System Resilience Under Extreme Natural Disaster January 15, 2020 Bhavana Katyal Tyson Niemann
Introduction The purpose of this study is to evaluate the impact of an extreme natural disaster on the reliability of the Bulk Electric System (BES) in the Western Interconnection (WI) in a Year 10 future. • The WI experiences extreme natural disasters such as yearly wild fires and occasionally extreme earthquakes. • This assessment investigates a wild fire in western California that is made more extreme due to high winds. • Identify possible resilience challenges of the WI • Intended to help transmission providers consider them in future planning studies. 2
Assessment Approach The outages created for the scenario include two main events based on the Tucker fire in California that began on July 2019. • Outage Event 1: Simultaneous outage of the Malin -Round Mt. 500-kV lines and the Malin -Hilltop 230-kV line • Outage Event 2: Following system adjustment, the outage of the Captain Jack -Olinda 500-kV line. • The outages was assumed to last for seven days. 3
What was studied Reliability risks to the BES in WI in Year 10 future that were analyzed using two different modeling tools : • Resource Adequacy ◦ PCM model using ABB’s GridView software to analysis - Unserved energy, reserve margin, utilization on major transmission paths, spillage of renewable resources, load-generation balance & inter region transfer. • System Stability ◦ PF model using GE’s PSLF software to analysis - transient and voltage stability. 4
Modeling Approach • The outages was assumed to last for seven days starting on Aug 7 th 2028 Hour 20 when flows on COI and PDCI were near their maximums in WECC 2028 ADS PCM Phase 1 V2.2 (ADS PCM Case). • The generation dispatch and load from the above hour were extracted from the ADS PCM Case and used to change the WECC 2028 Heavy Summer 1 base case to create a power flow (PF) case for the assessment. • One PCM case was modeled with both the outage events lasting seven days. • PF case was modeled to first analyze the outage Event 1, then Event 2. 5
Production Cost Model Results Unserved energy and Reserve Margins: There was no unserved energy and enough reserve margin for the system to ride the outage for the outage period. 6
Production Cost Model Results Inter-Reginal Flows – ADS PCM Case Inter-Reginal Flows – COI Outage • During the COI Outage: • There are overall reduced imports into California. region by 25%. • There is 85% reduction in net import to Northwest region. 7
Production Cost Model Results Total Generation for Outage Total Generation for Period (GWh) Outage Period (GWh) ADS PCM Case COI Outage % Change Energy Storage 35.12196 21.93247 -37.55% Biomass RPS 351.4176 357.4855 1.73% Combined Cycle 6470.929 6548.172 1.19% Steam - Coal 3455.224 3374.652 -2.33% Combustion Turbine 1062.314 1070.124 0.74% Other 2.19558 2.19558 0.00% DG/DR/EE - Incremental 1224.449 1224.449 0.00% Geothermal 552.1867 522.5834 -5.36% Solar 997.7851 997.2484 -0.05% Conventional Hydro 4095.069 4096.946 0.05% Small Hydro RPS 38.49429 38.56732 0.19% IC 46.93082 51.34173 9.40% Steam - Other 61.49449 62.90499 2.29% Nuclear 980.0979 980.0979 0.00% Wind 1806.343 1805.598 -0.04% Spillage 3.3 4.1 24.7% 8
Production Cost Model Results CA Generation at Peak Hour (MW) CA Generation at Peak Hour ADS PCM Case (MW) COI Outage % Change Biomass RPS 1129.4 1121.9 -0.7% Combined Cycle 21141.5 23186.9 9.7% Combustion Turbine 1504.1 1810.1 20.3% DG/DR/EE 9430.0 9430.0 0.0% Hydro 5430.0 5489.8 1.1% Geothermal 2464.7 2464.7 0.0% Nuclear 1079.1 1079.1 0.0% Small Hydro RPS 285.3 285.3 0.0% Solar 7717.1 7717.1 0.0% Steam - Coal 0.0 0.0 NA Steam - Other 250.0 175.0 -30.0% Wind 3608.7 3608.7 0.0% Energy Storage 231.6 690.3 198.0% Other (IC etc.) 47.6 221.4 365.1% • In both cases, the internal generation available to serve California is not sufficient to meet load, thus leading to required imports. • With the additional imports, California would be able to avoid unserved energy during the modeled extreme natural disaster. 9
Production Cost Model Results Under COI Outage: Transmission constraints prevent full utilization of renewables. But California can import sufficient energy to avoid unserved energy. 10
Production Cost Model Results The following metrics were used for this assessment to identify transmission Paths that are “highly utilized” for the duration of outage in the period 08/07/2028 Hr. 20 – 08/14/2028 Hr. 24: U75 designates Paths that are utilized at 75% or more of their rated capacities for 50% or more of the hours in the outage duration; U90 designates Paths that are utilized at 90% or more of their rated capacities for 20% or more of the hours in the outage duration; and U99 designates Paths that are utilized at 99% or more of their rated capacities for 5% or more of the hours in the outage duration. Any Path that meets one or more of these criteria is identified as “highly utilized.” 11
Production Cost Model Results 12
Production Cost Model Results 13
Power Flow and Transient Stability Analysis Results Outage Event 1 The post-transient study did not result in thermal overloads reaching 125% or more, a cascading test was not needed. The post-transient study did result in low voltages occurring on the 115-kV and 69-kV system in southern Oregon and two thermal overloads on the 500-kV system. The outage is an Extreme Event no NERC or WECC system performance criteria were violated. A reactive margin study was not performed in this assessment. 14
Outage Event 2 Outage Event 2 The post-transient study did not result any thermal violations or voltage violations The transient stability analysis did not result in any stability concerns 15
Bus Voltage 16
Bus Frequency 17
Generator Angles 18
Observations and Conclusions Under COI outage: The WI was found to be overall resilient to an extreme event during the COI outage. There are adequate resources and no unserved energy. There was higher utilization of some of the major paths but this did not limit the ability of the BES to deliver power to serve load. During COI outage, the current transmission system is not able to fully utilize and transfer renewable resources through inter regional transfers. No cascading outages were observed. Overloads and voltage violations were seen but were not considered to be of a concern because of the extreme nature of the event 19
Recommendations Study additional scenarios of contingencies caused by extreme natural disasters to evaluate the stability and adequacy of the interconnection affecting different parts of the Western Interconnection. 20
Contact: Bhavana Katyal bkatyal@wecc.org Tyson Niemann tniemann@wecc.org 21
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