SDG&E High Voltage DC WECC Path 46 Rating Increase Comprehensive Progress Report

SDG&E High Voltage DC WECC Path 46 Rating Increase Comprehensive Progress Report San Diego Gas & Electric, a Sempra Energy Utility SDGE HVDC Phase 1 Project No. 101512 Revision 01 11/29/2018

SDG&E High Voltage DC WECC Path 46 Rating Increase Comprehensive Progress Report Prepared for San Diego Gas & Electric, a Sempra Energy Utility SDGE HVDC Phase 1 San Diego, CA Project No. 101512 Revision 01 11/29/2018 Prepared by Burns & McDonnell Engineering Company, Inc. Kansas City, Missouri COPYRIGHT 2017 BURNS & McDONNELL ENGINEERING COMPANY, INC.

SDG&E HVDC CPR Revision 02 Table of Contents TABLE OF CONTENTS Page No. 1.0 EXECUTIVE SUMMARY... 1-1 2.0 INTRODUCTION... 2-2 2.1 Overview... 2-2 2.2 HVDC Project Background and Plan of Service... 2-2 2.3 Additional Benefits of the HVDC Project... 2-3 2.4 Study Objective and Scope... 2-4 2.5 Path 46, West of Colorado River... 2-5 3.0 STUDY DESCRIPTION AND METHODOLOGY... 3-1 3.1 Power Flow Analysis... 3-1 3.2 Transient Stability Analysis... 3-2 3.3 Post-Transient Stability Analysis... 3-6 4.0 SIMULTANEOUS INTERACTIONS... 4-1 5.0 STUDY RESULTS... 5-2 5.1 Non-Simultaneous Rating... 5-2 5.2 Power Flow Analysis Results... 5-2 5.3 Transient Stability Analysis Results... 5-3 5.4 Post-Transient Stability Analysis Results... 5-4 6.0 CONCLUSION... 6-1 APPENDIX A POWER FLOW RESULTS San Diego Gas & Electric i Burns & McDonnell

SDG&E HVDC CPR Revision 02 Table of Contents LIST OF FIGURES Page No. Figure 2-1: SDG&E s Existing System - SWPL... 2-3 Figure 2-2: SDG&E s Proposed HVDC Project... 2-3 Figure 2-3: Path 46, West of Colorado River... 2-6 Figure 3-1: Transient Voltage Drip Criteria, Delay Recovery... 3-5 Figure 3-2: Transient Voltage Drip Criteria, Normal Recovery 1... 3-5 Figure 3-3: Transient Voltage Drip Criteria, Normal Recovery 2... 3-6 San Diego Gas & Electric ii Burns & McDonnell

SDG&E HVDC CPR Revision 02 Executive Summary 1.0 EXECUTIVE SUMMARY San Diego Gas & Electric (SDG&E) is proposing a High Voltage Direct Current (HVDC) transmission line which will utilize the existing alternating current (AC) Southwest Powerlink (SWPL) Right of Way from North Gila to Imperial Valley to Miguel. This new HVDC line includes construction of approximately 120 miles, 425 kv, three (3) terminal, bipolar, double circuit, direct current (DC) transmission line with metallic return between the existing 500 kv bus at North Gila substation, the 500 kv bus at the Imperial Valley substation and the 230 kv bus at the Miguel substation (the HVDC Project), with a rating of 3000 MW. The HVDC line will replace the existing 500 kv alternating current (AC) line that runs from North Gila to Imperial Valley to East County (ECO) to Miguel. Part of the AC line which this HVDC Project replaces, North Gila-Imperial Valley 500 kv, is one of the transmission lines which comprise the Western Electricity Coordinating Council s (WECC) West of Colorado River Transmission Path (Path 46 or WOR). Accordingly, the HVDC will become part of the WOR Path and it is expected to provide significant increase in transmission capacity on Path 46 between Arizona and southern California. The proposed Project is expected to have a maxim transfer capability of 3,000 MW and would increase the non-simultaneous rating of Path 46 by 2,100 MW from 11,200 MW to 13,300 MW. With the North Gila-Imperial Valley #2 (NGIV#2), a project currently in Phase 2 of the WECC Path Rating Process, the non-simultaneous rating of Path 46 increases by 2,300 MW from 11,200 MW (current accepted rating) to 13,500 MW or increases by 1,050 MW over the proposed Path 46 rating of 12,450 with NGIV#2. The increase in Path 46 flow with NGIV#2 is slightly over the increase from this HVDC Project alone because both projects make improvements to the southern portion of Path 46 and thus both projects face the same limit on the southern portion of Path 46. Both Path 46 rating increases are with the existing Eldorado-Lugo series capacitors by-passed. With the proposed Southern California Edison (SCE) Eldorado-Lugo-Mohave Series Capacitor Project, which appears to address limits on the northern portion of Path 46, it is anticipated that additional increases to Path 46 above and beyond those described above (13,300 MW without NGIV#2 and 13,500 with NGIV#2) will be possible. That and other issues such as simultaneous ratings will be explored in Phase 2. The proposed HVDC Project can achieve a total transfer capability matching its full rating of 3,000 MW while meeting NERC reliability standards and WECC system performance criteria. San Diego Gas & Electric 1-1 Burns & McDonnell

SDG&E HVDC CPR Revision 02 Introduction The study identified the Hassayampa North Gila 500 kv line or the Hoodoo Wash-North Gila 500 kv line as both the critical outage and the limiting element. These are parallel paths with the critical contingencies being the loss of one side or the other. It is expected that this CPR will form the basis for the proposed Project to enter Phase 2 of the WECC three phase rating process. Once the 60-day comment period has passed and all comments have been addressed, a WECC HVDC Project Review Group will be assembled to help address the study requirements for Phase 2 and to conduct additional analysis that may be necessary to obtain a new WECC Accepted rating of 13,300 MW for Path 46 with the HVDC Project by itself or 13,500 MW with NGIV#2. 2.0 INTRODUCTION 2.1 Overview SDG&E asked Burns & McDonnell to help them conduct a path rating study to comply with the WECC procedure for Project rating, including a path rating study to determine the potential rating increase on the WECC Path 46 (West of River (WOR)), following the addition of the proposed HVDC Project. Burns & McDonnell completed the work necessary to prepare this WECC Comprehensive Progress Report (CPR) for increasing the rating on WECC Path 46. 2.2 HVDC Project Background and Plan of Service The planned in-service date for the HVDC Line is December 2021. The Project s plan of service includes: A new AC/DC converter station (rectifier) at the North Gila 500 kv bus with 3000 MW capacity A new AC/DC converter station (rectifier/inverter) at the Imperial Valley 500 kv bus with 3000 MW capacity A new converter station (inverter) at the Miguel 230 kv bus with 3000 MW capacity Two new 425 kv three terminal bi-pole DC lines between the existing 500 kv North Gila bus, the 500 kv Imperial Valley bus and the 230 kv Miguel bus Retirement of the existing 500 kv AC transmission line from North Gila to Imperial Valley to ECO to Miguel Reconfiguration of the existing 500 kv AC transmission line between Ocotillo and Suncrest, by adding a loop-in to the ECO substation so it becomes two 500 kv line two lines running from Ocotillo to ECO to Suncrest This Plan of Service is partially show in the Figures below. The existing system is shown in Figure1-1. San Diego Gas & Electric 2-2 Burns & McDonnell

SDG&E HVDC CPR Revision 02 Introduction Figure 2-1: SDG&E s Existing System - SWPL The system with the SDG&E s proposed HVDC line is shown below in Figure 1-2. Figure 2-2: SDG&E s Proposed HVDC Project 2.3 Additional Benefits of the HVDC Project The addition of the HVDC Line is also expected to provide the following additional benefits: San Diego Gas & Electric 2-3 Burns & McDonnell

SDG&E HVDC CPR Revision 02 Introduction Increased access to renewable generation o Specifically allows increased access to renewables in El Centro, California by helping to control flow on the interties between CAISO and IID o Provides an increase in diversity of the regional energy resource mix o Reduces Green House Gas (GHG) emissions and provides improved access to both instate and out-of-state renewables to meet 60% RPS goal (2030) and the 100% carbon free goal (2045) per SB 100 Removes the transmission bottleneck on North-Gila-Imperial Valley 500 kv, following the 2015 addition of the Hassayampa-North Gila #2 project Provides rapid and precise control over the flow of power into southern California, allowing quick incremental increases or decreases in power flow as needed during normal operations and pre- or post-contingency o This control provides significant interregional benefits by solving the loop flow issue for multiple parties (APS, SDG&E, IID, and CENACE) Reduces Greater IV/San Diego and Western LA Basin local LCR requirements by increasing the imports into the resource constrained southwest Increases San Diego import capability by mitigating worst N-1-1 contingency (Sunrise & SWPL) o Increases the import capability into the Southern California Import Transmission system Reducing available fault current in San Diego Gas & Electric s transmission system o Provides fault isolation Reduce system losses Increases reliability in the southwest Make efficient use of existing transmission corridors Increases West of River (WOR) path rating 2.4 Study Objective and Scope Burns & McDonnell conducted this Path Rating Study using a WECC approved 2018-19 heavy autumn power flow model that had previously used for the NGIV#2 Project s path rating study. Analysis performed as part of the study included power flow, transient stability and post-transient stability. The main objective of this study was to complete the work necessary to prepare a Comprehensive Progress Report that will enable the proposed HVDC Project and its associated WECC Path 46 rating increase to complete Phase 1 and enter Phase 2 of the WECC 3 phase rating process. This study demonstrated that the proposed Project will provide an incremental transfer capability of 2,300 MW on San Diego Gas & Electric 2-4 Burns & McDonnell

SDG&E HVDC CPR Revision 02 Introduction Path 46 above its current Accepted Rating of 11, 200 MW to a new Proposed Rating of 13,300 MW, while complying with North America Reliability Council s (NERC) reliability standards and WECC criteria. In conjunction with the North Gila-Imperial Valley #2 (NGIV#2), a project currently in Phase 2 of the WECC Path Rating Process, this study demonstrated that the non-simultaneous rating of Path 46 increased by 2,300 MW from the current Accepted Rating of 11,200 MW to a new Proposed Rating of 13,500 MW or increases by 1,050 MW over the NGIV#2 Proposed Rating of 12,450 MW. Recent Path 46 upgrade studies have shown that there are simultaneous relationships between Path 46 and the following WECC Paths and southwestern transmission operating parameters: Lugo-Victorville 500 kv line Path 61 Southern Nevada Transmission Interface (SNTI) Path 81 Southern California Import Transmission (SCIT) Nomogram In accordance with the WECC Project Coordination, Path Rating and Progress Report Processes manual, the simultaneous relationships between Path 46 and these other paths will be evaluated and addressed in Phase 2. Further, since the SCIT nomogram varies seasonally, the effect of the increase on the Path 46 rating on the SCIT nomogram will be evaluated during the Phase 2 of this Path Rating process. This CPR details the impact of the HVDC Project and the associated Path 46 rating increase on the WECC transmission system. 2.5 Path 46, West of Colorado River The Path 46 (WOR), is shown below in Figure 2-3, and is comprised of several of the major transmission lines in the southwestern United States, west of the Colorado River and connect southern Nevada and Arizona to southern California. San Diego Gas & Electric 2-5 Burns & McDonnell

SDG&E HVDC CPR Revision 02 Introduction Figure 2-3: Path 46, West of Colorado River WECC Path 46 consists of the following 14 transmission lines, which are divided into three (3) subsystems: Northern System Eldorado-Lugo 500 kv line (metered at Eldorado 500 kv) Eldorado-Cima-Pisgah No. 1 & 2, 230 kv lines (metered at Eldorado 230 kv) Mohave-Lugo 500 kv line (metered at Mohave 500 kv) Julian Hinds-Mirage 230 kv line (metered at Mirage 230 kv) Mead-Victorville 287 kv line (metered at Mead 287 kv) McCullough-Victorville Nos. 1 & 2, 500 kv lines (metered at McCullough 500 kv) Marketplace-Adelanto 500 kv line (metered at Marketplace 500 kv) San Diego Gas & Electric 2-6 Burns & McDonnell

SDG&E HVDC CPR Revision 02 Introduction Southern System North Gila-Imperial Valley 500 kv line (metered at N. Gila 500 kv) Palo Verde-Colorado River 500 kv line (metered at Colorado River 500 kv) Underlying System El Centro-Imperial Valley 230 kv line (metered at Imperial Valley 230 kv) Ramon-Mirage 230 kv line (metered at Mirage 230 kv) Coachella-Devers 230 kv line (metered at Devers 230 kv) The East to West non-simultaneous Accepted Rating of the Path 46 increased from 10,523 MW to 11,200 MW on July 18, 2014. The WOR non-simultaneous rating of 11, 200 MW is limited by the outage of Palo Verde-Colorado River 500 kv line or the Hassayampa-North Gila 500 kv line and subsequent implementation of the existing Blythe RAS. With the HVDC Project, the Path 46 definition of the Southern System will be changed from: To North Gila-Imperial Valley 500 kv line (metered at N. Gila 500 kv) North Gila-Imperial Valley 425 kv DC line (metered at N. Gila 500 kv) San Diego Gas & Electric 2-7 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Description and methodology 3.0 STUDY DESCRIPTION AND METHODOLOGY This analysis was conducted using the WECC approved 2018-19 heavy autumn power flow model previously used initially by the NGIV#2 Project s path rating study as its starting base case. The base case was had the Harry Allen Eldorado 500 kv line. A Path 46 upgrade study base case (post-hvdc base case) was developed from this starting base case by modeling the proposed HVDC project s plan of service. Power transfers were made from Arizona to southern California to increase the flow on the proposed HVDC and Path 46 till a critical facility limit is reached. Apart from the stated modeling assumptions, the transmission and load assumptions in the starting base case were not altered in developing HVDC base case. Power flow, post-transient stability and transient stability analyses were performed to ensure that the system performance criteria prescribed in the NERC reliability standards and WECC criteria were met. 3.1 Power Flow Analysis Power flow analysis was performed on the HVDC base cases. The study simulated the impact of the proposed NGIV2 project and the associated Path 46 rating increase on the existing transmission system during normal operating conditions (Category P0), single event (Category P1- P2) as well as multiple (Category P3-P7) events. The outages simulated included: Selected Category P1-P2 (230-500 kv) transmission circuit and transformer outages within Arizona, Nevada and California transmission systems. Selected critical P3-P7 events (230 kv and above) transmission and transformer outages within Arizona, Nevada and California transmission systems. The power flow analysis contingency list can be found in Attachment A. Applicable NERC reliability standard and the WECC System Performance Criteria were used to assess the adequacy of the study results. The power flow analysis evaluation criteria that were used are summarized below: Pre-contingency bus voltage must be between 0.95 per unit and 1.05 per unit unless specific minimum and maximum operating voltage requirements exists. San Diego Gas & Electric 3-1 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Description and methodology Pre-disturbance loading to remain within continuous ratings of all equipment and line conductors. Post-disturbance loading to remain within emergency ratings of all equipment and line conductors. Post-disturbance bus voltages to remain within applicable criteria: o Between 0.9 per unit and 1.10 per unit for Category P1-P7 events, unless lower standards have previously been adopted. Post-disturbance bus voltage deviation to remain within applicable criteria: o o Within 5% for Category P1-P2 events, unless lower standards have previously been adopted Within 10% for Category P3-P7 events, unless lower standards have previously been adopted. Load shedding was not allowed for Category P1-P2 events unless previously defined. 3.2 Transient Stability Analysis Transient stability studies were conducted on the HVDC study base case. Transient stability runs were simulated for 15 seconds, excluding a 1 second pre-outage run, to ensure the system is stable and positively damped. All simulated faults were three-phase with a 4-cycle breaker clearing time. System damping was assessed visually with the aid of stability plots. Selected critical disturbances were simulated. Provided below are the disturbances simulated: P1: Palo Verde- Colorado River 500 kv line (Palo Verde 500 kv bus faulted) P1: Hassayampa N. Gila 500 kv line (Hassayampa 500 kv bus faulted) P1: Hassayampa Hoodoo Wash 500 kv line (Hassayampa 500 kv bus faulted) P1: Palo Verde Westwing #1 500 kv line (Palo Verde 500 kv bus faulted) P1: Palo Verde Rudd 500 kv line (Palo Verde 500 kv bus faulted) P1: Imperial Valley Ocotillo 5000 kv line (Imperial Valley 500 kv bus faulted) P1: Ocotillo ECO 500 kv line (Ocotillo 500 kv bus faulted) San Diego Gas & Electric 3-2 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Description and methodology P1: Perkins Mead 500 kv line (Mead 500 kv bus faulted) P1: Mead Marketplace 500 kv line (Mead 500 kv bus faulted) P1: Harry Allen Mead 500 kv line (Harry Allen 500 kv bus faulted) P1: Navajo Crystal 500 kv line (Navajo 500 kv bus faulted) P1: Moenkopi El Dorado 500 kv line (El Dorado 500 kv bus faulted) P1: Adelanto Marketplace 500 kv line (Adelanto 500 kv bus faulted) P1: El Dorado Lugo 500 kv line (El Dorado 500 kv bus faulted) P1: Mohave Lugo 500 kv line (Lugo 500 kv bus faulted) P1: Lugo Victorville 500 kv line (Victorville 500 kv bus faulted) P1: Coachella Mirage 230 kv line (Coachella 230 kv bus faulted) P1: Ramon Mirage 500 kv line (Mirage 230 kv bus faulted) P1: Devers Mirage #1 230 kv line (Devers 230 kv bus faulted) P1: Devers - Valley #1 500 kv line (Devers 500 kv bus faulted) P6: Lugo El Dorado & Lugo Mohave 500 kv lines (Lugo 500 kv bus faulted) P6: Lugo El Dorado & El Dorado Mohave 500 kv lines (El Dorado 345 kv bus faulted) P6: Harry Allen Mead & Mead Marketplace 500 kv lines (Mead 500 kv bus faulted) P6: Coachella Mirage & Mirage Ramon 230 kv lines (Mirage 230 kv bus faulted) P7: Imperial Valley Ocotillo & Ocotillo ECO 500 lines (Ocotillo 500 kv bus faulted) P7: Palo Verde G-2 (Palo Verde 500 kv bus faulted) P7: Palo Verde Westwing #1 & 2 500 kv lines (Palo Verde 500 kv bus faulted) P7: Hassayampa N. Gila & Hassayampa Hoodoo Wash 500 kv lines (Hassayampa 500 kv bus faulted) P7: PDCI line P7: SWPL HVDC line The following WECC transient voltage dip and transient frequency criteria were used to evaluate the study results. San Diego Gas & Electric 3-3 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Description and methodology WECC transient voltage dip criteria: Following fault clearing, the voltage shall recover to 80% of the pre-contingency voltage within 20 seconds of the initiating event for all P1 through P7 events, for each applicable BES bus serving load. Following fault clearing and voltage recovery above 80%, voltage at each applicable BES bus serving load shall neither dip below 70% of pre-contingency voltage for more than 30 cycles nor remain below 80% of pre-contingency voltage for more than two seconds, for all P1 through P7 events. For Contingencies without a fault (P2.1 category event), voltage dips at each applicable BES bus serving load shall neither dip below 70% of pre-contingency voltage for more than 30 cycles nor remain below 80% of pre-contingency voltage for more than two seconds. WECC transient frequency criteria: WECC no longer has a transient frequency criterion. WECC transient oscillation criteria: All oscillations that do not show positive damping within 30-seconds after the start of the studied event shall be deemed unstable. A summary of the transient stability analysis evaluation criteria is provided in the figures below. San Diego Gas & Electric 3-4 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Description and methodology Figure 3-1: Transient Voltage Drip Criteria, Delay Recovery Figure 3-2: Transient Voltage Drip Criteria, Normal Recovery 1 San Diego Gas & Electric 3-5 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Description and methodology Figure 3-3: Transient Voltage Drip Criteria, Normal Recovery 2 3.3 Post-Transient Stability Analysis Post-transient stability analysis was performed on the proposed Path 46 rating increase. This included modeling flow on the Path 46 with at least a 5% higher than the proposed rating of 13,300 MW (or 13,500 MW) for single outage events and 2.5% higher for multiple outage events. In this analysis, the increased flow on Path 46 was achieved by modeling additional transfers from Arizona to southern California. The outage list for the post-transient stability analysis is follows: P1: Palo Verde- Colorado River 500 kv line P1: Hassayampa N. Gila 500 kv line P1: Hassayampa Hoodoo Wash 500 kv line P1: Palo Verde Westwing #1 500 kv line P1: Palo Verde Rudd 500 kv line P1: Imperial Valley Ocotillo500 kv line San Diego Gas & Electric 3-6 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Description and methodology P1: Ocotillo ECO 500 kv line P1: Perkins Mead 500 kv line P1: Mead Marketplace 500 kv line P1: Harry Allen Mead 500 kv line P1: Navajo Crystal 500 kv line P1: Moenkopi El Dorado 500 kv line P1: Adelanto Marketplace 500 kv line P1: El Dorado Lugo 500 kv line P1: Mohave Lugo 500 kv line P1: Lugo Victorville 500 kv line P1: Coachella Mirage 230 kv line P1: Ramon Mirage 500 kv line P1: Devers Mirage #1 230 kv line P1: Devers - Valley #1 500 kv line P6: Lugo El Dorado & Lugo Mohave 500 kv lines P6: Lugo El Dorado & El Dorado Mohave 500 kv lines P6: Harry Allen Mead & Mead Marketplace 500 kv lines P6: Devers Valley #1 & 2 500 kv lines P7: Imperial Valley Ocotillo & Ocotillo ECO 500 lines P7: SWPL HVDC line To meet the reliability criteria, the system must also have a positive reactive margin under the stated conditions. San Diego Gas & Electric 3-7 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Simultaneous interactions 4.0 SIMULTANEOUS INTERACTIONS Per WECC Project Coordination, Path Rating and Progress Report Processes, the CPR for the proposed Project shall include known simultaneous relationships. Recent Path 46 upgrade study showed that there are simultaneous relationships between Path 46 and each of the following known paths within the WECC transmission system: Lugo Victorville 500 kv line Path 61 Southern Nevada Transmission Interface (SNTI) Path 81 Southern California Import Transmission (SCIT) Nomogram These simultaneous relationships will be evaluated as part of the Phase 2 study of this Path rating process because of complexity of the interactions and SCE s proposed to the changes to Eldorado-Lugo-Mohave which may affect Path 61. San Diego Gas & Electric 4-1 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Results 5.0 STUDY RESULTS This section details the key study findings from the power flow, post-transient stability and transient stability analyses of the HVDC Project. NERC Reliability Standard and WECC System Performance Criteria were used to assess the adequacy of the study results. 5.1 Non-Simultaneous Rating With the HVDC Project, the non-simultaneous rating of Path 46 (WOR) increases 2,100 MW from 11,200 MW (the current Accepted Rating) to 13,300 MW (new Proposed Rating). With the addition of the NGIV#2, currently in Phase 2 of the WECC Path Rating Process, the nonsimultaneous rating of Path 46 increases by 2,300 MW from 11,200 MW (current Accepted Rating) to 13,500 MW (new Proposed Rating with HVDC and NGIV#2), which is an increase of 1,050 MW over the NGIV#2 Proposed Rating of 12,450 MW. The increase in Path 46 flow with NGIV#2 is slight over the increase from this HVDC Project alone because both projects make improvements to the southern portion of Path 46 and thus both projects face the same limit on the southern portion of Path 46. These non-simultaneous rating are achieved by allowing control features of HVDC lines, including rapid switching of the HVDC line either pre- or post-contingency. 5.2 Power Flow Analysis Results Some of the key findings from the power flow analysis include: Path 46 non-simultaneous rating can be increased from 11,200 MW (current Accepted Rating) to 13,300 MW (new Proposed Rating) with the HVDC Project (or 13,500 MW new Proposed Rating with HVDC and NGIV#2) and satisfy the NERC Reliability Standards and WECC System Performance Criteria. The Path 46 non-simultaneous rating of 13,300 MW (or 13,500 MW) is limited by contingency ratings on the following transmission lines associated with the southern portion of Path 46: o Hassayampa-North Gila 500 kv line (Critical outage: Hassayampa-Hoodoo Wash 500 kv line or Hoodoo Wash-North Gila 50 kv line) o Hoodoo Wash-North Gila 500 kv line (Critical outage: Hassayampa-North Gila 500 kv line) The overloads on these lines can be addressed by rapid switching on the dc converters. Both Path 46 rating increases are with the existing Eldorado-Lugo series capacitors by-passed. San Diego Gas & Electric 5-2 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Results Although not a limiting condition, heavy loading was noted on the following transmission lines associated with the northern portion of Path 46: o o o o o Imperial Valley-El Centro 230 kv (for multiple contingencies) is a known, existing problem that is handled by various SDG&E RAS and is helped by NGIV#2 in conjunction with the HVDC Project. Lugo-Mohave 500 kv line (for the loss of McCullough-Victorville No 1 and 2) which is resolved by either the Eldorado-Lugo-Mohave Series Capacitor Project or NGIV#2 in conjunction with the HVDC Project. Lugo-Victorville 500 kv line (for multiple contingencies) which is an existing problem with partially addressed by either the Eldorado-Lugo-Mohave Series Capacitor Project or NGIV#2 in conjunction with the HVDC Project. Julian Hinds-Mirage 230 kv (for multiple contingencies) which is an existing problem which is resolved by the Blythe Gen RAS and is helped by either the Eldorado-Lugo- Mohave Series Capacitor Project or NGIV#2 in conjunction with the HVDC Project. Marketplace-Adelanto 500 kv (for multiple contingencies, but only in the cases with the Eldorado-Lugo-Mohave Series Capacitor Project. Further study of this may be required in Phase 2. The Loss of the Bipolar HVDC line heavily loads the following elements: o o o Julian Hinds-Mirage 230 kv line Palo Verde-Colorado River 500 kv line Lugo-Victorville 500 kv line The loss of the Bipolar HVDC may also require a gen dropping RAS (dropping as much as 500-1000 MW of generation). The details of this gen dropping RAS can be worked out in Phase 2. Also, these heavy loadings are improved by the either the existing Blythe RAS, existing SDG&E gen dropping RAS, the Eldorado-Lugo-Mohave Series Capacitor Project or NGIV#2. 5.3 Transient Stability Analysis Results Transient stability analysis was performed on the HVDC base case and there were no violations of WECC transient stability criteria. Specially: San Diego Gas & Electric 5-3 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Study Results All outages resulted in transient stability with positive damping. No violation of WECC transient voltage dip criteria was found. No violation of WECC transient frequency criteria was found. 5.4 Post-Transient Stability Analysis Results Post-transient stability analysis was performed on the HVDC study base case using the WECC voltage stability criteria. This analysis was done by increasing the flow on Path 46 by 5% of the proposed rating from 13,300 MW to 13,965 MW (and from 13,500 MW with NGIV#2 to 14,175 MW) for Category P1 outages and increasing the flow by 2.5% of the proposed rating from 13,300 MW to 13,633 MW (and from 13,500 MW with NGIV#2 to 13,838 MW) for Category P6 outages. Power flow solutions were achieved for all the outages simulated. Accordingly, per WECC voltage stability criteria, positive reactive margins were achieved for all outages simulated. San Diego Gas & Electric 5-4 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Conclusion 6.0 CONCLUSION As described in this CPR, this study shows that the proposed Southwest Powerlink (SWPL) High Voltage Direct Current (HVDC) transmission line can achieve a maxim transfer capability of 3,000 MW and would increase the non-simultaneous rating of WECC Path 46 (West of Colorado River (WOR)) by 2,100 MW from 11,200 MW (current Accepted Rating) to 13,300 MW (new Proposed Rating) while also satisfying NERC reliability standards and WECC system performance criteria. In conjunction with the North Gila-Imperial Valley #2 (NGIV#2) Project, which is currently in Phase 2 of the WECC Path Rating Process, this HVDC and NGIV#2 increase the non-simultaneous rating of Path 46 by 2,300 MW from 11,200 MW (current accepted rating) to 13,500 MW while also satisfying NERC reliability standards and WECC system performance criteria. This is an increase of 1,050 MW over the NGIV#2 Proposed Path 46 rating of 12,450. This study found the critical outage and limiting element to be the parallel path of Hassayampa-North Gila 500 kv line and Hoodoo Wash-North Gila 500 kv line, where the loss of one over loads the other. Post contingency loading on these and other lines can be mitigated by the high-speed switching capabilities of the HVDC line. The limitations on these lines are the thermal ratings of the series capacitor on the Hoodoo Wash-North Gila 500 kv line, and the thermal rating of the series capacitor on the Hassayampa-North Gila 500 kv line. Further, the study results showed that the proposed Project would not cause significant inadvertent flow on the existing WECC transmission system. Known simultaneous interactions between Path 46 and other paths such Path 61, Path 81 and the SCIT nomogram will be evaluated during Phase 2 of this WECC Path Rating Process. It is expected that this CPR will form the basis for the proposed HVDC Project to enter Phase 2 of the WECC three phase rating process. Once the 60-day comment period has passed and all comments have been addressed, a WECC HVDC Project Review Group will be assembled to help address the study requirements for Phase 2 and to conduct additional analysis that may be necessary to obtain a new WECC Accepted rating of 13,300 MW for Path 46 with the HVDC Project by itself or 13,500 MW with NGIV#2. San Diego Gas & Electric 6-1 Burns & McDonnell

SDG&E HVDC CPR Revision 0 Conclusion APPENDIX A POWER FLOW RESULTS San Diego Gas & Electric 6-1 Burns & McDonnell

SDGE High Voltage DC WECC Path 46 Rating Increase Comprehensive Progress Report Appendix A - Power Flow Results Post HVDC Pre HVDC HVDC HVDC HVDC IVNG2 IVNG2 Eld-Lugo Eld-Lugo Rating (MVA) 11200 13300 13500 Monitored Facility Cont Name Base Cont %Load %Load %Load %Load %Load Comments 15021 PALOVRDE 500 24900 COLRIVER 500 1 1 1303_HVDC Bipole Outage_with Gen drop 2238 3031 99.8 14002 MOENKOPI 500 24042 ELDORDO 500 1 2 1110_Line Navajo-Crystal 500 kv ckt 1 2390 2390 90.9 90.34 92.97 91.64 14002 MOENKOPI 500 24042 ELDORDO 500 1 3 1110_Line Navajo-Crystal 500 kv ckt 1 1645.4 2381.6 90.95 15021 PALOVRDE 500 14933 PALOVRD3 24.0 1 1 1260_2 Gens Palo Verde double generator outage 1533 1533 91.3 91.33 91.34 91.34 91.35 15090 HASSYAMP 500 22342 HDWSH 500 1 1 1020_Line Hassayampa-North Gila 500 kv ckt 1 2579 2598 109.4 109.05 104.77 101.7 15090 HASSYAMP 500 22536 N.GILA 500 1 1 1030_Line Hassayampa-HooDoo Wash 500 kv ckt 1 2579 2598 109.31 108.95 104.96 101.9 resolved by dc switching 15090 HASSYAMP 500 22536 N.GILA 500 1 2 1030_Line Hassayampa-HooDoo Wash 500 kv ckt 1 1905 2572 109.19 108.84 104.85 101.79 18020 IRONMTN 230 18072 IRONMTN 138 1 1 1010_Line Palo Verde-Colorado River 500 kv ckt 1 300 370 92.15 19038 MEAD 500 26044 MARKETPL 500 1 1 1010_Line Palo Verde-Colorado River 500 kv ckt 1 2598 2858 91.89 93.69 19053 LIBERTY 345 19315 PEACOCK 345 1 1 1010_Line Palo Verde-Colorado River 500 kv ckt 1 508 609.6 91.25 90.6 1010_Line Palo Verde-Colorado River 500 kv ckt 1 500 600 92.56 92 19054 LIBTYPHS 230 19052 LIBERTY 230 2 1 1080_Line Perkins-Mead 500 kv ckt 1 500 600 90.27 Base Case 500 600 90.51 90.59 90.52 90.59 90.52 1060_Line Imperial Valley-Ocotillo 500 kv ckt 1 388 430 162.67 159.78 107.85 104.16 20102 RUM-230 230 20238 HRA-230 230 1 1 1070_Line Ocotillo-ECO 500 kv ckt 1 388 430 162.66 159.77 107.85 104.15 existing problem (other 1250_2 Lines Imperial Valley-Ocotillo & Ocotillo-ECO 500 kv 388 430 162.66 159.77 107.85 104.15 contingencies), resolved 1060_Line Imperial Valley-Ocotillo 500 kv ckt 1 388 430 178.6 175.65 122.98 119.25 by phase shifter 20118 ROA-230 230 20102 RUM-230 230 1 1 1070_Line Ocotillo-ECO 500 kv ckt 1 388 430 178.59 175.65 122.98 119.24 1250_2 Lines Imperial Valley-Ocotillo & Ocotillo-ECO 500 kv 388 430 178.59 175.65 122.98 119.24 22342 HDWSH 500 22536 N.GILA 500 1 1 1020_Line Hassayampa-North Gila 500 kv ckt 1 2579 2598 118.64 118.28 114.03 110.98 22342 HDWSH 500 22536 N.GILA 500 1 2 1020_Line Hassayampa-North Gila 500 kv ckt 1 1905 2572 119.04 118.69 114.42 111.35 Base Case 1905 2572 90.97 1060_Line Imperial Valley-Ocotillo 500 kv ckt 1 370 407 237.42 239.13 22356 IMPRLVLY 230 8332 ELCENTSW 230 1 1 1070_Line Ocotillo-ECO 500 kv ckt 1 370 407 237.43 239.13 1230_2 Lines Coachella-Mirage & Mirage-Ramon 230 kv 370 407 95.65 1250_2 Lines Imperial Valley-Ocotillo & Ocotillo-ECO 500 kv 370 407 237.43 239.14 1060_Line Imperial Valley-Ocotillo 500 kv ckt 1 796 850 94.11 93.12 22609 OTAYMESA 230 20149 TJI-230 230 1 1 1070_Line Ocotillo-ECO 500 kv ckt 1 796 850 94.11 93.11 1250_2 Lines Imperial Valley-Ocotillo & Ocotillo-ECO 500 kv 796 850 94.11 93.12 24042 ELDORDO 500 24086 LUGO 500 1 1 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 2858 3429 92.23 90.41 24042 ELDORDO 500 24086 LUGO 500 1 2 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 2858 3429 92.09 90.26 24042 ELDORDO 500 24086 LUGO 500 1 3 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 2858 3429 92.09 90.26 24042 ELDORDO 500 24086 LUGO 500 1 4 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 2858 3429 92.09 90.26 24042 ELDORDO 500 24086 LUGO 500 1 5 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 2858 3429 92.03 90.19 1010_Line Palo Verde-Colorado River 500 kv ckt 1 1386 1507 111.02 1130_Line Marketplace-Adelanto 500 kv ckt 1 1386 1507 104.23 24042 ELDORDO 500 24086 LUGO 500 BP 1 1150_Line Lugo-Mohave 500 kv ckt 1 1386 1507 103.91 1160_Line Lugo-Victorville 500 kv ckt 1 1386 1507 119.68 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 1386 1507 126.11 Base Case 1386 1507 97.75 24042 ELDORDO 500 26048 MCCULLGH 500 1 1 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 2598 2598 93.28 96.4 91.3 93.93 1010_Line Palo Verde-Colorado River 500 kv ckt 1 1386 1507 92.89 24086 LUGO 500 24097 MOHAVE 500 BP 3 1160_Line Lugo-Victorville 500 kv ckt 1 1386 1507 97.66 94.66 1316_2 Lines McCullough-Victorville 500 kv ckts 1 & 2 1386 1507 102.42 99.02 1010_Line Palo Verde-Colorado River 500 kv ckt 1 2400 2598 102.68 133.35 96.1 116.37 1140_Line Eldorado-Lugo 500 kv ckt 1 2400 2598 104.82 114.8 118.19 111.73 114.83 1150_Line Lugo-Mohave 500 kv ckt 1 2400 2598 93.41 113.46 24086 LUGO 500 26105 VICTORVL 500 1 1 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 2400 2598 132.76 146.81 151 141.51 144.67 1210_2 Lines Eldorado-Lugo 500 kv & Eldorado-Mohave 500 kv 2400 2598 104.82 114.8 118.19 111.73 114.83 1303_HVDC Bipole Outage_with Gen drop 2400 2598 113.0 1300_HVDC Bipole Outage 2400 2598 100.2 Base Case 2400 2598 98.95 97.33 24219 PISGAH 230 24041 ELDORDO 230 2 1 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 289 289 90.65 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 289 289 92.49 24219 PISGAH 230 24627 CIMA 230 1 1 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 289 289 90.82 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 289 289 92.57 24627 CIMA 230 24041 ELDORDO 230 1 1 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 289 289 90.19 91.9 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 289 289 93.63 90.56 24728 INYO 115 24730 INYO PS 115 1 1 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 56 62 91 90.31 Base Case 56 62 90.88 90.87 90.87 90.88 90.85 1010_Line Palo Verde-Colorado River 500 kv ckt 1 357 357 126.8 145.97 134.34 129.7 121.87 1140_Line Eldorado-Lugo 500 kv ckt 1 357 357 105.52 102.1 1160_Line Lugo-Victorville 500 kv ckt 1 357 357 100.15 111.03 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 357 357 104.39 112.11 113.74 107.59 108.64 25406 J.HINDS 230 24806 MIRAGE 230 1 1 1210_2 Lines Eldorado-Lugo 500 kv & Eldorado-Mohave 500 kv 357 357 105.52 1230_2 Lines Coachella-Mirage & Mirage-Ramon 230 kv 357 357 114.64 118.96 113.14 120.17 113.99 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 357 357 102.88 114.46 109.39 1303_HVDC Bipole Outage_with Gen drop 357 357 118.7 1300_HVDC Bipole Outage 357 357 102.3 Base Case 357 357 92.43 99.14 93.67 96.95 92.2 1010_Line Palo Verde-Colorado River 500 kv ckt 1 1558 1558 95.79 1140_Line Eldorado-Lugo 500 kv ckt 1 1558 1558 105.53 103.2 26044 MARKETPL 500 26003 ADELANTO 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 1558 1558 125.19 121.02 500 1 1 1210_2 Lines Eldorado-Lugo 500 kv & Eldorado-Mohave 500 kv 1558 1558 105.53 103.2 1316_2 Lines McCullough-Victorville 500 kv ckts 1 & 2 1558 1558 119.47 117.25 1636 2210 92.87 26044 MARKETPL 500 26003 ADELANTO 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 500 1 3 1636 2210 91.89 1316_2 LineS McCullough-Victorville 500 kv ckts 1 & 2 1636 2210 95.06 26048 MCCULLGH 500 26105 VICTORVL 500 1 1 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 1385.6 2078 90.72 Base Case 1385.6 2078 99.74 98.71 26048 MCCULLGH 500 26105 VICTORVL 500 1 2 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 1385 2078 92.38 26048 MCCULLGH 500 26105 VICTORVL 500 1 3 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 1385.6 2078 90.51 Base Case 1385.6 2078 99.9 98.92 26048 MCCULLGH 500 26105 VICTORVL 500 2 1 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 1385 2078 90.29 Base Case 1385.6 2078 97.83 96.83 26048 MCCULLGH 500 26105 VICTORVL 500 2 2 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 1385.6 2078 90.76 Base Case 1385.6 2078 99.48 98.46 26048 MCCULLGH 500 26105 VICTORVL 500 2 3 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 1385.6 2078 90.76 Base Case 1385.6 2078 99.48 98.46 26048 MCCULLGH 500 26105 VICTORVL 500 BP 3 1200_2 Lines Eldorado-Lugo 500 kv & Lugo-Mohave 500 kv 1385.6 2078 92.38 resolved by dc switching existing problem (other contingencies), resolved by existing SDG&E RAS existing, address by SCE Eldorado-Lugo-Mohave Project addressed by SCE Eldorado-Lugo_Mohave Project, or dc switching existing, address by SCE Eldorado-Lugo-Mohave Project existing, resolved by Blythe Gen RAS or dc switching; helped by Eldorado-Lugo-Mohave appears to be created by Eldorado-Lugo-Mohave, will need to be investigated further in Phase 2 Limiting Element Not Applicable Overload

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