Generation Interconnection Impact Study Results for Eurus Energy America Corporation s Eurus Combine Hills I, LLC Power Project.

Transcription

1 Generation Interconnection Impact Study Results for Eurus Energy America Corporation s Eurus Combine Hills I, LLC Power Project April 23, 2003 Introduction Eurus originally requested an interconnection capacity of 104 MW for their wind farm in north eastern Oregon. However, since extensive local transmission modifications might be required, Eurus also considered a reduced capacity of 41 MW. This report discusses the requirements at each level, Eurus subsequent selection of the 41 MW level, and detailed studies at the lower level. 41 MW Interconnection The wind farm can be interconnected to PacifiCorp s existing 69 kv line from the Walla Walla Central Substation to the Pendleton Substation, in the vicinity (south) of the Freewater Substation, via a radial line. The interconnection point would be 9.21 miles due east from the wind farm step-up transformer. PacifiCorp will require a breaker on the line. For this generation level, PacifiCorp recommends its standard conductor size of 397 ACSR (summer rating of 551 amps), as a minimum. For this generation level, EURUS plans to use a single step-up transformer rated at 30/40/50 MVA, with an impedance of 8% on a 30 MBA base. The high and low windings are both grounded wye. The wind turbines will be MHI 1000A. Alternatively, the wind farm could be connected to PacifiCorp s existing 69 kv Umapine Substation. This interconnection point would require approximately an 11 mile radial connection, due east from the wind farm step-up transformer about 8 miles, then north about 3 mile to Umapine Sub. A breaker will be required on the new radial line, preferable at the interconnection point, provided it can be properly coordinated. The Umapine Substation connects to PacifiCorp s existing 69 kv line from Walla Walla Central Substation to the Pendleton Substation at a tap point about 6.5 miles from Walla Walla Central. The tap point about 2.5 miles from the Umapine Sub. This radial tap is currently 4/0 ACSR and must be reconductored 1

2 to at least 397 ACSR. Again, for this generation level, PacifiCorp recommends its standard conductor size of 397 ACSR, as a minimum, for the new radial connection to Umapine. 104 MW Interconnection PacifiCorp s 69 kv line from Walla Walla s Central Sub to Pendleton is currently operated normally open at Weston, about 7 miles south of Freewater Sub, to avoid overloads in the event of a BPA 230 kv line outage. Future expected changes to the BPA system may allow PacifiCorp to operate this line closed, which PacifiCorp may wish to do. The existing conductor on this entire line (about 40 miles) will not support 104 MW. Therefore, interconnections at Freewater or Umapine will require re-conductoring the entire line. The Central Substation is connected to the Walla Walla Substation via two parallel 69 kv paths. One path is 2.5 miles of 397 ACSR. The other path includes about ¾ mile of 397 ACSR. The segments of 397 ACSR on both these paths will require reconductoring so that each path can carry the generator output to the Walla Walla Substation in the event that one of the paths is not available. Use of a scheme to transfer trip generation in the event of a line outage could avoid this reconductor requirement between Central and Walla Walla. There is an alternative new path that could avoid reconductoring approximately the last two miles of the Pendleton to Central 69 kv line (at the Central end), and the two 69 kv paths (or transfer trip scheme) from Central to Walla Walla. The new path would run from a new tap point, about two miles west of Central on the line from Pendleton to Central, and continue about 1.5 miles north to the Walla Walla Substation. This new path would parallel an existing 230 kv line from Walla Walla to Hurricane. It would effectively bypass the Central Substation. The breaker at the existing line at the Central Substation would be set to operate normally open. Additionally, an interconnection at Umapine will require reconductoring the 2.5 mile Umapine tap line. For this generation level, PacifiCorp recommends its standard conductor size of 1272 ACSR (summer rating of

3 amps), as a minimum, for new construction and for reconductoring. For this generation level, EURUS plans to use two step-up transformers each rated at 30/40/50 MVA, with an impedance of 8% on a 30 MBA base. The high and low windings are both grounded wye. EURUS has suggested a configuration that would require a new interconnection location west of Freewater and South of Umapine, at a point about eight miles east of the wind farm s step-up transformer. The new interconnection point would be connected to both the Umapine Sub and the previously mentioned interconnection point south of the Freewater Sub, and the existing 3.5 mile 69 kv segment from Umapine tap to Freewater (on the existing 69 kv line from Walla Walla Central Sub to Pendleton) would be removed. This alternative would still require reconductoring the remaining segments (31 miles from Pendleton to just below Freewater and 2.5 miles from Umapine Sub to Umapine Tap and 6.5 miles from Umapine Tap to Walla Walla Central, or about 4.5 miles from the Umapine Tap to the new tap point which will connect directly to the Walla Walla Substation). PacifiCorp suggests another alternative to eliminate reconductoring at this generation level a radial connection from the wind farm that bypasses Umapine Sub and connects directly to PacifiCorp s Walla Walla Central Substation. In this configuration, existing single circuit transmission structures from Umapine Sub to Walla Walla Central could be replaced by double circuit structures,if necessary. A 69 kv breaker position would be added at Walla Walla Central Substation. For this generation level, PacifiCorp recommends its standard conductor size of 1272 ACSR, as a minimum, for the new construction. Other Requirements For interconnection, EURUS will be required to design, procure and install sufficient reactive compensation to their 34.5 kv system to maintain unity power factor at the point of interconnection. EURUS transmission agent will be required to provide a detailed model of the wind farm generators and distribution 3

4 system suitable for use with the PTI Power System Stability Program. These additional studies will model if additional reactive support will be required to PacifiCorp s transmission system. Eurus Decision Regarding Wind Farm Size and Interconnection Configuration Subsequent to the above study phase and conclusions, Eurus decided that it would elect to construct a 41 MW wind farm development at this time. Eurus may request to expand the farm to a power level that can be carried by a 795 ACSR conductor (in summer, about 101 MW) at an unknown later date. Additionally, Eurus elected to deliver the power via new 69 kv transmission to an interconnection point just below PacifiCorp s existing Freewater Substation on the Pendleton-Walla Walla Central 69 kv line (about 9 miles). Except for the last mile (approximatley) of this line, Eurus has selected a conductor size of 795 ACSR. The last section will be constructed at 397 ACSR. If Eurus increases the capacity of the wind farm in the future, they may abandon the interconnection point and the last mile of line and redirect the line northward as a radial to the Walla Walla Substation as a new interconnection point, all with 795 ACSR. A short circuit analysis was performed on the 41 MW system and this interconnection configuration, to determine if the interconnection of the wind farm would cause the fault duty on PacifiCorp breakers to exceed the rating of the breakers. The study results showed that no breaker ratings would be exceeded. PacifiCorp will require a breaker to protect the radial interconnection and proposes that it be located at the high side of the Wind Farm s step up transformer. The addition of this breaker creates a three-terminal line and the best coordination with breakers at Walla Walla Central and Pendleton are achieved by placing the breaker at the west end of the radial interconnection. The interconnection point will require a motor-operated three-way switch. Minor protection changes may be required at the Walla Walla Central and Pendleton locations to implement deadline check on reclosing at Walla Walla Central and synch check at 4

5 Pendleton. Eurus will not be implementing reclosing at their 69 kv breaker. Communication can either be a microwave path from the wind farm or a combination of a fiber path to Eurus off-site O&M location and a leased line beyond that point. A microwave path will require the installation of a tower near the Wind Farm. Eurus has recently selected the microwave alternative. SCADA databases at the PacifiCorp control centers must be modified to recognize real time data. PacifiCorp anticipates that Eurus will own the radial interconnection. PacifiCorp will own the switches at the interconnection point. Load Flow and Transient Stability Analysis The load flow and transient stability used detailed models of the Combine Hills Wind Farm distribution system and its MHI 1000A wind turbines. The results are described in Appendix A and its significant conclusions are summarized below. Summary Conclusions 1) Eurus will install a 41 MW Wind Farm which will be interconnected via a radial 69 kv line at a point on the existing Walla Walla Central Pendleton line near the Freewater Substation. Eurus has selected a 795 ACSR conductor for their 10 mile radial line, except for the last mile at the interconnection end. The last mile will use 397 ACSR conductor. 2) The interconnection will require a breaker at the high side of the wind farm step-up transformer, and a motoroperated switch at the interconnection point. Minor protection modifications may be required at PacifiCorp s Walla Walla Central and Pendleton substations to accommodate reclosing. 3) Existing breakers in the vicinity of the Wind Farm will not require upgrading. 4) A communications tower will be required at the Wind Farm if microwave is selected. 5

6 5) Eurus must add sufficient reactive compensation to the Wind Farm to deliver a unity power factor at the point of interconnection. Note, there may be periods (eg, light load) when PacifiCorp will want Eurus to operate its reactive compensation in such a way that reactive power is absorbed at the interconnection point, to minimize high operating voltages on PacifiCorp s system. 6) PacifiCorp will require that Eurus design their system and reactive compensation to avoid voltage changes of 3% or greater o the PacifiCorp system. PacifiCorp has estimated that Eurus 5 MVAR size capacitor banks will exceed PacifiCorp s voltage limit on PacifiCorp s system. Additionally, PacifiCorp has estimated that these same capacitor banks will exceed manufacturer s voltage change limitations on Eurus wind turbines. PacifiCorp will not be responsible for the design of Eurus system to minimize voltage change impacts on the PacifiCorp or Eurus systems. 6

7 Appendix A System Impact Study For Combine Hills Wind Project April 23, 2003 Report Prepared by: PacifiCorp Transmission Planning

8 System Impact Study Combine Hills Wind Project TABLE OF CONTENTS I. Project Description 2 II. Study Objectives 2 III. Study Results 2 Existing System Post Combine Hills Generation IV. Voltage Fluctuation from Capacitor Switching 5 V. Stability Studies 5 VI. Recommendations 6 Appendices Diagram #1: Walla Walla Area Diagram 7 Power Flow Summary Tables 8 Power Flow Plots 10 Stability Case Summary Table 14 Stability Plots 15 Revised: ALW 1

9 System Impact Study Combine Hills Wind Project I. PROJECT DESCRIPTION The Combine Hills Wind Power Project (Combine Project) is located approximately 10 miles west of Freewater, Oregon. The project consists of volt, 1 MW wind turbine generators, connected to 34.5 kv distribution system. Each generator is connected to the distribution circuit via a kv transformer. A single, 3-phase, 69 / 34.5 kv, 30/40/50 MVA transformer is used to step up the voltage of the project to 69 kv. A 8.92 mile 69 kv, 795 ACSR "Drake" conductor transmission line connects to a one mile 397 ACSR transmission line which connects the project to the proposed West Freewater 69 kv substation. This study addresses the 41 MW output of the planned wind farm project. II. STUDY OBJECTIVES The study was conducted to discover any voltage or other transmission impacts from the integration of the Combine Project to PacifiCorp's transmission system in the Walla Walla area as network service. In addition, any existing outage limitations were studied. These outage limitations were studied because a case that modeled all of the PacifiCorp and BPA wind farm additions that have been added to the system was not previously available. System impacts targeted for identification in previous studies were examined as a result of the model change. The study investigated transmission system impacts under two different loading conditions: 1) Peak summer load conditions and 2) Spring minimum load conditions. Both existing system and the system with the Combine Hills Wind Project added were studied. The wind farm was modeled in detail to investigate any potential voltage impacts to the wind turbines. Stability studies were only conducted for the peak summer load conditions to determine overall effects on transmission stability due to the addition of the wind farm. III. STUDY RESULTS The N-0 system configurations were studied to determine if any normal loading problems are encountered for peak or minimum load conditions Several N-1 conditions were studied to determine if any system problems exist due to outages. These conditions were evaluated for peak summer load conditions and for light load conditions. The following outages were conducted to determine any deficiencies in system performance: Walla Walla - Vantage 230 kv Line Outage Walla Walla - N. Lewiston 230 kv Line Outage Walla Walla - Enterprise 230 kv Line Outage Walla Walla - Wallula 230 kv Line Outage Walla Walla - Mill Creek and Central 69 kv Line Outage Walla Walla (PAC) - Walla Walla (BPA) 69 kv Line Outage Bowman - Central 69 kv Line Outage Central - Umapine 69 kv Line Outage Walla Walla (BPA) - Pomeroy (BPA) 115 kv Line Outage Joso - Burbank 115 kv Line Outage McNary - Roundup 230 kv Line Outage Wallula - McNary 230 kv Line Outage The Combine Hills Wind Project was modeled to "mid-level" representation as shown on the next page in figure 1. Revised: ALW 2

10 System Impact Study Combine Hills Wind Project Figure 1 The model is a simplified model of the distribution network of the wind farm. Turbines are lumped together at electrical centers to model each major feeder of the wind farm. The equivalent model of the turbine involves modeling the generator as a fixed MW and MVAR device (uncompensated) along with fixed amount of 600 volt capacitors (capacitive compensation) to achieve an overall power factor dependent upon generation of the turbine. The following table provides information on how each turbine was modeled from minimum generation to maximum generation (it is assumed that each turbine has the same output): Achieved Total Each Each Uncomp. Turbine Targeted Comp. Plant Turbine Turbine Turbine Reactive Turbine Comp. Turbine Output Output Output Output Consumption Output Capacitor Output (MW) (kw) (pu) PF (kvar) PF (kvar) PF Heavy summer peak load conditions were modeled using the WECC 2003 HS4AP base case. Light load conditions were modeled using the WECC 2001 LSP1 base case, modeled with minimum expected loads for the Walla Walla area. Existing System (Pre Combine Hills Generation) Revised: ALW 3

11 System Impact Study Combine Hills Wind Project No problems were identified under light load conditions. Two major N-1 problems were identified for the existing system. The first problem occurs for a 69 kv outage between Central and Freewater during peak conditions. This outage results in unacceptable low voltages in the Freewater area (Freewater 69 kv voltage is pu). This indicates that the existing system cannot support the entire load on the Central - Pendleton 69 kv line from Pendleton only. No problems were identified for this outage under light loading conditions. Because the chance of this outage occurring at peak load is small, it is recommended that the 69 kv line continue to be operated open between Weston and Athena. If an outage between Central and Umapine occurs at peak loads, the entire Umapine load (10.4 MW) must be curtailed and the Weston load (13.5 MW) would be curtailed to 85% (11.5 MW) in order to meet acceptable voltage limitations. The second problem occurs for an outage of the McNary - Roundup 230 kv line during peak conditions. The result is a severe overload of the Hermiston - Pendleton 69 kv line (169%), an overload of the Weston - Athena 69 kv line (113%), and unacceptable low voltages in the Hermiston and Pendleton 69 kv areas (Athena 69 kv voltage is pu). Opening the Hermiston - Pendleton 69 kv line eliminates the overloaded line and prevents low voltages in the Hermiston area. However, the overload on the Central-Pendleton 69 kv line increases to 153%. Opening the Central-Pendleton 69 kv line between Weston and Athena eliminates this line overload. Voltages are still low in the Pendleton 69 kv area, but they are greatly improved (Athena 69 kv voltage is pu). Reactive additions in the Pendleton area should be investigated as they may alleviate the remaining problems. As these low voltages are an existing system problem, the solution is beyond the scope of this study and should be investigated by Network Planning. Post Combine Hills Generation No problems were identified under light load conditions. The first major N-1 problem identified for the existing system was investigated after the addition of the Combine Hills generation. The new generation does not improve the situation, and was therefore not studied in further detail. The Central - Freewater 69 kv line is not able to support the load at Umapine even with the addition of the Combine Hills generation. No system upgrades are required to solve the problem because the Combine Hills generation does not contribute to this system problem. The second pre-existing problem was also tested after the addition of the Combine Hills generation. This problem is also not improved by the addition of the new generation, and was therefore not studied in further detail. It is recommended the Hermiston - Pendleton 69 kv and Weston - Athena 69 kv lines continue to be operated open as needed for the existing system. No system upgrades are required to solve the problem because the Combine Hills generation does not contribute to this system problem. Revised: ALW 4

12 System Impact Study Combine Hills Wind Project IV. VOLTAGE FLUCTUATIONS FOR CAPACITOR SWITCHING The effect of switching the 5 MVAR capacitors at the Combine Hills generation was studied at maximum output (41 MW), 35 MW, 30 MW, 20 MW and 10 MW. The following table summarizes voltage effects at the wind turbines and the nearest load, Weston. It should be noted the voltage change at Weston exceeds PacifiCorp's voltage fluctuation limit of 3.0% for generation output greater than 30 MW. The wind turbines can experience from 5-8% voltage fluctuations for switching of a 5 MVAR bank. This amount of voltage fluctuation may be excessive for the wind turbines. Switching a 3 MVAR bank results in a 2.3% voltage change at Weston and a 6.7% voltage change at the wind turbines at full load. Generator Total Initial MVAR Switching Capacitor Output Turbine Weston W Freewater Turbine Weston W Freewater MW MVAR Flow Flow uncomp comp MVAR Voltage Voltage Voltage MW MVAR MVAR Voltage change Voltage change Voltage change MW MVAR 5 MVAR capacitor switch % % % % % % % % % % % % % % % % % % MVAR capacitor switch % % % % % % MVAR capacitor switch % % % % % % MVAR capacitor switch % % % % % % Note: Hi-lighted numbers indicate PacifiCorp bus voltage changes exceeding PacifiCorp's 3.0% standard V. TRANSIENT STABILITY STUDIES Transient stability studies were investigated to determine the effects for each of five three-phase fault scenarios: Three-phase fault at Walla Walla 230 and a loss of the Walla Walla - Wallula 230 kv line Three-phase fault at Walla Walla 230 and a loss of the Walla Walla - Vantage 230 kv line Three-phase fault at Wallula 230 and a loss of the Wallula - McNary 230 kv line Three-phase fault at Joso 115 and a loss of the Joso - Burbank 115 kv line Three-phase fault at Central 69 and a loss of the Walla Walla - Mill Creek and Central 69 kv line For the existing system, instability and low voltages in the Wallula area ( pu) occur following the three-phase fault at Wallula 230 and a loss of the Wallula - McNary 230 kv line if other wind farms in the area do not trip. An assumption was made that wind farms would trip due to voltage relays following one second of voltage less than 0.90 pu. Based on this assumption, the wind farms were tripped one second after the fault. When wind farms in the area trip, voltages return to acceptable levels and there are no system problems. Revised: ALW 5

13 System Impact Study Combine Hills Wind Project The addition of the Combine Hills generation causes the instability and low voltages to worsen if other wind farms in the area fail to trip. If wind farms in the area trip after one second of voltage less than 0.90 pu, voltages return to acceptable levels. Therefore, the system is not adversely effected by the addition of the Combine Hills generation. Another fault on the existing system causes instability and low voltage (0.58 pu at Burbank 115 kv) if wind farms in the area do not trip following the three-phase fault at the Joso 115 kv bus and a loss of the Joso - Burbank 115 kv line. Based on the assumption that wind farms will trip off line following one second of voltage less than 0.90 pu, the wind farms were tripped one second after the fault. When the wind farms trip, voltages return to acceptable levels and there are no system problems. The system response to this fault and outage is virtually unchanged following the addition of the Combine Hills generation. Therefore, the Combine Hills generation addition does not adversely effect the transmission system. None of the other fault and subsequent line outage scenarios studied resulted in any other system problems. The transient effects of switching a 5 MVAR capacitor at Combine Hills were also investigated. Capacitor switching does not cause system instability. The earlier section, Voltage Fluctuations for Capacitor Switching, summarizes the overall effects on bus voltages found in the transient study. VI. RECOMMENDATIONS Based on the results of this study, the following recommendations are noted: 1) The Weston - Athena 69 kv and Hermiston - Pendleton 69 kv transmission lines should continue to be operated open, as is the current practice. 2) Switching the 5 MVAR capacitors at Combine Hills does not generally result in excessive voltage change for PacifiCorp's load. When the generation output is 35 MW or greater, however, the voltage change at Weston does exceed PacifiCorp's allowable voltage fluctuation maximum of 3.0%. The voltage change seen at the wind turbines is greater and may be excessive for the generators. Investigation with the turbine manufacturer by the wind farm developer should be conducted to determine if the wind turbines can withstand voltage changes greater than 3.0%. To meet PacifiCorp s 3% voltage change requirements due to capacitor switching, a smaller capacitor size (3.0 MVAR or less), or a dynamic VAR device must be added. 3) High speed under voltage tripping is necessary to prevent system instability for close in faults. It is recommended that an under voltage relay on the 69 kv system connection be installed to trip the Combine Hills wind farm following one second of voltage at 0.90 pu or less. Revised: ALW 6

14 To Schultz To Columbia To Pomona 1008 To Hanford 1008 Vantage WALLA WALLA AREA TRANSMISSION SYSTEM DETAIL N. Lewiston To Hatwai To Shawnee 287 To Mattawa To Midway McNary Hatrock Cold Springs To Ross To Coyote 600 Wanapum To Horse Heaven Wallula Cascade Kraft Attalia Nine Mile F2 250 Franklin To Sacajawea Stateline Wind Farm (210 MW) (90 MW) Badger H2F2 Berrian Paterson 250 Burbank 9C Wind Dodd Rd 100 US Gen Joso Umatilla Touchet NO Stateline Nine Mile F1 (25 MW) (25 MW) 83.3 Walla Walla (PAC) Lagoon Hermiston Hinkle Pendleton (PAC) Buckaroo Roundup (25 MW) Vansycle NO 150 Walla Walla (BPA) Bowman Weston (BPA) NO 33.3 Prospect Central Umapine Freewater (PAC) Weston (PAC) Athena Pendleton (BPA) 33.3 Whitman Pilot Rk Mill Crk Waitsburg Freewater (BPA) Mission Dayton Combine Hills W. Freewater Ukiah Milton Dry Gulch Pomeroy (PAC) 20 Clarkston LEGEND 500 kv Lines 345 kv Lines 230 kv Lines 115 kv Lines 69 kv & Below Pomeroy (BPA) Dotted Lines Indicate Others' Ownership WALAWALA.VSD DAJ To LaGrande

15 Case: Existing System Normally Open System Configuration Transmission Overloads Minimum Voltage Volt. Change > 5% Outage RAS Used Line/Xfmr % Rating Location (pu) Location % Chg. Comments Walla Walla - Vantage 230 None Dayton PPL None Waitsburg Walla Walla - N. Lewiston 230 None Dayton PPL None Waitsburg Walla Walla - Enterprise 230 None Dayton PPL None Waitsburg Walla Walla - Wallula 230 None Dayton PPL None Waitsburg Walla Walla - Mill Creek and Central 69 Prospect - Walla Walla Dayton PPL Dayton PPL Waitsburg Waitsburg Mill Creek Mill Creek Pomeroy Pomeroy Prospect Walla Walla (PAC) - Walla Walla (BPA) 69 None None None Bowman - Central 69 Walla Walla - WW Cen T Dayton PPL None Weston P Central - Umapine 69 Athena - Pendleton Umapine Umapine Umapine Tap Umapine Tap Weston P Weston P Athena Athena Ukiah Ukiah Pilot Rock Pilot Rock Pendleton Pendleton Mission T Mission T Pendleton BPA Pendleton BPA Buckaroo Buckaroo Walla Walla (BPA) - Pomeroy 115 None Dayton PPL None Weston - Athena closed Joso - Burbank 115 Walla Walla - Nine Mi T Stateline W Stateline W Waitsburg Joso Tap Joso Tap Nine Mi T Nine Mi T McNary - Roundup 230 None Ukiah Ukiah Athena Athena Pilot Rock Pilot Rock Pendleton Pendleton Mission T Mission T Buckaroo Buckaroo Pendleton BPA Pendleton BPA Roundup Roundup Wallula - McNary 230 McNary - Umatilla Hermiston Hermiston Cold Springs Cold Springs Umatilla Umatilla McNary McNary Dayton PPL Waitsburg Enterprise Pomeroy Stateline W Stateline W

16 Case: Combine Hills Normally Open System Configuration Transmission Overloads Minimum Voltage Volt. Change > 5% Outage RAS Used Line/Xfmr % Rating Location (pu) Location % Chg. Comments Walla Walla - Vantage 230 None Dayton PPL None Waitsburg Walla Walla - N. Lewiston 230 None Dayton PPL None Waitsburg Walla Walla - Enterprise 230 None Dayton PPL None Waitsburg Walla Walla - Wallula 230 Dayton PPL None Waitsburg Walla Walla - Mill Creek and Central 69 Prospect - Walla Walla Dayton PPL Dayton PPL Waitsburg Waitsburg Mill Creek Mill Creek Pomeroy Pomeroy Prospect Walla Walla (PAC) - Walla Walla (BPA) 69 None None None Bowman - Central 69 Walla Walla - WW Cen T Dayton PPL None Weston P Central - Umapine 69 Athena - Pendleton CH CH Umapine Umapine Umapine Tap Umapine Tap W Freewater W Freewater Weston P Weston P Athena Athena Ukiah Ukiah Pilot Rock Pilot Rock Pendleton Pendleton Mission T Mission T Pendleton BPA Pendleton BPA Buckaroo Buckaroo Walla Walla (BPA) - Pomeroy 115 None Dayton PPL None Weston - Athena closed, no true solution Joso - Burbank 115 Walla Walla - Nine Mi T Stateline W Stateline W Waitsburg Joso Tap Joso Tap Nine Mi T Nine Mi T Nine Mi F Nine Mi F McNary - Roundup 230 None Ukiah Ukiah Athena Athena Pilot Rock Pilot Rock Pendleton Pendleton Mission T Mission T Buckaroo Buckaroo Pendleton BPA Pendleton BPA Roundup Roundup Wallula - McNary 230 McNary - Umatilla Hermiston Hermiston Cold Springs Cold Springs Umatilla Umatilla McNary McNary Dayton PPL Waitsburg Enterprise Pomeroy CH CH Stateline W Stateline W

17

18

19

20

21 Existing System Fault Location Trip Line Gen Trip Voltages < 0.9 Comments 3 phase Wallula 230 Wallula - McNary 230 none at 8.0 seconds, Stateline 2 units unstable Wallula 0.7 pu, Weston 0.8 pu 3 phase Wallula 230 Wallula - McNary 230 Stateline at 2.0 seconds, acceptable voltages after tripping 2.0 seconds Stateline pu 3 phase Joso 115 Joso - Burbank 115 at 6.0 seconds, Stateline 1 units unstable Joso 0.58 pu Weston 0.86 pu Load at Joso seconds due to undervoltage 3 phase Joso 115 Joso - Burbank 115 Stateline at 2.0 seconds, acceptable voltages after tripping 2.0 seconds Joso 0.70 pu Combine Hills Gen Added Fault Location Trip Line Gen Trip Voltages < 0.9 Comments 3 phase Wallula 230 Wallula - McNary 230 none at 8.0 seconds, Stateline 2 units unstable Combine Hills 0.38 pu Weston 0.61 pu Wallula 0.68 pu 3 phase Walla Walla 2Walla Walla - Wallula 230 none none none 3 phase Joso 115 Joso - Burbank 115 at 6.0 seconds, Stateline 1 units unstable Joso 0.58 pu Combine Hills 0.87 pu Weston 089 pu 3 phase Walla Walla 2Walla Walla - Vantage 230 none none 3 phase Wallula 230 Wallula - McNary 230 Stateline 2.0 seconds at 2.0 seconds, Joso 0.70 pu 3 phase Joso 115 Joso - Burbank 115 Stateline 2.0 seconds at 2.0 seconds, Wallula 0.80 pu 3 phase Central 69 Walla Walla - Mill Creek - Central 69 none none no fault 5 MVAR Capacitor Switching at none none Combine Hills 34.5

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43