P35.013: Overhead Line Ratings and Increased Power Flow

Apply Novel and Emerging Technologies: There are many providers in the grid-enhancing technologies space (GETs). EPRI routinely identifies the newest technologies and updates to existing technologies to increase member awareness. With the number of dynamic line rating (DLR) technologies increasing, it can be challenging to understand how to construct a pilot project, how to leverage a pilot to phase into operational use, and how to scope timelines and budgets. As part of 2026 efforts, the ratings team will provide recommendations based on lessons learned from multiple field evaluations with U.S. utilities.

Measure Emissivity and Absorptivity of Conductors from the Field: For line ratings, LiDAR modeling, and infrared (IR) inspection, it is important to have accurate numbers for conductor emissivity and absorptivity. These values are often assumed; however, EPRI has developed tests that can directly measure samples provided by utilities that are new or removed from service. In 2026, an update will be provided on test results and the potential cost/benefit tradeoffs of coatings from a ratings perspective.

Outline Benefits and Drawbacks of Increased Power Flow Scenarios: Utilities face many challenges in getting upgrades and new construction projects accepted. This task maps different upgrade scenarios to the challenge areas such as corona loss, electric and magnetic field (EMF), cyber security, etc., to aid engineers in identifying “least-regrets” options when considering upgrades to existing lines. A 2025 report addressed cyber security; 2026 research will focus on EMF challenges that occur based on different types of upgrade/uprating including the linkage between EMF and right-of-way width.

Document Uprating for Unique Scenarios: Data Centers, Storage, and Renewables: This task leverages existing EPRI learnings and upcomong utility projects to scope potential issues with unique capacity demands or unique upgrade types. While this can encompass a large range of challenges, the focus for 2026 will investigate the challenges of uprating existing lines to accomodate the high energy demand from data centers and AI.

Update The Platinum Book : The Increased Powerflow Guidebook (The Platinum Book) is updated annually and covers all aspects of uprating. The guide covers overhead lines, underground cables, substations, transformers, and the economics of staged upgrades. As part of this task, EPRI collates materials from published EPRI reports and industry standards for power flow such as IEEE, IEC, and CIGRE. For 2026, EPRI plans to update discussions of CIGRE TB 601 ensure sections for both twisted pair and coated conductor are brought up to date.

Document Grid-Enahancing Technologies Field Trials: Many utilities are working with EPRI to pilot an emerging technology, such as DLR sensors, to get hands-on expereince with the new tools and practices. EPRI collaborates with members to provide guidance, capture lessons learned, and provide data needed to do performance evaluations. The findings are brought back to members via presentations by the host utility, which are then added to the Transmission Resource Center.

Develop Guidance on Radial Conductor Temperatures and Ratings: Due to the fundamental properties of heat transfer, transmission conductors are hotter at the core than the outer surface. The increased core heat can lead to line sag being greater than projected in software tools. Following the plans shown in the 2025 report, lab testing and modeling will be performed during 2026.

Evaluate Weather Models and Forecasted Ratings: While historic weather data is readily available in many areas, what the forecasted weather conditions were is often not stored or available due to the extreme volumn of data to be managed. In 2026, the ratings team will gather forecasts looking forward for several weather models in multiple locations that can be verified against measurements in the field. This data can be used to help inform the uncertainty of short-term ambient adjusted rating (AAR) and DLR forecasting in future analysis once a statistically significant amount is collected.

Develop Guidance for Accurate LiDAR Measurement Technique: Errors in LiDAR data and line clearance models can contibute to false positives and false negatives when defining the need to upgrade the transmission system. Two recent reports have documented best practices for LiDAR data collection and understanding what options are available to mitigate clearance contraints based on cost and effectiveness. Ongoing study is underway to collect additional LiDAR data which can be validated by physical measurements, which will include performing LiDAR and photogammetry data collection at the EPRI Lenox, Massachusetts, lab using a range of technologies for data capture and analysis.

Document Utility Experience of Adoption of New Regulatory Requirements and Industry Standards: Utilities are required to adjust to ever-changing regulatory requirements and industry standards. This task seeks to provide workflows and best practices to help utilities navigate these changes efficiently and to capture the potential risk exposure of different adoption strategies. During 2026, this task will track utility experiences with adoption of FERC Order 881 in the United States and continue to catalog changes to exising capacity standards and regulations. Interim findings may be discussed at Task Force or similar meetings.

Provide Tools and Resources on the Transmission Resource Center: The following calculators, tools, result summaries, and references are planned to be available on the Line Ratings and Increased Power Flow Transmission Resource Center