SMUD Lidar

The Sacramento Municipal Utility District uses Light Detection and Ranging within its territory to assist in prioritizing elements of its wildfire mitigation plan. 

The California Public Utilities Commission's Wildfire Safety Advisory Board has reviewed all 50 of the 2020 wildfire mitigation plans by the state's publicly owned utilities and electric cooperatives and has arrived at guidelines for improvement in preventing utility-caused wildfires going forward.

Representatives of seven publicly owned utilities presented their plans to the WSAB at a Nov. 18 virtual workshop. One theme that emerged from the workshop is that POUs represent a diversity of sizes, terrains, topographies, assets, and number and type of customers that makes a one-size-fits-all approach virtually impossible.

The WSAB between now and March 1 will work with POUs and co-ops in California to refine guidelines for improving future WMPs. The WSAB's final board meeting will be held in December 2021, with WMP updates due in July.

Among the board's recommendations in its draft Guidance Advisory Opinion for 2021 Wildfire Mitigation Plans of Publicly Owned Electric Utilities and Electrical Cooperatives is a template to standardize information in future WMPs upfront in order to better assess the relevance of the plans to particular utilities and their circumstances.

The template will include the square mileage, number and type of customers in each utility's territory; detailed asset identification; location and topography of the territory; information about seasonal wind patterns; territory maps that include fire-threat regions and regions of concern overlaid with transmission and distribution assets; the impact of investor-owned utility public-safety power shut-off events on each public utility; and information on whether or under what conditions a public utility would expect to call PSPS events of its own.

The board also seeks information about various utilities' governing bodies and approval processes, details about how utilities measure the success of their plans, and how POUs will budget for planned mitigation efforts. Independent evaluators for the next round of WMPs should reduce the general information contained in their reports and provide examples of industry standards and recommendations for how individual utilities can meet those standards, the WSAB said.

Utilities presenting at the workshop ranged from the massive Los Angeles Department of Water & Power and the Sacramento Municipal Utility District, which have their own generation and transmission assets and serve millions, to the 6,000-meter Healdsburg Utility Department, which depends on Pacific Gas & Electric for transmission and whose customers are affected by the investor-owned utility's PSPS events that sometimes come with little or no warning.

Some POUs, including Anaheim Public Utilities, have more than 90 percent of their systems—including a substation—underground. Others have high-voltage transmission lines through high-fire-threat areas such as forests that require frequent vegetation management and face intensive system hardening.

The 2021 WMP updates are expected to include specific system-hardening measures and schedules for implementation. Examples include replacing expulsion fuses, undergrounding assets, adding covered conductors, increasing spacing between wires to prevent birds from causing ignitions, replacing wooden poles with wind- and fire-resistant poles, and applying more localized sectionalizing equipment. Specific goals and methodologies for achieving them should also be included in the 2021 plans, the WSAB said.

Regarding PSPSes, the WSAB recommended improving communication between IOUs and the POUs that are dependent on them for transmission. POUs should also assess system hardening or backup generation to lessen the impact of PSPS and other de-energization events on critical facilities such as hospitals. Utilities that provide water themselves or that power water utilities must also address delivery for drinking and firefighting, as well as hardening the water supply to sewage treatment plants in the event of a PSPS.

Utilities are increasingly using drones for routine equipment inspection, and in some cases higher-tech tools. SMUD is using Light Detection and Ranging along its transmission corridors to assist in risk determination and vegetation management. Artificial intelligence software processes drone imagery to assess risk from equipment defects, as Lora Anguay, interim chief grid strategy and operations officer for SMUD, demonstrated in her presentation during the workshop. The WSAB recommends increasing visual patrols on potentially impacted circuits, and asked POUs to give more information about what they are looking for during inspections and how problems uncovered would be addressed.

Specific risks associated with design and construction and how those relate to the CPUC's General Order 95, which governs overhead electric lines, should be included in future plans, the WSAB said in its guidelines. POUs are already attempting to comply with and in some cases exceed the order, the WSAB said, adding that the commission might consider modifying GO 95 to mandate topographical analysis before new poles are set and require utilities to identify wind behavior over ridgelines and other terrain. Engineering needs based on weather conditions in service territories should also be described in future POU plans. Situational-awareness technology such as weather stations, cameras and drones is generally less expensive and easier to implement than system upgrades, and can help inform a utility about aspects of and risks on its system.

The WSAB recommends a refined approach to vegetation management for wildfire mitigation in future plans. This should include analysis of new growth in cleared areas; species-dependent approaches to vegetation management informed by science; the ecological impact of a utility's vegetation-management plan; circumstances that indicate when vegetation management should go beyond the GO 95 standard; and how vegetation management differs depending on fire-threat levels. The WSAB suggested that qualified scientists should design and assess vegetation-management plans with the understanding they bring to growth and regeneration patterns, species traits and flammability, and the ecological role of vegetation in fire ignition and behavior.

Representatives at the workshop indicated that maintaining tree-trimming crews has been difficult in the push to reduce wildfire risk through vegetation management, as contractors have been in high demand by investor-owned utilities. The presence of qualified electrical workers and tree trimmers who meet training and experience standards is critical to ensuring worker safety while carrying out vegetation-management plans, the WSAB said. Innovative approaches such as requiring homeowners to create defensible space around their properties allow utilities to focus their mitigation efforts, the board said.

Staff Writer

Abigail Sawyer grew up in northwestern New Mexico near two massive coal-fired power plants. She spent many hours gazing out the car window at transmission lines on family road trips across the Southwest and now reports on the region from San Francisco.