There has been much discussion recently about the need for resiliency in the electrical grid, and specifically, why the customer view matters. Natural disasters have caused numerous power grid failures this year — from the California wildfires impacting the grid, to Hurricane Ida devastating Louisiana and causing flooding along the East Coast. The entire country is under threat as severe weather impacts electrical service. And the problems are only expected to worsen as climate change continues to reshape seasonal weather patterns.
As these conversations are happening, two distinct needs are being observed: the need for electrical grid reliability, and the need for grid resiliency. How these are measured and viewed will inform how they are improved in the years to come. Most importantly, however, is the need to keep customer experience at the heart of improvement efforts.
Understanding the differences between electrical grid reliability and resiliency
When you flip on a light switch, you generally expect the light to turn on, especially during fair weather conditions. Electrical grid reliability is measured by how well the system works on a daily basis. It factors in some power outages but excludes the major events that leave customers without electricity for prolonged periods, such as after a major storm. The two most common industry metrics for grid reliability are the System Average Interruption Duration Index (SAIDI), which counts the minutes that the average customer was without power over the course of the year, and the System Average Interruption Frequency Index (SAIFI), which measures the actual number of outages experienced by customers during the year.
More frequently than not, the SAIFI and SAIDI statistics exclude major events, as they are excluding events, as defined by IEEE 1366 or state defined exclusion criteria, that are outside of the utility’s control. What this means is that when we normally discuss SAIFI, SAIDI, and other traditional metrics, we need to be careful about which one we are referring to, either the all-inclusive set, or the set that excludes allowed events, and thus under-reports customer miseries associated with the excluded events.
In fact, studies have shown that most customers have only a two-day tolerance for being without power, and recent rulings and proposed legislation such as the New York Senate Bill S4824A allow for utility fines when customers are out of service for more than three days. Indeed, this is a high bar in areas where hurricanes have regularly left customers without power for eight days or more over the last few years. Additionally, no matter how good a utility’s reliability is, being without power for an extended period of time is cemented in a customer’s mind for years to come, often trumping otherwise good customer satisfaction scores.
For these reasons, the customers’ perspectives, and their miseries, should be accounted for in discussions about how well their utilities are serving their needs. Resiliency, rather than reliability, should be looked at with the perspective of the customer in mind. Resiliency should consider the grid’s ability to mitigate and prevent damage, as well as the utility’s ability to restore power to customers and communities afterward. It should address how quickly customers are restored, how quickly community centers are restored, and how utilities are working to ensure that fewer customers are impacted for any given weather event (e.g., as they modernize and harden their grid).
Resiliency is not easily measured or boiled down to one or more metrics. Knowing how many outages a utility has suffered, and how many minutes power was out is only part of the picture. How did customers’ comfort levels change during these outages, and how long were they inconvenienced or forced to take extraordinary measures to get through the event? What can be done to not only sustain the grid, but more importantly, to sustain people’s living requirements?
Customer experience curves as a proxy measure for resiliency
A utility can be reliable but not as resilient as needed. Having excellent blue-sky performance does not automatically mean the utility excels at major event restorations. One potential way to help us understand the difference between reliability and resiliency is looking at the performance of the utilities during the times when their performance is excluded from the annual reporting criteria. The faster the utility can restore service, the more resilient they are. Similarly, for those instances of failure, fewer customers impacted is another good indication of a resilient utility. Visually, this can be understood by analyzing the restoration curves for major events, where both the impact of the given weather event is evident, as well as the speed of restorations.
The storm restoration curve perspective of looking at a utility’s resiliency can represent how effective they are at preventing outages from occurring (comparing peak outage levels for the same storms), and how quick they are at restoring power (looking both at the overall duration of the storm restoration efforts, as well as how many customers they can restore in a given unit of time).
We can further divide the typical restoration curve into three zones — assessment and prioritization for immediate restoration, active restoration, and tail-end restoration efforts.
There are different strategies utilities can follow to prioritize how they wish to address the issues faced in these zones.
A methodology to prioritize and execute grid resiliency efforts
Considering the customer perspective when planning electrical grid resiliency improvements has economic and societal benefits. Hardening the electrical grid, which involves fortifying the system and upgrading infrastructure to better prepare for emergencies, improves overall function and reduces downtime. Crews don’t have to be sent out to make costly, time-intensive repairs after every storm, and customers have uninterrupted power when they need it.
Power grid resiliency also supports climate action plans and initiatives to limit and mitigate fire and ignition sources, damage from rising water levels, and prepare for future electrification requirements such as electric vehicle charging, energy storage, and others. Basic maintenance also includes managing excessive vegetation and taking care of diseased and damaged trees, which prevents damage to power lines as a result of downed limbs while improving the overall health of local ecology.
Ultimately, grid resiliency efforts need to produce better, safer power distribution for customers. Therefore, when prioritizing steps to improve resiliency, utility leaders need to consider how customers will be impacted by each potential action. With this in mind, we’ve broken down several key considerations to help power providers and utilities prioritize and execute resiliency efforts.
Implementing a prioritization model for energy grid resilience
To execute on the methodology listed above, utilities need to build a prioritization model which considers both quantitative and qualitative data to identify and prioritize which upgrades to work on first. This can include hardening infrastructure in areas of high fire hazard, those prone to water intrusion, and other assets vulnerable to any type of extreme weather events.
When there is a need to pursue more aggressive long-term resiliency planning in addition to conventional reliability hardening measures, this model will help leaders find out which assets are most vulnerable to focus on first. Having sight of and predicting the economic and societal impacts of various grid upgrade projects as well as integrating other key strategies is necessary to plot the best course forward and build a more resilient power grid. As extreme weather events become the norm, the need for resiliency is more important than ever to ensure safe and effective power distribution.
Gregg Edeson is PA Consulting’s utility reliability and resiliency lead. Wei Du is an energy and utilities expert with PA Consulting