HomeMy WebLinkAbout20190821Avista to Staff 135 Attachment D.pdfInterconnection System Impact Study
Interconnection System Impact Study
Project #49
May 4, 2017
Richard Maguire
Avista System Planning Engineer
Kevin Damron
Avista System Protection Engineer
Avista Project Account 77705292-186200
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PROJECT #49 May 4, 2017 Page 2 of 32
Executive Summary
On November 14, 2016, Avista received a completed Interconnection System Impact Study
Request from the Project #49 Developer for a proposed 144 MW wind generating facility located
near Lind, Washington. On February 8, 2017, Avista and the Project #49 Developer completed
the Interconnection System Impact Study Agreement. The Interconnection Customer gave a
projected initial operating date of September 1, 2018. The Interconnection System Impact Study
Agreement states that Avista will study the interconnection of Project #49 at 115 kV into a new
switching station southeast of Lind, WA.
This study presents interconnection impacts and cost estimates associated with the integration of
Project #49 as a Network Resource Interconnection Service and concurrently as an Energy Resource
Interconnection Service1. During the study process, Avista’s Transmission Planning and
Protection engineers conducted steady state power flow, short circuit, and dynamic studies to
determine Transmission System changes necessary to integrate Project #49 reliably.
This study concludes that Project #49 can be integrated reliably at the requested 144 MW output
with Transmission System upgrades costing approximately $17,343,500.
All construction costs are in 2018-year dollars based on engineering judgment alone with +/-
20% error. These cost estimates assume that the Project #49 developer is responsible for all
necessary facilities from their facility to the POI.
Transmission capacity impacts and upgrades beyond the Transmission Provider’s
Interconnection Facilities referenced in this report are provided for informational purposes only.
A complete analysis of these impacts associated with Project #49 and any facilities needed to
mitigate these impacts must be identified through the study process for Transmission Service,
once a request for Transmission Service has been submitted.
1 For this study, Energy Resource performance adequacy is assumed if Network Resource performance is proven.
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Table of Contents
EXECUTIVE SUMMARY ................................................................................................................................... 2
TABLE OF CONTENTS ..................................................................................................................................... 3
INTRODUCTION ................................................................................................................................................ 4
INTERCONNECTION SERVICE ............................................................................................................................... 4
POINT OF INTERCONNECTION .............................................................................................................................. 5
PROJECT #49 ONE-LINE DIAGRAM ........................................................................................................................ 6
SCOPE OF THE STUDY ......................................................................................................................................... 7
STUDY NOTES .................................................................................................................................................... 7
STUDY CASE DEVELOPMENT ........................................................................................................................ 8
CASES USED....................................................................................................................................................... 8
DYNAMIC MODELLING ..................................................................................................................................... 10
POWER FLOW IMPACTS OF PROJECT #49 IN THE BASE CASES ............................................................................... 11
2021 Heavy Summer .................................................................................................................................... 11
2021 Heavy Winter ...................................................................................................................................... 11
AFFECTED WECC PATHS AND TRANSMISSION FACILITIES ................................................................................. 13
STUDY RESULTS ............................................................................................................................................. 15
THERMAL PERFORMANCE ................................................................................................................................. 15
VOLTAGE PERFORMANCE ................................................................................................................................. 15
POWER/VOLTAGE (PV) ADEQUACY .................................................................................................................. 15
TRANSIENT STABILITY ...................................................................................................................................... 19
SHORT CIRCUIT ANALYSIS ................................................................................................................................ 25
CONCLUSION ................................................................................................................................................... 31
PROJECT REQUIREMENTS $17,343,500 .............................................................................................................. 31
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Introduction
Interconnection Service
In the application for Large Electric Generator Interconnection, the Project #49 Developer
requested the study of Project #49 be conducted for both Network Resource Interconnection
Service and Energy Resource Interconnection Service. Avista’s System Planning Group
contends that if a generator can connect for Network Resource Interconnection Service then it
can also connect for Energy Resource Interconnection Service.
Energy Resource Interconnection Service allows the Interconnection Customer to connect the
Large Generating Facility to the Transmission System and be eligible to deliver the Large
Generating Facility's output using the existing firm or non-firm capacity of the Transmission
System on an "as available" basis. Energy Resource Interconnection Service does not, in and of
itself, convey any right to deliver electricity to any specific customer or Point of Delivery.
For Network Resource Interconnection Service, the Transmission Provider must conduct the
necessary studies and construct the Network Upgrades needed to integrate the Large Generating
Facility in a manner comparable to that in which the Transmission Provider integrates its own
generating facilities to serve native load customers. Network Resource Interconnection Service
allows the Interconnection Customer’s Large Generating Facility to be designated as a Network
Resource, up to the Large Generating Facility's full output, on the same basis as existing
Network Resources interconnected to the Transmission Provider's Transmission System, and to
be studied as a Network Resource on the assumption that such a designation will occur.
Network Resource Interconnection Service in and of itself does not convey transmission service.
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Point of Interconnection
The Interconnection System Impact Study Agreement states that Avista will study the
interconnection of Project #49 at a proposed new station southeast of Lind. WA. Figure 1 depicts
the local transmission system for the area surrounding the POI. BLUE indicates 115 kV.
Figure 1: Project #49 map
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Project #49 one-line diagram
Figure 2 depicts the substation configuration and the various modeling data used in modeling
Project #49. The generation facility topology, equipment and corresponding impedances were
provided by the customer, and this information was used to build a model consistent with the
Western Electricity Coordinating Council (WECC) Wind Power Plant Power Flow Modeling
Guidelines.2 The actual POI station location is approximate and will be refined during the
Interconnection Facility Study process.
Figure 2: Project #49 One-line
2 https://www.wecc.biz/Reliability/WECC%20Wind%20Plant%20Dynamic%20Modeling%20Guidelines.pdf
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Scope of the Study
As outlined in Section 7.3 of Avista’s Large Generator Interconnection Procedures (LGIP), this
study evaluates the impact of the proposed interconnection on the reliability of the Transmission
System, and it consists of a power flow analysis, a short circuit analysis, and a dynamic stability
analysis. The study considers all existing generating facilities, pending higher queued
interconnection requests in Avista’s queue (including associated identified network upgrades).
This Interconnection System Impact Study report includes the following information:
Identification of facility thermal, voltage, and/or stability violations resulting from the
interconnection
Identification of any circuit breaker or equipment short circuit capability limits exceeded
because of the interconnection.
Description and non-binding, good faith estimated cost of facilities required to
interconnect the project to the Avista Transmission System and maintain reliable
performance.
Avista contacted neighboring systems at the commencement of this study, and those affected
neighbors will be sent a copy of the Project #49 Interconnection System Impact Study Report.
Study Notes
The transmission additions simulated in the study cases are based on the best information
available at the time the study was initiated. It is possible that the actual plan of service
will differ from the plan of service studied, and Avista reserves the right to restudy this
request if necessary.
Generator tripping will be required for certain local outages that island Project #49 from
the rest of the Transmission System.
Project #49 will be required to operate in voltage control mode with the ability to deliver
power to the POI at a 0.95 pu lead/lag power factor.
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Study Case Development
Cases Used
Two Avista Planning Cases were used for this study: the 2021 Heavy Summer and 2021 Heavy
Winter cases. Avista Planning cases are tailored from approved WECC cases, and each case
includes a set of 34,000 steady state and 1,342 dynamic contingency scenarios that are run to
analyze the impact of Project #49. These contingencies include outages within the Avista
Transmission System as well as select outages in adjacent Planning Coordinator and
Transmission Planner areas. Contingencies are also added or modified to include elements added
to the Transmission System for the purposes of this study.
Both cases were updated with Avista’s planned Saddle Mountain Station (Figure 3) and LGI
Project #46 (Figure 4).
Figure 3: Saddle Mountain Station
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Figure 4: Project #46
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Dynamic Modelling
Models for dynamic studies provided by the Project #49 developer were initially found to be
numerically unstable within PowerWorld Simulator. There is a known issue between how
PowerWorld and GE/Siemens software initializes some WECC Approved generator models, and
some parameters were changed in order for the models to both solve and provide realistic
performance. Table 1 presents the model parameters changed for this study.
Table 1: Dynamic Model changes
Model/Parameter Parameter Initial Value Studied Value Model Default
REGC_A (motor)
LVPLSW 0 1 1
Rrpwr 0.43 1.0 10.0
Zerox 0.4 0.5 0.5
LVPnt1 0.1 0.8 0.8
LVPnt0 0.0 0.2 0.4
Khv 0.5 0.7 0.7
REEC_A (exciter)
Tv 0.0167 0.0333 0.02
Tiq 0.0167 0.0333 0.02
REPC_A (plant controller)
Tfltr 0.02 0.0333 0.05
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Power flow impacts of Project #49 in the base cases
2021 Heavy Summer
This is the typical summer peak study where the balancing area load is heavy and the transmission system is
at its most limiting condition due to high temperatures.
Figure 5 shows power flow in the heavy summer case with Project #49 installed and operating at
full capacity.
Figure 5: Heavy Summer All Lines in Service
2021 Heavy Winter
This is the typical winter peak study where the balancing area load is at its heaviest. Figure 6
shows power flow in the light summer case with Project #49 installed and operating at full
capacity.
Figure 6: Heavy Winter All Lines in Service
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Affected WECC Paths and Transmission Facilities
Sensitivity analysis was performed in order to determine the various WECC monitored paths and
transmission elements affected by the proposed Project #49 interconnection. This analysis was
completed using the Power Transfer Distribution Factor (PTDF) tool within PowerWorld
Simulator. The point of receipt (POR) modeled was the proposed wind generation facility. The
selection of the point of delivery (POD) presumes an assumption on where the energy from the
interconnecting project is delivered, yielding different sensitivity results.3 This PTDF study
examines the POD as all generation within Avista’s Balancing Area (representing the
interconnecting project as a Network Resource) as well as the POD being all responsive
generators in WECC (representing an Energy Resource). These studies do not cover all
possibilities of where the energy from the interconnecting project may be scheduled, but they do
provide a strong indication of what WECC monitored paths and transmission elements are
affected. Table 2 provides percentage of flow impact on several WECC defined paths.
Table 2: PTDF Path Analysis Results
3 A more directed study of affected facilities will be completed if the Project #49 developer desires to pursue a
Transmission Service request with a defined POR/POD pair
Path AVA POD WECC POD
Name Number % PTDF % PTDF
ALBERTA - BRITISH COLUMBIA 1 -1.1 -7.6
NORTHWEST - CANADA 3 -9.3 -7.9
WEST OF CASCADES - NORTH 4 6.9 23.5
WEST OF CASCADES - SOUTH 5 -3.3 3.8
WEST OF HATWAI 6 34.2 74.9
MONTANA - NORTHWEST 8 3.6 -11.1
WEST OF BROADVIEW 9 1.5 -6.6
WEST OF CROSSOVER 11 0.6 -3.3
IDAHO - NORTHWEST 14 -1.6 -19.5
MIDWAY - LOS BANOS 15 -0.8 -26.6
IDAHO - SIERRA 16 0 3.5
BORAH WEST 17 -1.6 -13.3
MONTANA - IDAHO 18 1.1 -2.1
BRIDGER WEST 19 -0.6 -3.4
PATH C 20 0 -12
NORTHERN - SOUTHERN CALIFORNIA 26 0.8 23.9
TOT 2B 34 -0.2 3.7
TOT 3 36 -0.6 4
WEST OF COLORADO RIVER (WOR) 46 -0.8 -10.2
EAST OF COLORADO RIVER (EOR)49 -0.6 -9.1
BROWNLEE EAST 55 0.5 7.3
LUGO - VICTORVILLE 500 KV LINE 61 -0.2 -3
PERKINS - MEAD - MARKETPLACE 500 63 -0.1 -3
COI 66 0.9 42.2
SOUTH OF ALLSTON 71 1.5 6
NORTH OF JOHN DAY 73 7.5 35.6
MONTANA SOUTHEAST 80 1.1 -3.9
TOTBEAST 82 -0.5 -4
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Table 3 provides PTDF analysis for affected transmission facilities with sensitivity above 10% in
the heavy summer scenario with Project #49 balanced by AVA generation.
Table 3: PTDF Transmission Facility Impacts, Heavy Summer, POD at AVA Generation
From Number From Name To Number To Name Circuit % PTDF From Nom kV (Max) Owner Name 1
48362 SMART 48187 LIND 1 93.23 115 Avista Corp.
48187 LIND 48375 ROXBORO 1 92.22 115 Avista Corp.
48375 ROXBORO 48455 WARDEN A 1 90.01 115 Avista Corp.
48309 OTHELOSS 48393 SOTHELOT 1 38.63 115 Avista Corp.
48425 SADDLEMTN_115 48393 SOTHELOT 1 38.53 115 Avista Corp.
46087 SANDUNES 48455 WARDEN A 1 28.55 115 Grant PUD
48310 SADDLEMTN_230 48425 SADDLEMTN_115 1 26.88 230 Avista Corp.
48309 OTHELOSS 48455 WARDEN A 1 25.93 115 Avista Corp.
41111 VANTAGEN 46169 WANAPUM 1 24.9 230 Grant PUD
46089 SANDUNES 46087 SANDUNES 1 23.96 230 Grant PUD
40288 COULE R1 40287 COULEE 6 22.9 500 Bonneville Power Admin
40091 BELL BPA 40288 COULE R1 6 22.86 500 Bonneville Power Admin
43123 COYOTE 48519 COYO M2 1 22.28 500 Avista Corp.
40499 HANFORD 41113 VANTAGE 1 21.72 500 Bonneville Power Admin
48455 WARDEN A 46117 WARDEN T 1 20.61 115 Grant PUD
46119 WHEEL TI 46121 WHEEL TP 1 20.61 115 Grant PUD
46130 BASS JCT 46085 RUFF TP 1 20.57 115 Grant PUD
46130 BASS JCT 46119 WHEEL TI 1 20.57 115 Grant PUD
46085 RUFF TP 46091 SCHRAG T 1 20.55 115 Grant PUD
46091 SCHRAG T 46117 WARDEN T 1 20.54 115 Grant PUD
46039 LARSON 46121 WHEEL TP 1 20.02 115 Grant PUD
48310 SADDLEMTN_230 46169 WANAPUM 1 18.94 230 Avista Corp.
40553 HOT SPR 40551 HOT SPR 1 17.05 500 Bonneville Power Admin
40553 HOT SPR 41057 TAFT 1 17.05 500 Bonneville Power Admin
40091 BELL BPA 40092 BELL S4 1 16.95 500 Bonneville Power Admin
46043 MAE VL T 46089 SANDUNES 1 16.53 230 Grant PUD
46043 MAE VL T 46166 POTHOLEG 1 16.53 230 Grant PUD
41113 VANTAGE 41111 VANTAGEN 2 16.05 500 Bonneville Power Admin
41113 VANTAGE 41112 VANTAGES 1 15.53 500 Bonneville Power Admin
40521 HATWAI 40679 LOW GRAN 1 15.35 500 Bonneville Power Admin
40261 COLUMBIA N 46298 WQUINCYT 1 15 230 Grant PUD
46298 WQUINCYT 46299 NQUINCYT 1 14.9 230 Grant PUD
46300 ROCKYFDG 46299 NQUINCYT 1 14.83 230 Grant PUD
46151 LARSON 46300 ROCKYFDG 1 14.79 230 Grant PUD
48059 CAB GORG 48179 LAKEVIEW 1 14.61 230 Avista Corp.
48179 LAKEVIEW 48357 RATHDRUM 1 14.45 230 Avista Corp.
46166 POTHOLEG 40851 POTHOLES 1 12.89 230 Bonneville Power Admin
40369 DWORSHAK 40521 HATWAI 1 12.81 500 Bonneville Power Admin
40369 DWORSHAK 90046 DWOTAF11 1 12.78 500 Bonneville Power Admin
90046 DWOTAF11 41057 TAFT 1 12.78 500 Bonneville Power Admin
48308 LEE&REYN 48455 WARDEN A 1 12.71 115 Avista Corp.
48308 LEE&REYN 48307 OTHELLO 1 12.71 115 Avista Corp.
48307 OTHELLO 48309 OTHELOSS 1 12.7 115 Avista Corp.
48281 NOXON 40787 NOXONBPA 1 12.62 230 Avista Corp.
43123 COYOTE 40723 MCNARY 1 12.05 500 Bonneville Power Admin
48039 BENTNAVA 48425 SADDLEMTN_115 1 11.5 115 Avista Corp.
48039 BENTNAVA 40097 BENTON 1 11.5 115 Bonneville Power Admin
40974 SICKLER TX 47031 DOUGLAS 1 11.04 230 Bonneville Power Admin
40973 SICKLER 40974 SICKLER TX 1 11.03 500 Bonneville Power Admin
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Study Results
Thermal Performance
As seen in Figure 5 above, the following transmission lines must be rebuilt to accommodate the
output of Project #49 in the P0 state (all lines in service):
1. Lind – Warden 115 kV (21.7 miles plus some station facilities at Lind and Warden
stations)
2. Lind – Smart 115 kV segment (4 miles plus some station facilities at Lind Station)
Once the above facilities are upgraded, thermal performance is adequate for all contingencies
examined in this study; no additional thermal violations were noted.
Table 4 provides the reader an idea of contingent facility loading that is approaching facility
limits when Project #49 is operating at full capacity. The table presents those unique contingency
events whose loading only exceeds 90% when Project #49 is operating at full output. Of note is
the fact that all of the contingencies are multiple-facility P6 events, which allow system
reconfiguration between contingency events.
Table 4: Contingent facility loading exceeding 90% in Heavy Summer with the introduction of Project #49
Voltage Performance
Contingency analysis shows Project #49 creates no new voltage violations when generating at or
below 144 MW and operating within a 0.95 pu lead/lag power factor.
Power/Voltage (PV) Adequacy
Voltage adequacy studies were performed to determine the theoretical maximum output
allowable from Project #49 based on voltage performance. This maximum output was derived
evaluating contingencies and increasing the output from Project #49 until the voltage collapsed
(i.e. the case became numerically unstable). The power factor of Project #49 was initially set to
unity in order to simulate worst-case voltage performance where the project delivers no reactive
support.
Label Category Facility Percent
N-1: SaddleMtn - Walla Walla 230 kV + N-1: 3TM Larson - Sand Dunes - Warden 115 kV Branch Amp WHITE BL (41147) -> SNYDER (41009) CKT 1 at SNYDER 97.85
N-1: SaddleMtn - Walla Walla 230 kV + N-1: North Lewiston - Tucannon River 115 kV Branch Amp WHITE BL (41147) -> SNYDER (41009) CKT 1 at SNYDER 97.72
N-1: SaddleMtn - Walla Walla 230 kV + G-1: Brownlee Units 1-5 Branch Amp WHITE BL (41147) -> SNYDER (41009) CKT 1 at SNYDER 97.71
N-1: Dworshak - Hatwai 500 kV + N-1: Chelan - Stratford 115 kV Branch Amp WHITE BL (41147) -> SNYDER (41009) CKT 1 at SNYDER 97.64
T-1: Hatwai 500/230 kV + N-1: Othello SS - Warden #1 115 kV Branch Amp ASHE (40059) -> WHITE BL (41149) CKT 1 at WHITE BL 93.65
T-1: Hatwai 500/230 kV + N-1: Lind - Smart 115 kV Branch Amp ASHE (40059) -> WHITE BL (41149) CKT 1 at WHITE BL 93.51
N-1: Larson - Wheeler 230 kV + T-1: Hatwai 500/230 kV Branch Amp ASHE (40059) -> WHITE BL (41149) CKT 1 at WHITE BL 93.51
N-1: Benton - Midway 230 kV + N-1: SaddleMtn - Walla Walla 230 kV Branch Amp BENTNAVA (48039) -> BENTON (40097) CKT 1 at BENTNAVA 92.33
N-1: SaddleMtn - Walla Walla 230 kV + T-1: Benton 230/115 kV Branch Amp BENTNAVA (48039) -> BENTON (40097) CKT 1 at BENTNAVA 92.29
N-1: Benton - Midway 230 kV + N-1: SaddleMtn - Walla Walla 230 kV Branch Amp SADDLEMTN_115 (48425) -> BENTNAVA (48039) CKT 1 at SADDLEMTN_115 91.57
N-1: SaddleMtn - Walla Walla 230 kV + T-1: Benton 230/115 kV Branch Amp SADDLEMTN_115 (48425) -> BENTNAVA (48039) CKT 1 at SADDLEMTN_115 91.53
N-1: Dworshak - Taft 500 kV + N-1: Benton - Saddle Mountain 115 kV Branch MVA WHITE BL (41149) -> WHITE BL (41147) CKT 1 at WHITE BL 90.47
N-2 (ROW): Benton - Midway #2 230 kV and Benton - Midway #1 115 kV and Benton - Othello SS 115 kV Branch Amp ASHE TAP (40065) -> ASHE (40059) CKT 1 at ASHE TAP 90.4
N-1: SaddleMtn - Walla Walla 230 kV + N-1: Benton - Saddle Mountain 115 kV Branch MVA WHITE BL (41149) -> WHITE BL (41147) CKT 1 at WHITE BL 90.03
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Figure 7 shows base case voltage performance with Project #49 set to unity power factor. This analysis shows local voltage collapse
before Project #49 gets to full requested output, necessitating Project #49 operate at 0.95 lead/lag power factor.
Figure 7: PV Performance in Heavy Summer base case without reactive support from Project #49
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Figure 8 shows adequate voltage performance in the base case for full output of Project #49 when operating with a 0.95 lead/lag
power factor.
Figure 8: Adequate PV performance in Heavy Summer base case with Project #49 operating with lead/lag 0.95 pf
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The worst-case single facility contingency is the loss of the Saddle Mountain 230 kV bus, and both this and the base case are
presented for comparison. Both the base case and the worst-case contingency scenario show adequate voltage performance throughout
the requested output of Project #49 from 0 to 144 MW.
Figure 9: Voltage performance, Heavy Summer case, Base case and worst case contingency
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Transient Stability
Project #49 introduces minimal impact to dynamic performance of the Transmission System; no new stability violations were noted.
The following figures present a sample of performance impacts for several contingencies in the area. Base case results are shown first,
followed by results with Project #49 installed and generating full requested output.
Figure 10: Devil’s Gap - Lind 115 kV; 3Ø @Lind; Base Case
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Figure 11: Devil’s Gap - Lind 115 kV; 3Ø @Lind; Project #49 at full output
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Figure 12: Othello SS – Warden #1 115 kV; 3Ø @OSS; Base Case
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Figure 13: Othello SS – Warden #1 115 kV; 3Ø @OSS; Project #49 at full output
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Figure 14: Saddle Mountain – Wanapum 230 kV; 3Ø @Saddle Mountain; Base Case
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Figure 15: Saddle Mountain – Wanapum 230 kV; 3Ø @Saddle Mountain; Project #49 at full output
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Short Circuit Analysis
General:
The proposed Project #49 Wind generation is 144 MW in size and approximately 4 miles from
the Lind 115 kV bus. For the purposes of the System Protection System Impact Study, Project
#49 wind generation POI will be at the new Smart 115kV station. The assumptions for the
Project #49 model are:
1. The facility topology of collector strings to station GSU transformers was provided by
developer. An equivalent collector system per Table 1 of WECC Wind Power Plant
Power Flow Modeling Guide 2008 was used.
2. 1 – 198 MVA wye-wye-delta 3-winding transformer 138/34.5/13.8 kV step up with
impedances provided by developer.
3. 72 - Parallel 2MVA pad mount delta-wye 0.69/34.5 kV GSU transformers stepping up
the generation to a 34.5 kV collector system. The pad-mounted transformer positive-
sequence impedance is 9.8% on the transformer MVA base, with X/R ratio of 10.9. The
pad-mounted transformer zero-sequence impedance is 8.6% on the transformer MVA
base, with X/R ratio of 10.8.
4. 72 – 2 Megawatt Type 4 machines providing approximately 1 per unit fault current at 26
degrees.
5. The 115kV interconnection transmission line was modeled based on information
provided by Avista System Planning. Additional 115kV transmission lines rebuilt per
information provided by System Planning.
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ASPEN Model Development:
Station Transformers
The 138/34.5/13.8 kV 198 MVA wye-wye-delta three-winding transformer was modeled using
data provided by developer. The impedances are as follows:
Windings
MVA
Base R+ (p.u.) X+ (p.u.) Z+ (p.u.) R0 (p.u.) X0 (p.u.) Z0 (p.u.)
ZP-S 100.0 0.002126 0.079938 0.079966 0.001903 0.071524 0.071549
ZS-T 100.0 0.00097 0.025234 0.025253 0.000809 0.021028 0.021044
ZP-T 100.0 0.004852 0.126169 0.126263 0.004206 0.109347 0.109428
Collector String and Pad Mount GSUs
The impedances were converted a 100 MVA base is as follows:
Collector string -
The collector string equivalent line parameters were based on information provided by
developer. developer used the ‘WECC Guide for Representation of Photovoltaic Systems in
Large-Scale Load-Flow Simulations’ (January 2011) as the method to determine the line
parameters. The positive and zero-sequence impedances, based on 34.5kV and 144MVA base,
are shown below:
R1 (pu) X1 (pu) R0 (pu) X0 (pu) Bc
Capacitive
Susceptance
(pu)
0.010339 0.010708 0.034242 0.005373 0.040512
The collector string impedances were converted to a 100MVA base per the following
calculations.
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Pad Mount GSU – 72 units parallel
The positive and zero-sequence impedances were calculated using data provided by developer.
Wind Turbines
The generators for Project #49 were modeled as a single 144 MVA machine the equivalence of
72 – 2 MVA wind generators. The wind turbines were identified as Type IV. Type IV turbines
typically will not provide more than 1 per unit short circuit contribution at an angle of
approximately 26 degrees into the system. The wind turbine model used the worst case scenario
with all machines on line (150 MVA). Since the WTG transformer is a Wye-Delta blocking the
negative and zero sequence contributions to a single line to ground 115 kV transmission fault, all
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sequence parameters were set equal. The subtransient, transient and synchronous impedances
were all set the same. The 144 MVA machine parameters are as follows:
Fault Analysis Study
A short circuit analysis study was performed to determine if Avista’s installed equipment is
adequate for the proposed Project #49 POI. The following analysis was performed:
1. Perform 3LG and SLG close-in faults on each line terminal breaker at affected buses by the
interconnection.
2. Perform 3LG and SLG close-in faults on each bus affected by the interconnection
3. Compare resulting fault duties to breaker or power fuse interrupt ratings.
Fault Duty Comparisons
The changes in fault duties in amperes due to the addition of the Project #49 144 MW of
generation networked to the Smart station 115kV bus are shown below.
System
Location
3LG w/out
Generation
3LG with
Generation
Percent
Change
1LG w/out
Generation
1LG with
Generation
Percent
Change
Lind Bus 4594 4840 5% 2879 3763 31%
Lind/ Shawnee
Terminal
3777 4005 6% 2155 3183 48%
Lind/ Devils
Gap Terminal
3803 4029 6% 2349 3340 42%
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Lind/ Warden
Terminal
1668 2035 22% 1254 2475 97%
Lind/
Washtucna
Terminal
4594 4840 5% 2879 2314 -20%
Lind 13 kV Bus 1896 1832 -3% 1934 1866 -4%
Washtucna 115
kV Bus
1608 1592 -1% 899 982 9%
Ritzville 115
kV Bus
3000 3004 0% 1883 2037 8%
Ralston 115 kV
Bus
2513 2503 0% 1636 1719 5%
Roxboro 115
kV Bus
5935 6096 3% 3675 4105 12%
Delight 115 kV
Bus
2440 2476 1% 1408 1684 20%
Marengo 115
kV Bus
2909 2900 0% 2033 2130 5%
Warden 115 kV
Bus
10888 10999 1% 7677 7876 3%
Othello Sw.
Station 115 kV
Bus
10794 10793 0% 8527 8552 0%
Saddle
Mountain
115kV Bus
15173 15152 0% 15640 15619 0%
Saddle
Mountain
230kV Bus
9926 9914 0% 10593 10580 0%
Smart Sw.
Station 115kV
Bus
3800 4037 6% 2303 3323 44%
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Station Breaker/Device Ratings -
The three-phase and single line to ground fault magnitudes increased in the area as expected. The
Lind 115 kV breaker ratings are 40 kA symmetrical interrupt. The 115 kV power fuses at
Marengo, Washtucna, Ritzville and Lind are rated at 10,000 kA interrupt. The Mark III circuit
switcher rating at Roxboro is 6000/3000 interrupt. The addition of the Saddle Mountain and
LGIR #49 will exceed the fault duty capability of the Roxboro circuit switcher. The interrupting
devices at Ralston and Delight are not Avista assets so are not included in this study.
Summary
Integrating Project #49 Wind generation of 150 MW onto Avista’s 115 kV system increased
fault duties in the Big Bend area.
The addition of the Project #46 and Project #49 will exceed the fault duty capability of the
Roxboro circuit switcher.
The results show integrating Project #49 Wind generation onto Avista’s 115 kV system at the
requested POI will not impact the capability of the other substation line breakers to interrupt
three phase or single phase faults.
Non-Avista facilities in the area affected by the fault duties increase should be reviewed by the
facility owner.
All transmission and distribution relay settings will require a review and coordination
verification for the Big Bend area.
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PROJECT #49 May 4, 2017 Page 31 of 32
Conclusion
Project #49 is a feasible project based on the analysis performed in this study with a cost
estimate of $17,293.500
Project Requirements $17,343,500
Interconnection Customer Direct Assigned Costs
Collector Substation – engineering, design, procurement and installation of
protection and control $ 33,500
(1/3) Point of Interconnection Substation – engineering, design, procurement
and construction for ring bus 115 kV switching station $1,000,000
Subtotal Direct Assigned Costs $1,033,500
Transmission Provider Network Upgrades
Rebuild 4.5 miles of 115 kV transmission line – permitting, engineering,
design, procurement and construction $2,000,000
Lind Substation capacity upgrades - engineering, design, procurement and
installation of protection and control $600,000
Upgrades at Warden 115 kV Substation for capacity though the substation –
permitting, engineering, design, procurement and installation
(2/3) Point of Interconnection 115 kV Substation – engineering, design,
procurement and construction of (3) line positions, protection and control $2,000,000
Rebuild 22 miles of Lind-Warden115 kV transmission line – permitting,
engineering, design, procurement and construction $10,000,000
Construct Communications Path(s) for Operation of the (POI) 115 kV Smart
Switching Station –
construction, and installation
$500,000
Replacement of the Roxboro circuit switcher - engineering, design,
procurement and installation of protection and control $200,000
Warden Substation capacity upgrades - engineering, design, procurement
installation of protection and control $500,000
Othello Switching Station capacity upgrades - engineering, design,
procurement and installation of protection and control $500,000
Subtotal Network Upgrades $16,300,000
Transmission Provider Distribution Upgrades
POI Substation Construction Power from Big Bend Electric Cooperative
(BBEC) – engineering, design, procurement, and installation of $ 10,000
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Interconnection System Impact Study
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transformation, metering, protection, and 13 kV distribution service for
construction.
Subtotal Direct Distribution Upgrades $ 10,000
Total Costs
$16,260,000
Total Costs $17,343,500
All of these cost estimates are based on engineering judgment with +/- 20% error in 2018 dollars.
It should be noted that property and grading costs can be significantly different than estimated
due to site specifics. Detailed cost figures and direct assigned costs versus network upgrade costs
will be finalized during the Interconnection Facility Study process.
Staff_PR_135 Attachment D Page 32 of 32