Discussion of WECC Paths West of Colorado River (WOR) Path 46

Discussion of WECC PathsWest of Colorado River (WOR)Path 46This document is for technical review purposes only. It has not been endorsed or approved by the WECC Board ofDirectors, its Transmission Expansion Planning Policy Committee (TEPPC), the TEPPC Scenario Planning SteeringGroup (SPSG), or WECC Management.This brief provides observations regarding the West of Colorado RiverWECC path. These observations draw from current project developmentinformation, historical data, and forward looking congestion analysis.Readers should review the “Discussion of WECC Paths – Introduction” withthis document.ObservationsTransmission project development, historical congestion analysis, and forward lookingcongestion analysis were used to form the following observations concerning Path 46.Path 46 is not historically congested according to the metrics used in previous pathutilization studies. The path should continue to be evaluated by the TEPPC HistoricalAnalysis Work Group (HAWG) in their biannual path utilization report.There are many projects in development that could directly impact Path 46 flows.Path 46 was not congested in the 2020 expected future study case, or any other casesin the 2010 Study Program.DescriptionThe largest WECC path in terms of transfer capacity, Path 46 consists of numerous linesinterconnecting southern Nevada and Arizona to southern California. Operation of the path ismaintained within the boundaries of the Southern California Import Transmission (SCIT)nomogram, which is not included in the production cost model (PCM). Key path characteristicsdefined by the 2011 WECC Path Rating Catalog can be found inTable 1. Figure 1, on the next page, shows the physical cut plane that forms the WOR path. 1Deleted: Table 1Table 1: Path 46 CharacteristicsPath CharacteristicsRating E to W 10623 MWRating W to E NoneMax Voltage 500 kV1 WECC 2011 Path Rating Catalog: LinkPage 1 of 5

Discussion of WECC PathsWest of Colorado River - Path 46Figure 1: Path 46 DefinitionHistorical CongestionPath 46 was analyzed in the 2009 and 2008 Transmission Path Utilization Studies and was nothistorically congested based on the metrics used in the analysis. In the 2008 Study Path 46operated at U75 for only one percent of the year. The path never reached U90 and appeared tobe one of the least utilized paths in the Western Interconnection in 2008. The 2009 Study alsoshowed relatively low utilization of Path 46. It was calculated that there was 90 percentprobability that 3307 MW of unused capacity existed at any given time on Path 46. That equatesto 31 percent of the path’s total transfer capability. Actual flow data for historic years can befound in the duration plot in Figure 2. Although informative, the plot does not necessarily reflectthe metrics that support, or exclude, the path as being historically congested.Deleted: anlaysisDeleted: 1%Deleted: %Deleted: %Page 2 of 5

Figure 2: Path 46 Actual Flow Duration PlotDiscussion of WECC PathsWest of Colorado River - Path 46Project DevelopmentThe following projects were determined by stakeholders to be the most likely to have an impacton Path 46.Blythe – Devers (SCG Foundational Project)Centennial West Clean Line (Studied in 2010 Study Program)Chinook (Studied in 2010 Study Program)Harcuvar Transmission ProjectHigh Plains Express (Studied in 2010 Study Program)Navajo Transmission Project (Studied in 2010 Study Program)Palo Verde – BlythePalo Verde – N. Gila #2 (SCG Foundational Project)Southline ProjectSunZia (Studied in 2010 Study Program)TCP (Harry Allen to Eldorado/Mead)TransWest Express (Studied in 2010 Study Program)Zephyr (Studied in 2010 Study Program)Page 3 of 5

Flow (MW)Discussion of WECC PathsWest of Colorado River - Path 46The projects identified as an SCG Foundational Project were assumed constructed in the 2020dataset.Future Congestion AnalysisThe forward looking congestion analysis draws upon study case results from production costmodel runs based on 2019 and 2020 datasets. This work was done as a part of the 2010 StudyProgram.Expected FuturePath 46 was not heavily utilized or congested in the expected future case. The path neverexceeded U90 and operated at or above U75 for only 1.48 percent of the year. The duration plotin Figure 3 shows this light utilization. The chronological plot in the same figure shows theseasonality of the flows.Deleted: %Figure 3: Path 46 2020 Duration Plot12000Duration PlotPath 46 in 2020 Reference Case100008000Positive = E to WNegative = W to E6000400020000-20001 1001 2001 3001 4001 5001 6001 7001 8001Hour of YearFlow (MW) Duration Flow (MW) Positive/Negative LimitAlternative FuturesPath 46 did not pass the utilization screening in any of the 15 cases used to inform the 10-YearPlan. There was no combination of assumptions that caused the path to be highly utilized.Conditional CongestionCongestion along Path 46 is not contingent on any future evaluated in the 2010 Study Program.Project Development ImpactThere is extensive project development that could potentially impact Path 46 flows. Seven ofthese projects were evaluated as a part of the 2010 Study Program. Each transmissionexpansion case includes 12,000 GWh of resource relocation and incremental transmissioninfrastructure. The impacts on Path 46 U90 are reported in Table 2.Page 4 of 5

Table 2: Project Development Impact on Path 46Discussion of WECC PathsWest of Colorado River - Path 46Study CasesU902019 Base Case 0.55%2019 New Mexico Resource Relocation 2.21%2019 NM + Centennial West Clean Line 1.47%2019 NM + Navajo Transmission Project 2.28%2019 NM + High Plains Express & SunZia 3.68%2019 Wyoming Resource Relocation 0.81%2019 WY + Zephyr 3.05%2019 WY + TransWest Express 3.16%2019 Montana Resource Relocation 0.49%2019 MT + Chinook 7.65%Deleted: 3Deleted: 4Each of the resource relocations caused Path 46 utilization to increase over the level observedin the 2019 Base Case, as expected. Generally, when projects terminate east of Path 46,utilization of the path increases over the level observed in the resource relocation case. Theseprojects are able to deliver the resources to the east side of the path more efficiently and energyis transferred on WOR into California. When projects, such as the Centennial West Clean Line,terminate west of Path 46, utilization decreases from the level observed in the resourcerelocation. In this case, WOR is bypassed by the parallel line and utilization of the pathdecreases.Page 5 of 5