When electrical energy flows through resistive heating coils, the electrical energy is converted to thermal energy. This is how electric appliances such as toasters, space heaters, and stovetops convert electricity into heat.
In a similar way, when a fault (an undesired current path) occurs on electric power lines, the electrical energy that is released is converted to thermal energy in the form of a spark. In areas with enough combustible material near power lines, the spark from a fault can easily ignite materials like dry leaves, tree branches, and other trimmings. Once ignited, these burning materials can quickly lead to a wildfire.
In this blog post, we’ll take a deeper look at what factors influence power line-based wildfires. We’ll also briefly discuss measures that can be taken to prevent power line-based wildfires, which will be addressed in more detail in future posts.
What Factors Increase the Likelihood of a Wildfire?
Not all faults cause wildfires, but they are much more likely when there is a confluence of a few simple factors. These include the size and duration of a fault, size and content of the combustibles, and the distance between the two. Let’s explore that more:
Energy released at a fault location: The energy released by the spark influences whether nearby vegetation ignites. When a fault occurs, electrical energy is converted to thermal energy. The result of this conversion can be either an enormous, instantaneous energy release in the form of an explosion, or a smaller, long duration energy release, much like a slow-burning fire. Typically, energy release is dependent on distance from the substation.
Fault duration: The duration of a fault is a function of protective relaying schemes, which are devices that detect faults and initiate isolation to clear them. Faults on extra high voltage transmission lines are cleared in less than 100 milliseconds. Faults on medium voltage, neighborhood distribution lines will be cleared in more than 2 seconds. Low current faults can persist for tens of seconds.
Type, size, and moisture content of nearby vegetation: The energy needed to ignite combustible materials is determined by the material type, its moisture content, and its thickness. Dry, thin materials, such as leaves and twigs, are easily ignited. Thick, damp materials, such as tree trunks, are resistant to ignition. Additionally, moisture content due to climate and seasonal weather patterns impacts ignition time.
Distance between an arcing fault and nearby vegetation: The distance between an arcing fault and dry vegetation depends on the cause of the fault and vegetation management. This distance often determines whether the fault will cause a wildfire.
Each of these risks on their own may not be enough to start a fire, but when combined, a fire is all but guaranteed when a fault occurs.
What Kind of Electrical Faults Cause Wildfires?
There are many ways that faults occur, from the mundane to the one-in-a-million. The following examples illustrate potential failures that may lead to a fault, as well as the approximate ignition times of dry vegetation in each scenario:
An insulator on an overhead distribution line shatters, causing a fault that leads to a high energy electrical arc. The distance between the arc and dry vegetation could be measured in feet. Depending on the size of the arc, it may or may not ignite nearby vegetation, which would begin to burn immediately if contact occurred.
A crossarm on a power pole breaks during a windstorm, and an energized power line falls to the ground. The distance between the power line and dry vegetation is minimal. If the line falls onto a pile of dry brush or a stand of leafy plants, the likelihood of the area catching fire is quite high.
A tree falls onto a power line during a windstorm. The tree is in contact with the power line, and is therefore directly exposed to the electrical current. Though trees are poor conductors, they will burn when in direct contact with electrical energy.
The Prescient Solution for Power Line Wildfires
With everything we’ve covered above, the solution for preventing power line wildfires should seem simple. Either build fault models that properly take those four variable factors into account, or resolve faults before they can cause fires, or both! Yet, traditional systems still do not fully accounted for these factors and their interdependence.
This is why Prescient has developed two innovations to tackle this problem that affects so many people. First, we’ve developed a comprehensive wildfire risk assessment and analysis methodology to significantly reduce the risk of wildfires caused by faulted power lines. The second is our our patented Solenoid Series Reactors (SSRx), which can help prevent wildfires by reducing fault current levels to safer ranges. And both of these solutions can be implemented within the existing grid as an upgrade, not an overhaul.
Using our thoroughly-developed methodology and technology, the ability to eliminate power lines as a cause of wildfires is within our reach. Check out our website for more information about our wildfire risk assessment tool and SSRx technology. Follow our blog or contact us to learn more about Prescient’s innovative wildfire risk reduction ideas.