A subsidiary of Pinnacle West Capital Corporation · • Q107 Regulating bus is set at either the...

A subsidiary of Pinnacle West Capital Corporation

Q107 Generator Interconnection

Bagdad 115kV Line

Feasibility Study

APS Contract No. 52260

By

Arizona Public Service Company Transmission Planning

October 13, 2010

.

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Q107 Feasibility Study

TABLE OF CONTENTS

EXECUTIVE SUMMARY ........................................................................................................................... 2

1 Study Description and Assumptions ...................................................................................................... 3 1.1 Pre-Project Case Modeling ............................................................................................................. 5 1.2 Post Project Case Modeling ........................................................................................................... 5

2 Results and Findings ............................................................................................................................. 8 2.1 Power Flow Results ........................................................................................................................ 8 2.2 Fault Duty Analysis ....................................................................................................................... 10 2.3 Generation and Transmission Mitigation ...................................................................................... 10 2.4 Network Resource Analysis .......................................................................................................... 11

3 Cost and Construction Time Estimates ............................................................................................... 11

LIST OF APPENDICES

Appendix A - List of Contingencies Appendix B – Power Flow Plots

Q107 Feasibility Study APS Contract No. 52260

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EXECUTIVE SUMMARY This section summarizes the Feasibility Study (FeS) results for a proposed generation interconnection totaling 120MW in the Arizona Public Service (APS) transmission system. Specific details of the impact of the interconnection upon the surrounding transmission system can be found in the “Results and Findings” section of this report.

Disclaimer Nothing in this report constitutes an offer of transmission service or confers upon the Interconnection Customer, any right to receive transmission service. APS and other interconnected utilities may not have the Available Transmission Capacity to support the interconnection described in this report. It should also be noted that all power flow results for the FeS are highly dependent upon the assumed topology and timing of new projects in the Bagdad vicinity and nearby preceding generation interconnection requests, which are subject to change. The APS transmission and sub-transmission systems are continuously being evaluated; planned reinforcements and their in-service dates are often revised depending upon local area load growth.

Background: Under provisions of the Arizona Public Service Company (APS) Open Access Transmission Tariff (OATT), APS has entered into a Feasibility Study Agreement with Q107. The Q107 Applicant plans to install 120MW of wind generation in 2012. At the request of the Applicant this interconnection will be studied as both an Energy Resource and as a Network Resource. Figure 1 below shows a sketch of the project and nearby transmission grid.

Figure 1. Q107 Interconnection

What was studied This Feasibility Study (FeS) examined the effects of interconnecting the new generation to the surrounding transmission system. Analyses for the proposed interconnection consisted of computer-based power flow studies, and short circuit/fault duty analysis. This study modeled the interconnection under 2013 Summer Peak load conditions (forecasted peak load of 21,329MW in AZ). All N-1 contingencies potentially impacted by Q107 were simulated. Power flow results were monitored for APS, WAPA, and other neighboring systems; power flow and short circuit analyses were performed by the APS Transmission Planning.

Pinnacle Peak

Round Valley

Queue #107

(120MW)

Willowlake

Bagdad Mine

Yavapai


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System performance criteria used in the study The criteria applied in this study are consistent with NERC/WECC Reliability Criteria. Results The proposed generation resulted in one new thermal overload in the APS system under applicable (single element WECC Category B) outage conditions. Voltage criteria violations in the Bagdad system are caused by the interconnection. A +/- 20 MVAR SVC is required. The APS transmission plans continuously re-evaluate the in-service dates and need for planned projects. Many factors go into determining in-service dates for planned projects; including but not limited to load growth, resource locations, and scheduling needs. A change in one or more factors may lead to a change in a project’s in-service date. As of the date of this report there are no 10 year plan projects that affect the response of Q107 to system performance. Curtailments Planned generation capacity may be curtailed in lieu of a transmission system upgrade. The curtailment is needed if two 230/115kV transformers at Willowlake are not replaced. In addition, the loss of the Bagdad – Willowlake 115kV circuit will require a transfer trip of Q107. For a complete discussion on the generation curtailments, see section 2.3 “Generation and Transmission Mitigation.” Reinforcements The applicant may elect to upgrade the transmission system rather than curtail the planned generation capacity. The transmission mitigation project required to achieve full output is to replace two 230/115kV transformers at Willowlake. For a complete discussion on the transmission system upgrade see section 2.3 “Generation and Transmission Mitigation.”

1 Study Description and Assumptions This comprehensive study monitored the impact on all affected transmission systems. Affected parties have been identified as Salt River Project (SRP), Central Arizona Water Conservation District (CAWCD), and Western Area Power Administration (WAPA). The Study was comprised of power flow analysis, short circuit analysis, and network analysis. The following transmission/generation projects were assumed out-of-service:

• APS Q1 Desert Rock Power Plant and associated Navajo Transmission Project The following transmission/generation projects were assumed in-service:

• Morgan – Pinnacle Peak 500/230kV Line (Planned for 2010) The following generation was reduced to offset the 120MW of pre-project Network Resource generation:

• Sundance • WPHX GTs 1 & 2

One sensitivity case was run to assess the impacts of relatively uncertain but significant transmission characteristics:

• Bagdad Mine Load Offline (Thermal analysis only): Identify the reliability impacts with and without the Bagdad Mine Load.

A total of 4 basecases were created to properly study each sensitivity. The analysis used a 2013 summer APS Detailed Planning basecase as a starting point. This case was jointly built by the Arizona utilities, represents the most up-to-date transmission system topology, and includes the most recent APS load forecast for 2013. Table 1 summarizes the cases utilized in this generation interconnection study.


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Table 1. Basecase Modeling Summary

# Scenario Description Q10

7 G

ener

atio

n

Bagd

ad M

ine

Load

Onl

ine

Power Flow Analysis – 2013 Heavy Summer 1. Pre Project √ 2. Post Project √ √ 3. Pre Project – No Bagdad Load 4. Post Project – No Bagdad Load √


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1.1 Pre-Project Case Modeling The Pre-Project case simulated a high load, high generation condition for summer 2013. As a starting point, this FeS used an APS Detailed Planning case (“sm13#11.sav”), which includes modeling of the 69kV sub-transmission system. Additional modifications described below were implemented to create the cases. Pre-Project Case: “2013” Pre-Project Heavy Summer High Load/High Generation

1. Study base case “sm13#11.sav” was obtained from APS Transmission Planning. This basecase includes the planned Morgan – Pinnacle Peak 500/230kV line.

General Changes 2. Changed all isolated/islanded busses from Type “0” to Type "99".

Arizona Changes 3. The emergency rating of the Yavapai-Verde 230kV line was set to 374MVA. 4. The emergency rating of the Yavapai-Willow Lake 230kV line was set to 354MVA.

A summary of the Pre-Project power flow case attributes are listed in Table 2. Power flow diagrams of the transmission system for the Pre-Project normal “All Planned Projects In Service” condition are provided in Appendix A. 1.2 Post Project Case Modeling The modeling for the new generation utilized the machine characteristics provided by the Applicants. The arrangement of Q107 is depicted in Figure 2.

Figure 2. Q107 Arrangement at Bagdad

Post-Project Cases: “2013” Post-Project Heavy Summer

• Request #107 (120MW net output) is comprised of one 120MW unit. Each unit has a dedicated Generator Step-Up (GSU) transformer. The units are gathered together by a 34.5kV collector bus, then transformed to 115kV. One 10 mile 115kV line delivers the power to the Bagdad 115kV Point of Interconnection (POI). The conductor size and type was not specified by the applicant.

• The VAR capability for the 120 MW unit is assumed to be 37.5 MVAR boost and 37.5 MVAR buck.

• Q107 Regulating bus is set at either the Q107 34.5kV bus, or the Bagdad Mine 115kV bus, depending on the study scenario.

• 20 MVAR SVC is added to the 115kV bus at the Q107 generation facility. The MVAR size is determined in section 2.

The arrangement of the interconnection is depicted in Figure 2 above.

Bagdad Mine 115kV

Length: 10 Miles

115/34.5kV Collector Bus

0.69kV Queue #107

(120MW) +/- 20 MVAR SVC


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Bagdad Mine Load Offline:

• One dispatch scenario considered the Bagdad Mine Load to be offline. To offset the load reduction, generation units at Sundance and West Phoenix are reduced.

Power flow diagrams of the transmission system along with the new generation interconnection are provided in Appendix A. Table 2 summarizes the attributes for each case.


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Table 2. Case Attributes

With Bagdad Mine Load

Without Bagdad Mine Load

Pre-Project

Post-Project

Pre-Project

Post-Project

Major Path/Branch Flows:

Path 51 – Navajo South 869.2 820.4 813.1 794.9 Bagdad – Willowlake 115kV Line -82.7 36.6 -2.5 108.9 Yavapai – Willowlake 115kV Line 237 171.2 192.2 130.9 Willowlake 230/115kV #1 Xfmr 41.8 -18.5 1.3 -55.1 Willowlake 230/115kV #2 Xfmr 40.9 -18.1 1.3 -53.8 Prescott – Gavlin Peak 230kV Line 9 35.6 26.7 51.2 Peacock – Round Valley 230kV Line 50 30.7 37.7 19.1

Case 1 2 3 4


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2 Results and Findings This section details the results of the power flow analysis, fault duty analysis, and network analysis.

2.1 Power Flow Results Contingencies were applied to the power flow cases. The list of contingencies simulated is provided in Appendix B. Selected power flow plots from various system scenarios are included in Appendix A. Table 3 details the thermal overloads identified in the various case scenarios. The table identifies that the Q107 could contribute to (and result in) potential emergency overloads. The overloads arise when the Bagdad Mine Load is not in-service. Table 4 details potential voltage issues identified due to generation output variability. The table identifies that the Q107 could contribute to (and result in) potential voltage issues. With generation variability, Bagdad voltages will fluctuate. The results in Table 4 indicate that the Bagdad mine voltage is subject up to a 2kV impact due to generation variability with Q107 regulating the 34.5kV bus. It is required that generation variability due to any generation interconnection in the Bagdad area will not fluctuate voltages at the Bagdad mine. Therefore it is required that Q107 install a SVC on their side of the POI. Table 5 details results of flicker analysis with a SVC installed at the 115kV side of the generation interconnection. In order to size the SVC for adequate system support, a sensitivity case is created which includes maximum load conditions for the Bagdad Mine load (82 MW) and Bagdad Town Load (7MW). Based on the results, it is recommended that a +/- 20 MVAR SVC is to be installed at the Q107 location to account for voltage swings due to generation output variability.

Table 3. Thermal Loading Results

Outage/Overloaded Element Rating

N/E (MVA)

With Bagdad Mine Load

Without Bagdad Mine Load

Pre-Project

Post-Project

Pre-Project

Post-Project

N-1 Willowlake 230/115kV #1 Transformer

Willowlake 230/115kV #2 Transformer 83/83 99.7% <80% <80% 138.7% N-1 Willowlake 230/115kV #2 Transformer Willowlake 230/115kV #1 Transformer 83/83 99.7% <80% <80% 138.7%

Case 1 2 3 4

Table 4. Flicker

Generator MW Output

Generator MVAR Output Bagdad Mine Voltage Willowlake 230kV Voltage

100% 120MW 8.5 118.2 235.4

90% 108MW 3.8 118.9 235.6

60% 72MW -4.9 120.1 235.8

30% 36MW -5.8 119.9 235.5

10% 12MW -2.1 119 235


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Table 4. Flicker Analysis with SVC (Maximum Load Conditions)

Generator MW Output

Generator MVAR Output Bagdad Mine Voltage

100% 120MW 0 116.1

90% 108MW -6 116.1

60% 72MW -17 116.1

30% 36MW -14 116.1

10% 12MW -4 116.1

0% 0MW 5 116.1

Yavapai – Willowlake 230kV Outage

Generator MW Output

Generator MVAR Output Bagdad Mine Voltage

100% 120MW 0 114.4

90% 108MW -7 114.4

60% 72MW -17 114.4

30% 36MW -12 114.4

10% 12MW 1 114.4

0% 0MW 10 114.4


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2.2 Fault Duty Analysis Short circuit analysis of the proposed generator interconnection(s) was performed by the APS Protection Department, using the CAPE program and parameters supplied by the Applicant. Fault duties were calculated for both single-phase-to-ground and three-phase faults at substation busses in the immediate surrounding area before and after the proposed generator installation. The results presented here assume a “worst-case” scenario, with all of the project’s generating units assumed on-line. For this initial FeS, short circuit analysis primarily focused on busses in the immediate vicinity of the interconnection. Table 6 provides a comparison of fault duties at several local busses for both the Pre-Project and Post-Project conditions. The summary Table also provides the minimum circuit breaker rating at each of these substations.

Table 6. Short-Circuit Results W/O Sun Valley - Morgan 500kV line

Substation Pre-Project Post-Project Minimum

Breaker Rating (kA)

3 Ph. (kA)

Ph-G (kA)

3 Ph. (kA)

Ph-G (kA)

Bagdad 115kV 1.623 1.016 2.105 1.124 20 Willowlake 115kV 7.390 7.642 7.783 7.916 40 Willowlake 230kV 9.116 9.253 9.306 9.382 50

2.3 Generation and Transmission Mitigation This section discusses the potential generation curtailments or transmission upgrade projects needed to mitigate the thermal overloads and adverse voltage conditions caused by the interconnection. Implementing these curtailments and/or upgrade projects will mitigate the discovered reliability concerns. Reliability Concern #1: Two Willowlake 250/115kV Transformers Condition: Bagdad Mine Load offline, Full output of Q107

A N-1 of a Willowlake 230/115kV Transformer overloads the other.

Table 7. Generation and Transmission Mitigation Trigger Points Q107 Output

AZ Upgrade Requirement

0-88 No Upgrades Required

88-120 Replacement of (2) Willowlake 230/115kV Transformers to 150 MVA

Reliability Concern #2: Bagdad Voltage Condition: Variability of Bagdad Load and Q107 generation

With generation variability, Bagdad voltages will fluctuate. The results in Table 4 indicate that the Bagdad mine voltage is subject up to a 2kV impact due to generation variability with Q107 regulating the 34.5kV bus. It is required that generation variability due to any generation interconnection in the Bagdad area will not fluctuate voltages at the Bagdad mine. Therefore it is required that Q107 install a SVC on thei Interconnection Customer’s side of the POI. Results from Table 5 show that a +/- 20 MVAR SVC is sufficient to mitigate potential voltage fluctuations.

The System Impact Study results demonstrated that to ensure system reliability, the Generating Facility shall be required to meet the APS OATT power factor of 0.95 leading to 0.95 lagging, as measured at the POI. This Power Factor may be dispatched within this designated range by the APS Energy Control Center personnel as appropriate due to system conditions and without compensation.


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2.4 Network Resource Analysis As part of a Network Interconnection Request, this study determined the ability to integrate and deliver the output of the facility to serve APS native load customers in a manner comparable to that in which the Transmission Provider integrates its generating facilities. In the analysis of this interconnection request it was determined that the project could interconnect and deliver the output of the project to serve APS native load customers without any system upgrades beyond those identified in the reliability section of the report. Delivery of the project output to APS’s native load could be accomplished at the Point of Interconnection (Bagdad 115kV substation). With this project interconnecting into the Bagdad 115kV substation the output of the project could be delivered to APS at Bagdad where APS currently has the capacity to take the energy across the Bagdad – Willowlake 115kV line. At Willowlake APS’s transmission system can deliver energy to Northern Area native load. The project is therefore able to deliver its output to APS’s native load.

3 Cost and Construction Time Estimates Based on the results of this initial Feasibility Study there are only two potential costs for the Q107 project. One is the cost for the facilities needed to interconnect on the Bagdad – Willowlake 115kV line. The other cost is for implementing a Special Protection System (SPS) on the Bagdad – Willowlake 115kV line. This FeS does not include estimates for the approximately 10 miles of 115kV transmission line between the Interconnection Customer’s generating facility and the POI on the Bagdad – Willowlake 115kV line. That 115kV line is considered part of the Interconnection Customer’s Interconnection Facilities. In addition, this FeS also does not include the estimate for a +/- 20 MVAR SVC for the Q107 project which will be part of the Interconnection Customer’s Interconnection Facilities. The siting, permitting, and construction of the line are the responsibility of the Interconnection Customer. Bagdad 115kV interconnection: The assumed in-service date for the Q107 project is 2012. APS’s policy is to operate new 115kV substations as a ring bus up to and including four terminations. Q107 will interconnect into the Bagdad – Willowlake 115kV line, and require a 3 breaker ring bus as shown in Figure 3. Q107 will also require a transfer trip scheme for the loss of the Bagdad – Willowlake 115kV circuit. A rough, non-binding cost estimate for this work is provided below.


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Figure 3. Q107 115kV substation

To WillowlakeTo Bagdad

POI

To Q107

Substation Fence

Ownership Change

Table 8. Cost and Construction Time Estimates – Network Upgrades Facility Cost (2010 dollars) Schedule Q107 115kV Substation $3,120,000 24 months

Replacement of 230/115kV Transformers at Willowlake $5,566,000 24 months

Communications and Protection $1,300,000 24 months

Total $9,986,000 The interconnection costs identified above are considered Network Upgrades and therefore reimbursable to the Interconnection Customer through Transmission Credits or payback within twenty years. The interconnection at Bagdad could be accomplished in approximately 24 months, due to design, procurement and installation of equipment.

Table 9. Cost and Construction Time Estimates – Interconnection Facilities Facility Cost (2009 dollars) Schedule 115kV line $800,000 12 months

Total $800 ,000 The interconnection costs identified above in Table 9, are considered Transmission Provider’s Interconnection facilities. These costs are for the 115kV conductor and associated structure to bring the 115kV generator tie line from the Bagdad 115kV bus to the first structure outside the substation fence, at which point the ownership would change to the Interconnection Customer.

Appendix A

CONTINGENCY LIST

APPENDIX A – CONTINGENCY LIST

A-1

List of Applied Contingencies:

line_1 "Line PPAPS W 230.0 to PINPK 230.0 Circuit 1" 1.000 line_2 "Line WESTWNGW 230.0 to PINPK 230.0 Circuit 1" 1.000 line_3 "Line YAVAPAI 230.0 to VERDE N 230.0 Circuit 1" 1.000 line_4 "Line YAVAPAI 230.0 to WILOWLKE 230.0 Circuit 1" 1.000 line_5 "Line FORTROCK 230.0 to ROUNDVLY 230.0 Circuit 1" 1.000 line_6 "Line FORTROCK 230.0 to JUNIPRMT 230.0 Circuit 1" 1.000 line_7 "Line WILOWLKW 230.0 to PRESCOTT 230.0 Circuit 1" 1.000 line_8 "Line WILOWLKW 230.0 to WILOWLKE 230.0 Circuit 1" 1.000 line_9 "Line JUNIPRMT 230.0 to SELIGMAN 230.0 Circuit 1" 1.000 line_10 "Line LIBERTY 345.0 to PEACOCK 345.0 Circuit 1" 1.000 line_11 "Line MCCONICO 230.0 to DAVIS 230.0 Circuit 1" 1.000 line_12 "Line MCCONICO 230.0 to GRIFFITH 230.0 Circuit 1" 1.000 line_13 "Line PINPK 230.0 to PINPKSRP 230.0 Circuit 1" 1.000 line_14 "Line PINPK 230.0 to PINPKSRP 230.0 Circuit 2" 1.000 line_15 "Line HILLTOP 230.0 to MCCONICO 230.0 Circuit 1" 1.000 line_16 "Line GRIFFITH 230.0 to PEACOCK 230.0 Circuit 1" 1.000 line_17 "Line PEACOCK 230.0 to HILLTOP 230.0 Circuit 1" 1.000 line_18 "Line RNDVLYTP 230.0 to ROUNDVLY 230.0 Circuit 1" 1.000 line_19 "Line RNDVLYTP 230.0 to PEACOCK 230.0 Circuit 1" 1.000 line_20 "Line MOENKOPI 500.0 to YAVAPAI 500.0 Circuit 1" 1.000 line_21 "Line YAVAPAI 500.0 to WESTWING 500.0 Circuit 1" 1.000 line_22 "Line WHTHILLS 345.0 to MEAD 345.0 Circuit 1" 1.000 line_23 "Line WHTHILLS 345.0 to PEACOCK 345.0 Circuit 1" 1.000 line_24 "Line FRANCONI 230.0 to GRIFFITH 230.0 Circuit 1" 1.000 line_25 "Line MCCONICO 230.0 to MERC230 230.0 Circuit 1" 1.000 line_26 "Line PRSCOTWA 230.0 to PRESCOTT 230.0 Circuit 1" 1.000 line_27 "Line PRSCOTWA 230.0 to RNDVLYTP 230.0 Circuit 1" 1.000 line_28 "Line GAVLINWA 230.0 to GAVILNPK 230.0 Circuit 1" 1.000 line_29 "Line GAVLINWA 230.0 to PINPK 230.0 Circuit 1" 1.000 line_30 "Line GAVLINWA 230.0 to PRSCOTWA 230.0 Circuit 1" 1.000 line_31 "Line PRESCOTT 115.0 to BAGCAP 115.0 Circuit 1" 1.000 tran_32 "Tran PRESCOTT 230.00 to PRESCOTT 115.00 Circuit 1PRESCT1T 12.50" tran_33 "Tran PRESCOTT 230.00 to PRESCOTT 115.00 Circuit 2PRESCT2T 12.50" tran_34 "Tran PEACOCK 345.00 to PEACOCK 230.00 Circuit 1 0.00" 1.000 tran_35 "Tran PINPKBRB 345.00 to PINPK 230.00 Circuit 1 0.00" 1.000 tran_36 "Tran PINPKBRB 345.00 to PINPK 230.00 Circuit 2 0.00" 1.000 tran_37 "Tran PINPKBRB 345.00 to PINPK 230.00 Circuit 3 0.00" 1.000 tran_38 "Tran YAVAPAI 500.00 to YAVAPAI 230.00 Circuit 1YAVAP 1T 12.47" 1.000 tran_39 "Tran YAVAPAI 500.00 to YAVAPAI 230.00 Circuit 2YAVAP 3T 12.47" 1.000 line_40 "Line Q107 Tie Line to Bagdad" 1.000

Appendix B

POWER FLOW PLOTS

APPENDIX B – POWER FLOW PLOTS

B-1

Case1: Pre-Project, With Bagdad Mine Load


B-2

Case 2: Post-Project, With Bagdad Mine Load


B-3

Case 3: Pre-Project, Without Bagdad Mine Load


B-4

Case 4: Post-Project, Without Bagdad Mine Load


B-5

Mitigation Case: Q107 Curtailed to 86MW net output, N-1 Willowlake 230/115kV Transformer (MW/%RATE)

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