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Rolling Blackouts: The Last Choice for Wildfire Prevention

Updated: Jun 6

Though often called rolling blackouts in the news, a better term for an outage used as a safety measure to prevent wildfires is preemptive blackout. Preemptive blackouts should be the last choice to prevent wildfires, but they are currently one of the first lines of defense that electric utility companies rely on for wildfire prevention.

During preemptive blackouts, power is shut off to specific power lines when high or extreme wildfire danger is predicted. During hot, dry, and windy weather, power might be cut to lines that run through forested areas for anywhere from 15 minutes to several days. This is to prevent a tree or tree branch from falling onto an energized power line, which could spark a fire.

Because preemptive blackouts can last hours to days, they are a major issue for all who experience them. People risk losing food or medications without necessary refrigeration, or suffer heat-related illness from lack of air conditioning. Employees who depend on power for lights or Wi-Fi cannot work; businesses can be shut down for days, losing necessary income. Plus, other essential services, including traffic lights, water treatment, and sewage treatment are often shut down.

Instead of using preemptive blackouts, electric utilities should assess their lines to determine the risk of each line sparking a wildfire, and strategic modifications should be implemented. Prescient has created a unique wildfire risk assessment technique to streamline this process for electric utility companies. Our assessments help companies choose specific enhancements to design and operating practices to reduce the risk of lines causing wildfires. We locate specific areas where wildfires are a threat and provide recommendations to minimize risk.

Let’s take a deeper look at preemptive outages and better solutions to wildfire prevention.

Preemptive Outages Explained

Preemptive outages implemented as wildfire prevention are different than rotating outages used to reduce customer load during extreme heat or cold. When used to prevent wildfires, preemptive outages are implemented when extreme fire conditions are predicted or occurring. Power lines are simply deenergized in a specific area so that they cannot spark a wildfire. The power will remain out until the extreme danger has passed.

For example, preemptive outages would be implemented in California during a windstorm in August. California often experiences drought and heat waves during this time, meaning wildfire threat is already high; if a windstorm were to occur, wildfire threat would become extreme. During the windstorm, trees or tree branches could fall onto energized power lines, which would immediately cause the wood to catch on fire. Even a small ember carried on the wind into a dry forest or field could lead to a massive blaze, like the Camp Fire in 2018.

To prevent this rapid spread of fire, electric utility companies will deenergize their power lines until the danger has passed. This could take a few hours or up to several days, meaning customers without power are at risk of losing perishable items, which can include food and lifesaving medicines.

Prescient’s Risk Assessment Methodology

Prescient assesses power lines in fire-prone areas as part of our risk assessment matrix. We consider protective relaying schemes, distance from substation, right of way (ROW) conditions, and more. Our observations are entered into our proprietary algorithm, which gives us a specific risk score.

Prescient then compiles findings into an easy to view graph, as well as a report outlining prudent improvements to reduce wildfire risk along power lines. With a specific risk score established, strategic modifications can be implemented to reduce wildfire risk. These modifications can be selected using a variety of criteria, including time to implement, cost of implementation, percentage of risk reduction, and more. Prescient’s risk algorithm can be used to determine the specific percentage of risk reduction. Two specific areas to consider for modification are vegetation management, and rapid fault detection and isolation.

Vegetation Management

One enhancement that is already in use in vegetation management. However, most utilities approach vegetation management as an all or nothing strategy. Utilities frequently remove hazard and danger trees, while leaving other nearby vegetation, including brush piles.

Instead, a more strategic approach to vegetation management could provide specific risk reduction in targeted areas. Prescient's wildfire risk assessment will help electric utility companies determine where increased vegetation management would be beneficial. Prescient’s assessment provides utilities with a detailed report outlining the ignition time of dry materials compared to the specific fault clearing time of each utility’s power line.

Rapid Fault Detection and Isolation

During high to extreme fire danger, detecting and isolating faults rapidly is the key to preventing a faulted power line from sparking a wildfire. To do this, protective relays should be equipped with sensors to detect a variety of weather-related factors, including relative humidity, ambient temperature, wind speed, and more. These parameters can be used to calculate vegetation moisture content and ignition probability, which will optimize protective relay actuation settings.

Algorithms using the inputs from these sensors will optimize settings within microprocessor-based relays. Settings can be automatically changed either to optimize sensitivity (i.e., trip at 1 amp) or to optimize coordination (i.e., trip at 100 amps). This will allow the relay to rapidly actuate for low fault currents during high wildfire risk conditions. When low energy faults are rapidly isolated, the possibility of wildfire ignition is minimized.

For example, during wet conditions, setpoints can be increased so that tap fuses open for faults before protective relays actuate. During extreme wildfire risk conditions, however, protective relays will be allowed to actuate before tap fuses open for faults.

Wildfire Risk Reduction

Wildfires caused by faulted power lines can be relegated to ancient history. With today’s technology and understanding of key factors, electric utilities should be able to selectively interrupt fault current before nearby dry vegetation is ignited. Selective fault current interruption differs from preemptive outages because power will be shut off immediately after a fault occurs, rather than preemptively before a fault occurs.

When a fault occurs, updated fault detection and isolation methods will interrupt the fault quickly enough that a wildfire cannot ignite. Strategic vegetation management will ensure that no combustible material is within the vicinity of a fault as an additional safeguard.

The alternative is that power is shut off for an indetermined amount of time during high to extreme wildfire conditions, which will prevent a fault from occurring but also cause much disruption for every person or business that loses power. At Prescient, we believe that a rapid reaction paired with strategic vegetation management is far more effective than a preemptive outage.

Read more about our wildfire risk analysis service, or contact us to learn more about Prescient’s wildfire risk assessment and analysis methods. Together, we can reduce the risk of wildfires sparked by faulted power lines.

Learn More with Prescient’s On-Demand Wildfire Webinars

Check out all of Prescient's webinars on wildfires and other topical areas, available on our website and YouTube channel. Or contact us to schedule a live presentation for your company.

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