Storm preparedness is a constant, year-long effort intended to mitigate or minimize issues related to severe weather. When seasons roll in that tend to bring intense storms, they test how resilient the grid can be in the face of extreme weather. Winter especially presents unique challenges with ice and snow, and the cold temperatures make it that much more important for customers’ power to stay on.

As utilities plan for severe weather, four key aspects to consider when analyzing their systems and determining their priorities include data, devices, design and dispatch.

Data

As utilities strategize for grid-hardening improvements, the best place to start is by analyzing system data. Data indicate which areas of the system are prone to outages and help utilities determine improvement priorities.

Many utilities rely on System Average Interruption Duration Index (SAIDI) and System Average Interruption Frequency Index (SAIFI) to assess system performance. While these are the most common reliability metrics utilities use globally, in many cases they exclude Major Event Days (MEDs). However, these are the very events utilities must better understand to prepare for storms.

In fact, the data show an urgent need to consider the impact of MEDs. Without MEDs, the U.S. linear trend line for SAIDI grew at a rate of approximately 2.2 minutes per year from 2013 through 2021. In contrast, the U.S. linear trend line for SAIDI with MEDs grew at a rate of 40.2 minutes per year. The gap between these two data sets is increasing at an alarming rate of 38 minutes each year.

Examining only SAIDI and SAIFI can also mask problems at the individual customer level. Because SAIDI and SAIFI are average customer experiences across the broader system, these calculations hide outliers in the data – the customers who experience outages more frequently than the average. With this in mind, focusing on granular, customer-centric metrics, such as Customers Experiencing Multiple Interruptions (CEMI), Customers Experiencing Multiple Momentaries (CEMM), and Customers Experiencing Long Interruption Durations (CELID) help utilities pinpoint areas on the grid that require more immediate attention.

Examining a range of data – starting from a systemwide analysis that includes MEDs and then drilling down into customer-specific metrics – provides utilities with a more holistic view of their system. This ultimately helps prioritize starting points for distribution upgrades that will enhance the customer experience.

Design

As utilities plan their initiatives to enhance resilience, reassessing system design can lead to foundational and long-lasting improvements. Sometimes, more ground-up changes can seem expensive or time-consuming. and that it is easier to rebuild the grid after each storm. However, with the increased frequency of severe storms, the cost of restoration efforts can exceed the cost of preemptive system redesigns. In the last decade, there has been a significant rise in MEDs whose restoration costs have totaled more than $1 billion.

Weighing these costs can make it easier to invest in grid-hardening solutions. This is especially true in the case of undergrounding lines. Often regarded as a more capital-intensive endeavor, the benefits of burying lines and minimizing exposure to severe weather can result in significant long-term savings by avoiding the cost of rebuilding overhead lines after storm damage.

Whether lines are overhead or underground, utilities can also consider changing radial circuits into looped configurations. These loop circuits involve connecting two or more circuits from different substations or generation sources, which creates a beneficial redundancy on the system. When a permanent fault occurs, utilities can isolate the issue and reroute power from an alternate source, restoring any customers who are not in the faulted segment.

Devices

One of the most important aspects of preparing for winter storms is choosing advanced technology that can mitigate and minimize issues. In winter, snowy, icy conditions can make roads too hazardous to drive and delay crews from getting into the field. That can result in customers waiting long times without power and living without essentials such as heat and clean water. But smart switching devices can be the first to respond and react quickly when storms arise.

Fault-testing technologies are a critical component of storm-preparedness plans. In winter storms, when wind and snow can bend tree branches, many issues are temporary in nature. Fault-testing devices can quickly and automatically restore service and keep these temporary faults from becoming permanent outages, ultimately avoiding unnecessary truck rolls. This not only saves costs but also protects line crews from risky working conditions during severe weather.

Fault-testing technologies can now be placed anywhere throughout the distribution system, providing end-to-end advanced protection from the substation to the grid edge. This also helps utilities segment the grid into smaller, more manageable portions and keep fewer customers from experiencing an outage. On looped circuits, advanced technologies can handle two-way power flow and automatically reroute power in the event of a permanent fault.

For communications-enhanced devices, one of the challenges during the peak of any storm can be the volume of messages devices transmit because of numerous events occurring on the grid. Wading through thousands of messages in a system with centralized intelligence can be time-consuming for utilities and make it difficult to distinguish which are the highest priorities. The value of distributed and localized intelligence on the grid is highlighted during these times because it enables devices to work in teams, analyze real-time system information and autonomously make restoration decisions. Not only does this relieve some work for utilities during high-pressure situations, but it restores power to customers in unfaulted areas within a matter of seconds.

Dispatch

Having advanced technology in key areas throughout the distribution system has a direct impact on the overall speed of restoration efforts. Because fault-testing devices keep temporary faults from becoming permanent outages, these devices save utilities from unnecessarily having to dispatch crews for issues that can be solved automatically.

This means the only outages that remain are for permanent issues, so utilities know when crews are dispatched, they will be going to locations that likely have damage and require more involved repair work. Ultimately, this helps create efficiency and ensures crews are dispatched to priority areas that need servicing.

Furthermore, when outages occur, the grid must be restored from the substation to the grid edge, in that order—so when crews are dispatched, they work from the substation out. Subsequently, this leaves the grid edge as the last area to be restored, often resulting in prolonged outages for customers at the end of the line.

Advanced end-to-end lateral protection decreases the need to dispatch crews to the grid edge. By avoiding these truck rolls, utilities can save crews from avoidable work during a period of intensive restoration efforts and ultimately reduce the overall time it takes to bring power back to all customers after a storm.

As winter weather sets in, extreme conditions reinforce the importance of storm preparedness and grid resilience. It is a fitting time to examine holistic system data and advance preparedness planning. Considering system design and innovative devices can help mitigate and minimize outages in times when it matters most. Ultimately, this ensures the efficient dispatch of crews, reduces overall restoration time and keeps power on for customers, even during the storm.