North Coast Resiliency Initiative

The North Coast Resiliency Initiative Report is now available here. The report was presented at an information session on July 11, with the recording linked below.

Summary of the NCRI

The Challenge

Over the last decade, California has experienced increasingly intense, record-breaking wildfires. Fires attributed to power lines, though a minority overall in terms of number, comprise roughly half of the most destructive fires in California history. To reduce wildfire risk from electrical infrastructure, utilities have used Public Safety Power Shutoffs (PSPS) to de-energize power lines during severe fire weather conditions. PSPS events can impact either distribution or transmission lines or both simultaneously. 

In the past, the North Coast segment of Pacific Gas and Electric Company’s (PG&E) electric grid has been significantly impacted by PSPS events. For example, transmission and distribution lines in the North Coast area were de-energized during the October 26 and 29, 2019 PSPS events, affecting approximately 245,000 customers. This is partially due to the designation of much of this area as either Tier 2 or Tier 3 High Fire Threat Districts (HFTDs). HFTDs are areas at higher risk for destructive fires and where stricter fire-safety regulations apply. This means that transmission and distribution lines serving customers in the region might need to be de-energized when certain weather and fuel conditions are present to avoid wildfire risk. 

However, many customers in the North Coast who are otherwise “safe-to-energize” also lose power during PSPS events. In this case, safe-to-energize refers to customers who are located outside of the conditions that triggered the need for a PSPS event, but are served by a transmission line or lines that have been de-energized. If the grid configuration were different, they would be able to remain online.

Addressing the Challenge

The California Public Utilities Commission (CPUC) founded the North Coast Resiliency Initiative (NCRI) in 2021 to determine the causes of, and to craft mitigations for, electrical outages that impact customers along California’s North Coast during wildfire season. Along with the CPUC, representatives from other state energy agencies, PG&E, and two Community Choice Aggregators (CCAs) comprised the NCRI’s Steering Committee which was responsible for the majority of the initiative’s work.

Specifically, the NCRI focused on transmission-level PSPS outages affecting otherwise safe-to-energize customers. For the purposes of the NCRI, the “North Coast” was defined as Marin, Sonoma, Napa, and portions of Mendocino, Lake, and Solano counties. The CPUC determined these geographic boundaries at the beginning of the initiative, based on the locations of actual and predicted future PSPS events and on the structure of the local electrical grid.

The NCRI Steering Committee then developed a four-phase problem solving framework and began working through each of the key steps. This framework could be used to address other regional grid challenges that require multijurisdictional collaboration.

• Phase 1: Build the foundation
• Phase 2: Define the problem
• Phase 3: Explore and compare mitigations
• Phase 4: Conduct comprehensive regional planning

The Solution

The NCRI Steering Committee completed the first two phases in the problem-solving framework, but stopped short of completing Phases 3 and 4. This occurred for three reasons:

First, by mid-2022, PG&E identified mitigations for PSPS impacts at the Calistoga and Monticello substations. The Monticello substation has an existing transmission switching option which will allow it to be served from a separate line during PSPS events. PG&E also plans to deploy a clean substation microgrid capable of powering the Calistoga substation through PSPS events. These substations had the highest number of direct PSPS impacts in the North Coast in PG&E’s 10-year modeling effort, the first of two major types of transmission-level PSPS impacts explained in more detail in the full report.

Second, PG&E’s updated PSPS modeling, which became available in early 2023 after the NCRI was well underway, showed fewer impacts from transmission-level PSPS events along the North Coast than prior years’ models. With each passing iteration, PG&E’s PSPS modeling tools became more granular, the company’s grid conditions improved, and the model incorporated a new year of weather data.

Third, during Phase 3 of the initiative, PG&E’s analysis showed that repairing or replacing several components on transmission lines in the North Coast could reduce the likely number of indirect transmission-level PSPS events in the region from nine events to three over a 10-year period, well below the threshold of 10 direct PSPS impacts previously adopted by the CPUC for prioritization of substation microgrid solutions (See D.22-11-009). Indirect impacts are the second of two major types of transmission-level PSPS impacts. PG&E estimated that these repairs and replacements could be implemented before the end of 2023 at a cost of potentially less than $500,000. Phase 3 concluded early with the Steering Committee unanimously approving this cost-effective mitigation, which was already in PG&E’s workplan, and there was no longer a need to conduct comprehensive regional planning (Phase 4).

In short, clear preferable mitigations emerged in the course of the NCRI which allowed the initiative to conclude without the need to consider a broader set of more costly mitigation alternatives.

With this information in hand, the NCRI concluded earlier than initially anticipated. Regardless, the insights gained through the NCRI are worth documenting and sharing with the public. While the NCRI targeted a geographically specific resiliency problem, the initiative’s structure, framework, and analytical approach could serve as a blueprint to those working to address other regional energy challenges which may require multijurisdictional collaboration across government agencies, utilities, and other stakeholders to better understand and then identify, compare, select, and eventually implement preferred mitigations.

For any questions, contact Daniel Tutt at Daniel.Tutt@cpuc.ca.gov.