Tres Amigas, LLC
March 27, 2015
Tres Amigas 2015 Annual Report
Summary
Tres Amigas (TA) is developing the Phase I of the Tres Amigas Super Station (TASS) which will be an
HVDC back to back connection between the Western Electric Coordinating Council (WECC) and the
Southwest Power Pool (SPP) systems. The Phase I will consist of a 750MW back to back HVDC system
utilizing voltage source converter (VSC) technology. Phase II is anticipated to provide an interconnection
between the SPP and ERCOT interconnects. Successive phases may increase the TASS capacity between
the interconnects.
The Tres Amigas project was placed in the WECC portal on September 17, 2010. The Initial Progress
Report for the project was submitted to the WECC on February 23, 2012, which initiated the Project
Coordination Process and periodic updates have been provided. The Comprehensive Progress Report,
submitted on April 6, 2013, provided an overall description of the Phase I Project, results of studies
performed by PNM and status of the TASS.
TASS more recently has been working with WestConnect, the overlying Regional Planning Area where it
has presence with its interconnection to PNM, for inclusion in the WestConnect 2015 transmission plan.
TASS continues to update the new WestConnect Portal as well as the WECC portal on its status.
TASS
The TASS will be constructed on property controlled by TA north of Clovis, NM. The site is large enough
to allow significant expansion of the TASS as the regional transmission capacity is expanded. Figure 1
provides information about the site which is located approximately 20 miles north of Clovis, New
Mexico.
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March 27, 2015
Figure 1
TASS Site Information
TASS Site
On the WECC side, the TASS will be connected to the Blackwater 345 kV substation via an approximately
22 mile single circuit 2-conductor bundle, 1272 kcmil single circuit 345kV transmission line. The
Blackwater station is a 200MW back to back HVDC station owned by PNM. The TASS is proposed to
connect to the existing 345 kV Tolk substation in the SPP electric grid via an approximately 56 mile, 2conductor bundle, 1272 kcmil 345kV transmission line. Each line is designed for a thermal rating of
approximately 1600Mva. Figure 2 provides a one line of the proposed interconnections and the TASS.
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March 27, 2015
Figure 2
TASS Interconnection Points
The HVDC portion of the TASS will be based on voltage source converter technology (VSC). VSC
technology provides advantages over line-commutated HVDC systems in areas where significant voltage
support is needed for higher levels of power transfer.
TA will register as a Balancing Authority within WECC.
There are no WECC defined Paths adjacent to the TASS.
Studies
TA requested a wires-to-wires interconnection with the SPP and PNM systems and began formal analysis
in the spring of 2011. This request was for a zero flow interconnection and did not include a request for
firm transmission service from any existing transmission owners within WECC or SPP. It was understood
by the parties that as users of the TASS were identified, that these parties would be making transmission
service requests based on their source and sink locations and on their needs. Study scopes for the
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March 27, 2015
System Impact Studies (SIS) (required as part of the Interconnection Agreement assessments) were
developed with the SPP and PNM and formed the basis for the study results. The primary purpose of
the SIS was to identify any reliability concerns associated with the interconnection of the TASS and
support the approval process of the interconnection request with PNM and the SPS/SPP.
Studies for inclusion in the SIS on the WECC side of the interconnection were performed by PNM.
Studies for the SIS on the SPS/SPP side were performed by TA and coordinated with several affected
parties, including the WECC, who, through this designation, has access to all analyses performed on the
SPP side.
The SIS, which includes the steady state, short circuit and dynamic stability studies with and without the
project at various flow conditions, are complete for both sides of the TASS. PNM has posted its SIS to its
OASIS. The SIS for the SPP side can be found on the SPP website, to which the WECC should have access
to review. Facility Studies (FS) identifying the minimum required facilities for interconnection without
power transfer have been completed by PNM for the Blackwater station. SPS has also completed a FS
for the Tolk substation. Further design analysis is ongoing with PNM and SPS/SPP which upon its
completion might expand identified equipment required to interconnect TASS. If necessary the FS and
Interconnection Agreement (IA) will be amended to complete the interconnection process.
The Interconnection Agreements (IA) with PNM, SPS and SPP have been approved by the FERC. Design
of the TASS and associated transmission lines is currently underway.
On February 4, 2014, Tres Amigas and Broadview Energy, LLC (Broadview) announced the execution of
agreements that would facilitate the development and construction of up to 500 MW of wind
generation in northeast New Mexico. This will enable Broadview Energy to deliver high-quality New
Mexico wind power starting by year-end 2016 and also enables the project to utilize the additional
services to be offered by Tres Amigas when Phase I becomes fully operational in2018.
Modeling Data
The HVDC back to back component of the TASS is based on voltage sourced converter technology. This
technology was selected due to its improved operating characteristics which can be exploited when
located in a part of the system where voltage support is needed for the anticipated power transfers
through the HVDC station. The location of the TASS is in such an area with few large transmission lines,
but with significant transmission system additions being planned. The VSC technology will be provided
by Alstom.
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March 27, 2015
The TASS will be interconnected to the WECC and SPP systems as shown in Figure 2. The system
components include:



The 345kV lines between the TASS and Blackwater on the WECC side and between the TASS and
Tolk on the SPP side.
The VSC transformers and
The VSCs and associated control systems.
Appendix 1 includes the steady state information for modeling the TASS in a load flow model. The
actual TASS back-to-back DC system would be modeled either as a load or generator as are the other
back-to-back stations along the WECC interface with SPP. Block diagrams and other modeling data for
dynamic modeling of the TASS VSCs can also be found in Appendix 1. The PSLF and PSS/E files for the
models are provided electronically with this report for filing by WECC in the library of user models.
Additional modeling is being performed in PSCAD as the VSC control system is developed to analyze
design performance of the TASS relative to other HVDC controls in the area and other design verification
studies. PNM and Xcel-SPS are working with TA on these studies. They are expected to be completed in
2016. TA will provide any necessary updates to the models accompanying this report as the more
detailed design studies are developed for the TASS VSC controls.
Analysis to Date
The analysis of the TASS impacts to the PNM/WECC system was performed by PNM during the
development of the SIS. The SIS report is posted for review by interested parties on the PNM OASIS.
The TASS and its interconnection at the Blackwater station are located on the extreme east side of the
PNM system at the end of the BA to Blackwater line, also referred to as the Eastern Interconnect Project
(EIP). Major considerations for the SIS included:

The TASS is located on the PNM system in parallel with the existing Blackwater HVDC back to
back station. System flows with the Blackwater station at its maximum rating were considered.

The TASS is located at the eastern end of the 223 mile EIP 345kV line. The flows along this line
are significantly affected by the low surge impedance loading (SIL) of the line and require
voltage support when flows exceed certain levels.

Several wind farms are located along the EIP 345kV line. Their use of the line and their variable
output can cause rapid adjustments in the amount of transmission capacity available for the
TASS.
Steady state and dynamic stability analysis was performed by PNM at a variety of flow levels and system
configurations. The results of this analysis are summarized in the SIS prepared by PNM for the TASS,
which is posted on the PNM OASIS. Interested parties can review the results of the analysis there. This
analysis was developed in accordance with WECC Criteria and NERC Reliability Standards.
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March 27, 2015
The steady state analysis identified the following maximum flow limits considering certain system
improvements. The flows are summarized in Table 1.
Table 1
Maximum Flows with System Improvements
The system improvements modeled in the SIS to support the 950MW level of transfer on an “as
available” basis included:






250 MVA synchronous condenser to be located at the TASS
3-150MVAR switched static capacitor banks to be located at the Guadalupe 345kV station
+/- 250 MVAR static VAR compensator to be located at the Guadalupe 345kV station
Expand the Blackwater Station from a single breaker to a three breaker 345kV ring bus station
Reconductor the EIP along the BA-Guadalupe section
Replace the communication wave trap on the BB line
The SIS also identified the maximum transfer in or out of the TASS absent the system improvements
identified above other than expansion of the Blackwater switchyard. These maximum transfers are
summarized in Table 2.
Table 2
Maximum Flows without System Improvements
Dynamic stability analysis indicated that a breaker failure contingency at the BA substation indicates a
run back in the output of the TASS is needed in order for the system to remain stable after the fault is
cleared. The contingency modeled involved a delayed clearing event that removed both lines to Rio
Puerco.
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March 27, 2015
Due to the existing transmission system commitments and senior queued transmission requests, all of
the flows from the TASS project were considered non-firm and “as available” in the PNM SIS. Additional
transmission lines will be needed in the area to support firm transmission service.
The “as available” transmission capacity will depend on several factors, such as the amount of wind
energy being transported by the system and the transmission schedules through the Blackwater station.
Although the 750MW rating of the TASS is established by its HVDC components, the actual flow level
that can be scheduled through the TASS to remain in compliance with the NERC and WECC requirements
is dependent on the system conditions at the time the schedule is requested and the actual system
improvements made.
Detailed steady state and dynamic stability results can be found in the Appendices of the SIS on the
PNM OASIS. More detailed analysis will be performed using PSCAD to determine the actual system
improvements needed along the EIP line for certain flows. The studies were initiated in January 2013
and are expected to extend through 2016.
Path Rating
Because the TASS has a fixed rating based on the capabilities of its HVDC system, TA does not consider it
necessary to perform a path rating on the TASS. Also, the TASS does not influence the rating of any
WECC defined Paths directly or indirectly, being at the far eastern end of the long, radial EIP
transmission line. Due to the location of the TASS Project relative to defined WECC Paths, the TASS is
not a subset of any defined Path and neither of the tests in Appendix D of the WECC Project
Coordination and Path Rating Processes is applicable to the TASS project and its influence on a WECC
Path. The TASS received a Waiver of Significant Project Status in 2013. Figure 3 provides the location of
the TASS with respect to the nearest WECC defined Path, Path 48 (NNM Path).
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March 27, 2015
Figure 3
Location of TASS in Relation to WECC Defined Path 48 (NNM Path)
Tres Amigas
Super Station
(TASS)
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Tres Amigas, LLC
March 27, 2015
Additional Studies
The analysis of the TASS for the SIS was performed with generic models of the VSC since the actual
control models were unavailable. Detailed design of the actual control system began in the first quarter
of 2013 and will continue throughout the project. When the actual controls model is available, system
studies will be performed in PSCAD to review in detail the potential for controls interaction between the
TASS VSC, the Blackwater line commutated back to back station and the wind farm controllers. This
analysis will also be performed to review the specific system improvements needed to provide certain
levels of transfer along the EIP 345kV line.
Schedule
The following milestones are being scheduled for the TASS project:

Facilities studies complete – April 2012

Interconnection agreements completed – January 2013

Construction started – Third quarter 2015

PSCAD and all other studies completed - Third quarter 2016

Broadview connection – Fourth quarter 2016

VSC Commercial operations – Fourth quarter 2018
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March 27, 2015
APPENDIX 1
TASS MODELING DATA
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Tres Amigas Super Station Steady State Load Flow Data_January 2013
Bus
BUS-NO
NAME
KV
TP
VSCHED
BLACKWTR
345
1
1.05
1.0495
525549
TOLK 345
345
1
0.9885
13407
3AMIGAS2
345
1
13404
3AMIGAS
345
1
13405
3AMIGAS DC
399
13406
3AMIGS DC
399
13402
V-PU
DEG
ISLAND
AREA
68.88
2
10
1.0218
-11.28
314
1.025
1.025
-10.85
1.05
1.05
69.05
2
1.05
1.0778
2
1.025
1.0531
ZONE
ISOL_ST
VMAX
VMIN
134
0
0
0
526
900
0
1.1
0.9
314
526
900
0
1.1
0.9
2
526
900
0
1.1
0.9
75.57
2
526
900
0
1.1
0.9
-17.85
314
526
900
0
1.1
0.9
ST
R-PU
Transmission Line
FROM
FNAME
FKV
TO
TNAME
TKV
CK
SE
X-PU
B-PU
MVA1
MVA2
MVA3
MVA4
13402
BLACKWTR
345
13404
3AMIGAS
345
1
1
1
0
0.0005
0
0
0
0
0
13407
3AMIGAS2
345
525549
TOLK 345
345
1
1
1
0.002127
0.027928
0.469952
0
0
0
0
X
BMAG
Transformer
FROM
FNAME
FKV
TO
TNAME
TKV
CK
S
MVA
R
ALOSS
TERT
13404
3AMIGAS
345
13405
3AMIGAS DC
399
1
1
825
0
0.157
0
0
0
13407
3AMIGAS2
345
13406
3AMIGS DC
399
1
1
825
0.0019
0.157
0
0
0
Transformer Tap
FROM
FNAME
FKV
13404
3AMIGAS
345
13407
3AMIGAS2
230
TO
1340
5
1340
6
TNAME
3AMIGAS
DC
3AMIGS
DC
TK
V
CK
ST
T
TCULTA
P
ANGL
P
VMA
X
VMI
N
STEP
P
TMA
X
TMI
N
TAPF
P
TAPF
S
399
1
1
1
1
0
0
0
0
0
0
1
1
399
1
1
1
1
0
0
0
0
0
0
1
1
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