generator interconnection study - 300 mw solar at luna 345

Microsoft Word - Generator Interconnection Study - 300 MW Solar at Luna 345.docGENERATOR INTERCONNECTION
FEASIBILITY STUDY
August 2006
Generator Interconnection Feasibility Study i El Paso Electric Company 300 MW Solar Photovoltaic Plant August 2006
TABLE OF CONTENTS 1.0 EXECUTIVE SUMMARY ...........................................................................Page 1 2.0 PURPOSE......................................................................................................Page 7 3.0 INTRODUCTION .........................................................................................Page 8
3.1 Performance Criteria................................................................................Page 9 3.1.1 Voltage Violation Criteria ..........................................................Page 10 3.1.2 Voltage Drop Violation Criteria.................................................Page 11 3.1.3 PNM’s additions and exceptions to the NERC/WECC Criteria - Voltages ......................................................................Page 11
3.1.4 Tri-State’s additions and exceptions to the NERC/WECC Criteria - Voltages ......................................................................Page 11
3.1.5 Loading Violation Criteria .........................................................Page 12 3.1.6 Reactive Margin (Q-V) Criteria .................................................Page 12 3.1.7 Arroyo Phase Shifting Transformer (PST) Maximum Angle Requirement ...............................................................................Page 12 3.1.8 Criteria Violations ......................................................................Page 12 4.0 METHODOLOGY ........................................................................................Page 13 4.1 Assumptions..........................................................................................Page 13 4.2. Procedure ..............................................................................................Page 13 4.2.1 Base Case Development and Description of Cases without the XXX Project: Benchmark Cases ................................................Page 13 4.2.2 Base Case Development and Description with the XXX Project Modeled..........................................................Page 16 4.2.3 Modeling of the XXX Project in the Cases................................Page 17 4.2.4 Sensitivity Cases with the XXX Project Modeled......................................................................................Page 18 4.2.5 Powerflow Analysis Methodology.............................................Page 18 4.2.6 List of Contingencies..................................................................Page 19 4.2.7 Short Circuit Analysis ................................................................Page 20
Generator Interconnection Feasibility Study ii El Paso Electric Company 300 MW Solar Photovoltaic Plant August 2006
5.0 POWERFLOW ANALYSIS RESULTS .......................................................Page 21 5.1 All-Lines-in-Service (ALIS) Analysis Results for Overloaded Elements Benchmark Cases (without the XXX Project) ......................Page 21
5.2 Single-Contingency (N-1) Analysis Results for Overloaded Elements Benchmark Cases (without the XXX Project) ......................Page 21 5.3 Double-Contingency (N-2) Analysis Results for Overloaded
Elements Benchmark Cases (without the XXX Project) ......................Page 22 5.4 All-Lines-in-Service (ALIS) Analysis Results for Overloaded Elements in All Cases with the XXX Project Modeled ................................................................................................Page 23 5.5 Single-Contingency (N-1) Analysis Results for Overloaded
Elements in All Cases with the XXX Project Modeled……………..………………………. .....................................Page 23
5.6 Sensitivity Case Modeling Only Two Diablo 345/115 kV Autotransformers……..………………………. ...................................Page 24
5.7 Double-Contingency (N-2) Analysis Results for Overloaded Elements in All Cases with the XXX Project Modeled……………..………………………. .....................................Page 25
5.8 Non-Converging Contingencies............................................................Page 26 5.9 Results of Voltage Violations ...............................................................Page 26 5.10 Sensitivity Involving No Third Party Generation Online (All Third Party Generation Offline ...................................................Page 29 5.11 Sensitivity Involving New Alamogordo-Holloman 115 kV Line – Voltage Effects...................................................................................Page 38 5.12 Arroyo PST Phase Angle Values Analysis...........................................Page 41 6.0 Q-V REACTIVE MARGIN ANALYSIS RESULTS ...................................Page 43 7.0 SHORT CIRCUIT ANALYSIS.....................................................................Page 45 7.1 Short Circuit Analysis Modeling ……...………………..…………….Page 45 7.2 Results of the Short Circuit Analysis ………………..………………. Page 48 7.3 Short Circuit Analysis Conclusions ………….………..…………….. Page 53 8.0 COSTS ESTIMATES ....................................................................................Page 54 8.1 XXX Generator Interconnection Cost……...………………………….Page 55 8.2 SNM Facility Additions/Modifications Assumed to be in place prior to the XXX Project ……………..……………… .. …..………………Page 56 8.3 System Upgrade Costs Due to the XXX project ……..……………….Page 57 8.4 Total Costs……………..………………..…………………..……….. Page 57 9.0 DISCLAIMER ...............................................................................................Page 58 10.0 CERTIFICATION .........................................................................................Page 59
Generator Interconnection Feasibility Study iii El Paso Electric Company 300 MW Solar Photovoltaic Plant August 2006
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 1 El Paso Electric Company 300 MW Solar Photovoltaic Plant August 2006
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 non- binding 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 2011. These cases represent the “boundaries” in which the SNM and NNM system may operate with and without the XXX project.
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 556.5 ACSR to 795 ACSR
conductor (modeled in the 2011 HS benchmark case). 4. Reconductor Newman-FB2-GR-Vista 115 kV line from 556.5 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: 6. Reconductor Austin-Dyer 69 kV line from 4/0 CU to 556.5 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 4.2.1.
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. 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 single- contingency 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 – 33.07 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.
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
of SNM Facility Additions/Modifications Needed due to the XXX Project
SYSTEM MODIFICATION COSTS
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.
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 + 130 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.
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.
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.
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 2004. 2. 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.
The performance criteria utilized in monitoring the SNM and northern New Mexico (NNM) area are shown in Table 1.
Table 1: Performance Criteria.
0.95 - 1.05 69kV and above 0.95 - 1.10 Artesia 345 kV
0.95 - 1.08 Arroyo 345 kV PS source side Normal < Normal Rating
0.90 - 1.05 Alamo, Farmer, Rgc Lobo,
Sierra Blanca and Van Horn 69kV
0.925 - 1.05 60 kV to 115 kV 0.95 - 1.10 7 % Artesia 345kV
0.95 - 1.08 7 % Arroyo 345kV PS source side
0.90 - 1.05 Alamo, Farmer, Rgc Lobo,
Sierra Blanca and Van Horn 69kV
EPE
0.95 - 1.05 7 % Hidalgo, Luna, or other 345 kV buses
Normal < Normal Rating 0.95 - 1.05 60kV and above LOS ALAMOS Contingency < Emergency
Rating 6% 60kV and above
Normal < Normal Rating 0.95 - 1.05 60kV and above TSGT Contingency < Emergency
Rating 0.90 - 1.10 60kV and above
Normal < Normal Rating 0.95 - 1.05 60kV and above
6 % 60kV and above PNM Contingency < Emergency
Rating 7 % Luna, Mimbres, Hermanas,
Hondale, and Deming 115kV
Normal < Normal Rating 0.95 - 1.05 60kV and above TNMP Contingency < Emergency
Rating 0.925 - 1.05 6 % 60kV and above
Normal < Normal Rating 0.95 - 1.05 100kV and above AZ Contingency < Emergency
Rating 0.925 - 1.05 5 % 100kV and above
3.1.1 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.
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 pre- contingency voltage. For example, if the pre-contingency voltage at the Luna 345kV bus is 1.030 pu, and the voltage drops to 0.9579 pu during the contingency, the voltage drop would be 7%, calculated as:
dv = (Vpre-Vpost) / Vpre = (1.030 – 0.9579) / 1.030 = 0.0721/1.030 = 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. 3.1.3 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.
3.1.4 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 pre-
to post-contingency must be no greater than 8% for N-1 contingencies and no greater than 10% for N-2 contingencies.
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. 3.1.6 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. 3.1.7 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. 3.1.8 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.
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. 4.2.1 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 2011. 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.
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 556.5 ACSR to 795 ACSR
conductor (modeled in the 2011 HS benchmark case). 4. Reconductor Newman-FB2-GR-Vista 115 kV line from 556.5 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:
6. Reconductor Austin-Dyer 69 kV line from 4/0 CU to 556.5 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
ARROYO) ARROYO PST SCHEDULE
ARROYO) ARROYO PST SCHEDULE
EPE (OATT) -104 -104 EPE (SSI) -20 -20 TSGT -50 -50 PNM -25 -25 PNM (AFTON GENERATION THROUGH ARROYO PST TO PNM)
+141 0
* 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.
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 4.2.1.
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.
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 2006. 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 198.8 MW and 21.1 MVAR in the 2009 case and with a gross output of 332.3 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 2011. 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.
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 4.2.1 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 5.10. 4.2.5 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 all- lines-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.
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. 4.2.6 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.
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.
4.2.7 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.
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 4.2.1 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 400 120.6 Blk Mesa 230 kV/BMA.3WP3 100 kV Transformer 2011 HS AZ 40 116.8 Blk Mesa 230 kV/BMA.4WP3 100 kV Transformer 2011 HS AZ 40 111.5
Cholla 345 kV/ Cholla 7 100 kV Transformer 2011 HS AZ 203 102.7 Cholla 230 kV/ Cholla 7 100 kV Transformer 2011 HS AZ 203 101.6
N.Havasu 230 kV/N.HAV3WP 100 kV Transformer 2011 HS AZ 80 100.1 Tucson 138 kV/TUC.3WP 100 kV Transformer 2011 HS AZ 100 100.1
Blythe-Buckblvd 161 kV Line 2011 HS AZ 440 109.6 Blk Mesa 230 kV/BMA.3WP3 100 kV Transformer 2011 HS AZ 44.8 104.3
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 4.2.1 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.
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 Rating (MVA) % Loading Contingency Description
Lordsbrg 115/69 Kv Transformer 2009 HS PNM/ TNMP 27.0 111.0 Hidalgo-Turquoise 115 kV
Line (RAS)
Lordsbrg 115/69 Kv Transformer 2011 HS PNM/ TNMP 27.0 107.2 Hidalgo-Turquoise 115 kV
Line (RAS)
Central-Silver 69 kV Line 2011 HS PNM/TN MP 27.0 102.0 Turquois 115/69 kV
Transformer
Leo-Milagro 69 kV Line 2009 HS EPE 69.4 121.4 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 4.2.1 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.
Table 5. Post-Contingency (N-2) Thermal Violations, Benchmark Cases, SNM Elements
Lordsbrg 115/69 Kv Transformer 2009 HS PNM/ TNMP 27.0 120.5 Hidalgo 345/115 kV T1
& T3 Transformers
Lordsbrg 115/69 Kv Transformer 2011 HS PNM/ TNMP 27.0 121.4 Hidalgo 345/115 kV T1
& T3 Transformers
Hidalgo-Turquoise 115 kV Line 2009 HS PNM/ TNMP 153.0 131.4 Hidalgo 345/115 kV T1
& T3 Transformers
Hidalgo-Turquoise 115 kV Line 2011 HS PNM/ TNMP 153.0 133.8 Hidalgo 345/115 kV T1
& T3 Transformers
Hidalgo-Turquoise 115 kV Line 2009 HS PNM/ TNMP 153.0 100.9
Luna-Afton 345 kV Line & Luna 345/115 kV
Transformer
Transformer
Central- Turquoise 115 kV Line 2011 HS PNM/ TNMP 133.4 112.2 Hidalgo 345/115 kV T1
& T3 Autotransformers
Central- Turquoise 115 kV Line 2009 HS EPE 133.4 110.6 Hidalgo 345/115 kV T1 & T3 Transformers
Mesa-Rio Grande 115 kV Line 2009 HS EPE 195.6 100.5 Newman-Afton &
Caliente-Newman 345 kV Lines
Reducing generation at Lordsburg and Pyramid should mitigate the overloads shown in Table 5 for the Hidalgo 345/115 kV T1 and T3 autotransformers outage. Reducing generation at Lordsburg and Pyramid should also mitigate the overloads shown in Table 5 for the Luna-Afton 345 kV line and Luna 345/115 kV transformer outage. 5.4 All-Lines-in-Service (ALIS) Analysis Results for Overloaded Elements in All
Cases with the XXX Project Modeled There were no SNM elements overloaded with the XXX project modeled that were not already overloaded in the benchmark cases (without the XXX project) with ALIS. 5.5 Single-Contingency (N-1) Analysis Results for Overloaded Elements in All
Cases with the XXX Project Modeled Each of the cases with the XXX project, as described in Section 4.2.2 was examined under single contingency conditions. Table 6 shows the post-contingency overloaded SNM elements present in the cases with the XXX project modeled under N-1 conditions. If an element (line or transformer) was overloaded under ALIS conditions or post- contingency conditions in the cases modeling the same conditions without the XXX project, the element was considered overloaded and not attributable to the XXX project and was not included in Table 6.
Table 6. Post-Contingency (N-1) Thermal Violations, Cases with the XXX Project Modeled, SNM Elements
Green-AE 345/230 Transformer 2011 HS ARIZONA SWTC 193 103.1 PYoung-Winchester 345 kV
Line As shown in Table 6, the Green-AE 345/230 kV transformer owned by SWTC (Southwest Transmission Cooperative, Inc) is overloaded during a single-contingency 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 on Table 6. 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. However, this violation is noted for this report and may be included as a cost in the next XXX study. Note that this feasibility study will not re-examine the effectiveness of these solutions or any new problems that may arise as a consequence of the solutions identified. EPE did coordinate through XXX to make arrangements with SWTC for the study of the overloading of the Green-AE 345/230 kV under the above N-1 condition to verify if this element is overloaded. This overload will be examined in any follow up study for the XXX project. 5.6 Sensitivity Case Modeling Only Two Diablo 345/115 kV Autotransformers Referring to Section 4.2.1, there were certain elements modeled in the benchmark cases (cases without the XXX project) associated with Newman 5. Because the addition of a third Diablo 345/115 kV autotransformer is not associated with the additions and modifications assumed with Newman 5, this third autotransformer was examined in a sensitivity case. To accomplish this, the status of a third Diablo 345/115 kV autotransformer (of three autotransformers total) was changed from on to off in the 2009 HS benchmark case. Under a single contingency involving the Afton-Newman 345 kV line, it was found that the two remaining Diablo 345/115 kV autotransformers (existing today) that were modeled as on in the case overload under this single outage. Therefore, a third Diablo 345/115 kV autotransformer is needed prior to the XXX project. Because this addition (a third Diablo 345/115 kV autotransformer) is needed before the XXX project is modeled, this will be considered an exception to the criteria, will not have a penalizing effect when evaluating the XXX project, and the cost to correct it will not be charged to the XXX project.
5.7 Double-Contingency (N-2) Analysis Results for Overloaded Elements in All Cases with the XXX Project Modeled
Each of the cases with the XXX project, as described in Section 4.2.2 was examined under double contingency conditions. Table 7 shows the post-contingency overloaded SNM elements present in the cases with the XXX project modeled under N-2 conditions. Table 7 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 7. Post-Contingency (N-2) Thermal Violations, Cases with the XXX Project Modeled, SNM Elements
Luna 345/115 kV Autotransformer 2009 HS PNM 224 101.2
Luna-Hidalgo & Luna-Diablo 345 kV Lines (the XXX project Stays In
During the Outage) *
Luna-Hidalgo & Luna-Diablo 345 kV Lines (the XXX project Stays In
During the Outage) *
Luna-Hidalgo 345 kV Line & Luna 345/115 kV Autotransformer
(the XXX project Stays In During the Outage)
As shown in Table 7, some post-XXX project post-contingency thermal violations were observed on some SNM lines and transformers for some double contingencies. There was one transformer, Luna 345/115 kV, which was overloaded in the post-XXX project a double outage. There was one TSGT 115 kV line that was overloaded in the post-XXX project under double outages: the ElButte-Picacho 115 kV lines. For the purposes of 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 a 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 thermal violations will help the owners of the SNM system identify what procedures or new automatic or manual operating procedures need to be in place as a result of the XXX project.
EPE did coordinate through XXX to make arrangements with TSGT for the study of the overloading of the TSGT line under the above N-2 condition to verify if this element is overloaded. This overload will be examined in any follow up study for the XXX project. Powerflow maps for instances in which an element experienced the highest overload under a single or double contingency for the XXX project Cases are shown in Appendix 3. Maps for the benchmark cases and all cases modeling the XXX project with ALIS also appear in Appendix 3. 5.8 Non-Converging Contingencies The following contingencies did not converge for this study: 1) ElBut_US-El_Butte 115 kV line, 2) Amrad-AlamoTap 115 kV line, 3) Caliente-Amrad 345 kV line, and Caliente- Amrad and Caliente-Newman 345 kV line double contingency. See Section 5.10 for more on the Amrad-AlamoTap 115 kV line single-contingency. PNM plans on installing the third source to Alamogordo 115 kV and also plans on installing an SVC at Alamogordo 115 kV in 2009 and this should help with the Caliente- Amrad 345 kV line single contingency, and Caliente-Amrad and Caliente-Newman 345 kV line double contingency. These non-converging contingencies will be examined further in any follow up study for the XXX project. 5.9 Results for Voltage Violations
Because there were numerous minor voltage violations, engineering judgment (in the interest of time) dictated that only the voltage violations due to the XXX project be summarized in this report. The voltage violations due to the XXX project are shown in Table 8 for single-contingencies and in Table 9 for double contingencies. These tables show the name, base voltage, and area of the affected bus, and the per-unit voltage observed in each case with the XXX project. A blank entry in the table indicates that the voltage was within limits for the specified condition. If a voltage violation occurred for the same case prior to the XXX project, the violation was considered pre-existing and not attributable to the XXX project and was not included in Table 8 or in Table 9.
Table 8. Voltage Violations due to the XXX Project, Single-Contingencies (N-1)
Bus Name kV (Area) Case ALIS Voltage
N-1 Voltage (pu)
ALIS or Single-Contingency Under which Voltage Violation Occurred
OJO 115 (PNM) 2009 HS 1.0479 1.0505 Hidalgo-PYoung 345 kV line
HERMANAS (PNM) 2009 HS 1.0385 1.0505 Mimbres-Airport 115 kV Line
NORTON 1 115 (PNM) 2009 HS 1.0488 1.0506 Luna-Hidalgo 345 kV line, the XXX project Stays In During Outage*
TESUQUE 115 (PNM) 2009 HS 1.0490 1.0509 Luna-Hidalgo 345 kV line, the XXX project Stays In During Outage* HOLLYWOOD 115
(TNMP) 2011 HS 0.9849 0.925 6.08 Caliente-Newman 345 kV line
GAVILAN 115 (TNMP) 2011 HS 0.9849 0.925 6.08 Caliente-Newman 345 kV line
RUIDOSO 115 (TNMP) 2011 HS 0.9849 0.925 6.08 Caliente-Newman 345 kV line
ASPEN 115 (PNM) 2011 HS 1.0482 1.0505 Luna-Hidalgo 345 kV line, the XXX project Stays In During Outage*
BECKNER 115 (PNM) 2011 HS 1.0483 1.0506 Luna-Hidalgo 345 kV line, the XXX project Stays In During Outage*
SANDIA 1 115 (PNM) 2011 HS 1.0477 1.0519 Luna-Hidalgo 345 kV line, the XXX project Stays In During Outage*
TYRONE 69 (TNMP) 2011 HS 0.9823 0.9236 5.98 Luna 345/115 kV Autotransformer, the XXX project Stays In During Outage*
Table 9. Voltage Violations due to the XXX Project, Double-Contingencies (N-2)
N-2 Voltage (pu)
Double Contingency Under which Voltage Violation Occurred
TYRONE 69 (TNMP) 2009 HS 0.9876 0.9249 6.35 Luna-Hidalgo 345 kV line and Luna 345/115 kV Autotransformer, the XXX project Drops During Outage
WHITE SANDS 115 (EPE) 2011 HS 1.0274 0.9249 9.98 Amrad-Artesia 345 kV line and
Amrad 345/115 kV Autotransformer SPARKS 69 (EPE) 2011 HS 1.038 0.9244 10.94 Caliente-Newman and Newman-Afton 345 kV lines
SE 1 115 (EPE) 2011 HS 1.0023 0.9235 7.86 Caliente-Newman and Newman-Afton 345 kV lines
* This outage was examined with the XXX project dropping out upon this outage and the voltage violations on Table 9 were not observed for this outage.
For voltage violations in which voltages of 1.05-1.0504 p.u. occurring during a single- contingency or double-contingency in the analysis, these overvoltages are assumed to be caused by the modeling in the cases used in this study. There were no voltage violations that did not already exist in the benchmark case for cases with the XXX generation Interconnection modeled for the Arizona area. As can be seen in Table 8, for single contingencies, there are some under voltage violations of the study criteria caused by the XXX generation Interconnection. In these occurrences, it was found that in the benchmark cases, similar voltage drops at the same buses happen for the same single contingencies although the voltage drop is not enough to violate the study criteria. The over voltage violations occur under the same single outages that cause other NM buses to be above 1.05 p.u. in both the benchmark cases and cases with the XXX generation Interconnection. As can be seen in Table 9, for double contingencies, there are some under voltage violations of the study criteria caused by the XXX generation Interconnection. In these occurrences, it was found that in the benchmark cases, similar voltage drops happen at the same buses for the same double contingencies although the voltage drop is not enough to violate the study criteria. PNM has planned system additions that would mitigate the low voltages seen in Table 9 at Hollywood 115 kV, Gavilan 115 kV, Ruidoso 115 kV and Tyrone 69 kV. These system additions include the addition of an SVC at Alamogordo by 2009 and may include the third source to Alamogordo by the end of 2007.
5.10 Sensitivity Involving No Third Party Generation Online (All Third Party Generation Offline)
There were sensitivity cases developed in which the third party generation described as a-e in Section 4.2.1 was turned off in the benchmark cases without the XXX Project modeled (cases 1 and 2 in Section 4.2.1) and in the cases with the XXX Project modeled (cases 3 and 4 in Section 4.2.2). The cases in which the third party generation described as a-e in Section 4.2.1 was turned off will be referred to as cases with no third party generation (and is actually no third party generation in SNM). Because third party generation project b (141 MW of generation interconnected at Afton 345 kV Substation) was turned off, the Arroyo PST schedule was set to the 201 MW N-S schedule as described in Table 2 of Section 4.2.1 for all cases. Another change was that in the benchmark cases (without the XXX Project modeled) there was one 54 MVAR Springerville-Luna 345 kV line reactor on in the cases as opposed to two 54 MVAR Springerville-Luna 345 kV line reactors in the cases with the XXX Project modeled. Also examined, is a sensitivity in which all third party generation specified in Section 4.2.1 is turned off and the effects of the XXX project are examined. Another change from cases 1-4 with all third party generation modeled in which three Diablo 345/115 kV autotransformers were modeled was that in this sensitivity cases were modeled with two Diablo 345/115 kV autotransformers. The detailed results for this sensitivity can be found in Appendix 6. 5.10.1 All-Lines-in-Service (ALIS) Analysis Results for Overloaded Elements
Benchmark Cases (without the XXX Project) – No Third Party Generation Cases - Sensitivity
Each of the cases with system benchmark conditions (without the XXX project) and no third party generation was examined with all lines in service (ALIS). Table 10 shows the base case overloads present in the cases without the XXX project.
Table 10. Pre-Contingency Thermal Violations, Benchmark Conditions – No Third Party Generation Cases
Element Case Owner Rating(MVA) % Loading
Blythe-Buckblvd 161 kV Line 2011 HS AZ 400 120.6 Blk Mesa 230 kV/BMA.3WP3 100 kV Transformer 2011 HS AZ 40 116.1 Blk Mesa 230 kV/BMA.4WP3 100 kV Transformer 2011 HS AZ 40 110.9
Verde N-Yavapai 100 kV Line 2011 HS AZ 319 102.0 Tucson 138 kV/TUC.3WP 100 kV Transformer 2011 HS AZ 100 100.1
Blythe-Buckblvd 161 kV Line 2011 HS AZ 440 109.6 Blk Mesa 230 kV/BMA.3WP3 100 kV Transformer 2011 HS AZ 44.8 103.6
Table 10 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 two lines and three transformers. These contingency criteria violations listed in Table 10 will not have a penalizing effect on the evaluation of the XXX project. 5.10.2 Single-Contingency (N-1) Analysis Results for Overloaded Elements
Benchmark Cases (without the XXX Project) – No Third Party Generation Cases - Sensitivity
The benchmark cases with no third party generation were examined under single contingency conditions. Table 11 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 11. Table 11 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 11. Post-Contingency (N-1) Thermal Violations, Benchmark Cases, SNM Elements – No Third Party Generation Cases
Central-Silver 115 kV Line 2011 HS PNM/ TNMP 27.0 101.2 Turquois 115/69 kV
Transformer As shown in Table 11, one pre-XXX project post-contingency thermal violation was observed on one SNM line. This contingency criteria violation listed in Table 11 will not have a penalizing effect on the evaluation of the XXX project.
5.10.3 Double-Contingency (N-2) Analysis Results for Overloaded Elements Benchmark Cases (without the XXX Project) – No Third Party Generation Cases - Sensitivity
The benchmark cases with no third party generation were examined under double contingency conditions. Table 12 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 12. Table 12 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 12, some pre-XXX project post-contingency thermal violations were observed on two SNM lines. These contingency criteria violations listed in Table 12 will not have a penalizing effect on the evaluation of the XXX project.
Table 12. Post-Contingency (N-2) Thermal Violations, Benchmark Cases, SNM Elements, No Third Party Generation
Transformer
Transformer
Algodone-Moriarty 115 kV Line 2009 HS TSGT 66.0 101.3 Luna-Afton & Springerville- Luna 345 kV Lines
Reducing generation at Lordsburg and Pyramid should also mitigate the overloads shown in Table 12 for the Luna-Afton 345 kV line and Luna 345/115 kV transformer outage.
5.10.4 All-Lines-in-Service (ALIS) Analysis Results for Overloaded Elements in All Cases with the XXX Project Modeled – No Third Party Generation Cases - Sensitivity
There were no SNM elements overloaded in the cases with XXX project and no third party generation modeled that were not already overloaded in the benchmark cases (without the XXX project and with no third party generation modeled) with ALIS. 5.10.5 Single-Contingency (N-1) Analysis Results for Overloaded Elements in All
Cases with the XXX Project Modeled – No Third Party Generation Cases – Sensitivity
Each case, with the XXX project and no third party generation modeled, was examined under single contingency (N-1) conditions. There were no SNM elements overloaded in the cases with XXX project and no third party generation modeled that were not already overloaded in the benchmark cases (without the XXX project and with no third party generation modeled) under N-1. 5.10.6 Double-Contingency (N-2) Analysis Results for Overloaded Elements in All
Cases with the XXX Project Modeled – No Third Party Generation Cases – Sensitivity
Each case, with the XXX project and no third party generation modeled, was examined under double contingency (N-2) conditions. There were no SNM elements overloaded in the cases with XXX project and no third party generation modeled that were not already overloaded in the benchmark cases (without the XXX project and with no third party generation modeled) under N-2. 5.10.7 Non-Converging Contingencies – No Third Party Generation Cases –
Sensitivity The following contingencies did not converge for these cases: 1) Hidalgo T1 & T3 345/115 kV double contingency, 2) Amrad-AlamoTap 115 kV line, 3) Caliente-Amrad 345 kV line, and Caliente-Amrad and Caliente-Newman 345 kV line double contingency. Note that the Hidalgo T1 & T3 345/115 kV double contingency did converge in the cases with all third party generation modeled. PNM plans on installing the third source to Alamogordo 115 kV and also plans on installing an SVC at Alamogordo 115 kV in 2009 and this should help with the Caliente- Amrad 345 kV line single contingency, and Caliente-Amrad and Caliente-Newman 345 kV line double contingency. These non-converging contingencies will be examined further in any follow up study for the XXX project.
5.10.8 Results for Voltage Violations – No Third Party Generation Cases – Sensitivity
Because there were numerous minor voltage violations, engineering judgment (in the interest of time) dictated that only the voltage violations due to the XXX project be summarized in this report. The voltage violations due to the XXX project are shown in Table 13 for single-contingencies and in Table 14 for double contingencies for the cases with the XXX project and no third party generation modeled. These tables show the name, base voltage, and area of the affected bus, and the per-unit voltage observed in each case with the XXX project. A blank entry in the table indicates that the voltage was within limits for the specified condition. If a voltage violation occurred for the same case prior to the XXX project, the violation was considered pre-existing and not attributable to the XXX project and was not included in Table 13 or in Table 14.
Table 13. Voltage Violations due to the XXX Project, Single-Contingencies (N-1) – No Third Party Generation Cases – Sensitivity
N-1 Voltage (pu)
ALIS or Single-Contingency Under which Voltage Violation Occurred
TYRONE 69 (TNMP) 2009 HS 0.9831 0.9249 5.92 Central-Hurley 115 kV line
SILVERC 69 (TNMP) 2009 HS 0.9723 0.9204 5.34 Hidalgo-PYoung 345 kV line
IVANHOE 115 (TNMP) 2009 HS 0.9916 0.9209 7.13 Hurley-Luna 115 kV Line
Table 14. Voltage Violations due to the XXX Project, Double-Contingencies (N-2) – No Third Party Generation Cases – Sensitivity
N-2 Voltage (pu)
Double Contingency Under which Voltage Violation Occurred
CHINO 115 (TNMP) 2011 HS 1.0066 0.9249 6.35 Luna 345/115 kV Autotransformer, the XXX project Drops During Outage
PDTYRONE 115 (TNMP) 2011 HS 0.9975 0.9233 7.44 Luna 345/115 kV Autotransformer, the XXX project Drops During Outage
CENTRAL 69 (TNMP) 2009 HS 0.9945 0.9187 7.62 Luna 345/115 kV Autotransformer, the XXX project Drops During Outage
IVANHOE 115 (TNMP) 2009 HS 0.9916 0.9216 7.06 Luna 345/115 kV Autotransformer, the XXX project Drops During Outage
TYRONE 69 (TNMP) 2009 HS 0.9831 0.9222 6.19 Luna 345/115 kV Autotransformer, the XXX project Drops During Outage
IVANHOE 115 (TNMP) 2011 HS 0.9942 0.9096 8.51 Luna 345/115 kV Autotransformer, the XXX project Drops During Outage
TYRONE 69 (TNMP) 2011 HS 0.9851 0.9189 6.72 Luna 345/115 kV Autotransformer, the XXX project Drops During Outage
MORIARTY 115 (TSGT) 2011 HS 0.9670 0.9232 4.53 Luna 345/115 kV Autotransformer, the XXX project Drops During Outage
SILVERC 69 (TNMP) 2011 HS 0.9740 0.9206 5.48 Afton-Newman & Luna-Afton 345 kV Double Contingency, the XXX project Drops During Outage
DEMINGPG 69 (TSGT) 2009 HS 0.9918 0.9173 7.51 Afton-Luna & Springerville-Luna 345 kV Double Contingency, the XXX project Drops During Outage
PLAYAS 69 (TSGT) 2011 HS 1.0036 0.9246 7.87 Afton-Luna & Springerville-Luna 345 kV Double Contingency, the XXX project Drops During Outage
WILLARD 115 (TSGT) 2011 HS 0.9650 0.9248 4.17 Afton-Luna & Springerville-Luna 345 kV Double Contingency, the XXX project Drops During Outage
ESTANCIA 115 (TSGT) 2011 HS 0.9611 0.9213 4.14 Afton-Luna & Springerville-Luna 345 kV Double Contingency, the XXX project Drops During Outage
TYRONE 69 (TNMP) 2011 HS 0.9851 0.9233 6.27 Springerville-Luna 345 kV, the XXX project Drops During Outage
There were no voltage violations that did not already exist in the benchmark case for cases with the XXX generation Interconnection modeled for the Arizona area. As can be seen in Table 13, for single contingencies, there are some under voltage violations of the study criteria caused by the XXX generation Interconnection. In these occurrences, it was found that in the benchmark cases, similar voltage drops at the same buses happen for the same single contingencies although the voltage drop is not enough to violate the study criteria. As can be seen in Table 14, for double contingencies, there are some under voltage violations of the study criteria caused by the XXX generation Interconnection. In these occurrences, it was found that in the benchmark cases, similar voltage drops happen at the same buses for the same double contingencies although the voltage drop is not enough to violate the study criteria. PNM has planned system additions that would mitigate the low voltages seen in Table 9 at Hollywood 115 kV, Gavilan 115 kV, Ruidoso 115 kV and Tyrone 69 kV. These system additions include the addition of an SVC at Alamogordo by 2009 and may include the third source to Alamogordo by the end of 2007.
5.10.9 Summary of Results for No Third Party Generation Cases – Sensitivity The following are the results of this sensitivity:
• In cases with no XXX project, one Springerville-Luna 345 kV line reactor was modeled as on versus two Springerville-Luna 345 kV line reactors modeled as on in the cases with the XXX project.
• With no third party generation modeled, the Arroyo PST schedule was modeled as 201 MW N-S.
• With no third party generation modeled the Arroyo PST schedule was modeled as 201 MW N-S, the two Diablo 345/115 kV autotransformers modeled did not overload under any contingency run (N-1 or N-2).
• There were no overloads under single or double contingencies caused by the XXX project.
• With no third party generation modeled, the Hidalgo T1 & T3 345/115 kV transformer double outage did not converge. With third party generation modeled, this contingency converges. This non-converging double contingency will be examined further in any follow up study for the XXX project.
• With no third party generation modeled, there were minor voltage violations observed under single contingencies in the cases with the XXX project modeled that were not violations in the cases without the XXX project modeled. In these occurrences, it was found that in the benchmark cases, similar voltage drops at the same buses happen for the same single contingencies although the voltage drop is not enough to violate the study criteria. PNM is planning some system additions that may help the voltage profiles in SNM.
• With no third party generation modeled, many of the elements that were overloaded in the cases with third party generation were not overloaded. Specifically, the Green-AE 230/115 kV transformer under a single contingency in the cases with the XXX project modeled and the Luna 345/115 kV and the ElButte-Picacho 115 kV line under a double contingency in the cases with the XXX project modeled were not overloaded in the cases without third party generation modeled.
5.11 Sensitivity Involving New Alamogordo-Holloman 115 kV Line – Voltage Effects
There was a sensitivity case examined in this study involving the addition of a new line from Alamogordo-Holloman 115 kV line. In the 2009 and 2011 cases with the XXX Generation Interconnection, this Alamogordo-Holloman 115 kV line was added. The outages for this study were performed for these two cases. The net effect of this line addition was that this line resulted in no consequential difference in the thermal overloading results already recorded in the previous sections (in which this line is off). The main difference this line made was in the voltages during outages: specifically, in the voltages involving outages involving the Alamogordo, Amrad, and Holloman buses. For the purposes of this section, only single-contingencies will be addressed. There were no voltage violations in these sensitivity cases for single-outages involving 115 kV lines connecting to the Alamogordo, Amrad, and Holloman buses. However, there are voltage violations in two different single-contingencies, an outage of the Alamogcp-Amrad 115 kV line and an outage of the Amrad 345/115 kV transformer, which merit further consideration. The results for these two key

generator interconnection study - 300 mw solar at luna 345

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