In 2015, Pedernales Electric Cooperative was hit with massive rainfall and flooding that interrupted service in large parts of its territory, which stretches across 8,100 square miles in the Texas Hill Country.
In a stroke of bad luck, it was hit with more of the same just a year later.
But the second time around, some high-tech system-hardening helped the nation’s largest electric co-op, with more than 300,000 accounts, recover more quickly.
Eric Bitzko, Pedernales’s technical services supervisor, says a key part of that hardening was a new approach the co-op took to its vegetation-management regimen.
“The tree damage incurred during the  flood solidified the need to take a more aggressive approach to the preventative trimming programs we have in place,” Bitzko says. “By improving the strategic processes with which we decide what areas to trim, we were able to better prepare ourselves for coming storms as well as flooding.”
In 2015, after the immediate priority of restoring power had been dealt with, Pedernales vegetation management personnel analyzed system damage data to improve proactive maintenance.
The analysis would evolve beyond simply tracking vegetation locations and line proximities to looking at tree varieties, their growth rates, and their health to develop a predictive maintenance model that would deal with vegetation encroachment before it became a problem.
The co-op had just begun experimenting with drone systems when the first flood hit, and so it also committed to an unmanned aerial vehicle (UAV) program to improve line inspection, data collection, and system repair. New data management software allowed overlays of historical and current information gathered through aerial and on-the-ground inspection by the co-op’s arborists and other analysts.
The approach continues to grow in sophistication. A contractor provides 3D mapping using LIDAR, which uses laser light to measure objects and distances, but the co-op is looking at acquiring its own LIDAR sensor for use with its drone by the end of the year. The data would be shared by vegetation, engineering, and geographic information system (GIS) staff, Bitzko says.
They’re also planning to purchase an NDVI (Normalized Difference Vegetation Index) sensor, which bounces both infrared and red light off the leaves of plants.
“By cross indexing those two, you can tell the amount of chlorophyll it’s giving off, and from that, you can tell the health of the plant,” Bitzko says.
Knowing a plant’s health allows arborists to provide predictive analysis on the likelihood of failure in a storm or over time, he notes. Integrated with other data, such information can help hone vegetation management schedules, allowing the co-op to prioritize at-risk areas before failure occurs.
“The density of the data that comes back gives us the opportunity to really look at things with a new level of accuracy,” Bitzko says. “Not only are we going to be able to tell the distance from trees to the line, we can tell if they’re diseased, dying, or dead.”
Pedernales uses PowerLine Inspector software to handle the drone data. The platform can integrate GIS mapping, high-resolution images and graphics, infrared pictures, and LIDAR shape files.
“We’re getting much more and better data coming back to us and better platforms to manage that data,” Bitzko says. “So we’re able to make better decisions where we allocate our assets for vegetation management and other system maintenance.”
Those decisions can play a significant role in improving system reliability. Davey Resource Group (NRECA Associate Member), a wholly owned subsidiary of the Davey Tree Expert Company, conducted an analysis of outages at two large North American electric suppliers and found that over a five-year period, trees and other vegetation accounted for 20 percent of customer minutes of interruption (CMI).
Before Pedernales began leveraging new technology to improve its vegetation management, 6 percent of the co-op’s outages were tree related. That number has fallen to 3.5 percent.
“I think once we fully incorporate LIDAR and NDVI, you’re going to see vegetation be less than 1 percent of outages,” Bitzko says.
The fuller picture of vegetation that today’s data-capturing and analytics tools provide allows for planning that can significantly improve a system’s resilience, says Jack McCabe, Davey Resource Group’s vice president and general manager of utility vegetation management.
“Some tree varieties tend to lose branches. Other species are much more prone to complete failure,” McCabe says. “By monitoring which trees are causing problems and how, by using the technology to create a better awareness of what’s really happening on your system, you’re able to make longer-term plans about converting the vegetation around your facilities to things that are going to be more desirable, require less maintenance, and cause fewer outages.”
Strengthening systems against storms has been a motivation to improve vegetation management for several co-ops, particularly in response to the severe hurricanes that have hit the East and Gulf coasts in recent years, says Mike Mittiga, vice president of utility operations, Atlantic for The Davey Tree Expert Company.
“On the heels of those storms over the last decade, we’ve seen more aggressive vegetation management practices,” Mittiga says. “You’re seeing more awareness of the need for storm preparation, working to help systems survive … trying to mitigate proactively, rather than [just] trying to put the wires back in the air afterwards.”
These efforts include more attention to the work that has been part of vegetation management since cooperatives stuck their first poles in the ground: trimming and removing trees to provide greater line clearance, using herbicides to keep underbrush controlled and rights-of-way accessible, and working with property owners to make sure they understand the importance of keeping lines clear.
But today’s technology plays an important role in the process, he adds, with better data and analytics making for more efficient planning and resource management. Both Mittiga and Bitzko note that the benefits are extended when combined with other technology, such as ultrasonic and infrared inspections that can identify failing switchgear, transformers, or other components.
When integrated, the data can provide a holistic view of system health that can greatly improve reliability.
“We’re making huge gains in system hardening and reliability just from taking the data and sharing it through all the different departments that can use it,” Bitzko says.
The benefits sometimes extend into the broader cooperative community. When Hurricane Harvey struck part of the Pedernales service territory in 2017, Bitzko says, the cooperative was able to get back on its feet more quickly because of the new technologies and proactive measures. That meant crews could help other co-ops along the coast that faced more severe damage.
He expects the use of sophisticated sensors and analytic software for vegetation management to spread in the coming years.
“What you’re going to see is LIDAR and NDVI are going to be a lot more commonplace,” Bitzko says, “and you’re going to be able to accurately take that data and integrate it into your workflow and decision-making process. Whether it’s three or five or seven years down the road, it’s going to make a big difference.”