20180329PAC to Staff WY DJ Retirement Assessment.pdf

Transmission Assessment of
Dave Johnston Plant Retirement
Impacts to New Wyoming Wind
Generation Integration
Preliminary Study Report
Revision 1.0
November 2017
Prepared by
PacifiCorp -Transmission Planning
PreliminaryTransmission Assessment
of Dave Johnston Plant Retirement Impacts to
New Wyoming Wind Generation Integration
Table of Contents
Executive Summary..............................................................................................1
1 Introduction ....................................................................................................4
1.1 Purpose.....................................................................................................4
1.2 Plan of Service .........................................................................................5
1.3 Planned Operating Date ...........................................................................5
1.4 Scope ........................................................................................................5
2 Study Criteria..................................................................................................6
2.1 Thermal Loading......................................................................................6
2.2 Steady State Voltage Range....................................................................7
2.3 Post-TransientVoltage Deviation...........................................................7
2.4 Transient Stability Analysis Criteria.......................................................7
2.5 Transient Voltage Response....................................................................7
3 B ase Case Development.................................................................................9
3.1 Base Case Selection .................................................................................9
3.2 GeneratingFacility Additions................................................................10
3.3 Base Case Modification and Tuning......................................................11
4 Contingency Studies .....................................................................................12
4.1 Steady-StateAnalysis.............................................................................12
4.2 Stability Analysis ...................................................................................14
5 Results and Solution .....................................................................................15
5.1 Steady-StateAnalysis Results-Planning Events .................................15
5.2 Stability Analysis Results......................................................................18
6 Sensitivity Analysis......................................................................................l8
7 Study Conclusions........................................................................................19
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Executive Summary
This preliminaryassessment was conducted to evaluate impacts to the Wyomingtransmission
system of advancing the retirement of the Dave Johnston Power Plant (currentlyplanned for
2027)and integrating new wind generationresources planned for southeast Wyomingby 2020.
The addition of Gateway West D.2 Project (Bridger/Anticline-Aeolus)transmission facilities
were not included in the analysis.
The WECC 2021-22 HW power flow base case was utilized for the analysis.Once the Dave
Johnston Generating Plant (Dave Johnson Plant)generation (717.6 MW,net)was removed
from the base case,up to l169 MW of anticipated'new wind generationresources were added
to increase the TOT 4A2 (Path 37)transmission path flows up to a point where the path was
resource limited.Due to the geographical separation of the retired Dave Johnston Plant and the
anticipated new wind generation resources,new/rebuilt 230 kV transmission facilities were
added to the model to achieve higher transfer levels while maintaining transmission system
reliability required by the NERC and WECC.
For purpose of this analysis,the assumption was made that new generation added were treated
as network resources utilizing PacifiCorp's Energy Supply Management (PacifiCorp ESM)
Network Operating Agreement (NOA)west of Jim Bridger Power Plant (Jim Bridger Plant)to
transmit power to the Utah load center.
Contingenciesthat were considered in this analysis included all Wyomingtransmission system
contingencies performed as part of the TPL-001-4 annual assessment.
For this transmission assessment,an interaction3 between the TOT 4A path and the TOT 4B
path was evaluated;however,the interaction with other transmission paths (YellowtailSouth,
Bridger West,TOT lA and TOT 3)were monitored throughout the study to assure path ratings
were not exceeded.
As part of the Dave Johnston retirement assessment,a sensitivity analysis was also performed
to evaluate how much additional wind could be accommodated with the existing transmission
i Anticipated generation resource currently in the PacifiCorp (PAC)-Large Generation Interconnection (LGI)
queue were used as a proxy for new resources.While generator models for all new and repowered resources added
reflected new technology,the output of repowered facilities was maintained at current LGIA capacity levels.
2 The existing TOT 4A (Path 37)path is comprised of the Riverton*-Wyopo 230 kV,Platte -Standpipe*230
kV and Spence*-Mustang 230 kV transmission lines.(*meter location)
3 As there is a known simultaneous interaction between the TOT 4A and TOT 4B transmission paths,it is
anticipated that there will be a simultaneous interaction between the modifiedTOT 4A and TOT 4B transmission
paths.This interaction wouldbe fully explored as part of the WECC Path Rating analysis of the modified TOT
4A transmission path.
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system,if no new transmission system improvements were made or no additional generation
tripping Remedial Action Schemes (RAS)were implemented.
Conclusions
Technical studies demonstrated that by retiring the Dave Johnston generation and adding
new/rebuilt 230 kV transmission facilities (identified below),up to 1169 MW of new4 wind
generation can be integrated with the southeast Wyoming transmission system.Under this
transmission configuration the modified6 TOT 4A transmission path can transfer 1528 MW6
east to west,simultaneously with flows of 164 MW on the TOT 4B transmission path,thereby
increasing the transfer levels across Wyoming by 553 MW.System performance evaluated
will meet all NERC and WECC performance criteria.
Power flow findings indicated that the followingtransmission system improvements will be
required (see Figure 1):
Addition of a new Bridger -Latham 230 kV,Latham -Freezeout 230 kV,Freezeout -
Shirley Basin 230 kV and Shirley Basin -Windstar 230 kV lines (two-1272 ACSR,
Bittern/phase).
Rebuild the Point of Rocks -Bitter Creek 230 kV,Bitter Creek -Bar X 230 kV,Bar
X -Echo Springs 230 kV,Echo Springs -Latham 230 kV,Latham -Platte 230 kV,
Platte -Standpipe 230 kV and Standpipe -Freezeout 230 kV lines (two-1272 ACSR,
Bittern/phase).
Replace the existing three -345/230 kV (200 MVA)autotransformers at Jim Bridger
with two -345/230 kV (600/685 MVA,normal/emergency)autotransformers.
Rebuild the followingsubstations:Point of Rocks,Bitter Creek,Bar X,Echo Springs,
Latham,Platte,Standpipe,Freezeout,Shirley Basin and Windstar to support higher
transmission line capacity.
Addition of a dynamic voltage control device at Latham 230 kV substation,including
Static VAr Compensator (SVC)(+350/-125 MVAr)and five -40 MVAr switched
shunt capacitors.
4 Southeast Wyoming Resources:Existing Wind:1124 MW,Dave Johnston zero (0)MW *RETIRED*,Repower
Wind:zero (0)MW,New Wind:1169 MW at various locations
*The modifiedTOT 4A path would include the proposed Latham*-Bridger230 kV line,which would be in
parallel with the existing 230 kV lines that are included in the TOT 4A path.(*meter location)
6 With the addition of the 230 kV facilities identified,the modified TOT 4A path is resource limited.
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The power flow analysis also indicated that the location (and output level)of new and
repowered wind resources can influence the transfer capability level across the TOT 4A
transmission path.
Figure 1:
Wyoming 230 kV Line Improvementsto Support Additional Wind
Windstar
I Dave
/Johnston
I
I
Difficulty
Shirley BasinMustangDunlap 111 MW
Li e build
Aeolus (Future)
Une Re d Standpi¢e reezeout 7 Mile Hill 118.5 MW
Foote Cree
135 MW
Point of Bitter
Rock Creek Bar X <230 kV Existing
Existing Wind Gen 230 kV Existing High Plains 99 MW
---230 kV Future McFadden Ridge 28.5MWProposedWindGen345kVExisting
While a wide range of disturbances were evaluated,dynamic stability analysis for critical N-1
outages indicated that the voltages,frequencies and rotor angles were stable and well damped.
There were no cascading issues identified and none of the generation pulled out of
synchronism.The stability analysis demonstrated that all planned system events met the
stability performance criteria.
As part of the Dave Johnston retirement analysis,a sensitivity analysis identified that up to 100
MW of new wind generation in the Freezeout area can be added to the existing transmission
system without any system improvements or additional RAS to drop generation.
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1 Introduction Figure 2:Southeast Wyoming Resource Profile
1.1 Purpose
Windstar WindThepurposeofthisstudyistoevaluate
impacts to the Wyoming transmission ToWyodak
system of advancing the retirement of the Windstar
ToCasper
Dave Johnston Power Plant (currently DaveJohnson
ToCasper ToStegall Existing Repower Newplannedfor2027)and integrating new ToLaramleRiver
wind generation resources planned for DJCoal Retirement
southeast Wyomingby 2020.The addition
AmasaofGatewayWestD.2 Project
(Bridger/Anticline-Aeolus)transmission
facilities were not included in the analysis.
O Plant Retirement -Coal Gen
Due to the geographical separation of the
retired Dave Johnston Power Plant (Dave AmasaWind
Johnston Plant)and the anticipated new Difficulty Existing x Repower
wind generation resources (see Figure 2),New
new/rebuilt 230 kV transmission facilities
ShirleyBasin Windwereaddedtothemodeltoachievehigher
transfer levels while maintaining
transmission system reliability required by ShirleyBasin
the NERC and WECC.
Existing =Repower NewForpurposeofthisanalysis,the
assumption was made that new resources Aeolus Wind
added were treated as network resources
utilizing the PacifiCorp ESM NOA Existing =Repower New
agreement west of Jim Bridger Plant to ^lus -FreezeoutWind
transmit power to the Utah load center.
Freezeout
This report summarizes the power flow
and dynamic stability study findings for a
Existing -Repower Newtransmissionassessmentthatevaluatedthe
performance of the Wyoming Bulk StandpipeWind
Electric System (BES)based on the Standpipe
assumed retirement of the Dave Johnson
ToJimBridger
Plant in 2020 and subsequent integrating -Existing =Repower New
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1169 MW of new/repowered wind generation resources and associated new/rebuilt 230 kV
transmission facilities.
1.2 Plan of Service
The following230 kV transmission additions/modifications were identified by the study (see
Figure 1):
1.Addition of the new Bridger -Latham -Freezeout -Shirley Basin -Windstar 230 kV
lines (two-1272 ACSR (Bittern/phase).
2.Rebuild the Point of Rock -Bitter Creek 230 kV,Bitter Creek -Bar X 230 kV,Bar X
-Echo Springs 230 kV,Echo Springs -Latham 230 kV,Latham -Platte 230 kV,Platte
-Standpipe 230 kV and Standpipe -Freezeout 230 kV lines (two-1272 ACSR,
Bittern/phase).
3.Replace the existing three -345/230 kV (200 MVA)autotransformers at Jim Bridger
with two -345/230 kV (600/685 MVA,normal/emergency)autotransformers.
4.Rebuild the followingsubstations:Point of Rock,Bitter Creek,Bar X,Echo Springs,
Latham Platte,Standpipe,Freezeout,Shirley Basin and Windstar to support higher
transmission line capacity.
5.Addition of a dynamic voltage control device at Latham 230 kV substation,including
Static VAr Compensator (SVC)(+350/-125 MVAr)and five -40 MVAr switched
shunt capacitors.
1.3 Planned OperatingDate
The plan of service for the facilities to be operational is by November 2020.
1.4 Scope
The Dave Johnston Plant retirement assessment assumes the addition of up to l 169 MW of
anticipatedi new and repowered wind generation facilities noted in Table 1,which are
necessary to increase TOT 4A transmission path flows up to a point where the path was
resources limited.For purpose of this analysis,the assumption was made that new resources
added were treated as network resources utilizingthe PacifiCorp ESM NOA agreement west
of Jim Bridger Plant to transmit power to the Utah load center.
The study was performed using a 2021-22 heavy winter WECC approved case,which was
modified to remove the Dave Johnston Plant and to add increasing levels of wind generation
and associated new/modified 230 kV transmission facilities,which were selected to mitigate
facility thermal overloads and voltage violations.The system model assumed summer line
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ratings to assess the thermal limitation of the Wyoming system.Load served from Platte is
normally represented as an open point between Platte -Whiskey Peak 115 kV.The system
configuration with Platte l 15 kV normallyopen is presently the most limitingscenario for the
existing TOT 4A/4B nomogram.
Table 1:GeneratingResource Scenario
East Wyoming Jim Bridger East Wyoming Repowered Wind New SE
Thermal Gen Plant Gen level Existing Wind (MW)Wyoming.
(MW)(MW)(MW)Wind (MW)
Dave Johnston 1400 -2100 1124 0.0 1169
Plant -OFF .(Foote Creek,Rock Repowering wmd See
Wyodak (268/67)River,High Plains,turbine Table 4
-SevenMile Hill,representation(PacifiCorp/Black
Hills)Dunlap,Root was updated in
Creek,Top of the the system model
World,Glenrock,but the output was
Three Buttes,limited to existing
Chevron)LGIA levels
2 Study Criteria
2.1 Thermal Loading
For system normal conditions described by the P0'event,thermal loading on BES transmission
lines and transformers is required to be within continuous ratings.
For contingency conditions described by Pl-P7 category planning events,thermal loading on
transmission lines and transformers should remain within 30-minute emergency ratings.
The thermal ratings of PacifiCorp's BES transmission lines and transformers are based on
PacifiCorp's Weak Link Transmission Database and Weak Link Transformer Database as of
March 31,2017.
7 Facility outage events that are identifiedwith "P"designations are referenced to the TPL-001-4 NERC standard.
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2.2 Steady State Voltage Range
The steady state voltage ranges at all PacifiCorp BES buses shall be within acceptable limits
as established in PacifiCorp's Engineering Handbook section 1B.3 "Planning Standards for
Transmission Voltage""as shown below.
Table 2:Voltage Criteria
Contingency Conditions (P1-Operating System Normal Conditions (PO)P7)Configuration
Vmin (pu)Vmax (pu)Vmin (pu)Vmax (pu)
Looped 0.95 1.06 0.90 1.10
Radial 0.90 1.06 0.85 1.10
Steady state voltage ranges at all applicable BES buses on adjacent systems were screened
based on the limits established by WECC regional criteria as follows:
95%to 105%of nominal for P0 event (system normal),
90%to l10%of nominal for Pl-P7 events (contingency).
2.3 Post-Transient Voltage Deviation
Post-contingency steady state voltage deviation at each applicable BES load serving bus
(having no intermediate connection)shall not exceed 8%for Pl events.
2.4 Transient StabilityAnalysis Criteria
All voltages,frequencies and relative rotor angles are required to be stable and damped.
Cascading or uncontrolled separation shall not occur and transient voltage response shall be
within established limits.
2.5 Transient Voltage Response
Transient stability voltage response criteria are based on WECC Regional Performance Criteria
WRl.3 through WRl.5 as follows:
Transient stability voltage response at the applicable BES buses serving load (having
no intermediate connection)shall recover to at least 80%of pre-contingency voltage
8 PacifiCorp Engineering Handbook "Planning Standards for Transmission Voltage,"April 8,2013.
In some situations,voltages may go as high as 1.08 pu at non-load buses,contingent upon equipment rating
review.
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within 20 seconds of the initiating event for all Pl-P7 category events,for each
applicable bus serving load.
For voltage swings followingfault clearing and voltage recovery above 80%,voltage
dips at each applicable BES bus serving load (having no intermediate buses)shall not
dip below 70%of pre-contingency voltage for more than 30 cycles or remain below
80%of pre-contingency voltage for more than two seconds for all Pl-P7 category
events.
For contingencies without a fault (P2-1 category event),voltage dips at each applicable
BES bus serving load (having no intermediate buses)shall not dip below 70%of pre-
contingency voltage for more than 30 cycles or remain below 80%of pre-contingency
voltage for more than two seconds.
The followingcriteria were used to investigate the potential for cascading and uncontrolled
islanding:
Load interruption due to successive line tripping for thermal violations shall be
confined to the immediate impacted areas and shall not propagate to other areas.The
highest available emergency rating is used to determine the tripping threshold for lines
or transformers when evaluating a scenario that may lead to cascading.
Voltage deficiencies caused by either the initiating event or successive line tripping
shall be confined to the immediate impacted areas,and shall not propagate to other
areas.
Positive damping in stability analysis is demonstrated by showing that the amplitude of power
angle or voltage magnitude oscillations after a minimum of 10 seconds is less than the initial
post-contingency amplitude.Oscillations that do not show positive damping within a 30-
second time frame shall be deemed unacceptable.
Stability studies shall be performed for planning events to determine whether the BES meets
the performance requirements.
Single contingencies (Pl category events):No generating unit shall pull out of
synchronism (excludes generators being disconnected from the system by fault clearing
action or by a special protection system).
Multiple contingencies (P2-P7 category events):When a generator pulls out of
synchronism in the simulations,the resulting apparent impedance swings shall not
result in the tripping of any transmission system elements other than the generatingunit
and its directlyconnected facilities.
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Power oscillations are evaluated by exhibiting acceptable damping.The absence of
positive damping within a 30-second time frame is considered un-damped.
3 Base Case Development
3.1 Base Case Selection
The base case developmentprocess involves selecting an approved WECC base case,updating
the models to represent existing and planned facilities and then tuningthe cases to maximum
transfer conditions on the WECC transmission path(s)being studied.For this study purpose,
the published WECC base case that is close to the projects'in-service date of November 2020,
which has average load conditions based on 2021 load projections and the availability of a
stability case,was selected.The WECC approved base case 2021-22 HW (created on August
19,2016)was selected,which meets these criteria.This study was focused in the Wyoming
area and two major transmission paths:TOT 4A and TOT 4B;however,other transmission
pathsl°includingYellowtail South,Bridger West and TOT 3 were monitored throughout the
study to assure path ratings were not exceeded.
The various key parameters for this study from selected 2021-22 HW base case are listed
below:
Table 3:Wyoming Load,Generation and Platte Normal Open Configuration in Base Case
North Wyoming PAC Load (including Wyodak auxiliary 391 MWloadof42MW)
North Wyoming -Western Area Power Administration 211 MW(WAPA)Load
Eastern Wyoming PAC Load (including Dave Johnston 474 MWauxiliaryloadof56MW)
Eastern Wyoming PAC loads on WAPA system 95 MW
Central Wyoming Load (including Jim Bridger Plant 434 MWauxiliaryloadof130MW)
Yellowtail South Path Flow 192 MW
Yellowtail Generation 140/260MW (Online/Max)
WAPA's Existing Small Generation"in North Wyoming 26/50 MW(Online/Max)
io The definitionof transmission paths identifiedin this study are included in the WECC Path Rating Catalog.
"WAPA's small generation in north Wyoming includes;Boysen,BBill,Heart MT,Shoshone,Spring Mountain
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WAPA's Existing Small Generationl2 in Eastern Wyoming 484/584 MW(Online/Max)
Wyodak Generation (PacifiCorp/Black Hills)350/380 MW (Online/Max)
Dry Fork Generation (Basin Electric)420/440 MW (Online/Max)
Gross Laramie River Generation I (WAPA's swing
.605 MW(Max)machine)
Gross Laramie River Generation II 590/605 MW(Online/Max)
Gross Dave Johnston (DJ)Generation 700/774 MW(Online/Max)
Total Existing PAC East Wyoming Windl3 Generation 885.7/1124 MW (Online/Max)
Rapid City DC Tie 130 W2E (200 MW-bidirectional)
Stegall DC Tie 100 E2W (110 MW-bidirectional)
Sydney DC Tie 196 E2W (200 MW-bidirectional)
TOT 4A Path Flow 627 MW
TOT 4B Path Flow 469 MW
Jim Bridger (JB)Plant Generation 2200 MW
Bridger West Path Flow 2027 MW
TOT 3 Path Flow 1259.1 MW
TOT lA Path Flow 195 MW
Platte -Mustang 115 kV Normal Open point Platte -Normal Open
3.2 Generating Facility Additions
Because the specific size and location of new and repowered Wyoming wind generation are
not known,proxy new generationresources were selected based on requests in the PacifiCorp
Large Generation Interconnection (LGI)queue.The followinggenerating facility assumptions
were made and added into the base case.
12 WAPA's small generation in eastern Wyoming includes;Alcova,Fremont,Glendo,Guernsy,Kortes,Seminoe,
CLR 1,SS Genl AND CPGSTN
13 PAC southeastern Wyoming wind generation includes;Root Creek,Three Buttes,Top of the World,Glenrock,
Rolling Hills,Dunlap,Seven Mile Hill,Foote Creek and High Plains
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Table 4:Assumed Generation Projects
Proposed New Wind Facilities Project size Point of Interconnection
Aeolus/Freezeout/Shirley Basin Area 320 MW Freezeout 230 kV
250 MW Aeolus 230 kV
250 MW Shirley Basin 230 kV
250 MW Shirley Basin 230 kV
Foote Creek Area 99 MW Foote Creek-High Plains 230 kV line
230 kV
Repowered Wind Facilitiesl4
High Plains/McFadden Ridge I Gen 0.0 MW High Plains 230 kV
Repowering (+29.75 MW)
SevenMile Hill Gen Repowering (+27.65 0.0 MW Freezeout230 kV
MW)
Dunlap Gen Repowering (+26 MW)0.0 MW Shirley Basin 230 kV
Glenrock Gen Repowering I (+27.65 MW)0.0 MW Windstar 230 kV
Glenrock Gen Repowering II (+27.65 0.0 MW Windstar 230 kV
MW)
TOTAL 1169 MW
Dave JohnstonPlant (gross)-717 MW,Dave Johnston230 kV
net (retired)
See Appendix A for detail on repowered and new wind farm modelling assumptions.
3.3 Base Case Modification and Tuning
The 2021-22HW base case was modified to reflect the most recent Foote Creek,High Plains,
Top of the World and Three Buttes wind generation modeling per the most recent MOD-032
data submitted by each generator owner (GO).Transmission line impedances between Dave
Johnston and Standpipe were verified and updated and the transmission line ratings in the
2021-22 heavy winter case were modified to summer ratings,which represent the most
14 The repowered generation was modeled,but the repowered MW output was not increased in the base case,i.e.
increase machine size was modeled,but output was limited to existing LGI agreement
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conservative thermal limitations.The Platte -Standpipe 230 kV dynamic line rating of
608/666/680 MVA was assumed during the analysis.
By utilizingavailable data obtained from various wind generation facilities at the time of this
analysis,the base cases were reviewed and adjusted to ensure voltages on the collector system
of wind generation facilities were below 1.05 p.u.and that there was no reactive power loop
flow between the main generator step-up transformers GSUs for wind generation facility.This
process involved tuning transformer and generator parameters such that generators were
producing appropriate reactive power output.Additionally,within the 230 kV transmission
system it was verified that the shunt reactive devices were accurately represented,voltage
profiles were normal,reactive power flows were within normal operating ranges and
transmission system voltage was maintained to match acceptable PacifiCorp Transmission
Voltage Schedules.
The Dave Johnston Plant was taken offline,the new wind resources listed in Table 4 were
added to the base case and existing repowered wind farm generator and collector system data
were updated.Due to the geographical separation of the retired Dave Johnston Plant and the
anticipated new wind generation resources (see Figure 2),new/rebuilt 230 kV transmission
facilities were added to the model to achieve higher transfer levels while maintaining
transmission system reliability required by the NERC and WECC.The TOT 4A path was
stressed by maximizingthe output on all of the existing and new wind generationfacilities,the
repowered wind generation facilities outputs were limited to the existing LGIA agreements.
The additional generation in southeast Wyoming was re-dispatched with central and southern
Utah generation for load balancing purposes.The TOT 4B flows were limited to 170 MW to
maximize the power flow on TOT 4A,without stressing Yellowtail South path to its maximum.
For purpose of this analysis,the assumption was made that new resources added were treated
as network resources utilizingthe PacifiCorp ESM NOA agreement west of Jim Bridger Plant
to transmit power to the Utah load center.
The San Juan,Gladstone and Shiprock phase shifting transformers in New Mexico were
modified to regulate flow across the phase shifters as per base case power flow values.
4 Contingency Studies
4.1 Steady-State Analysis
The steady-state simulations were performed for planning events in Wyoming to assess system
performance.For this study purposes only Pl,P2,P4,P5 and P7 planning events were
considered.The planning events P3 and P6 planning events,which involve loss of a first
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planning event (Pl)followed by system adjustment,then loss of a second planning event (N-
1-1),were not included in the study.Followingis the list of the number of outages that were
studied:
Table 5:Number of Planning Events Studied for Steady State Analysis
TotalPlanningEventDescriptionCategoryContingency
P1:
1.Loss of Generator Pl-1 45
2.Loss of Transmission Circuit Pl-2 139
3.Loss of Transformer Pl-3 105
4.Loss of Shunt Device Pl-4 47
5.Single Pole of a DC line Pl-5 n/a
P2:
1.Opening of a line section w/o fault P2-1 56
2.Bus Section Fault P2-2 22
3.Internal Breaker Fault (non-Bus-tie)P2-3 64
4.Internal Breaker Fault (Bus-tie)P2-4 2
P4:Loss of multipleelements by a stuck breaker for fault on the following:
1.Generator P4-1 0
2.Transmission Circuit P4-2 8
3.Transformer P4-3 2
4.Shunt Device P4-4 2
5.Bus Section P4-5 1
6.Stuck Bus-tie Breaker attempting to clear a fault on the P4-6 1
associated bus
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TotalPlanningEventDescriptionCategoryContingency
P1:
P5:Non-redundant relay failure for fault on the following:
1.Generator P5-1 n/a
2.Transmission Circuit P5-2 6
3.Transformer P5-3 3
4.Shunt Device P5-4 n/a
5.Bus Section P5-5 n/a
P7:
1.Loss of two adjacent circuits on common structure P7-1 2
2.Loss of a bipolar DC line P7-2 n/a
Total:507
4.2 StabilityAnalysis
The stability analysis was performed for selective planning events in Wyomingto determine
whether the BES meets the desired performance requirements or if system improvements are
needed.The stability cases were first examined for a system normal condition to verify correct
base case initialization.Thirteen critical Pl planning events of selective 230 kV line outages
were included for dynamic simulations,these contingencies are expected to produce the most
severe system impacts.The outages are as follows:
1.Loss of Latham -Point of Rocks 230 kV line
2.Loss of new Latham -Bridger 230 kV line
3.Loss of Platte-Standpipe 230 kV line
4.Loss of Platte-Latham 230 kV line
5.Loss of Dave Johnston -Casper 230 kV line
6.Loss of Amasa-Difficulty230 kV line
7.Loss of Dave Johnston -Amasa 230 kV line
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8.Loss of Windstar -Shirley Basin 230 kV line
9.Loss of Shirley Basin -Aeolus 230 kV line
10.Loss of Freezeout -Latham 230 kV line
11.Loss of Aeolus -Freezeout 230 kV line
12.Loss of Riverton -Wyopo 230 kV line
13.Loss of Shirley Basin -Freezeout 230 kV line
5 Results and Solution
5.1 Steady-State Analysis Results -Planning Events
The developed stressed base case with Dave Johnston Plant offline and the addition of 1169
MW of new/repowered wind in southeast Wyoming and associated new/modified 230 kV
transmission facilities was analyzed for various planning events as listed in Table 5.The
existing Standpipe RAS for the Standpipe -Platte 230 kV line outage and the Amasa RAS for
the Dave Johnston -Amasa 230 kV line outage,were re-evaluated for power flow analysis
followingthe system improvements added to the case.
The addition of 1169 MW of southeast Wyoming wind caused various 230 kV segments
between Point of Rocks and Dave Johnston to overload above continuous ratings under normal
conditions,and above emergency summer ratings under system outage conditions and caused
voltage violations.As a result of steady-state analysis the following system issues and
improvements were identified:
1.Planning event Pl-2,the N-1 outage of any of the 230 kV lines between Point of Rocks
and Dave Johnston substations lead to thermal overload of the remaining 230 kV
facilities above their 30 minutes emergency rating and low voltage below 0.90 p.u.
Therefore,a new 230 kV line [two -1272 ACSR (Bittern/Phase)conductor]between
Bridger -Latham and Latham -Freezeout is required.The new 230 kV line will need
to be terminated at Bridger because there is no available bay for a line termination or
space for substation expansion at the Point of Rocks 230 kV yard.
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2.Planning event Pl-2,the N-1 of outage of Freezeout -Aeolus 230 kV or Dave Johnston
-Amasa 230 kV with the Amasa RAS,or Amasa -Difficulty 230 kV or Difficulty -
Shirley Basin 230 kV line overloads the Dave Johnston -Amasa 230 kV line,Amasa
-Difficulty 230 kV line,Difficulty -Shirley Basin 230 kV line,and Freezeout -
Aeolus 230 kV line above 30 minutes emergency rating.Therefore,a new 230 kV line
[two -1272 ACSR (Bittern/Phase)conductor]line between Windstar and Shirley Basin
is required.For improved system reliability the 230 kV line will be extended from
Shirley Basin -Freezeout 230 kV substation.
3.Planning event Pl-2,the N-1 outage of DJ -Amasa 230 kV line with Amasa RAS to
trip Root Creek generation or N-1 of Amasa -Difficulty 230 kV line outage or N-1 of
Difficulty-Shirley Basin 230 kV line causes low voltage below 0.9 p.u.at Latham and
Echo Springs 230 kV substation;therefore,a Latham SVC +350/-125 MVAR and five
-40 MVAr switched shunt capacitors are required.
4.Planning event P2-3,the circuit breaker failure at Rock Springs substation can cause
outage of the Rock Springs -Raven and Rock Springs -Firehole 230 kV lines,
overloading Jim Bridger 345/230 kV autotransformer #1,#2 and #3 above the
emergency rating.Therefore,two new 345/230 kV (600/685 MVA),auto transformers
at Jim Bridger (replace the existing three -200 MVA autotransformers)are required.
The other outages critical to Jim Bridger transformer #3 overloads above emergency
rating are Jim Bridger 345 kV circuit breakerfailure causing outage of the Jim Bridger
345/230 kV transformer #1 and #2 or Jim Bridger 230 kV circuit breaker failure
causing outage of the Jim Bridger 345/230 kV transformer #1,#2 and the Jim Bridger
-Mustang 230 kV line.
5.Planning event Pl-2,the new Bridger -Latham 230 kV line outage with 600 MW of
RAS causes an overload above emergency rating on the Point of Rocks -Bitter Creek
230 kV line,Bitter Creek -Bar X 230 kV line,Bar X -Echo Springs 230 kV line to,
and Echo Springs -Latham 230 kV line.Therefore,a rebuild of the existing 230 kV
line between Point of Rocks and Latham with two-1272 ACSR (Bittern/Phase)is
required.
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PreliminaryTransmission Assessment
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New Wyoming Wind Generation Integration
6.Planning event Pl-2,the new Latham -Freezeout 230 kV line outage with 600 MW of
RAS causes an overload above emergency rating on the Latham -Platte 230 kV line
and Platte -Standpipe 230 kV line with DLR emergency rating of 680 MVA.
Therefore,a rebuild of the existing 230 kV line between Latham and Freezeout with
two-1272 ACSR (Bittern/Phase)is required.
7.Rebuild the followingsubstations:Point of Rocks,Bitter Creek,Bar X,Echo Springs,
Latham,Platte,Standpipe,Freezeout,Shirley Basin and Windstar to support higher
transmission line capacity.
As a result of the transmission facility additions noted above,the existing Amasa RAS were
eliminated.This study was performed per the interconnection queue order and the generation
trip was limited to 600 MW to identify system limitations followingthe outage of a 230 kV
line.
Followingthe implementation of the system improvements identified above,the transfer levels
on various WECC transmission paths and generation output is shown below:
Table 6:Wyoming major transmission path flows and generation with Dave Johnston
plant offline,addition of new southeast Wyoming wind generation facility,Latham SVC,
replaced Jim Bridger 345/230 kV transformers,new 230 kV lines between Windstar -Shirley
Basin,Shirley Basin -Freezeout,Freezeout -Latham,Latham -Bridger,and rebuilt all 230
kV line sections between Point ofRocks and Freezeout.
TOT 4A Path Flow 1528 MW
TOT 4B Path Flow 164 MW
Jim Bridger Plant Generation 1894 MW
Bridger West Path Flow 2400 MW
TOT 3 Path Flow 1366 MW
Yellowtail South Path Flow 522 MW
Wyodak Generation 350 MW
Dave Johnston Generation 0 MW
See Appendix B for power flow plots for bases case,and outage cases.
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PreliminaryTransmission Assessment
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New Wyoming Wind Generation Integration
5.2 StabilityAnalysis Results
The stability analysis was performed using GE provided model (GE0501)for repowered and
new wind generation as identified in Table 4.Additionally,the generic model for Root Creek
wind model was updated to GE0501 (GE 1.85 units),Top of the World and Three Buttes were
updated to GE 1.5 wind turbine model provided by GE for PTI V33.The stressed base case
with flow conditions noted in Table 6 was initialized for steady-state conditions and the case
initialized without any issues.Dynamic simulations were performed on thirteen critical Pl
planning events as mentioned in section 4.2 and did not identify any stability issues in the
PACE system.The voltages,frequencies and rotor angles were stable and well damped.There
were no cascading issues identified and none of the generation modeled pulled out of
synchronism.See Appendix C for dynamic simulation plots for thirteen N-1 outages that were
evaluated.
6 Sensitivity Analysis
Sensitivity analysis was performed to evaluate adding new wind generation to the existing
system,without any system improvements or additional RAS to drop generation.Only power
flow analysis was performed to identify the generation limit.The sensitivity analysis was
performed on the base case identified in Section 3 starting with a 320 MW project at Freezeout.
Study result identified that up to 100 MW generation can be added to the existing system
without any system improvements or new RAS.The system with an additional 100 MW of
generation in southeast Wyomingcauses Latham voltage to drop to 0.91 p.u.for the Amasa -
Difficultyline outage with Amasa RAS or Difficulty-Shirley Basin 230 kV line outage.The
voltage will drop further as the load served from Platte is reduced.Additionally,the Latham -
Echo Springs or Echo Springs -Point of Rocks or Latham -Platte 230 kV line outages cause
the Dave Johnston -Amasa 230 kV line to overload up to 102%of 551 MVA (emergency
rating).The Platte -Standpipe 230 kV line outage will continue to require the Standpipe RAS
(existing)to meet performance requirements.
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7 Study Conclusions
Technical studies demonstrated that by retiring the Dave Johnston generation and adding
new/rebuilt 230 kV transmission facilities (identified below),up to 1169 MW of new4 wind
generation can be integrated with the southeast Wyoming transmission system.Under this
transmission configuration the modified6 TOT 4A transmission path can transfer 1528 MW6
east to west,simultaneously with flows of 164 MW on the TOT 4B transmission path,thereby
increasing the transfer levels across Wyoming by 553 MW.System performance evaluated
will meet all NERC and WECC performance criteria.
Power flow findings indicated that the followingtransmission system improvements will be
required (see Figure 1):
Addition of a new Bridger -Latham 230 kV,Latham -Freezeout 230 kV,Freezeout -
Shirley Basin 230 kV and Shirley Basin -Windstar 230 kV lines (two-1272 ACSR,
Bittern/phase).
Rebuild the Point of Rocks -Bitter Creek 230 kV,Bitter Creek -Bar X 230 kV,Bar
X -Echo Springs 230 kV,Echo Springs -Latham 230 kV,Latham -Platte 230 kV,
Platte -Standpipe 230 kV and Standpipe -Freezeout 230 kV lines (two-1272 ACSR,
Bittern/phase).
Replace the existing three -345/230 kV (200 MVA)autotransformers at Jim Bridger
with two -345/230 kV (600/685 MVA,normal/emergency)autotransformers.
Rebuild the followingsubstations:Point of Rocks,Bitter Creek,Bar X,Echo Springs,
Latham,Platte,Standpipe,Freezeout,Shirley Basin and Windstar to support higher
transmission line capacity.
Addition of a dynamic voltage control device at Latham 230 kV substation,including
Static VAr Compensator (SVC)(+350/-125 MVAr)and five -40 MVAr switched
shunt capacitors.
The power flow analysis also indicated that the location (and output level)of new and
repowered wind resources can influence the transfer capability level across the TOT 4A
transmission path.
While a wide range of disturbances were evaluated,dynamic stability analysis for critical N-1
outages indicated that the voltages,frequencies and rotor angles were stable and well damped.
There were no cascading issues identified and none of the generation pulled out of
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PreliminaryTransmission Assessment
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New Wyoming Wind Generation Integration
synchronism.The stability analysis demonstrated that all planned system events met the
stability performance criteria.
As part of the Dave Johnston retirement analysis,a sensitivity analysis identified that up to 100
MW of new wind generation in the Freezeout area can be added to the existing transmission
system without any system improvements or additional RAS to drop generation.
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