300 MW SOLAR PHOTOVOLTAIC PLANT,
GENERATOR INTERCONNECTION
FEASIBILITY STUDY
El Paso Electric Company
System Planning
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
300 MW Solar Photovoltaic Plant
i
El Paso Electric Company
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
300 MW Solar Photovoltaic Plant
ii
El Paso Electric Company
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
300 MW Solar Photovoltaic Plant
iii
El Paso Electric Company
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 nonbinding good-faith construction timing estimate.
The XXX project was studied at two net MW output levels. The cases modeled the net
MW output from the XXX project as the following: 180 MW and 300 MW for the years
2009 and 2011, respectively, with the study period analyzed as the Heavy Summer (HS)
season. The output was scheduled to WECC. Each case was studied using the criteria
and methodologies described in subsequent sections of this study report. The proposed
interconnection point, Luna 345 kV Substation, is jointly owned by El Paso Electric
Company (EPE), Public Service Company of New Mexico (PNM), and Texas-New
Mexico Power Company (TNMP).
This Study analyzed powerflow, Q-V reactive margin, and short circuit analyses.
Two (2) Western Electricity Coordinating Council (WECC) GE format base case
powerflow cases called the benchmark cases (i.e. cases without the XXX project) were
jointly developed by EPE and PNM for this analysis. These benchmark cases reflect load
forecast, transmission configuration upgrades in southern New Mexico (SNM) and
northern New Mexico (NNM), and facilities associated with each of the prior requestors’
interconnection projects for the years 2009 and 2011. These cases represent the
“boundaries” in which the SNM and NNM system may operate with and without the
XXX project.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
1
El Paso Electric Company
August 2006
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.
b.
c.
d.
e.
570 MW of generation interconnected at the Luna 345 kV Substation (scheduled to
WECC).
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).
160 MW of generation interconnected at TNMP’s Hidalgo 115 kV substation
(scheduled to WECC).
80 MW of generation interconnected at TNMP’s Lordsburg 115 kV substation
(scheduled to WECC).
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).
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
2
El Paso Electric Company
August 2006
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-toWestmesa.
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
3
El Paso Electric Company
August 2006
Case 4:
2011 Heavy Summer (HS) benchmark case with the XXX project modeled with the net
output from the XXX project at 300 MW (as metered at Luna 345 kV). The output is
scheduled to WECC in the cases.
It should be noted that this Study was not meant to analyze every scenario that could
occur on the NM and AZ systems with the XXX Project. The Study analyzed the
primary boundaries around which the NM and AZ systems may operate, under the
scenarios agreed to by EPE, XXX, and PNM.
Utilizing engineering judgment, proposed system modifications to correct the criteria
violations found in the analyses and estimated costs for those proposed modifications are
included in this Study. However, this feasibility study does not include additional studies
to validate the effectiveness of any proposed remediations.
Results of the powerflow analyses show that various criteria violations occur on the
existing AZ and NM systems with the XXX project.
Powerflow analysis results show that the Green-AE 345/230 kV transformer owned by
SWTC (Southwest Transmission Cooperative, Inc) is overloaded during a singlecontingency of the PYoung-Winchester 345 kV line in the 2011 HS case with the XXX
project modeled. This overload is not present prior to the addition of the XXX project.
Therefore, for this study, it will be assumed that adding a second Green-AE 345/230 kV
autotransformer will alleviate this overload that will be assigned as a direct consequence
of the XXX project for the net MW output studied in the applicable study year identified
in Section 5.5. This is noted for this report. EPE did coordinate through XXX to address
the overloading of the Green-AE 345/230 kV under the above N-1 condition. This
overload will be examined in any follow up study for the XXX project.
The results in Section 5.11 indicate that with the XXX project net MW of 300 MW at the
Luna 345 kV bus), the angle range of the Arroyo PST is affected. Specifically, with a
schedule of 201 MW N-S on the Arroyo PST an angle of – 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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
4
El Paso Electric Company
August 2006
Some post-XXX project post-contingency thermal violations were observed on some
SNM lines and transformers for some double contingencies (see Table 7, Section 5.7).
However, in this report, it is assumed that the thermal violations during double
contingencies will be used to help identify which elements get overloaded as a result of
the XXX project. In this study, it will be assumed that XXX will not be required to build,
add or modify elements showing a thermal violation for a double contingency (such as
the ones showing up in Table 7) as a result of the XXX project; rather, these overload
violations will help the owners of the these facilities identify what procedures or new
automatic or manual operating procedures need to be in place as a result of the XXX
project.
In order to study the XXX project further, there were some cases developed in which
cases 1-4 were examined without the third party generation labeled a-e previously.
The results of the analysis on these cases revealed minor voltage violations caused by the
XXX project and no overloading violations as a result of the XXX project. There are
some future system additions in SNM that may help with the voltage violations observed.
Total Costs Due to the XXX Project
The total costs of the XXX project are the sum of the interconnection costs plus the costs
of the NM system modifications to alleviate the impacts to the NM system because of the
XXX project. These total costs are shown on Table A.
Table A
Estimated Total Costs: XXX Project Costs and Costs
of SNM Facility Additions/Modifications Needed due to the XXX Project
SYSTEM MODIFICATION COSTS
XXX Generator Interconnection costs to the Luna 345 kV Bus
Total Costs to Interconnect the XXX Project
YEAR
2009
ESTIMATED
COST (2006$)
$ 2,500,000
$ 2,500,000
Note that is the report, the costs associated with adding a second Green-AE 345/230 kV
transformer to relieve an overload caused by the XXX project in 2011 were not included
in the costs assigned to the XXX project. Therefore, any equipment and related costs
associated with and including a second Green-AE 345/230 kV transformer does not
appear on Table A. However, this violation is noted for this report and may be included
as a cost in the next XXX study.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
5
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
6
El Paso Electric Company
August 2006
2.0 PURPOSE
The purpose of this Feasibility Study (FS) is to provide a fatal flaw feasibility analysis of
the New Mexico (NM) and Arizona (AZ) transmission systems, determine any violations
of criteria due to the XXX project described in the next section, recommend facilities
needed to accommodate the XXX project, and provide associated non-binding good faith
cost estimate for those facilities. As such, this Study will to identify potential major
impacts associated with the XXX project.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
7
El Paso Electric Company
August 2006
3.0 INTRODUCTION
XXXXXXXXXXXXXXXXXX (XXX) has submitted a valid request for a generator
interconnection to the EPE system. Therefore, as per the requirements of the Federal
Energy Regulatory Commission (FERC) Large Generator Interconnection Procedures
(LGIP), EPE is initiating a Feasibility Study (FS) to study the interconnection of a 300
MW Solar photovoltaic plant (the XXX project) to the Luna 345 kV Switching Station in
Deming, NM (“the XXX Generator Interconnection”). This FS was performed in
response to XXX’s request to determine any impacts on the New Mexico (NM) and
Arizona (AZ) systems including the El Paso Electric (EPE) system due to the
interconnection of the XXX project that was studied at two net MW output levels. The
cases modeled the net MW output from the XXX project as the following: 180 MW and
300 MW for the years 2009 and 2011, respectively. The output from the plant was
scheduled to WECC. The XXX project was connected through a 115/345 kV, 340/360
MVA step-up transformer. Each case was studied using the criteria and methodologies
described in subsequent sections of this study report.
The study was performed as a joint analysis by EPE and Public Service Company of New
Mexico (PNM). EPE, XXX, and PNM developed a Study Scope for this study
(Appendix 1). This scope included the examination of different Scenarios for the XXX
Generator Interconnection (see Base Case Development under Methodology).
The study periods analyzed in this study were the 2009 Heavy Summer (HS) and 2011
HS load seasons. EPE and PNM did not analyze any other seasons with different import
levels, load levels, and/or generation patterns in this FS.
This Study was performed in order to identify potential major impacts associated with the
XXX Generator Interconnection, to provide a preliminary view of the efforts, identify the
facility additions and modifications to the NM system that will mitigate those impacts
(remediations) that are a result of the XXX project for the scenarios outlined in the Study
Scope (Appendix 1), and to provide good faith estimates of the costs that would be
needed to achieve the XXX project with a good-faith estimate of the construction time.
As part of the evaluation process in studying the impact of the XXX generation on the
NM and AZ transmission systems, this FS included powerflow, Q-V reactive margin, and
short circuit analyses. The study results were evaluated using contingency voltage and
loading requirements and criteria under All-Lines-in-Service (ALIS), single contingency
(N-1) conditions, double contingency (N-2) conditions, in addition to the reactive margin
criteria identified in the sections that follow. However, this feasibility study does not
include additional studies to validate the effectiveness of any proposed remediations.
The impacts of the XXX project on the southern New Mexico (SNM) system were noted
and included for the purposes of remediations and associated costs.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
8
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
9
El Paso Electric Company
August 2006
The performance criteria utilized in monitoring the SNM and northern New Mexico
(NNM) area are shown in Table 1.
Table 1: Performance Criteria.
AREA
CONDITIONS
LOADING
LIMIT
VOLTAGE
(P.U.)
0.95 - 1.05
0.95 - 1.10
Normal
< Normal Rating
VOLTAGE
DROP
0.95 - 1.08
0.90 - 1.05
EPE
Contingency
< Emergency
Rating
0.925 - 1.05
0.95 - 1.10
7%
0.95 - 1.08
7%
0.90 - 1.05
0.95 - 1.05
Normal
LOS ALAMOS
Contingency
Normal
TSGT
Contingency
Normal
< Normal Rating
< Emergency
Rating
< Normal Rating
< Emergency
Rating
< Normal Rating
7%
0.95 - 1.05
6%
Contingency
Normal
TNMP
Contingency
0.95 - 1.05
60kV and above
60kV and above
0.95 - 1.05
Normal
AZ
3.1.1
Contingency
< Emergency
Rating
< Normal Rating
< Emergency
Rating
< Normal Rating
< Emergency
Rating
60kV and above
0.90 - 1.10
60kV and above
6%
PNM
COMMENTS
69kV and above
Artesia 345 kV
Arroyo 345 kV PS source
side
Alamo, Farmer, Rgc Lobo,
Sierra Blanca and Van
Horn 69kV
60 kV to 115 kV
Artesia 345kV
Arroyo 345kV PS source
side
Alamo, Farmer, Rgc Lobo,
Sierra Blanca and Van
Horn 69kV
Hidalgo, Luna, or other
345 kV buses
60kV and above
7%
0.95 - 1.05
0.925 - 1.05
6%
0.95 - 1.05
0.925 - 1.05
60kV and above
Luna, Mimbres, Hermanas,
Hondale, and Deming
115kV
60kV and above
60kV and above
100kV and above
5%
100kV and above
Voltage Violation Criteria
The voltage criteria used in this study is shown in Table 1. All voltages 69 kV or above
in cases with ALIS must have per unit voltages between 0.95 and 1.05 pu. Under
contingency conditions, voltage drops cannot exceed the voltage drop criteria. For all
cases during contingencies the per unit voltages cannot exceed 1.05 pu.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
10
El Paso Electric Company
August 2006
3.1.2
Voltage Drop Violation Criteria
The voltage drop criteria used in this study is shown in Table 1.
It should be noted that the voltage drop criteria is specified as a percentage of the precontingency voltage. For example, if the pre-contingency voltage at the Luna 345kV bus
is 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 preto post-contingency must be no greater than 8% for N-1 contingencies and no
greater than 10% for N-2 contingencies.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
11
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
12
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
13
El Paso Electric Company
August 2006
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.
b.
c.
d.
e.
570 MW of generation interconnected at the Luna 345 kV Substation (scheduled to
WECC).
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).
160 MW of generation interconnected at TNMP’s Hidalgo 115 kV substation
(scheduled to WECC).
80 MW of generation interconnected at TNMP’s Lordsburg 115 kV substation
(scheduled to WECC).
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:
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
14
El Paso Electric Company
August 2006
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-toWestmesa (see Table 2, next, for schedule details).
Table 2. Arroyo PST Schedule*
SCHEDULING
ENTITY
EPE (OATT)
EPE (SSI)
TSGT
PNM
PNM (AFTON GENERATION
THROUGH
ARROYO PST TO PNM)
WAPA
60 MW N-S (WESTMESA TO
ARROYO) ARROYO PST
SCHEDULE
-104
-20
-50
-25
+141
201 MW N-S (WESTMESA TO
ARROYO) ARROYO PST
SCHEDULE
-104
-20
-50
-25
0
-2
-2
* Negative denotes Westmesa to Arroyo schedule.
Positive denotes Arroyo to Westmesa schedule.
The Arroyo PST angle setting in each case is included in this report in Section 5.12 in
order to document that Arroyo PST maximum angle criteria was not exceeded.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
15
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
16
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
17
El Paso Electric Company
August 2006
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 alllines-in-service (ALIS) for both loading and voltage criteria violations. Next, single and
double contingency powerflow analysis was performed on these benchmark cases by
taking single and double contingencies on most lines and transformers with base voltages
of 100 kV and above in the SNM area and 69 kV and above in the EPE area as
determined by engineering judgment (see Section 4.2.6). All bus, lines, and transformers
with base voltages greater than or equal to 60 kV in the New Mexico area including the
EPE control area were monitored in all study cases. All generators were modeled with
regard to self-regulating or remote bus regulating as they are modeled in the submitted
WECC GE format powerflow data. All generators which control a high side remote bus
will be set at the pre-disturbance voltage at the terminal bus. The single and double
contingencies were taken one at a time. When modeling a single or double contingency
involving an autotransformer or line that is connected to the Luna 345 kV bus (e.g. any
345 kV line connected to the Luna 345 kV bus: Springerville-Luna, Luna-Arroyo, LunaHidalgo, Luna-Newman, and/or the Luna 345/115 kV autotransformer), the XXX unit
was modeled in two separate ways: 1) as tripped, outage takes out the XXX project
simultaneously, and 2) as not tripped, outage does not take out the XXX project.
Engineering judgment was used to determine if the XXX project unit was also tripped for
a single or double contingency involving any other element(s) in the system.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
18
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
19
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
20
El Paso Electric Company
August 2006
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
Blythe-Buckblvd 161 kV Line
Blk Mesa 230 kV/BMA.3WP3 100 kV Transformer
Blk Mesa 230 kV/BMA.4WP3 100 kV Transformer
Cholla 345 kV/ Cholla 7 100 kV Transformer
Cholla 230 kV/ Cholla 7 100 kV Transformer
N.Havasu 230 kV/N.HAV3WP 100 kV Transformer
Tucson 138 kV/TUC.3WP 100 kV Transformer
Blythe-Buckblvd 161 kV Line
Blk Mesa 230 kV/BMA.3WP3 100 kV Transformer
Case
2011 HS
2011 HS
2011 HS
2011 HS
2011 HS
2011 HS
2011 HS
2011 HS
2011 HS
Owner
AZ
AZ
AZ
AZ
AZ
AZ
AZ
AZ
AZ
Rating(MVA)
400
40
40
203
203
80
100
440
44.8
% Loading
120.6
116.8
111.5
102.7
101.6
100.1
100.1
109.6
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
Benchmark Cases (without the XXX Project)
for
Overloaded
Elements
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
21
El Paso Electric Company
August 2006
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
Lordsbrg 115/69 Kv Transformer
2009 HS
Lordsbrg 115/69 Kv Transformer
Central-Silver 69 kV Line
Leo-Milagro 69 kV Line
Owner
PNM/
TNMP
PNM/
2011 HS
TNMP
PNM/TN
2011 HS
MP
2009 HS
EPE
Rating
(MVA)
% Loading
27.0
111.0
27.0
107.2
27.0
102.0
69.4
121.4
Contingency Description
Hidalgo-Turquoise 115 kV
Line (RAS)
Hidalgo-Turquoise 115 kV
Line (RAS)
Turquois 115/69 kV
Transformer
Milagro-Newman 115 kV
Line
As shown in Table 4, some pre-XXX project post-contingency thermal violations were
observed on some SNM lines and transformers. These contingency criteria violations
listed in Table 4 will not have a penalizing effect on the evaluation of the XXX project.
5.3 Double-Contingency (N-2) Analysis Results for Overloaded Elements
Benchmark Cases (without the XXX Project)
The benchmark cases as described in Section 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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
22
El Paso Electric Company
August 2006
Table 5. Post-Contingency (N-2) Thermal Violations, Benchmark Cases, SNM
Elements
Rating
(MVA)
% Loading
27.0
120.5
27.0
121.4
153.0
131.4
153.0
133.8
PNM/
TNMP
153.0
100.9
2011 HS
PNM/
TNMP
153.0
100.4
Central- Turquoise 115 kV Line
2011 HS
PNM/
TNMP
133.4
112.2
Central- Turquoise 115 kV Line
2009 HS
EPE
133.4
110.6
Mesa-Rio Grande 115 kV Line
2009 HS
EPE
195.6
100.5
Element
Case
Lordsbrg 115/69 Kv Transformer
2009 HS
Lordsbrg 115/69 Kv Transformer
2011 HS
Hidalgo-Turquoise 115 kV Line
2009 HS
Hidalgo-Turquoise 115 kV Line
2011 HS
Hidalgo-Turquoise 115 kV Line
2009 HS
Hidalgo-Turquoise 115 kV Line
Owner
PNM/
TNMP
PNM/
TNMP
PNM/
TNMP
PNM/
TNMP
Contingency Description
Hidalgo 345/115 kV T1
& T3 Transformers
Hidalgo 345/115 kV T1
& T3 Transformers
Hidalgo 345/115 kV T1
& T3 Transformers
Hidalgo 345/115 kV T1
& T3 Transformers
Luna-Afton 345 kV Line &
Luna 345/115 kV
Transformer
Luna-Afton 345 kV Line &
Luna 345/115 kV
Transformer
Hidalgo 345/115 kV T1
& T3 Autotransformers
Hidalgo 345/115 kV T1
& T3 Transformers
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 postcontingency 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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
23
El Paso Electric Company
August 2006
Table 6. Post-Contingency (N-1) Thermal Violations, Cases with the XXX Project
Modeled, SNM Elements
Element
Case
Owner
Rating
(MVA)
% Loading
Contingency Description
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
24
El Paso Electric Company
August 2006
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
Element
Case
Owner
Rating
(MVA)
% Loading
Luna 345/115 kV Autotransformer
2009 HS
PNM
224
101.2
Luna 345/115 kV Autotransformer
2011 HS
PNM
224
110.2
ElButte-Picacho 115 kV Line
2011 HS
TSGT
40
105.3
Contingency Description
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
25
El Paso Electric Company
August 2006
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 CalienteAmrad 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 CalienteAmrad 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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
26
El Paso Electric Company
August 2006
Table 8. Voltage Violations due to the XXX Project, Single-Contingencies (N-1)
Bus Name kV (Area)
Case
ALIS
Voltage
N-1
Voltage Drop
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)
HOLLYWOOD 115
(TNMP)
GAVILAN 115 (TNMP)
2009 HS
1.0490
1.0509
Luna-Hidalgo 345 kV line, the XXX project Stays In During Outage*
2011 HS
0.9849
0.925
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
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)
Bus Name kV (Area)
TYRONE 69 (TNMP)
WHITE SANDS 115
(EPE)
SPARKS 69 (EPE)
SE 1 115 (EPE)
Case
ALIS
Voltage
N-2
Voltage Drop
Voltage (pu)
(%)
2009 HS
0.9876
0.9249
6.35
2011 HS
1.0274
0.9249
9.98
Double Contingency
Under which Voltage Violation Occurred
2011 HS
1.038
0.9244
10.94
Luna-Hidalgo 345 kV line and Luna 345/115 kV Autotransformer, the XXX project Drops During
Outage
Amrad-Artesia 345 kV line and
Amrad 345/115 kV Autotransformer
Caliente-Newman and Newman-Afton 345 kV lines
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
27
El Paso Electric Company
August 2006
For voltage violations in which voltages of 1.05-1.0504 p.u. occurring during a singlecontingency 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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
28
El Paso Electric Company
August 2006
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
Blythe-Buckblvd 161 kV Line
Blk Mesa 230 kV/BMA.3WP3 100 kV Transformer
Blk Mesa 230 kV/BMA.4WP3 100 kV Transformer
Verde N-Yavapai 100 kV Line
Tucson 138 kV/TUC.3WP 100 kV Transformer
Blythe-Buckblvd 161 kV Line
Blk Mesa 230 kV/BMA.3WP3 100 kV Transformer
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
Case
2011 HS
2011 HS
2011 HS
2011 HS
2011 HS
2011 HS
2011 HS
29
Owner
AZ
AZ
AZ
AZ
AZ
AZ
AZ
Rating(MVA)
400
40
40
319
100
440
44.8
% Loading
120.6
116.1
110.9
102.0
100.1
109.6
103.6
El Paso Electric Company
August 2006
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
Element
Case
Owner
Rating
(MVA)
% Loading
Contingency Description
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
30
El Paso Electric Company
August 2006
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
Element
Case
Owner
Rating
(MVA)
% Loading
Hidalgo-Turquoise 115 kV Line
2009 HS
PNM/
TNMP
153.0
103.9
Hidalgo-Turquoise 115 kV Line
2011 HS
PNM/
TNMP
153.0
103.3
Algodone-Moriarty 115 kV Line
2009 HS
TSGT
66.0
101.3
Contingency Description
Luna-Afton 345 kV Line &
Luna 345/115 kV
Transformer
Luna-Afton 345 kV Line &
Luna 345/115 kV
Transformer
Luna-Afton & SpringervilleLuna 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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
31
El Paso Electric Company
August 2006
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 CalienteAmrad 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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
32
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
33
El Paso Electric Company
August 2006
Table 13. Voltage Violations due to the XXX Project, Single-Contingencies (N-1) – No Third Party Generation Cases –
Sensitivity
Bus Name kV (Area)
Case
ALIS
Voltage
N-1
Voltage Drop
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
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
34
El Paso Electric Company
August 2006
Table 14. Voltage Violations due to the XXX Project, Double-Contingencies (N-2) – No Third Party Generation Cases –
Sensitivity
Bus Name kV (Area)
Case
ALIS
Voltage
N-2
Voltage Drop
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
CENTRAL 69 (TNMP)
2011 HS
0.9974
0.9072
9.04
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
CENTRAL 115 (TNMP)
2011 HS
1.0008
0.9168
8.39
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
DEMINGPG 69 (TSGT)
2009 HS
0.9918
0.9173
7.51
PLAYAS 69 (TSGT)
2011 HS
1.0036
0.9246
7.87
WILLARD 115 (TSGT)
2011 HS
0.9650
0.9248
4.17
ESTANCIA 115 (TSGT)
2011 HS
0.9611
0.9213
4.14
TYRONE 69 (TNMP)
2011 HS
0.9851
0.9233
6.27
Afton-Newman & Luna-Afton 345 kV Double Contingency, the XXX project Drops During Outage
Afton-Luna & Springerville-Luna 345 kV Double Contingency, the XXX project Drops During
Outage
Afton-Luna & Springerville-Luna 345 kV Double Contingency, the XXX project Drops During
Outage
Afton-Luna & Springerville-Luna 345 kV Double Contingency, the XXX project Drops During
Outage
Afton-Luna & Springerville-Luna 345 kV Double Contingency, the XXX project Drops During
Outage
Springerville-Luna 345 kV, the XXX project Drops During Outage
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
35
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
36
El Paso Electric Company
August 2006
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
37
El Paso Electric Company
August 2006
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 outages, in which the AlamogordoHolloman 115 kV line is modeled in the case, appear in Table 15 and Table 16. It must
be noted, however, that these voltage violations also existed in the applicable benchmark
case without the XXX project; therefore, the voltage violations shown in Table 15 and
Table 16 do not occur as a consequence of the XXX project and are only shown so that a
comparison can be made between the 2009 and 2011 cases with the XXX project and the
Alamogordo-Holloman 115 kV line modeled as off (Table 15) and the 2009 and 2011
cases with the XXX project and the Alamogordo-Holloman 115 kV line modeled as on
(Table 16). By comparing Table 15 to Table 16, the main effect of the AlamogordoHolloman 115 kV line upon SNM voltages during these two key single contingencies can
be seen. As far as the effect of the Alamogordo-Holloman 115 kV line on power flows,
this line provides another feed into Holloman and Alamogordo (AlamoGCP) 115 kV
buses; as can be seen by comparing Table 15 to Table 16, this additional line allows the
Alamogcp-Amrad 115 kV line single outage to converge in the cases with AlamogordoHolloman 115 kV line modeled as on (Table 16) versus non-convergence when this line
is modeled as off (Table 15).
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
38
El Paso Electric Company
August 2006
Table 15. Voltage Violations with XXX Project with Holloman-Alamogordo 115 kV Line Modeled Off (Study Cases with XXX
Project) for Key Single-Contingencies (N-1)
Bus Name kV (Area)
Case
ALIS
Voltage
2009 HS
Contingency
Under which Voltage Violation Occurred
Alamogcp-Amrad 115 kV line
DOES NOT CONVERGE
2011 HS
HOLLYWOOD/GAVILAN/
RUIDOSO 115
(TRIS/TNMP)
ALAMOGPG 69 (TSGT)
ALAMOGCP 115 (TNMP)
ALAMOGPG 115 (TSGT)
HOLLOMAN 115 (EPE)
HOLLYWOOD 69 (TSGT)
AMRAD 115 (EPE)
LARGO 115 (EPE)
MAR 115 (EPE)
HOLLYWOOD/GAVILAN/
RUIDOSO 115
(TRIS/TNMP)
ALAMOGPG 69 (TSGT)
N-1
Voltage Drop
Voltage (pu)
(%)
Alamogcp-Amrad 115 kV line
2009 HS
0.9849
0.8734
11.32%
Amrad 345/115 kV Autotransformer
2009 HS
2009 HS
2009 HS
2009 HS
2009 HS
2009 HS
2009 HS
2009 HS
1.0148
0.9942
0.9941
1.0375
1.0348
1.0267
1.0272
1.0265
0.8973
0.8946
0.8945
0.9234
0.914
0.9202
0.9193
0.9183
11.58%
10.02%
10.02%
11.00%
11.67%
10.37%
10.50%
10.54%
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
2011 HS
0.9857
0.8718
11.56%
Amrad 345/115 kV Autotransformer
2011 HS
1.0229
0.9004
11.98%
Amrad 345/115 kV Autotransformer
ALAMOGCP 115 (TNMP)
2011 HS
0.9923
0.8901
10.30%
Amrad 345/115 kV Autotransformer
ALAMOGPG 115 (TSGT)
2011 HS
0.9922
0.89
10.30%
Amrad 345/115 kV Autotransformer
HOLLOMAN 115 (EPE)
2011 HS
1.0368
0.9190
11.36%
Amrad 345/115 kV Autotransformer
HOLLYWOOD 69 (TSGT)
2011 HS
1.0346
0.9110
11.95%
Amrad 345/115 kV Autotransformer
AMRAD 115 (EPE)
2011 HS
1.0272
0.9175
10.68%
Amrad 345/115 kV Autotransformer
LARGO 115 (EPE)
2011 HS
1.0274
0.9162
10.82%
Amrad 345/115 kV Autotransformer
MAR 115 (EPE)
2011 HS
1.0266
0.9152
10.85%
Amrad 345/115 kV Autotransformer
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
39
El Paso Electric Company
August 2006
Table 16. Voltage Violations with XXX Project with Holloman-Alamogordo 115 kV Line Modeled On (Sensitivity Cases) for
Key Single-Contingencies (N-1)
Bus Name kV (Area)
HOLLYWOOD/GAVILAN/
RUIDOSO 115
(TRIS/TNMP)
HOLLYWOOD/GAVILAN/
RUIDOSO 115
(TRIS/TNMP)
HOLLYWOOD/GAVILAN/
RUIDOSO 115
(TRIS/TNMP)
ALAMOGPG 69 (TSGT)
ALAMOGCP 115 (TNMP)
ALAMOGPG 115 (TSGT)
HOLLOMAN 115 (EPE)
HOLLYWOOD 69 (TSGT)
AMRAD 115 (EPE)
LARGO 115 (EPE)
MAR 115 (EPE)
HOLLYWOOD/GAVILAN/
RUIDOSO 115
(TRIS/TNMP)
ALAMOGPG 69 (TSGT)
Case
ALIS
Voltage
N-1
Voltage Drop
Voltage (pu)
(%)
Contingency
Under which Voltage Violation Occurred
2009 HS
0.9997
0.9236
7.61%
Alamotap-Amrad 115 kV line
2011 HS
1.0008
0.9180
8.27%
Alamotap-Amrad 115 kV line
2009 HS
0.9997
0.8821
11.76%
Amrad 345/115 kV Autotransformer
2009 HS
2009 HS
2009 HS
2009 HS
2009 HS
2009 HS
2009 HS
2009 HS
1.0304
1.0076
1.0075
1.0136
1.0385
1.0267
1.0218
1.021
0.9065
0.9022
0.9022
0.9057
0.9127
0.9189
0.9149
0.9140
12.02%
10.46%
10.45%
10.65%
12.11%
10.50%
10.46%
10.48%
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
2011 HS
1.008
0.8806
12.64%
Amrad 345/115 kV Autotransformer
2011 HS
1.0273
0.8997
12.42%
Amrad 345/115 kV Autotransformer
ALAMOGCP 115 (TNMP)
2011 HS
1.006
0.8979
10.75%
Amrad 345/115 kV Autotransformer
ALAMOGPG 115 (TSGT)
2011 HS
1.0059
0.8978
10.75%
Amrad 345/115 kV Autotransformer
HOLLOMAN 115 (EPE)
2011 HS
1.0122
0.9014
10.95%
Amrad 345/115 kV Autotransformer
Amrad 345/115 kV Autotransformer
HOLLYWOOD 69 (TSGT)
2011 HS
1.0387
0.9099
12.40%
AMRAD 115 (EPE)
2011 HS
1.0271
0.9162
10.80%
Amrad 345/115 kV Autotransformer
LARGO 115 (EPE)
2011 HS
1.0217
0.9118
10.76%
Amrad 345/115 kV Autotransformer
MAR 115 (EPE)
2011 HS
1.0209
0.9108
10.78%
Amrad 345/115 kV Autotransformer
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
40
El Paso Electric Company
August 2006
5.12
PST Phase Angle Values Analysis
The Arroyo PST angle was investigated at several key schedules of interest. The PST
angle was investigated simply by changing the PST schedule (as metered at the
Westmesa 345 kV bus) in the cases used in this study. Note that with a 201 MW N-S
schedule on the Arroyo PST, the Afton GT schedule of 141 MW was scheduled to
WECC and not through the Arroyo PST.
The results of this analysis appear in Table 17.
Table 17. Arroyo PST Angle with Various Schedules for All Study Cases
CASE
2009 HS
BENCHMARK
2009 HS
BENCHMARK
2009 HS
BENCHMARK
2009 HS
with the XXX Project
at 180 MW
2009 HS
with the XXX Project
at 180 MW
2009 HS
with the XXX Project
at 180 MW
2011 HS
BENCHMARK
2011 HS
BENCHMARK
2011 HS
BENCHMARK
2011 HS
with the XXX Project
at 300 MW
2011 HS
with the XXX Project
at 300 MW
2011 HS
with the XXX Project
at 300 MW
PST MW FLOW
METERED AT
WESTMESA 345 kV
ARROYO PST
BUS
ANGLE (DEGREES)
(N-S)
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
-30.1
6.81
60
- 4.79
201
-24.03
-30
2.37
60
-9.31
201
-28.86
-30
5.91
60
- 5.86
201
- 24.74
-30
-1.64
60
-13.60
199.3
-33.07
41
El Paso Electric Company
August 2006
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, the
results in Table 17 indicate that the XXX project has an affect on the PST angle when
compared to the benchmark cases. Note that in the 2011 HS case with the XXX project
(with the XXX project net MW of 300 MW at the Luna 345 kV bus), 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 was an additional sensitivity examined in this study, this case had the following
assumptions: this case was based on the 2011 HS case with the XXX project (with the
XXX project net MW of 300 MW at the Luna 345 kV bus), with a schedule of 201 MW
N-S on the Arroyo PST, and the Afton GT schedule of 141 MW was scheduled to PNM
through WECC and not through the Arroyo PST. In this sensitivity case, the angle range
of the Arroyo PST (+/- 34 degrees) was hit at the – 34 degree end with the XXX project
and that the schedule of 201 MW N-S is not able to be accomplished. The violation of
the Arroyo PST angle range as a result of the XXX project in the 2011 HS case will be
noted in this study. However, due to the schedule under which the violation occurs, there
will be no costs assigned to the XXX project in this study.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
42
El Paso Electric Company
August 2006
6.0 Q-V REACTIVE MARGIN ANALYSIS RESULTS
Q-V analyses were conducted in order to verify that the cases with the XXX project
comply with the WECC Voltage Stability and Reactive Margin Criteria. Q-V analysis
provides a way to investigate the potential for voltage collapse during the post-transient
period within 3 minutes after the disturbance. Q-V analyses were performed on all cases
to verify that the WECC criterion for reactive power margin was met under the worst
contingencies on the EPE system. 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. As proscribed
by the WECC method, 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.
The following was used in the Q-V analysis. For all cases, EPE load was increased by 5
% as per WECC methodology. The worst single contingency impacting reactive power
margin in the benchmark case was the Afton-Newman 345 kV line contingencies
(although, the analysis was performed for the worst two single-contingencies, the next
worst single contingency being the Luna-Diablo 345 kV line single contingency).
Q-V analysis for double contingencies was not performed in this study. Q-V plots were
performed for the worst single contingencies at the buses most impacted, the 345 kV
buses that follow: Arroyo, Diablo, Hidalgo, Luna, Newman, and Caliente. The most
critical bus in the case with the XXX project was either EPE’s Caliente 345 kV bus or
EPE’s Diablo 345 kV bus. From here, Q-V plots were created showing the margins
available at the 345 kV buses previously identified.
The end results were that for the XXX project cases (with a 5 % EPE load increase) there
was positive margin at the weakest bus (Caliente 345 kV or Diablo 345 kV) under the
worst contingency (the Afton-Newman 345 kV line) in both the 2009 and 2011 HS cases.
The resulting plots and reactive power margins of the analyses can be found in
Appendix 7. The tables that follow show the reactive power margins available and the
most critical bus in each case. Please note that a negative number indicates that there is
sufficient reactive power to meet WECC criteria and a positive number would indicate
that the system is deficient in reactive power and does not meet the criteria.
The results in Table 18 show the results for the QV analysis portion of this study.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
43
El Paso Electric Company
August 2006
Table 18. Summary of Q-V Reactive Margin Results for all Cases,
Weakest Bus (Caliente 345 kV Bus),
Worst Single Contingency (Afton-Newman 345 kV Line Outage),
5 % EPE Load Increase Methodology
CASE
WEAKEST BUS
WORST OUTAGE
XXX GENERATOR
INTERCONNECTIO
N
MODELED
ARROYO
PST SCHEDULE
MW (N-S)
REACTIVE
MARGIN
(MVAR) >
CASE DESCRIPTION
2009 HS
2011 HS
2009 HS
with the XXX Project
2011 HS
with the XXX Project
BENCHMARK
at 180 MW
BENCHMARK
at 300 MW
Caliente 345
Caliente 345
Caliente 345
Caliente 345
Afton-Newman 345 Afton-Newman 345 Afton-Newman 345 Afton-Newman 345
kV Line
kV Line
kV Line
kV Line
NO
YES
NO
YES
60
60
60
60
- 193.0
- 192.8
- 217.5
- 214.5
As can be seen in the above table, there were no reactive power margin deficiencies in
any of the cases in this study.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
44
El Paso Electric Company
August 2006
7.0 SHORT CIRCUIT ANALYSIS
This section covers the short circuit analysis performed for the XXX project. When
generation is added to a system, the available fault current of that system increases.
Therefore, a study, called a short circuit study, has been performed to determine if the
SNM existing substation circuit breakers in the substations electrically near the new
generation have adequate short circuit interruption duties. This short circuit analysis
portion of the study was performed jointly between by EPE, Public Service Company of
New Mexico (PNM), and Mark Galey of Electrical Systems Consultants (consultant to
XXX).
7.1
Short Circuit Analysis Modeling
In the powerflow cases used in this study, the XXX project was represented as a
generator and a load (representing manufacturing plant and other auxiliary load at the
XXX site) connected to the XXX # 1 115 kV bus. From here the XXX #1 115 kV bus is
connected to the XXX #1 345 kV bus via a 200/266/340/360 MVA 115/345 kV step-up
transformer. The XXX #1 345 kV bus is then connected to the Luna 345 kV bus via a
345 kV transmission line section.
The following was the representation used by the XXX consultant. The new generation
proposed by XXX is sited at a new XXX 34.5 kV substation (XXX #1 34.5 kV). In the
representation used by the XXX consultant for the purposes of determining the short
circuit contribution of the XXX project, the XXX project was represented as a generator
and a load (representing manufacturing plant and other auxiliary load at the XXX site)
connected to the XXX # 1 34.5 kV bus. From here the XXX #1 34.5 kV bus is connected
to the XXX #1 345 kV bus via a 200/266/340/360 MVA 34.5/345 kV step-up
transformer. The XXX #1 345 kV bus is then connected to the Luna 345 kV bus via a
345 kV transmission line section.
For the short circuit representation of the XXX project, Mr. Mark Galey states:
“In setting up the 2009 and 2011 WECC load flow (PSSE) base cases, the solar generator
model developed was consolidated as a "synchronous machine" with a 0.90 per unit
resistive component and 0.024 degree phase angle of the subtransient impedance on a 337
MVA generator base (331.5 MW + j 61 MVAR = 337 MVA). This model of the
photovoltaic generation will actually approach 1.1 per unit fault current (generator base)
at near zero degree phase angle, with respect to the internal machine voltage, during short
circuit conditions.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
45
El Paso Electric Company
August 2006
A "synchronous machine" usually (in PSSE for example) can be set with a control
voltage to regulate a remote bus such as the 345-kV bus at the 34.5-345-kV step-up
transformer during normal conditions. Minus (negative) loads, such as Norton current
sources representing photovoltaic generators do not have any voltage regulation
capabilities in the simulation software. The photovoltaic generation (plus possible SVC)
can produce greater than 331 MW and 81.9 MVAR, with a net export of 300 MW + j 61
MVAR into the grid, so voltage regulation is not an issue.
A PSSU (power simulator software) model was developed of the Photovoltaic System
(138-2.4 MW inverters) which explicitly represents numerous three-phase fault current
contributions of discrete 2.4 MW inverter units from the PV system into the utility grid.
This model provides an individually represented series of constant current sources
injecting "fault" current into a remote fault from the inverters. The PV generation can be
either represented in the PSSU model as constant current sources(138 inverters), or as
typical generation during fault conditions using 138 "synchronous machines" with 0.909
per unit resistive component of subtransient impedance.
The base case uses a 362.25-kV high side tap, with SVC at 95 MVAR at the 34.5-kV bus
(104.5 MVAR output at 105% voltage).
Hence, in modeling the contribution of the XXX project into the system, a detailed PSSU
model of the PV system was developed from the 550-volt AC side of the inverter to the
345-kV bus at the Luna Substation. The model was then run in a computer program with
an iterative algorithm, rather than the typical matrix solution, to calculate short circuit
currents. The phase difference between the fault current contributed by the utility, and
that of the photovoltaic generation, yields a magnitude of short circuit (phasor sum) not
significantly more than the fault current contributed by the utility. The maximum fault
current contribution of the PV sources inject a composite peak fault current into the
utility network equal to approximately 110% of the peak generated current during normal
conditions, but at no phase angle difference with the voltage. ”
In addition to the new generation connected to the XXX #1 34.5 kV bus, existing and
potential projects in southern New Mexico were also modeled in the short circuit
analysis.
The following third party generation in EPE’s generator interconnect queue as well as
existing third party generation was modeled:
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
46
El Paso Electric Company
August 2006
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 PST south-to-north to PNM and reducing San Juan
generation).
c. 160 MW of generation interconnected at Texas-New Mexico Power Company’s
Hidalgo 115 kV substation (scheduled to WECC).
d. 80 MW of generation interconnected at Texas-New Mexico Power Company’s
Lordsburg 115 kV substation (scheduled to WECC).
e. 94 MW of generation interconnected at Afton 345 kV Substation (scheduled to
WECC).
These additional generators were modeled in the study to provide a “worst case” scenario
in the event that all are interconnected into EPE’s system before the proposed XXX # 1
generation is interconnected.
Maximum fault currents were then determined at the XXX #1 34.5 kV, XXX #1 345 kV,
Luna 345 kV, and Luna 115 kV buses and other EPE substations of interest or
importance. Maximum fault currents were then determined at all buses that were 1 bus
beyond the XXX project bus(es).
The resulting fault current was then compared to the circuit breaker interruption ratings
of the breakers at each of the above mentioned substations.
These included the following:
Afton 345 kV
Arroyo 345 kV
Diablo 345 kV
Diablo 115 kV
Hidalgo 345 kV
Hidalgo 115 kV
LEF 345 kV
Mimbres 115 kV
Newman 345 kV
Newman 115 kV
Rio Grande 115 kV
Rio Grande 69 kV
The resulting fault current was then compared to the circuit breaker interruption ratings
of the breakers at each of the above mentioned substations.
Note that the information used for the short circuit part of the analysis was updated as of
April 2005.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
47
El Paso Electric Company
August 2006
7.2
Results of the Short Circuit Analysis
The circuit breakers used in the SNM System at 345 kV, 115 kV, and 69 kV buses vary
between the substations. The following is a list of the existing circuit breakers, along
with the interruption rating, at each of the relevant substations:
Breaker
Substation
Afton
Breaker
Voltage
345
345
345
345
345
345
345
Arroyo
345
345
345
345
345
345
345
2418B
2458B
4348B
3018B
5428B
7548B
2098B
40,000
40,000
40,000
40,000
40,000
40,000
40,000
Diablo
345
345
345
1888B
2138B
2258B
40,000
40,000
40,000
Diablo
115
115
115
115
115
115
1586B
1636B
1706B
1806B
2876B
4326B
40,000
40,000
40,000
40,000
40,000
31,500
Hidalgo
345
345
345
345
09782
04982
02782
03882
40,000
40,000
40,000
40,000
Hidalgo
115
115
115
115
115
115
115-968
115-970
115-974
115-980
115-984
115-988
50,000
47,000
40,000
47,000
47,000
47,000
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
Number
6498B
3348B
7628B
4548B
8578B
9728C
CB-CTG1-01
48
Interruption
Rating (Amps)
50,000
50,000
50,000
50,000
50,000
50,000
50,000
El Paso Electric Company
August 2006
Breaker
Substation
LEF
Breaker
Voltage
345
345
345
Number
36682
34482
35582
Interruption
Rating (Amps)
40,000
40,000
40,000
Luna
345
345
345
345
345
345
345
345
345
01982
03082
04182
07482
09682
08582
10682
11782
15082
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
Luna
115
115
115
32162
34362
33262
20,000
20,000
20,000
Mimbres
115
115
115
115
115
10662
12862
13962
14062
15162
17,500
22,000
22,000
17,500
17,500
Newman
345
345
345
345
2448B
6018B
8378B
0538B
40,000
40,000
40,000
40,000
Newman
115
115
115
115
115
115
115
115
115
115
115
115
115
115
115
11950
11101
15601
N-115-1
11951
11401
N-115-7
11957
N-115-8
11952
11601
N-115-3
11953
15501
N-115-19
40,000
50,000
40,000
40,000
40,000
40,000
43,000
43,000
43,000
40,000
50,000
40,000
40,000
40,000
40,000
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
49
El Paso Electric Company
August 2006
Breaker
Substation
Newman
(continued)
Breaker
Voltage
115
115
115
115
115
115
115
115
115
Number
11967
N-115-20
N-115-21
11968
N-115-22
N-115-23
11969
N-115-24
N-115-2
Interruption
Rating (Amps)
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
40,000
Rio Grande
115
115
115
115
115
115
115
115
115
115
115
115
1516B
3316B
4456B
4616B
1766B
2296B
2426B
5146B
1126B
2186B
3856B
5376B
40,000*
23,000
23,000
40,000
40,000
23,000
23,000
40,000
40,000*
23,000
23,000
40,000
Rio Grande
69
69
69
69
69
69
69
69
69
69
69
69
69
69
5009
5003
5907
5005
5006
5007
5701
5501
1254B
5601
5918
5401B
5010
5032
40,000*
40,000
24,000
40,000
40,000
26,000
40,000
31,500
31,500
31,500
40,000
31,500
40,000
40,000
* Currently these breakers have ratings ranging between 19,000-20,000 amperes. They are
expected to be replaced with breakers having 40,000 ampere ratings as part of EPE’s
normal breaker replacement program.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
50
El Paso Electric Company
August 2006
The following describes the procedure used in this short circuit analysis. The short circuit
analysis was first performed with no new XXX project modeled at XXX#1 115 kV (all other
third-party generation projects in service). This gave the “base case” fault duties of the circuit
breakers. The portion of the study that yielded short circuit fault current values, at the key
buses, prior to the XXX project being modeled was performed by EPE. From here, the short
circuit fault current values prior to the XXX project being modeled, at the key buses, were sent
to Mark Galey. Mr. Galey was then able to approximately match EPE fault values in his
PSSU model that did not include the XXX project by changing his model. Mr. Galey then
added the XXX#1 model into the corrected PSSU model at which point, the fault current
contribution due to the XXX project was able to be calculated at the key buses considered for
this short circuit study. These XXX project short circuit fault currents were sent back to EPE
for inclusion in this report as these values yielded the impact of the XXX project on the
existing circuit breakers in the SNM system.
The short circuit (fault) currents for each case at all of the possibly impacted substations are:
Three Phase Line to Ground:
Substation Faulted
Afton 345 kV Bus
Arroyo 345 kV Bus
Diablo 345 kV Bus
Diablo 115 kV Bus
Hidalgo 345 kV Bus
LEF 345 kV Bus
Luna 345 kV Bus
Luna115 kV Bus
Mimbres 115 kV Bus
Newman 345 kV Bus
Newman 115 kV Bus
XXX#1 345 kV Bus
XXX#1 34.5 kV Bus
Rio Grande 115 kV
Rio Grande 69 kV
No XXX project
Fault Current (Amps)
8,628.0
5,974.0
5,154.0
17,820.0
8,473.0
12,227.0
12,290.0
9,827.0
8,516.0
8,276.0
24,918.0
N/A
N/A
19,716.0
18,513.0
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
51
With XXX project
Fault Current (Amps)
8,658.0
5,928.0
5,172.0
17,863.0
8,480.0
12,4270
12,495.0
9,861.0
8,529.0
8,265.0
24,928.0
11,447.0
42,681.0
19,761.0
18,579.0
El Paso Electric Company
August 2006
Single Phase Line to Ground:
Substation Faulted
Afton 345 kV Bus
Arroyo 345 kV Bus
Diablo 345 kV Bus
Diablo 115 kV Bus
Hidalgo 345 kV Bus
LEF 345 kV Bus
Luna 345 kV Bus
Luna115 kV Bus
Mimbres 115 kV Bus
Newman 345 kV Bus
Newman 115 kV Bus
XXX#1 345 kV Bus
XXX#1 34.5 kV Bus
Rio Grande 115 kV
Rio Grande 69 kV
No XXX project
Fault Current (Amps)
8,173.0
5,143.0
4,637.0
17,569.0
6,874.0
12,525.0
12,520.0
11,459.0
8,678.0
8,391.0
29,309.0
N/A
N/A
20,851.0
22,005.0
With XXX project
Fault Current (Amps)
8,208.0
5,137.0
4,623.0
17,612.0
6,888.0
13,476.0
13,488.0
11,775.0
8,702.0
8,400.0
29,342.0
13,202.0
40,476.0
20,890.0
22,022.0
Comparing these fault currents to the appropriate existing circuit breaker interruption ratings
shows that the interconnection of the XXX project, in the configuration and parameters as
given by XXX, will not cause any existing circuit breaker to operate outside its design rating.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
52
El Paso Electric Company
August 2006
7.3
Short Circuit Analysis Conclusions
A short circuit study was performed on the Southern New Mexico system comparing the
maximum fault current on the system at various substations: Luna Substation (both 345 kV
and 115 kV) and each substation directly connected to Luna, both with and without the XXX
project. The results of this study show that the maximum fault current with the XXX project
is less than the minimum interruption rating of any effected existing circuit breaker:
Substation
Afton 345 kV
Arroyo 345 kV
Diablo 345 kV
Hidalgo 345 kV
LEF 345 kV
Luna 345 kV
Newman 345 kV
Diablo 115 kV
Luna 115 kV
Mimbres 115 kV
Newman 115 kV
Rio Grande 115 kV
Rio Grande 69 kV
Minimum Circuit Breaker
Interruption Rating (Amps)
50,000
40,000
40,000
40,000
40,000
40,000
40,000
31,500
40,000
17,500
40,000
23,000*
24,000*
Maximum Fault Current
with XXX project (Amps)
8,658.0
5,977.0
5,172.0
8,635.0
13,476.0
13,488.0
8,400.0
17,864.0
11,775.0
8,702.0
29,342.0
20,890.0
22,022.0
Therefore, the operation of the XXX project with the parameters as given by XXX connected
to the Luna 345 kV bus will not cause any existing circuit breaker to operate outside its
interruption rating limit.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
53
El Paso Electric Company
August 2006
8.0 COST ESTIMATES
The following cost estimates are for system modifications required to meet WECC
reliability criteria if XXX interconnects its proposed solar project into the Luna 345 kV
bus in the 2009 through 2011 time frame. Costs for each case are listed separately.
Project dollar amounts shown are in 2006 U.S. dollars. Labor and overhead costs are
included in these estimates.
It should be noted that the system modifications for the 2009 cases may occur before
2009 depending on the EPE load growth. Hence, the costs associated with these
modifications will also be needed prior to 2009. The same is true for the 2011 case.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
54
El Paso Electric Company
August 2006
8.1
XXX Generator Interconnection Costs
Table 18 below shows the estimated costs for interconnecting the proposed the XXX
project Generation to the Luna 345 kV bus.
Table 18
Facility Additions Needed Interconnect the proposed the XXX Project to the
Luna 345 kV bus
Estimated Cost
Material/Labor/Overhead
$ 2,500,000
TOTAL INTERCONNECTION COSTS
$2,500,000
The costs above only reflect costs at Luna 345 kV substation and the interconnection
arrangements being assumed for the Luna 345 kV substation in Appendix B (Project
Diagrams) of the Study Scope which is contained in Appendix 1 of this study. Looking at
the project diagrams, these costs include a bus expansion of Luna 345 kV Substation at
the west end, two 345 kV gas circuit breakers and associated equipment (accounting for
one position for the interconnection), other equipment (metering, relaying,
communications), and labor/overhead costs. As mentioned previously, this study did not
examine the practicality of solutions therein (in this case if there is enough room at the
Luna 345 kV substation to accommodate this bus expansion).
The costs for regulatory expenses, legal expenses, delays, permitting, land, transmission
costs, and tax costs are not included in this estimate
The estimated interconnection costs shown above include only the costs of the substation
itself, and do not include any of the required network improvements.
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
55
El Paso Electric Company
August 2006
8.2
SNM Facility Additions/Modifications Assumed to be in place prior to the
XXX Project
As stated in section 4.2.1., but shown in this section for clarity, this study models certain
SNM elements in the cases that are associated with the modeling of Newman 5
generation as described in the aforementioned section.
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).
Should the Newman 5 project not materialize in the timeframes assumed in this study, the
study would have to re-examined to see if any item above needs to be added or modified
as a consequence of the XXX project and in what year the addition or modification needs
to be in place. For the purposes of this study, the costs of items 1-5 above will be
assigned to the Newman 5 project.
There were two additional system additions modeled in the 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).
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.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
56
El Paso Electric Company
August 2006
8.3 System Upgrade Costs Due to the XXX Project
The study results show that there are impacts to the AZ and SNM system because of the
XXX project. Powerflow analyses revealed criteria violations due to the addition of the
XXX Generation Interconnection. However, as will be explained in this section, the
costs for the facilities that would remediate the impacts to the SNM system because of
the XXX project will not be included in this study.
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 will not be
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.
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.
See Section 5.5 for more on the facilities violations noted in this section.
8.4
Total Costs
The total estimated costs required to interconnect the proposed the XXX project
generation to the Luna 345 kV bus is shown in Table 19 below.
Table 19 – Estimated Costs of SNM Facility Additions/Modifications Needed due to
the XXX Project
STUDY YEAR
2009 HS
INTERCONNECTION
COST (2006$)
$2,500,000
SYSTEM UPGRADE
COST (2006$)
$2,500,000
TOTAL
TOTAL COST
(2006$)
$2,500,000
$2,500,000
The total estimated cost for the XXX Generation Interconnection is $2,500,000 required
to be spent on projects before 2009.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
57
El Paso Electric Company
August 2006
9.0
DISCLAIMER
This study assumes certain generators will exist in the interconnection queue under
specific system configurations. Should any of these generators have any change to their
project (output level of proposed units or project not materializing) before the proposed
project is interconnected, the results of this Study will have to be reevaluated. Likewise,
any major change in the SNM system will also required a reevaluation of this Study.
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
58
El Paso Electric Company
August 2006
10.0 CERTIFICATION
El Paso Electric Company (EPE) has performed this 300 MW Solar Photovoltaic Plant,
Generator Interconnection Feasibility Study for XXXXXXXXXXXXXXXXXX (XXX)
pursuant to XXX’s Interconnection Feasibility Study Agreement dated February 10,
2006. The Study determined the impacts to the NM system due to the interconnection of
the proposed the XXX Solar photovoltaic plant to the Luna 345 kV bus. The study
recommended facility modifications to correct the impacts due to the addition of the
proposed XXX project and estimated costs for installing the required system
modifications. The generator, step-up transformer and other parameters for the XXX
project were supplied by XXX’s consultant. EPE performed powerflow, Q-V reactive
margin analyses, and short circuit analysis for this study.
Name:
Title:
Signature:
Date:
Generator Interconnection Feasibility Study
300 MW Solar Photovoltaic Plant
59
El Paso Electric Company
August 2006