability Analysis Results Transient Stability Analysis Conclusion COST ESTIMATES GENERAL COST ASSUMPTIONS DISCLAIMER CONCLUSIONS Project ii

4 List of Figures Figure IEEE Flicker Curve List of Tables Table 0-1 Cost Estimate... 3 Table 3-1 Pre-Project 2014 N-1 Flow Violations... 9 Table N-1 Post-project Power Flow Analysis Results Table 5-1 Generator Short Circuit Modeling Data Table 5-2 Distribution Line Table XXXXXX Solar Generation Short Circuit Summary Results Table 6-1 Voltage Flicker at the POI Due to Project Table 6-2 Frequency of Voltage Flicker Due to PV Output Changes Table 6-3 Generator Models Used for Studies Table 6-4 Stability Post-Project Case Scenarios Table Stability Analysis Results for both Peak and Off-Peak Cases Appendices Appendix A Appendix B Appendix C XXXXXX Solar Feasibility Study Statement of Work Power Flow Contingency List Stability Plots Project iii

5 EXECUTIVE SUMMARY The objective of this Feasibility Study (Study) was to determine the impact that the proposed XXXXXX Solar generation (the Project) for 10 MW (net output) of Photovoltaic (PV) generation, interconnecting to the 13.8 kv bus of the future Patriot 115/13.8 kv substation, would have on the El Paso Electric Company (EPE) and Southern New Mexico transmission systems, as well as the EPE future Patriot Substation distribution system. The requested Commercial Operation date for this project is July 15, Three (3) interconnection projects in the EPE study queue that have signed Interconnection Agreements (IA) with EPE were included in this Study. The three (3) interconnection projects included in this SIS are: 1. Montana Power Station: 420 MW gas fired combustion turbine project with varying inservice dates located 2 miles east of the Caliente 345/115 kv substation. 2. DS92S: 92 MW solar powered project interconnected to the Diablo-Santa Teresa 115 kv line, 5.7 miles from Diablo 115 kv station. 3. AA100W: 100 MW wind powered project interconnected to the Amrad-Artesia 345 kv line, 65 miles east of Amrad 345 kv substation. The generation from the DS92S project was modeled as delivered to all entities in the Western Electricity Coordinating Council (WECC) except EPE, while the generation from the AA100W was modeled to deliver to all WECC entities except EPE and New Mexico. The Montana Power Station project was modeled as delivered to local EPE network load. The Study Area was limited to the WECC Area 11 - EPE (TX) and Area 10 - PNM (NM). Steady State Transmission Results The power flow analysis was conducted using 2014 peak and off peak load conditions. The off peak load conditions were modeled as fifty percent (50%) of the peak load. The Arroyo Phase Shifter was modeled as being out of service in both peak and off peak cases. The power flow analysis results showed that the addition of the 10 MW of Project generation would not require any network upgrades to the EPE and Southern New Mexico transmission systems, as modeled in the 2014 peak and off peak load flow cases. The 10 MW of Project generation will be used primarily to feed the load (9.8 MW under 2014 Peak conditions) at the future 13.8 kv Patriot bus, therefore there will be very little export to the 115 kv EPE transmission system in the area. The analysis showed that the XXXXXX Solar generation does not have an adverse impact on the EPE and Southern New Mexico transmission systems. Project

6 Short Circuit Results A short circuit analysis was performed to determine if the addition of the XXXXXX Solar generation to the EPE transmission system would cause any of the existing substation circuit breakers on EPE s transmission system to exceed their interrupting capability ratings. The results of this short circuit study showed that the maximum fault currents with the XXXXXX Solar project in service did not exceed any of the breaker interrupting capabilities on the EPE transmission system. Distribution Results Several analyses were performed to determine if the addition of the XXXXXX Solar generation would have any adverse effects on El Paso s underlining distribution system in the immediate Study Area. These analyses included a closer look at the requirements necessary to interconnect and model PV generation under IEEE standards, the impact of changes in sun exposure at the solar farm, and a transient stability analysis on the distribution system in the immediate Project Area. The analysis showed that the XXXXXX Solar generation does not have an adverse impact on the immediate EPE distribution system in the project area. Cost Estimates Good faith cost estimates are presented. The cost estimates are in 2013 dollars (no escalation applied) and are based upon typical construction costs in the area. These costs include all estimated applicable labor and overheads associated with the engineering, design, and construction of any new EPE facilities. These estimates did not include the Generator Interconnection Costs 1 for any other Interconnection Customer owned equipment or associated design and engineering except for the Point of Interconnection (POI) facilities. The estimated total cost for the required upgrades is $635,000. This breaks down to $635,000 for the EPE Interconnection Costs 2 and $0 for Network Upgrades Cost 3. Generator Interconnection Costs have not been estimated as part of this study. Table 0-1 details the cost per facility. 1 Generator Interconnection Costs: cost of facilities paid for by Interconnection Customer and owned and operated by the Interconnection Customer from the generator facilities to the Change of Ownership Point, which is typically on the first dead-end at the Point of Interconnection substation. Not subject to transmission credits. 2 EPE Interconnection Costs: cost of facilities paid for by Interconnection Customer but owned and operated by EPE from the Change of Ownership Point to the Point of Interconnection. Not subject to transmission credits. 3 Network Upgrades Cost: Cost of facilities from the Point of Interconnection outward, paid for by the interconnector but owned and operated by EPE. Subject to transmission credits. Project

7 Table 0-1 Cost Estimate Facility Patriot 13.8 kv Station Construction (Including: Voltage Regulators; Switchgear Expansion; Breakers; and Labor) Construction of a 1.5 mile 13.8 kv line connecting the Project to the future Patriot 13.8 kv Bus Distribution: Metering, Switches; Protective Equipment Underground Getaway and Material Generator Interconnection Cost EPE Interconnection Cost Network Upgrade Cost Total N/A $230,000 N/A $230,000 N/A $290,000 N/A $290,000 N/A $85,000 N/A $85,000 N/A $30,000 N/A $30,000 TOTAL N/A $635,000 $0 $635,000 The estimated time frame for Engineering, Procurement, and Construction of Network Upgrades is approximately 12 months upon notice to proceed with construction from the Interconnection Customers. Project

8 Figure 0-1 Below details the interconnection. Figure 0-1: XXXXXX Solar POI and Future Patriot 13.8 Substation One-line Unit 1 10 MW PV Patriot Solar PV Generating Site Change of Ownership 0.69 kv 13.8 kv 13.8/0.69 kv Wye-Grounded/Wye-Grounded 10 MVA Transformer (Six 1.5 MVA and One 1 MVA) Disconnect Switch Revenue Metering M 13.8 kv 1.5 Mile Express Line EPE Load 13.8 kv Point of Interconnection To Cromo Color Code Network Upgrades Existing Facilities 115 kv To Newman Patriot Substation EPE Interconnection Facilities Interconnection Customer Equipment Conclusion This Feasibility Study showed that the proposed XXXXXX Solar generation will not have an adverse impact on the EPE and Southern New Mexico transmission systems or the EPE Patriot distribution system. Project

9 1.0 INTRODUCTION The Interconnection Customer proposed the interconnection of 10 MW of solar PV generation to the 13.8 kv bus of EPE s future Patriot 115/13.8 kv substation. The FERC Open Access Transmission Tariff (OATT), under the Small Generator Interconnection Procedures (SGIP), requires that a Feasibility Study be performed for Interconnection Customers who desire to interconnect their generation facilities to a Transmission Provider s transmission system. The proposed Commercial Operation date for the XXXXXX Solar project is July 15, Performance Criteria The Study was performed according to Western Electricity Coordinating Council (WECC), North American Electric Reliability Corporation (NERC), and EPE standards. The EPE local reliability standards can be found in Section 4 of EPE s FERC Form No The steady state analysis was performed using the GE PSLF Version 18 software. Transformer tap and phase-shifting transformer angle movement, as well as static VAR device switching were allowed to move for the steady state pre-contingency analysis. All regulating equipment such as transformer controls and switched shunts were fixed at pre-contingency positions when the contingency analysis was performed. All facility loadings, as well as bus voltages 69 kv and greater, were monitored within the El Paso, New Mexico and Arizona control areas. Pre-contingency flows on lines and transformers were required to remain at or below the normal rating, while post-contingency flows on lines and transformers were required to remain at or below the emergency rating. Flows above 100% of an element s rating, either pre- or post-contingency, were considered violations. Post-project voltage criteria violations that did not exacerbate or improve an existing pre-project violation were not considered an adverse impact to the system. The performance criteria utilized in identifying violations in the study area are shown in Table 1. Project

10 Table 1-1 EPE and New Mexico Performance Criteria Area Conditions Loading Limits EPEC PNM Tri- State Normal (ALIS) Contingency Normal (ALIS) Contingency N-1 Contingency N-2 Normal ALIS Contingency N-1 Contingency N-2 Normal Rating Emergency Rating Voltage (p.u.) Voltage Drop Application kv and above Artesia 345 kv Arroyo 345 kv PST source side Alamo, Sierra Blanca and Van Horn 69 kv % 60 kv to 115 kv % Artesia 345 kv % Arroyo 345 kv PST source side Alamo, Sierra Blanca and Van Horn 69 kv % Hidalgo, Luna, or other 345 kv buses Normal Rating kv and above* Emergency Rating Emergency Rating *** 6 %** 46 kv to 115 kv *** 6 %** 230 kv and above *** 10 % 46 kv and above* Normal Rating All buses Emergency Rating Emergency Rating % % % * Taiban Mesa and Guadalupe 345 kv bus voltage must be between 0.95 and 1.10 p.u. under normal and contingency conditions. ** For PNM buses in southern New Mexico, the allowable N-1 voltage drop is 7%. *** Provided operator action can be utilized to adjust voltages back down to 1.05 Tri-State buses in the PNM Service Area (list provided by Tri-State) Tri-State buses in southern and northeastern New Mexico (list provided by Tri-State) All buses Project

11 2.0 STUDY METHODOLOGY 2.1 Assumptions The following assumptions are consistent for all study scenarios unless otherwise noted. This study assumed that all system expansion projects as planned by area utilities by the year under analysis are completed, and that any system improvements required by the interconnections senior to the Project generation are implemented. This study did not analyze any transmission service from the interconnection point to any specific point on the grid for the interconnections senior to the Project generation. 2.2 Procedure The Study included only Steady State Analysis as stated in Section 6.0 of the EPE Small Generator Interconnection Procedures Feasibility Study Agreement. A description of the procedures used to complete the analyses is presented below Development and Description of Cases A 2014 WECC power flow case at 100% summer peak load was used and modified, as listed below, to establish a 2014 benchmark case without the proposed XXXXXX Solar generation. The 10 MW XXXXXX Solar generation was modeled as being dispatched to serve EPE system native load. The Arroyo Phase Shifter was modeled out of service as it is not planned to be completed until after the 2014 study year. The off-peak case was created by reducing the WECC Area 11 (EPE) and Area 10 (PNM, TSGT) loads and generation by 50% and adjusting area interchange Benchmark 2014 Cases: The 2014 benchmark, peak and off-peak cases included the following existing third party generation: (a) 420 MW of generation (Montana Power Station) with varying in-service dates interconnected to the Caliente 115 kv bus and scheduled to EPE native load. (b) 92 MW of generation (DS92S) interconnected on the Diablo-Santa Teresa 115 kv line, 5.7 miles from Diablo 115 kv station and scheduled to all WECC except EPE. (c) 100 MW of generation (AA100W) interconnected on the Amrad-Artesia 345 kv, 65 miles east of Amrad 345 kv substation and scheduled to all WECC entities except EPE and New Mexico. (d) Peak and off-peak 2014 post-project cases were created from the benchmark cases as described above. Project

12 2.2.2 XXXXXX Solar PV Generation Modeling The XXXXXX Solar generation consisting of 10 MW from a yet unknown number of PV inverters, was modeled as being interconnected at a new XXXXXX Solar 13.8 kv bus (POI) via a 1.5 mile express feeder from the Patriot 13.8 kv Substation bus. The 10 MW of solar PV generation was modeled as a single 10 MW unit at 0.69 kv, stepped up to 13.8 kv at the Solar Farm (POI). The generator step-up (GSU) transformers (0.69 kv/13.8 kv) information provided (6 GSUs at 1.5 MVA and 1 GSU at 1.0 MVA are mentioned in the interconnection application) calls for an aggregate of 10 MVA normal and emergency ratings to be used. Provided that the planned Project generation operates at 10 MW, these individual GSUs will be overloaded if the Project is at maximum output and providing the required +/-0.95 Power Factor (PF) of VAR support to EPE system. EPE directed that this study was to be performed assuming a Unity PF for the Project generation. The Project output and GSU specification should be confirmed before this Project proceeds. If the EPE required +/-0.95 PF is adhered to, the individual GSU s will overload. Furthermore, the interconnection application also states that these GSU s will be Wye-Delta (low to high) configurations. This configuration will need to be changed, such that the interconnecting high side is a grounded Wye Contingency List All outages (69 kv and above within EPE) were modeled in the subsystem files. The list of contingencies used in this study is included in Appendix B. These contingencies were selected to represent a good cross section of potential contingencies that would stress the EPE and PNM s southern New Mexico systems. This study was only performed for N-0 and N-1 conditions. Project

13 3.0 STEADY STATE POWER FLOW ANALYSIS 3.1 Pre-Project Power Flow Evaluation Peak and off peak base cases were evaluated for overloaded facilities under both normal and contingency conditions prior to the addition of the XXXXXX Solar generation Pre-Project N-0 Flow Violations Power flow study analysis results showed no transmission facilities were overloaded in the EPE, PNM, or Tri-State (TSGT) areas under pre-contingency system conditions prior to the addition of the XXXXXX Solar generation Pre-Project N-1 Flow Violations Power flow contingency analysis results showed that few overloads existed in El Paso prior to the addition of the Patriot generation, as shown in Table 3-1. Table 3-1 Pre-Project 2014 N-1 Flow Violations From Bus kv To Bus kv Ckt ID DONA_ANA (*) Area Rating (MVA) 115 PICACHO JORNADA 115 ARROYO JORNADA 115 ARROYO (*) Denotes that this line is owned by Tri-State. Contingency LUNA-MIMBRES 115 kv LE1-JORNADA 115 kv LE1-ARROYO 115 kv Off Peak Peak % of Emergency Rating Post-Project Power Flow Evaluation The inclusion of the XXXXXX Solar generation showed no adverse effects to the El Paso and New Mexico areas. The post-project analysis was performed under both normal and contingency conditions Post-Project N-0 Power Flow Analysis Power flow study results for the EPE and PNM areas showed that the addition of the XXXXXX Solar generation to the existing system would not cause any power flow violations under non-contingency system conditions Post-Project N-1 Power Flow Analysis Power flow study results for the EPE and PNM areas showed that the addition the XXXXXX Solar generation to the existing system would not have an adverse impact on the El Paso and New Mexico transmission systems, as shown in 3-2. Project

14 Table N-1 Post-project Power Flow Analysis Results Peak or Off-peak From Bus kv To Bus kv Ckt ID Area Rating (MVA) Contingency Without Project % of Rating With Project % of Rating Delta % of Rating Peak JORNADA 115 ARROYO LE1-JORNADA 115 kv Peak DONA_ANA 115 PICACHO LUNA-MIMBRES 115 kv Off-peak JORNADA 115 ARROYO LE1-JORNADA 115 kv Off-peak JORNADA 115 ARROYO LE1-ARROYO 115 kv Project

15 3.3 Power Flow Analysis Conclusion The analysis showed that the addition of the XXXXXX Solar generation to the system would not have an adverse impact on the EPE or New Mexico transmission systems. For the peak load case, the 9.8 MW load as modeled at the 13.8 kv Patriot Bus keeps the 10 MW of Project generation local to the 13.8 kv distribution system without flowing onto the 115 kv transmission system in the area. Depending upon the protection scheme at the Patriot Substation, this may create a possibility of islanding for loss of the 13.8/115 kv transformer. For the off-peak case, EPE should expect back flow on to the 115 kv system from the Project. Project

16 4.0 STEADY STATE VOLTAGE ANALYSIS Bus voltages within the Study Area were compared under both normal and contingency conditions, with and without the XXXXXX Solar generation in service. The Performance Criterion shown in Table 1 was considered when analyzing bus voltages for violations. The voltage analysis results showed that after the addition of the XXXXXX Solar generation, the Study area transmission network voltages stayed within criteria limits or did not significantly change from the pre-project voltage levels. See Appendix C for detailed results. Project

17 5.0 SHORT CIRCUIT ANALYSIS A short circuit analysis was performed to determine if the addition of the XXXXXX Solar generation to the EPE transmission system would cause any of the existing substation circuit breakers on EPE s transmission system to exceed their interrupting capability ratings. 5.1 Short Circuit Analysis Modeling Pre and post-project cases were developed to perform this analysis showing the impact of the integration of the XXXXXX Solar generation on the circuit breakers in the EPE transmission system. As mentioned in earlier sections, any planned or proposed third party generation listed in EPE s study queue ahead of the Project were also modeled in the two cases. The generator data used in the study is shown in Table 5-1 and the impedance data used for the 1.5 mile distribution line is shown in Table 5-2. This analysis evaluated the impact of the XXXXXX Solar generation by comparing the pre- and post- XXXXXX Solar generation fault current levels. Project

18 Table 5-1 Generator Short Circuit Modeling Data Project Total Output (MW) AA100W 100 DS92S 92 XXXXXX Solar Generation Unit ID Pmax (MW) Interconnection Customer Qmax (MVAR) Qmin (MVAR) Z subtransient (p.u) Rating (MVA) GSU Voltage (kv) Z Subtransient (p.u) P j / j P j G j / j0.085 G j / j G *0.00 +j / j0.133 * - Denotes that subtransient impedance values were not available, so default values found in ASPEN were used. Table 5-2 Distribution Line From Bus To Bus kv Ckt. ID Length (mi.) Line Impedance (p.u) R1 X1 R0 X0 XXXXXX Solar Patriot Project

19 5.2 Short Circuit Analysis Procedure The initial short circuit analysis was performed with all other third-party generation projects ahead of the XXXXXX Solar generation in the study queue in service and XXXXXX Solar generation out of service. This identified the base case fault duties of the circuit breakers. The short circuit analysis was performed again with XXXXXX Solar generation in service on the 2014 ASPEN One Liner case provided by EPE. Three phase, two phase, and single-phase line-to-ground faults were simulated at selected buses in the EPE system with terminal voltages at 69 kv and above. EPE also requested faults on all transformer tertiary buses. ASPEN One Liner and Batch Short Circuit Module were used to perform the short circuit analysis. The short circuit fault analyses were performed with the following settings: Transmission line G+jB ignored. Shunts with positive sequence impedance ignored. Transformer line shunts ignored The pre-fault voltage was calculated using a Flat bus voltage of 1.05 per unit. The difference between the fault current values in the two cases demonstrates the post-project fault contribution of the XXXXXX Solar generation to the pre-project fault current levels in the EPE system. The resulting fault currents in the post-project scenario were compared to the lowest breaker interruption ratings at each of the substations to determine whether or not the XXXXXX Solar project caused any adverse impact. Project

20 5.3 Short Circuit Analysis Results The results of this short circuit study showed that the existing maximum fault currents (without the XXXXXX Solar generation in service) exceeded the breaker interrupting capability at some substations. These are existing criteria violations that EPE is currently addressing, and will not be discussed in this report. The short circuit analysis results for the monitored buses in the immediate EPE Project area (2 busses away) are shown below in Table 5-3 below. Table XXXXXX Solar Generation Short Circuit Summary Results Lowest Pre Post Breaker Bus Fault On: Fault Current Pre X/R Current Rating (ka) (ka) (ka) CROMO 115kV 40 NEWMAN 115kV 50 PATRIOT 13.8kV PATRIOT 115kV XXXXXX SOLAR 13.8kV TBD TBD TBD Post X/R Delta (Amps) 3LG LG LG LG LG LG LG LG LG LG LG LG LG LG LG Short Circuit Analysis Conclusions The results of this short circuit study showed that the post-project fault currents with the XXXXXX Solar generation on-line increases fault levels at the existing Patriot 13.8 kv bus by approximately 1.9 ka, but does not cause fault currents to exceed the breaker interrupting capability of any breakers in the EPE transmission system. Therefore, the project generation does have an adverse impact to the EPE transmission breaker duties. EPE Substation and Protection Engineering verified the minimal breaker ratings at all the sites listed in the table. Project

21 6.0 DISTRIBUTION ANALYSIS Several analyses were performed to determine if the addition of the XXXXXX Solar generation would have any adverse effects on El Paso s distribution system fed out of the Patriot Substation in the immediate Project Area. These analyses included a closer look at the requirements necessary to interconnect and model PV generation under IEEE standards, the impact of changes in sun exposure at the solar farm, and a low level transient stability analysis on the immediate Project Area. 6.1 General Requirements IEEE Standards The Interconnection Request did not specify the model of PV inverters that will be used for this Project. However, in order for the Project to move forward to the Facilities Study phase of the Interconnection process, the PV inverters to be used will need to be specified and adhered to the following IEEE standards and guidelines: IEEE Standard , IEEE Standard for Interconnecting Distributed Resources with Electric Power Systems. UL Standard 1741, Inverters, Converters and Charge Controllers for Use in Independent Power Systems. IEEE Standard , IEEE Recommended Practice for Utility Interface of Photovoltaic (PV) Systems Noise and Harmonics The inverter is certified IEEE 1547, compliant and the Total Harmonic Distortion (THD) is given at less than 3.0%. 6.2 Voltage Flicker Analysis Voltage flicker is defined as a voltage variation sufficient in duration to allow visual observation of a change in electric light intensity of an incandescent light bulb. The IEEE curve showing fluctuations per time period versus borderline of visibility and borderline of irritation is shown below. The suggested operating criteria is that the magnitude of voltage flicker must be limited to less than 3% and that the frequency of flicker fluctuations be less than the border line of irritation boundary. Project

22 Figure 6-1 IEEE Flicker Curve Clouds shading the PV panels adversely impact the output of a PV system. As a cloud shadow passes over a PV system the output will decrease due to the reduction in sunlight. The change in PV system output on a distribution circuit may cause a fluctuation of voltage that might be seen by electric customers. This fluctuation would be classified as a voltage flicker. A rapid change in load cannot be compensated by the voltage regulation equipment installed on a distribution system. Most utilities use a typical time delay setting of 60 seconds for substation LTCs and 90 seconds for line voltage regulators. This time delay means that an LTC or voltage regulator will not respond to voltage changes until the voltage has been outside of the bandwidth for a low of 60 or 90 seconds. This helps to control hunting of the multiple devices trying to control the voltage. As a cloud passes over a PV system the output will decrease to a lower value. Given the amount of PV system output reduction due to clouds is not known, the assumption is that it goes to zero and returns to full output once sunlight returns. The voltage at the Patriot 13.8 kv Substation bus is anticipated to be fixed at 1.05 p.u. with and without the Project for peak and off peak load periods. Table 6-1 summarizes the balanced voltage and the calculated voltage flicker magnitude. Project output will exhibit relatively slow variations due to cloud cover shading rather than spike between full on and off. Consequently, the results shown in Table 6-1 represent a worst-case scenario, such as a sudden shutdown of the PV plant. Project

23 Table 6-1 Voltage Flicker at the POI Due to Project Project POI Bus Voltage Case Off Peak Load Peak Load Without Project kv kv With Project* kv kv % Voltage Flicker NOTE: % Voltage Flicker calculated as With Project minus Without Project divided by Without Project times 100. *The Project is set to operate at Unity power factor. Table 6-2 is based on an interpolation of the flicker frequency from the IEEE flicker graph. Cloud movement is slow; therefore the frequency of the voltage fluctuations will be less than the frequency limits shown in Table 6-2. The calculated magnitude of the flicker due to the Project is much less than the 3% limit criterion. The distribution voltage flicker resulting from changes in the Project output is not anticipated to have an adverse effect. Table 6-2 Frequency of Voltage Flicker Due to PV Output Changes % Voltage Flicker Based on GE Flicker Curve Border Line of Visibility Border Line of Irritation < 1/sec < 1/sec < 1/sec < 1/sec NOTE: Fluctuation per time period extrapolated from the IEEE flicker graph 6.3 Transient Stability Analysis EPE requested TRC to take a closer look at the impacts of the Project on their Distribution System in the Project area. In order to ensure the damping effects of the EPE system in the area, a Transient Stability Analysis was completed. The simulations were conducted using the General Electric, Inc. PSLF load flow and dynamic simulation software package, Version 18. Dynamic stability simulations were conducted for peak and off-peak load conditions with the XXXXXX Solar generation units on at full capacity and off. EPE provided the base cases and dynamic file data for this part of the study. The Interconnection Customer did not provide any data for modeling of their facility. As a result, typical modeling data for solar facilities was used as per WECC modeling standards. The XXXXXX Solar generation was modeled as one PV plant with a maximum output of 10 MW. Project

24 Table 6 shows the models used for the studies. Table 6-3 Generator Models Used for Studies Project Turbine Type Notes PSLF Model XXXXXX Solar Unknown Used Typical Type 4 Wind Turbines for model data and parameters as per WECC Standards WT4G, WT4E Transient Stability Study Case Development Two base cases were used to simulate Peak and Off-Peak conditions. The analysis compared the system response to the fault simulations before and after the XXXXXX Solar generation was added. The dynamic study cases are listed in 6-4. Table 6-4 Stability Post-Project Case Scenarios Descriptions Year Heavy Load Case Light Load or Off-Peak Case 2014 Senior Queued Projects in-service Arroyo PST out of service Afton in service Transient Stability Analysis Results Senior Queued Projects in-service Arroyo PST out of service Afton out of service The stability analysis showed that the EPE Patriot distribution system and the EPE transmission system remained stable for all simulated faults before and after the addition of the Project. Simulated fault locations, time durations, and the system response are shown in 6-5. The stability plots for these faults can be found in Appendix D Transient Stability Analysis Conclusion The study area remains stable and well damped for all the contingencies analyzed. The Project addition to the system does not pose any concern to system stability performance. Project

25 Table Stability Analysis Results for both Peak and Off-Peak Cases 2014 Results # Fault Location Event Description Clearing (cycles) Off Peak Load Project Off Project On Project Off Peak Load 1 XXXXXX 115kV Three Phase fault at XXXXXX 115 kv XXXXXX 115 kv= 6.0, Open bus. XXXXXX-Patriot 115kV Line Stable Stable Stable Stable 2 Patriot 115 kv Three Phase fault at Patriot 115 kv bus. Patriot 115 kv= 6.0 Stable Stable Stable Stable 3 Patriot 13.8 kv Three Phase fault at Patriot 13.8 kv bus. Patriot 13.8 kv= 6.0 Stable Stable Stable Stable Project On Project

26 7.0 COST ESTIMATES Good faith cost estimates have been determined. The cost estimates are in 2013 dollars (no escalation applied) and are based upon typical construction costs in the area for previously performed similar construction. These estimated costs include all applicable labor and overheads associated with the engineering, design, and construction of these new facilities. These estimates did not include the cost for any other Interconnection Customer owned equipment or associated design and engineering except for those located at the POI. The estimated total cost for the required upgrades is $635,000. This breaks down to $635,000 for the EPE Interconnection Cost 4 and $0 for Network Upgrades Cost 5. The Generator Interconnection Cost 6 estimates are not included. 7.1 General Cost Assumptions 1. The cost estimates provided are good faith scoping estimates. 2. Estimates do not include land or permitting. 3. Interconnection Customer to secure POI site and transfer ownership to EPE. 4. Permitting time frames are included. Actual time frames will vary due to local and Federal requirements. 5. Estimates are in 2013 U.S. dollars. 6. Where applicable, the Interconnection Customers are responsible for funding and construction of all transmission facilities from the proposed generator substation to the Points of Interconnection including disconnect switches, use and reset existing relays, and reset relays at remote ends. 7. Interconnection Customer is responsible for Engineering, Procurement, and Construction for all and any FACTs and other transmission and distribution compensation devices at their generation site or along their long interconnecting transmission or distribution lines to just outside the POI sites EPE Interconnection Cost: Cost of facilities paid for by interconnector but owned and operated by EPE from the Change of Ownership Point to the Point of Interconnection. Not subject to transmission credits. Network Upgrades Cost: Cost of facilities from the Point of Interconnection outward, paid for by the interconnector but owned and operated by EPE. Subject to transmission credits. Generator Interconnection Cost: Cost of facilities paid for by interconnector and owned and operated by the interconnector from the generator faculties to the Change of Ownership Point, which is typically at the Point of Interconnection substation first dead-end. Not subject to transmission credits. Project

27 8.0 DISCLAIMER If any of the project data provided by Interconnection Customer and used in this study varies significantly from the actual data after the XXXXXX Solar generation equipment is installed, the results from this study will need to be verified with the actual data at the Project Interconnection Customer's expense. Additionally, any change in the generation in EPE s Interconnection Queue that is senior to the XXXXXX Solar generation may require a re-evaluation of this Study. Project

28 9.0 CONCLUSIONS This XXXXXX Solar Feasibility Study, consisting of a Steady State, Short Circuit, Transient Stability and Voltage Flicker Analysis, for a net 10 MW of generation interconnecting to the EPE transmission and distribution systems has demonstrated that the XXXXXX Solar generation will NOT have an adverse impact on the EPE and Southern New Mexico transmission systems or the EPE distribution system. The estimated cost for integrating the XXXXXX Solar generation onto the EPE and Southern New Mexico transmission systems is $635,000. The good faith estimate of the time frame to Engineer, Procure, and Construct all facilities is 12 months. Project

29 APPENDIX A XXXXXX Solar Feasibility Study Statement of Work Project Appendix A

30 APPENDIX B Power Flow Contingency List Project Appendix B

31 APPENDIX C Stability Plots Project Appendix C