T&D World Magazine
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Utility Wildfire Risk Management

What is risk? Risk is the combination of the probability of an event occurring and the consequence or expected loss.

The last two articles have been about power line-initiated wildfires and this article will build further on that topic, specifically with a focus on risk management.

What is risk? Risk is the combination of the probability of an event occurring and the consequence or expected loss.

As a utility, where do you start? What might be the expected loss of a wildfire event? In the first article in this series I provided costs for a number of wildfires. The amounts were in the hundreds of millions. Utility-related damages in the 2007 southern California fires were reported to be in the range of $2 billion. If you are looking to manage a risk it would not be advisable to minimize the risk.

Perhaps some insurance company data can provide guidance. A report by Lloyd’s[1] shows average economic losses due to wildfires which occurred in the USA between 1984 and 2013 to be $278 million per event. The Canadian costs are even higher at $323 million per event. Australia, which experiences a high frequency of wildfires, had costs of $88 million per event. I would suggest utilities in western North America use as a minimum $300 million as the expected loss. There may be reason, such as having a relatively high population in Wildland Urban Interface, to use a much higher expected loss. Colorado’s Waldo Canyon Fire resulted in insurable costs of $454 million. The Lloyd’s report indicates insurable losses are running at about 47% of total losses.

If wildfires have been a part of the natural landscape that you serve then you must recognize that it will continue so and in many areas, due to improved, timely fire suppression, the current fuel loading is higher than historical levels such that wildfires will be hotter and bigger.

Here are some questions for consideration.

Have there been any major wildfires in your part of the country? Do such fires occur fairly regularly or are they limited to drought conditions? If there is a wildfire in your area what is the value at risk; average; worst case? Is the risk of a power line initiated wildfire uniform across your service territory?

The answer to the latter question is no. Your forest service agencies will have information and likely mapping of fire risk which considers fuel types, fuel load and continuity of fuels. These agencies will also have information on the conditions which lead to the most intense fires, rapidly spreading fires, etc. There is typically a pattern. There is seasonality and usually winds from a certain direction. For example, here in Alberta the fire season starts in March and historically the worst month is May. For much of the month of May the ground cover consists of last year’s dry grasses. It also happens that in the spring of the year we commonly experience winds from the south and southeast, opposite to the prevailing winds, which make trees more susceptible to failure. Consequently, there should be a focused concern where there are communities to the north and northwest particularly if there are contiguous fingers of potential fuel entering the community. Another example is California where most of the southern half of the state has westerly prevailing winds. However, it is the easterly Santa Ana winds that are highly correlated to wildfire events. This suggests that you should divide your service territory geo-spatially for wildfire risk.

In addition to the questions of if a fire were to start here which direction is it likely to go and what is at risk, you might also ask such questions as, given fires can spread at rates of 14 mph, how much time might there be for evacuation orders, how long would it take emergency services to get there, would a fire cut off escape routes? Prioritize accordingly.

The other side of the equation is the likelihood of utility assets starting a wildfire. Again, if you don’t have the data, your local forest service personnel will have it. Due to the wider right of ways the number of fire starts arising from transmission will be low. I’ve seen numbers from 1% all the way to 11% of all wildfire ignitions being attributed to distribution systems. Let’s assume your forest service informs you, your utility was responsible for 1% of all wildfire starts and that number happened to be ten last year. What is the probability that a fire ignition will lead to that catastrophic wildfire where damages are in the hundreds of millions to billions of dollars? That is why I suggested that in North America, if you assume the average cost $300 million per fire it will lead to appropriate policy and action.

When you start tallying up all the wildfires attributable to your utility over a period of years you may tempted to discount the risk because none of those incidents turned into “the big one”. The fact that the highest fire risk days provide conditions that greatly increase the likelihood of tree failure and phase slap should give you pause. A Royal Commission report on Victorian Bushfires in 2009 found that while typically utilities account for 1-4% of all bushfire ignitions, across the three major, catastrophic bushfires the state has experienced, utilities were responsible for a disproportionately high number of ignitions. That provides confirmation when environmental conditions are such that wildfire risk is extreme coincides with when utility infrastructure will contribute most to fire starts. This should also inform you that if wildfires are only a risk during drought conditions that there should be a responsive mitigation plan.

Having divided your service territory based on the risk of a major wildfire you can design a strategy where mitigation intensity corresponds to the risk.

Then let’s look at the operational side. What have you done and what can you do to limit fire starts? What actions reduce the risk of molten metal falling to the ground? There are many paths to reducing the risk of phase slaps including shorter spans, wider cross arms, bundled conductor, using a coated conductor for the center phase, etc.  On high wildfire risk days do you set reclosers to single shot? An Australian Taskforce studying means of reducing bushfire risk found that the installation of automatic circuit reclosers and limiting the number of reclose functions on single phase lines based on the fire risk could reduce the risk 50%. A similar strategy for multi-phase lines was said to reduce fire ignition risk 70%.

One of the major risks for wildfire starts is trees falling into conductors, usually trees from outside the maintained right of way. I’ve repeatedly stated that I do not believe that it is economically feasible to eliminate this risk. However, it’s up to either each utility or a utility group to prove it. If you prove this by determining your tree exposure and demonstrating that the cost to undertake a walking Level 1 risk assessment of every tree that on failure could contact the line is not socially acceptable, you are still not done. From this should flow your chosen frequency and intensity of tree assessment patrols, responsive to variations in the wildfire risk across your service territory and an identification of what actions you can take to decrease the risk of fire ignition. Creating a database of arborist investigated tree-caused service interruptions will provide information on tree species vulnerabilities that can be used to further focus the identification of tree hazards.

It should be clear from the foregoing that assuming your tree contractor will manage your wildfire risk constitutes a foolhardy, if not reckless approach. Wildfire risk management needs to start at the very top of the utility organization. I’ve laid out questions and considerations. As you dig into this you will likely uncover more. Start now. That’s risk management.

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