COLUMBIAGRID 2018 SYSTEM ASSESSMENT DRAFT STUDY PLAN

COLUMBIAGRID 2018 SYSTEM ASSESSMENT DRAFT STUDY PLAN January 11, 2018 ColumbiaGrid 8338 NE Alderwood Road, Suite 140 Portland, OR 97220 www.columbiagrid.org (503) 943-4940

8338 NE Alderwood Road, Suite 140 Portland, OR 97220 www.columbiagrid.org Disclaimer: The data and analyses contained in this report are not warranted by ColumbiaGrid or any other party, nor does ColumbiaGrid accept delegation of responsibility for compliance with any industry compliance or reliability requirement, including any reliability standard. Any reliance on this data or analyses is done so at the user s own risk.

Table of Contents Introduction... 1 System Assessment Timeline... 1 Base Case Development Process... 3 Study Years & Base Cases... 3 Determining Study Years... 4 Selecting Base Cases... 4 Major Assumptions.... 5 Base Topology & Ten-Year Plan... 5 Loads... 5 Resources... 6 Interchanges... 6 Contingencies... 7 TPL Contingencies & Automatic Actions... 7 Processing Contingencies... 7 Limit Monitoring... 7 Post Contingency Solution Settings... 7 Results Review Methodology... 8 Identify Order 1000 Needs... 8 Transient Stability Studies... 9 Other Studies... 9

Introduction The foundation for the Biennial Transmission Expansion Plan (BTEP) is the ColumbiaGrid System Assessment. The System Assessment study effort focuses on an evaluation of whether or not the Northwest planned transmission grid meets established reliability standards; primarily from North American Electric Reliability Corporation (NERC) and Western Electricity Coordinating Council (WECC) Transmission Planning. It also includes a study to identify Order 1000 Needs, a re-evaluation of previous year Order 1000 projects, and other various planning activities. The ColumbiaGrid System Assessment report is issued in July of each year. The draft 2018 System Assessment Study Plan includes several sections that describe the activities required to complete the major elements of the assessment. These activities include (1) Reliability Assessment Study, (2) Order 1000 Related Activities, (3) Transient Stability Study, and (4) Other Activities. Among these, the first section of the plan details key elements and associated timelines of each activity. The second section describes the process of which ColumbiaGrid develops the base cases and base case content. Followed by the details of major assumptions in each base case (transmission projects that will be built within the 10 year planning horizon); anticipated electricity demand (load levels); resources; and target power flow on key transmission interchanges. The remaining section elaborates on how the contingency descriptions are established for Reliability Studies. Furthermore, the end of this document provides the descriptions of other activities in addition to the Reliability Assessment that may be conducted by ColumbiaGrid as part of System Assessment. These include part of FERC Order 1000 activities which require ColumbiaGrid to evaluate Potential Order 1000 Needs suggestions as part of the System Assessment, Transient Stability, and other studies that may be conducted by ColumbiaGrid. System Assessment Timeline Table 1 provides an approximate timeline and lists the key activities for the 2018 System Assessment.; with a launch date of November 2017 and an intended completion date by the 3rd quarter of 2018. 1

Study Plan Meeting: Select Base Planning / Stability Cases Review and Update Modeling Assumptions Review TPl / Stability Contingency & Automatic Action File Assumptions to be requested Develop Base Study and Discuss Sensitivity Study Plans Provide Available WECC Approved Base Cases & Dynamics Files for Updates (Group A) Distribute Ten-Year Plan for Review Solicit Order 1000 Potential Needs suggestions Finalize Ten-Year Plan Provide Any Remaining Base Cases & Dynamics Files Approved by WECC after the Initial Set of Cases for Updates (Group B) Review and Finalize Group A Study Cases & Dynamics Files (Due by End of Month) Review and Finalize Group B Study Cases & Dynamics Files (Due by End of Month) Load 2017 Contingency & Automatic Action Models into Finalized Cases and Note Consistency Issues Reaffirm base and sensitivity study plan Provide Initial Contingency & Automatic Action Models for Review and Updates (Due by End of Month) Process & Review Contingency Results for Light Load Case, One 5 Year Case, and Both 10 Year Cases Evaluate Order 1000 Potential Needs Process & Review Transient Stability Study Contingency Results Prepare System Assessment Identify Order 1000 Needs Prepare Needs Statement Finalize System Assessment Recommend Study Teams for Proposed & Order 1000 Needs Build Additional Near Term and 5 Year Study Cases for Members (Start After Finalizing Initial Cases) Table 1: System Assessment Timeline 2

Base Case Development Process ColumbiaGrid members identified coordinated base case development as a valuable process in order to provide a common starting point to use for their own assessments. The goal is to provide base cases, which can be used as the starting points for technical studies that are required by applicable reliability standards (Transmission Planning (TPL) standard TPL-001-4 and others). The assessment work performed by ColumbiaGrid will be done on a subset of these cases. Additional cases may be produced, as a result of the study work that cannot be accommodated. ColumbiaGrid completes this activity by the first quarter of every year. This section provides descriptions and background of the cases that will be created by ColumbiaGrid. Study Years & Base Cases NERC TPL-001-4 standard requires analysis to be done on base assumption cases for several scenarios where high electricity demands are anticipated. These include year one or year two peak load, short-term year five peak load, one to five year off-peak load, and long-term peak load. To meet the case requirements, ColumbiaGrid will develop at least seven base cases in 2018. These include two base assumption cases for each of the peak load cases (heavy summer 1, 5, and 10 year cases and heavy winter 1, 5, and 10 year cases) and one 5 year off-peak case. Such cases would be a starting point to accommodate all steady state and transient study scenarios required by TPL-001-4. Typically, applicable approved WECC cases are selected as a starting point to create these cases. The process starts by determining the study years and selecting base cases. Other cases may be developed based on study needs for planned sensitivities, Order 1000 work, or to provide members with studies for their use. The information regarding these study scenarios as required by TPL-001-4 is listed in Table 2 below. Additional cases may be created later, upon request from members. Study Timeframe Year One or Year Two Short-Term Long-Term Loading Condition Peak Load Table 2: Base Case Study Timeframe Needs for Loading Conditions Off-Peak Load After the cases are finalized, they may be used in several technical studies performed by ColumbiaGrid and other entities. Table 3 summarizes potential utilization of these cases. X X X X 3

Study Scenarios Study Timeframe Steady State Base Steady State Sensitivity Short Circuit Transient & Voltage Stability Year One or Year Two X X Short-Term X X X X Long-Term X X Table 3: Base Case Possible Scenario Uses for Study Timeframe DETERMINING STUDY YEARS For each timeframe, study years are determined by the projected end of the System Assessment process; which is mid-summer of the current Assessment year. All case study years were determined and discussed with the members. Additional cases may be developed for member use to account for different interpretations of required study years and study schedules. SELECTING BASE CASES The strategy for selecting base cases is to utilize recent approved WECC cases that closely represent current system topology and desired seasonal system conditions. Alternatively, previous year s System Assessment cases may be selected if WECC case availability is limited. The topology and resources for these cases are adjusted to create the study cases. Table 4 lists the study years that were selected as the base cases for the 2018 System Assessment. Initial WECC Case Study Year Study Case Study Plan 18HW3-OP 2019 1-2 yr Heavy Winter Member Use 21LSP1-S 2021 Near Term Light Load Study 23HS1 2023 5 yr Heavy Summer Study 23HW2 2023 5 yr Heavy Winter Member Use 28HS1 2028 10 yr Heavy Summer Study 28HW1 2028 10 yr Heavy Winter Study Table 4: WECC seed cases and System Assessment Base Case Study Years 4

Major Assumptions After the base cases are selected, the study cases are developed with the intent to complete them prior to building the contingency lists. This section describes a summary of key assumptions that will be used to create the base cases. However, additional adjustments may be made after the issuance of this document. In such incident, a summary of these adjustments will be reported in the 2018 System Assessment and made available upon request after the cases are finalized. Base Topology & Ten-Year Plan As outlined in Table 1, the base case development process starts with ColumbiaGrid issuing the initial cases for the members to provide updates to case topologies. Updates should include corrections to case errors and project adjustments to match the Ten-Year Plan. The ColumbiaGrid Ten-Year Plan comprises a list of projects which planning participants are committed to build (in the permitting, design, or construction phases) within the coming years, to address known transmission deficiencies. The projects in the Ten-Year Plan fill a variety of needs such as serving load, integrating new resources, or facilitating economic transfers. The projects may have been generated in a variety of forums such as earlier System Assessments, studies completed by the study teams, or individual planning participant studies. A summary of the Ten-Year plan is summarized in Appendix A that will be included in the final version of this Study Plan. To maintain data quality, the Ten-Year Plan will not be adjusted after it has been finalized unless the changes are determined as critical elements that would invalidate the System Assessment. This determination may be made by ColumbiaGrid participating parties. Loads Similar to topology modeling; members will direct ColumbiaGrid on load adjustments in their areas, for the System Assessment cases from the starting WECC cases. Members should provide (1) a file that updates the loads for each of the cases to the desired levels or (2) provide specific levels for ColumbiaGrid to scale their loads. Unless directed otherwise; ColumbiaGrid would adjust a participant s designated scalable load in the base case, until all of the participant s loads reach the desired level. A constant P/Q ratio would be maintained. Any expected changes to block loads for scaling should also be provided. A summary of the load levels that were modeled in ColumbiaGrid base cases after the adjustment will be included in the final version of this Study Plan. 5

Resources Generation patterns for the System Assessment cases will initially be set to the associated seasonal WECC base case. Adjustments to this pattern would include corrections to better represent expected generation patterns (such as adjusting wind generation output levels) or justified changes such as a new resources or the retirement of an existing resource. Balancing of the area will be done via interchange adjustments; typically from California for winter cases and the Columbia River hydro for summer cases. Interchanges Interchanges are used to balance and stress the case. This is primarily done with California and Canadian interchanges, whereas the remaining interchanges are typically untouched. The California interchange is used to balance the system in winter cases and the Columbia River hydro system is used for summer cases. The Canadian interchange is used to stress the system and is set to 2300 MW North-to-South for summer peak cases and 1500 MW South-to- North for winter peak cases, reflecting current firm transmission service commitments on the Westside Northern Intertie (Path 3). After the loads, resources and interchanges are adjusted; the study cases will be sent out for final review. If the cases are accepted by the members, they will be used to build the contingency. Table 5 details the initial study case resource and interchange assumptions to be used for the 2018 System Assessment. Initial WECC Case Study Year Generation Wind Hydro Remaining Idaho/ Montana Interchange Adjustments BC COI/PDCI Loads 18HS4-OP 2019 Off Balance Typical Maintain 2300 NS Maintain 18HW3-OP 2019 Off Typical Typical Maintain 1500 SN Balance 50% not exceed 50% not exceed 21LSP1-S 2021 Cap Factor (30-40%) Balance Typical Maintain Maintain Maintain typical 23HS1 2023 Off Balance Typical Maintain 2300 NS Maintain 23HW2 2023 Off Typical Typical Maintain 1500 SN Balance 28HS1 2028 Off Balance Typical Maintain 2300 NS Maintain 28HW1 2028 Off Typical Typical Maintain 1500 SN Balance 50% not exceed 50% not exceed 50% not exceed 50% not exceed Table 5: 2018 System Assessment Initial Base Case Assumptions 6

Contingencies TPL Contingencies & Automatic Actions After the study cases are finalized; ColumbiaGrid and the members will jointly develop contingency files, in compliance with TPL-001-4 and WECC criterion TPL-001- WECC-CRT-2.1. A detailed description of what needs to be submitted is described in the ColumbiaGrid System Assessment Contingency Methodology paper. By suggestion, a base list will be created for the One-Year cases and then provide individual change files for each Ten-Year Plan project or each of the 5 year and the 10 year cases. The previous year s contingency may be used as a starting point for this list. Processing Contingencies This section describes the method used to process contingency lists. LIMIT MONITORING The following limit monitoring settings are used for System Assessment contingencies: Seasonal normal and post contingency/ emergency branch thermal limits are monitored based on WECC s convention (i.e. summer normal = limit A, summer emergency = limit B, winter normal = limit C, winter emergency = limit D, etc.). Radial lines and buses are not monitored. Only elements in Area 40 (Northwest) are monitored. Branch violations are only flagged if branch flow increases by more than 1%. Bus violations are only flagged if bus voltages change by more than 0.02 per unit. Bus voltage monitoring settings are supplied by participants. Bus voltage change of greater than 5% (based on WECC criteria). Voltage angle change of more than 5 degrees across branches opened in a contingency. Only angles more than 30 degrees are reported. POST CONTINGENCY SOLUTION SETTINGS The post contingency solution settings differ from the default pre-solution settings by not allowing most Switched Shunts, Load Tap Changing Transformers (LTCs), and Phase Shifters from mimicking the system conditions right after the contingency occurs. Static Var Compensator (SVC) devices and automatically controlled shunts are allowed to operate. Participants must provide which shunts are automatically controlled to properly model the post contingency system condition. Post contingency solution settings are used for any contingency that has a solution embedded into the contingency definition. This allows participants to document the system condition for PRC-023 for N-1-1 conditions. 7

RESULTS REVIEW METHODOLOGY All study cases are initially reviewed for violations without outages (N-0 conditions). Any voltage violations or facility overloads that could not be resolved through tuning the cases are provided to the participants and reported in the System Assessment. The provided TPL-001-4 and WECC criterion TPL-001-WECC-CRT-2.1 contingencies are then processed. All results are reviewed for accuracy and provided to participants for review. The results are pared down for additional study by the following criteria: N-1-X: All contingencies results with initial outage conditions (i.e. P3 or P6) are studied for informational purposes only. Results are sorted to identify contingency combinations that have more than one participant. Additional study work may be done if requested by the participants. Single System: The System Assessment focuses on joint issues where the outages and associated violations are owned by multiple participant utilities and where joint transmission planning may be needed. Instances where the outage and overloaded facilities are owned by the same utility (and are assumed to be the responsibility of that utility to mitigate); will not be reported in the System Assessment. Identify Order 1000 Needs Order 1000 Potential Needs that are submitted to ColumbiaGrid, will be evaluated with the option to be included in the System Assessment. In this planning cycle, the process kicks-off in January 2018 with notification to solicit suggestions regarding Order 1000 Needs. Suggestions are due prior to the Order 1000 Needs Meeting and will be discussed during that time. Following the Order 1000 Needs Meeting, the process continues with the evaluation of the submissions to identify Order 1000 Needs that are vetted during the System Assessment process. ColumbiaGrid will implement applicable screening studies of the Order 1000 ColumbiaGrid Planning Region using the Order 1000 Planning criteria and Order 1000 Needs Factors. The results of the validation are reported in the System Assessment and Needs Statement documents that are developed as part of the System Assessment. The remaining violations and any unsolved outages are further explored for validity. All confirmed and valid violations are reported in the System Assessment. 8

Transient Stability Studies or possible future issues caused by policy changes. In conjunction with building the study cases; the WECC transient stability data will be updated allowing the ability to run studies on the developed cases. The data for the cases will be reviewed and test simulations (such as no fault run, Chief Joseph Braking test, and Double Palo Verde tests) are performed to verify satisfactory dynamic performance. Modeling data errors and potential problems are identified and fixed. The proposed changes to the base case will be discussed in the planning meeting as basic assumptions for performing the transient stability study. With the base case ready, contingencies submitted by members will be simulated and results will be discussed with members, if unexpected issues are identified. As discussed in the transient stability workshops; unstable contingencies, WECC transient limit violations, and generation tripping are reported in the System Assessment. Other Studies Other studies may be included in the System Assessment report from sensitivities requested by ColumbiaGrid members or from work done outside the process. The scope of these studies is determined by the members and typically addresses identified issues in the system, studies associated with new planning standards, 9