Using Applied Science to Determine Facility Ratings

January 25, 2023

As the North American Electric Reliability Corporation (NERC) increases enforcement of FAC 008 guidelines, electric utilities need a cost-effective, safe, and accurate solution to demonstrate compliance. To meet these standards, electric utilities must identify the most limiting component within the entire Bulk Electric System (BES), including the conductors, jumpers, and risers. To determine for certain which component’s ampacity is most limited in the BES, all components must be examined. To accomplish this documentation, the first method NERC provides, and the most preferred by utilities, is to use manufacturers’ published data.

The Challenge

For components like transformers, switches, and circuit breakers, obtaining the data from the manufacturer to determine ampacity can be ascertained by reading the data plate affixed to the component. However, conductors are more challenging. To determine the manufacturer’s specifications, utilities need precise measurements of the conductor diameter, strand diameter, and the strand count. The known values allow a utility to, in combination with existing records, to identify the conductor codes listed in manufacturers’ tables.

Using precise measurements of the conductor’s diameter and cross-referencing to the manufacturer’s tables to deduce the codes, the corresponding ampacity can be determined. Measuring the conductors by hand is expensive and time-consuming, but finding that diameter to the necessary degree of precision without using a caliper was problematic before SAM engineered an alternate method.

A major utility on the east coast asked SAM if we could provide a faster, safer, and reliable solution. After considering and testing several alternative technology solutions, SAM conducted a pilot project with the client to demonstrate and test a few theories for an improved solution.

Originally planned using multiple bucket trucks or climbing crews with a digital caliper for direct measurement, the client was facing a five-year project to inspect the entire transmission system. Moreover, the cost of these traditional methods, as well as the need to de-energize and re-route power between substations, meant the estimated cost to complete was over $25 Million. The utility anticipated they would have additional challenges beyond cost and schedule. Safety and fall danger would be ever-present for crews. Some transmission lines couldn’t be accessed by heavy utility trucks in rugged terrain. Weather limitations would inevitably disrupt the planned schedule and resources required to complete the program. All these variables increased the risk for safety, schedule, and budget.

SAM’s Patent-Pending Solution

Working in close partnership with the client, both parties understood the challenge of finding an alternate solution would be an iterative process. Before SAM created this patent-pending process, our team explored different approaches, including terrestrial LiDAR and unmanned aircraft (drones). Bryan Fitzpatrick, who has decades of experience in GIS, unmanned systems, and remote sensing, wanted to explore a different approach. Bryan collaborated with SAM’s other scientists, including surveyors, photogrammetrists, and software developers. The team developed a remote sensing and indirect method utilizing close-range terrestrial photogrammetry to measure conductors in a reliable, accurate, and safer method. Bryan enhanced the data collection process by creating a GIS field form for cataloging uniform, georeferenced images to enable multiple, redundant measurements from various perspectives. The results were validated in the field and confirmed in the office for quality assurance in near real-time.

Once the accuracy of this method was tested and verified, we demonstrated the process to the client in a full-scale field collection mode. The client representatives asked SAM to independently measure conductors where known direct measurements using the caliper method were employed. Since the utility had reliable records available, we focused on verification rather than calculating the ampacity. However, when reliable records were not available, SAM delivered accurate ampacity using the same technique.

Exceptional Results

Since that first successful pilot project, our team has:

  • Collected over 10,000 measurements with proven accuracy and precision
  • Gained thousands of hours of on-site experience
  • Made data management and delivery more efficient with SAM InspectTM

We have realized several advantages of employing remote sensing to collect spatial data for the measurements. First and foremost, it is safer. No one has to climb or get into a bucket truck, so there is no risk of falling or working in close proximity to electrical lines. Since the crews collect the images at a distance using long focal length HD cameras outside the substation fence, there is no risk of contact with power lines, and the lines can stay energized. Our innovative solution reduces the number of people needed to one or two person crews. In addition, since all the equipment necessary fits in a single backpack, our crews can walk to the conductor locations in conditions that would be inaccessible for bucket trucks.

What has been most impressive about this method is how quickly the data can be collected. The only other way to get the same level of accuracy is to climb or use a bucket truck to directly measure the conductors with a caliper. In practice, we can collect as many as twenty measurements per day with a single person and a safety coordinator. The full turnaround and delivery to the client is often the same day or the next day after the images and observations are collected in the field using an indirect, remote sensing method.

SAM’s Advanced Technology group has integrated the processing to provide additional quality assurance (QA) into SAM InspectTM for repeatable, uniform measurements, utilizing computer vision and automated edge detection. Utilizing the customized GIS web forms, the data and documentation are available in near real-time for tracking the program’s status.

Impact for our Client

In the end, the client’s timeline was reduced from five years to two. Their cost savings can be measured in millions of dollars. And most importantly, all the safety issues with climbing were eliminated for this project. The methodology used in this project passed a Southeastern Electric Reliability Council (SERC) audit in the fall of 2022, permanently establishing that using SAM’s method meets the challenge of FAC 008 compliance.

To learn more about SAM’s approach to client solutions, and our innovative Applied Science for Facility Ratings, visit our webpage or contact Bryan Fitzpatrick directly at


Utility Engineering