Utility-caused wildfires

Utility-caused wildfires are a subsection of human-caused wildfires that are directly ignited by utilities, usually power lines. They are unplanned ignitions that can cause wild burns.^[1] Hotter and drier weather as a result of climate change has been liked to lower moisture content in vegetation, which, along with high tree mortality has created ideal wildfire conditions.^[2] Ignition often occurs when power lines come in contact with vegetation, whether elevated or on the ground.^[1]

Industry critics claim that the industry is not doing enough to mitigate these disasters.^[3]

Throughout the world, utilities, especially overhead power lines, have caused wildfires.^[4] In 2023, downed power lines sparked fires in Lahaina, Hawaii.^[5] In February 2024, on the Texas Panhandle, a decayed utility pole fell on dry grass and sparked the largest wildfire in state history.^[6] The 2018 Camp Fire, the deadliest and most destructive wildfire in California state history, was caused by a single faulty hook on a PG&E transmission line.^[7][8] In the notorious 2009 'Black Saturday' fires in Victoria, Australia fires sparked by power lines killed 159 people and caused more than $4 billion (AUS) dollars in damages.^[9] In Greece, on August 11th, a wooden electricity pillar with a loose cable held with a clothes hanger, sparked a fire that killed one woman and burned over 10,000 hectares.^[10]

Utility-cased wildfires can be started by a variety of factors.

The vast majority of transmission lines, over 70%, in the United States are outdated, and are near 25 years old.^[11] The average age for power transformers that power over 90% of the country is 40 years old.^[12] Power lines, whether old or new, are susceptible to storm damage, and, in 30% of cases, the power line does not automatically shut off.^[13] This can happen when the fallen line draws too little electric current to activate a fuse or circuit breaker.^[13] These high-impedance faults (HiZ) can cause high-energy, high-temperature arcing that can cause ignition.^[13]

Vegetation contact, and contact with foreign objects, such as trees, are leading causes of wildfires.^[1] In California, these factors were responsible for 35%, and 18%, respectively, of utility-related fires larger than 10 acres.^[1] Strong winds have been known to exacerbate these problems.^[1] Live wires can ignite dry vegetation and fuels, and fallen trees can result in downed lines.^[13]

Power lines are traditionally designed with significant clearance between conductors, this prevents them from contacting under normal operating conditions.^[14] Under poor conditions, line conductors can slap against one another; this causes high energy arcing, and, occasionally, small bits of molten metal (generally aluminum) are ejected.^[15] These ejected pieces of molten aluminum can ignite wildfires.^[13]

Many components, such as switches, transformers and insulators, contain thousands of complex circuits and parts.^[16] While often able to effectively provide service for decades, they do eventually fail.^[13] Occasionally, before complete failures, there is electric arcing and sparks that are too small to be detected by fail-safe sensors.^[13] These sparks and electric arcs can result in the ignition of vegetation or foreign objects.^[13]

Electric companies are investigating solutions such as burying power lines, installing sensors, and using software to monitor cables and automatically shut them off.^[3] In 2023 wildfire mitigation plans, Californian utility companies proposed over $9 billion to mitigate factors that cause wildfires.^[17]