Field Guides: EPRI’s field guides give personnel access to in-service inspection guidance for dozens of transmission line components, with the convenience of remote access. As transmission line research advances, the knowledge related to inspection and assessment of various assets is identified and developed into a mobile field guide that provides a media-rich transfer of information that includes the asset condition and actions to take. In 2025, EPRI intends to update the media content and update conditions assessment to reflect the most recent learnings and improve the accessibility of the guides.

Evaluation of New and Emerging Inspection Technologies: This task focuses on evaluating inspection technologies or methodologies and helping users understand how to use them efficiently and effectively. This project aims to keep a pulse on new and emerging technologies for inspection, assessment, and maintenance of overhead transmission lines. These technologies will be shared with the funding members and possibly evaluated for their efficacy.

Unmanned Aerial Vehicle (UAV) Inspections: Large strides have been made in the hardware and software development of UAVs and their corresponding accessories. In 2025, the goal of this task is to summarize the use cases of UAV inspection techniques for overhead transmission and perform laboratory testing of emerging drone capabilities. Light Detection and Ranging (LiDAR) Inspections: This task aims to evaluate the state of LiDAR technology and its application in inspecting overhead transmission lines.

Investigation into the Feasibility of an Asset Performance Model (APM): This task focuses on analyzing the implementation of an APM. There exist many methods for analyzing and documenting the performance of overhead transmission assets. In 2025, EPRI intends to perform research on the current methodologies for scrutinizing asset performance and explore potential best practices for the industry.

All Aluminum Conductor (AAC), Aluminum Conductor Alloy Reinforced (ACAR) Conductor, and All Aluminum Alloy Conductor Corrosion: Aluminum strand degradation may occur because of intergranular corrosion and manifests itself as exfoliation, resulting in a brittle aluminum strand. Preliminary research has shown that a comparison of tensile strength and torsional strength may provide a reliable metric for determining the remaining service life of an all-aluminum conductor. The corrosion resistance of the different aluminum alloys used in overhead conductor is also intended to be studied in this task. The goal of this task is to understand and categorize the severity of the degradation in terms of this new metric, correlate that metric with service life, and use that information to select where all-aluminum conductor performance will be maximized.

Conductor Inspection Tools: EPRI intends to continue the development of its own conductor inspection technology based on spectroscopy and a 2D profiler. The current version of the C-Corr is drone based to allow more flexibility in the inspection process. In parallel, EPRI intends to monitor for new and emerging conductor corrosion inspection technologies that can be of potential interest for its members.

Evaluation of New Conductor Grease: Greased conductors have been found in laboratory experiments to offer significantly more corrosion protection than non-greased conductors. Ongoing research is exploring the advantages and limitations of using greased conductors as well as new and emerging grease products. EPRI intends to continue to investigate a new grease that chemically bonds to the galvanizing and becomes a stable patina to resist corrosion. The benefit of this bond to the galvanizing is that the grease dropping point is eliminated and higher operating temperatures may be implemented without losing the corrosion protection.

Atmospheric Corrosivity Maps for Conductor Modeling: EPRI intends to continue its development of atmospheric corrosion maps to allow engineers to model the degradation rates of various metals and overhead components based on the surrounding environment or geographic locations. The vision of use is for utilities to identify locations where their conductors, shield wires, and hardware are at risk because of corrosion and allow optimizing of inspection program and reconductoring projects.

Condition Assessment of In-Service Conductors or Conductor Failure: EPRI intends to continue adding results from conductor health assessments into a report to help utilities understand how conductors degrade and the environments that caused the degradation. This task produces a living document covering the initiation mechanisms specific to each construction material and type of conductor. It provides guidance on selecting the appropriate test techniques to quantify each sensitivity and identify or eliminate that as a cause of failure. The realized value to the utility is that an understanding of what causes conductor degradation in the field may be considered in the design and installation.

Selection and Application of Conductors for Severe Service Environments: EPRI intends to develop an end-of-life calculator that incorporates the effects of conductor attributes and the surrounding environment corrosivity on the conductor’s durability. This information may be used by a utility to prioritize conductor inspection and select the right conductor for a specific location.

Corrosion Management Reference Book (The Rust Book): This reference book contains asset management information for inspection, assessment, mitigation, and remediation of corrosion on transmission lines. The guidebook contains the fundamentals of corrosion, guidance for inspection and assessment, and a description of mitigation methods that align with the environment. Future sections are intended to be developed to support underground transmission, substations, and distribution.

Advanced Conductors Corrosion Study: This task aims to evaluate the corrosion degradation of advanced conductors, reviewing the materials used in the construction of the conductor. The components used in the construction are then exposed to environmental factors to study the response. Once the components have been evaluated, the assembly is aged in a simulated service environment to study the performance and potential failure mode because of corrosion.

Engineered Backfills and Conductive Concrete: Findings to date are that conductivity and compressive strength are inversely related when the water-to-cement ratio is varied. This new learning allows both the grounding engineer and the structural engineer to find a compromise for cost and performance in the design. In 2025, the project intends to initiate aging of concrete cylinders that contain a steel test coupon, which represents the rebar, and then measure the corrosion rate at specific time intervals. The corrosion rate measurements are intended to be validated by removing the coupons and determining mass loss through gravimetry.

Corrosion Due to Stray Direct and Circulating Alternating Currents: This task explores the methods to screen and quantify the effects of stray direct currents and circulating alternating currents. Once the source and magnitude of the currents are known, a mitigation strategy may be identified that is compatible with the environment. In 2025, this task aims to develop new methods to measure corrosion currents and evaluate them for accuracy and ease of use, which may provide utilities with a simple and effective method to understand the impact.

Corrosion Management Guidebook: This reference book contains asset management information for inspection, assessment, mitigation, and remediation of corrosion on transmission lines. The guidebook contains the fundamentals of corrosion, guidance for inspection and assessment, and information on mitigation methods that align with the environment. A new chapter focused on concrete management guidelines was added in 2023, and a section on engineered and wood pole management was added in 2024. In 2025, this task aims to add content on the development and operation of the corrosion monitoring system to provide an understanding of how dynamic stray current events may be understood and quantified.

Corrosion Due to the Operation of HVDC Transmission Systems: Severe corrosion may result from the operation of high-voltage direct current (HVDC) transmission systems. This task intends to evaluate the interaction between HVDC lines and other utilities or commercial activities within the same right of way. The findings may allow determination of the best practices and procedures for reducing and mitigating the risk of corrosion. Areas of future growth and gaps for corrosion inspection and corrective actions have been identified in renewables such as offshore wind and offshore drilling. The project plans to review how renewable generation may affect corrosion rates at the transmission line interconnect in 2025.

Corrosion and Corrosion Control Workshop: This workshop is held every two years; it provides both theory and practical experience in understanding corrosion and how to assess and implement various types of corrosion control technologies. A workshop is planned for 2025 at the EPRI Charlotte campus to support asset managers, engineers, maintenance managers, and field crews in gaining practical knowledge for extending the service life of their assets.

Modeling Asset Degradation Through an Understanding of Soil Corrosivity: Environmental models and maps are being developed by harvesting soils at utility service territories and cross-referenced to the U.S. Department of Agriculture (USDA) soil series. This allows a corrosion rate for steel, zinc, and copper to be understood and applied to engineering design and operation and maintenance (O&M) operations at each structure location within a service territory.

Ongoing research is focused on bringing soil chemistry, texture, and corrosion rates into a general model for the USDA soil series. This research is intended to support guidelines for screening a service territory for “at-risk” structures and allow asset managers to make life-cycle decisions. The goal for 2025 is to increase map coverage and data resolution, with a focus on additional factors such as topography and the impact of surface and ground water.

New and Emerging Coating Systems for Atmospheric, Subgrade, and Marine Service: Each year, EPRI evaluates new and emerging coating systems for addition to the coating library. Many of these coating systems are designed for application in a manufacturing facility, but many are also designed for repairs in the field. The value that utilities receive from this task is the ability to select a coating system for optimal performance in their service territory.

New coating formulations are intended to be added to the coating system library in 2025, with a focus on intumescent fire protection coatings. This research supports the development of a coating selection and web application, allowing utilities to understand coating system performance in their service territory and identify a coating system that is compatible with their service territory based on the environment. It will reside on the subscriber website for access by project funders.

Understanding the Degradation of Anchors and Recommended Inspection Methods: This task explores the mode of failure for various anchor designs and how to determine if that anchor is at risk because of stray or circulating current corrosion. This task is based on new learning that will allow utilities to understand why anchor systems degrade and how to mitigate that corrosion.

The project plans to focus on understanding circulating and stray currents in high soil resistivity and high ground water levels in 2025. This research is intended to support the development of inspection, assessment, and mitigation guidelines for transmission line structures.

Determining Key Locations for Lattice Structure Corrosion: Crevice corrosion requires specific environmental conditions to occur in bolt details in soil exposure. Grillage connections to towers are a primary location, and this task is focused on quantifying the environmental factors and resulting corrosion rates. Understanding these conditions will allow application of the appropriate corrosion control measures in line design guidelines. The project plans on using the results from the first set of experiments to continue literature reviews and formulate new methodologies for testing in 2025.

Cathodic Protection Design, Installation, and Maintenance: This application is designed to assist utilities in designing cathodic protection systems for their requirements and provide guidance on installation and maintenance operations. The goal is to migrate the information into a cathodic protection design web app in 2025.

Evaluation of Connector Inspection Technologies. Various connector inspection technologies are expected to be identified, reviewed, and evaluated. EPRI intends to provide updates on different digital radiography devices available for traditional conductors and connectors. In 2025, EPRI aims to include updates on new and emerging inspection techniques as well as a catalog of failure mechanisms for traditional conductors and connectors to the Connector Inspection Guide.

Analysis of Failed or Removed-from-Service Connectors. Connectors that have failed in service or have been removed from service are evaluated in a laboratory to better understand aging and failure modes. Tests may include resistance measurements, thermal responses, infrared (IR) measurements, radiographic analysis, and dissection or mechanical tensile testing to failure. EPRI aims to include and track this information in a database to identify trends in the industry. In 2025, EPRI plans to update the report Evaluation of Aged Connectors.

Degradation of Single-Stage Compression Fittings at 93°C. EPRI has provided guidelines to assist utilities with the inspection and management of line connectors based on previous EPRI empirical testing of traditional conductors and connectors. In 2025, EPRI intends to start testing newly developed single-stage compression fittings for traditional conductors operating at 93°C to understand their performance and degradation mechanisms over a simulated 40-year lifespan.

Guidelines for Management of Connectors. Guidelines help utilities manage connectors through their lifetime, including scheduling of inspections, selection inspection methods, data collection and use, prioritizing, and mitigation strategies. In 202 5, additional acceptance criteria for the various inspection techniques are intended to be included in the published Compression Connector Management Guide.

Effects of Joint Compound Application in Overhead Transmission Compression Connector Performance. Accelerated aging at 93°C of test lines assembled with different amounts of joint compound is to be continued into 2026 to evaluate the impact of joint compound on the thermal and electrical performance of two-stage compression connectors. In 2025, thermal mechanical aging is anticipated to continue on two-stage compression fittings with different amounts of joint compound applied, and data will be shared with the funding members at task force meetings.

Degradation of T-tap Connectors and Installation and Inspection Guidance. This task seeks to outline the types of t-tap connectors, possible degradation mechanisms, and inspection methods. Case studies from field evaluations will be provided to share lessons learned with the funding members.

Composite Structures Application Guide Update. Over the last several years, EPRI has been producing an application guide for composite structures built on research performed in this project. The guide covers topics such as composite pole and crossarm manufacturing, degradation modes, installation, and maintenance. In 2025, EPRI plans to issue an update to this guide to incorporate highlights from recent research into composite structures. Updates may include the creation of design recommendations for composite structures and results from artificial aging tests on composite materials.

Full-Scale Mechanical Testing of Ductile Iron Utility Poles There exists no industry standard methodology to quantify the mechanical capacity of ductile iron utility poles. Although some manufacturer testing has been completed, engineers must have a high degree of confidence in the mechanical strength of ductile iron poles to ensure that they meet the appropriate loading criteria. EPRI plans to initiate a series of full-scale loading to failure tests on ductile iron poles to understand the reliability of published strength values, variability in strength, and failure modes.

Ductile Iron Structure Application Guide Update. In parallel to performing tests on ductile iron poles, EPRI is undergoing a multi-year effort to develop an application guide for utility engineers. In 2025, an update to this guide will be produced, incorporating findings from full-scale mechanical tests. Other additions may include an overview of current ductile iron pole manufacturers and design recommendations.

Optimal Pole Material Selection Guide Update. In partnership with P35.007, EPRI’s Line Design research project, a guide is being produced to compare the five primary materials used for utility structures: wood, steel, concrete, fiber-reinforced plastic (FRP) composites, and ductile iron. In 2025, EPRI aims to produce representative structural designs of all five materials under various loading conditions. This will help engineers make more informed decisions to select an optimal pole material for their application.

Access to Information Exchange Sessions on Ductile Iron and Composite Structures. In 2025, EPRI plans to host two online information exchange sessions covering ductile iron and composite structures. The goals of these sessions will be to encourage inter-utility dialog on the use of these materials and help engineers network with peers in the industry. Session content may include utility application case studies of ductile iron and composite structures, perspectives from structure manufacturers, and identification of research priorities for utilities.

Improved Lightning Shielding Failure Approach for Tall Structures. Since the introduction of ultra-high voltage (UHV) lines with tall support structures, utilities have experienced a significantly high number of lightning outages caused by shielding failures. The shielding failures in most cases are not predicted by the traditional calculation methods. In 2025, this task aims to evaluate the new simplified Rizk model against documented cases of shielding failures and report the findings.

Electromagnetic Surveys to Estimate Soil Resistivity. Unanticipated grounding electrode improvements are both costly and time-consuming when constructing a new transmission line. A good estimation of the soil resistivity along the line during the planning phase of a project is necessary to correctly select a ground electrode design. Advances in electromagnetic surveying could speed the process dramatically compared to Wenner surveys, more typically used by utilities. In 2025, this task intends to review different electromagnetic technical solutions from aerial to terrestrial to estimate the soil resistivity.

Lightning Impulse Performance of Brace Post Insulators. Lightning impulse data for dimensioning polymer insulators are based on tests performed on porcelain insulator strings installed in the 1960s. This information is not always applicable because polymer insulators are applied in several different configurations today, and the flashover value for the same insulator length may be different. In 2025, this task intends to focus on brace post insulators and to test different installation arrangements that could impact their lightning impulse strength.

Lightning and Grounding Reference Book (The Gray Book). EPRI has amassed a large knowledge base of lightning and grounding information. This task intends to develop a single resource that consolidates previous EPRI lightning and grounding research. The reference material enables utilities to quickly find information and relevant tools to improve the outage performance of their overhead lines. Some of those tools are hosted on EPRI’s transmission.epri.com site to help utilities compare technical solutions and to provide additional training materials. The reference book (available in electronic format) is updated with new information each year.

Transmission Line Workstation—Generation 2 (TLW-Gen2): Lightning Performance and Power Frequency Grounding Modules. New version of the Lightning Performance Analysis Module (TFlash). This is a software module for determining the lightning performance of lines that is part of TLW-Gen2. This task intends to update this tool with the latest research results to improve and expand its modeling capabilities. Participants in this project get access to the Lightning Performance module of TLW-Gen2.
Updating the Power Frequency Grounding Module. This is a software module for calculating fault current division and circulating currents on transmission lines. This task intends to update the software to expand its capabilities. Participants in this project get access to the Power Frequency Grounding module of TLW-Gen2.

EPRI Transmission Line Reference Book: Conductor and Structure Motion. EPRI intends to expand the initial research into the efficacy of anti-vibration fasteners to include more systems and additional testing to validate results. In addition, the project aims to improve the guidance on design for magnetic attraction between sub-conductors in a bundle in 2025.

Optimal Pole Material Selection Guide . In partnership with P35.005, Ductile Iron and Composite Structures Project, EPRI intends to publish a new guide comparing the five primary materials used for utility structures: wood, steel, concrete, fiber-reinforced polymer (FRP) composites, and ductile iron. In 2025, EPRI aims to produce representative structural designs of all five materials under various loading conditions. This will help engineers make more informed decisions to select an optimal pole material for their application.

Overhead Line Design Guide: Extra-High-Voltage Line Design Checklist. Last produced in 2018, EPRI’s AC Overhead Line Design Guide helps engineers navigate the multi-faceted tasks associated with transmission line design. In 2025, EPRI aims to update the guide with an extra-high-voltage (EHV) line design checklist. This addition will serve as a roadmap for engineers unfamiliar with EHV design and will include topics such as phase geometry design, corona, audible noise, and minimum approach distance (MAD) calculations.

Safe Design Tension of ACSS Conductor. Determining a safe conductor tension is a multi-faceted problem that requires understanding of the self-damping performance and fretting fatigue endurance of a conductor. This new initiative, which is a collaborative effort with P35.015, aims to help solve this problem for aluminum conductor steel supported (ACSS) conductor because its self-damping and fatigue properties vary significantly from those of aluminum conductor steel reinforced (ACSR) conductor.

Online Training for Orange Book: EPRI aims to start the production of selected training modules covering key chapters in the Orange Book. These events will be held in conjunction with EPRIU4T.

Online Training/Workshop: Calculation of Overhead Line Loads: Training on the fundamentals for the quantification of overhead line design loads will be hosted in conjunction with EPRIU4T, with reference to National Electric Safety Code (NESC) and American Society of Civil Engineers (ASCE) recommendations.

Transmission Line Workstation Gen 2: Design Modules Vibration (TLW-Gen2) v13.0: The EPRI software tool was developed to facilitate engineers in evaluating different design options effectively. Algorithms in some of the design programs may require updating based on EPRI research. Updating of this software may also be required to improve user features, add new functionalities, or be compatible with other industry software used by the design engineers.

Practical Determination of Dynamic Load Impact Factors. EPRI has been conducting ongoing fundamental research into quantifying loads experienced by structures during broken wire events. These loads are then translated into dynamic impact load factors used by engineers to design high-resiliency structures. In 2025, EPRI aims to conclude this research effort by developing a procedure to apply dynamic impact load factors in the transmission design process.

Failure Event Loading Workshop. Engineers looking to enhance the resiliency of their systems may incorporate failure event load cases into the design process. Not all failure events are identical, however, because broken conductors affect a system far differently than cascading structures. This workshop is planned to present EPRI’s recommendations on the subject built on research into broken conductor and cascading events. The workshop aims to enhance the knowledge of transmission engineers at all experience levels.

Learning from Failure: Case Studies in Improved Engineering. With every structural or mechanical failure event, there is a potentially valuable lesson to be learned by line design engineers. The continued increase in failure events means that there is no shortage of potential events from which valuable design lessons may be extracted. Very often the events leading to failure are multi-dimensional and not the result of a single point of discrepancy. When the root causes and possible preventive actions from these events are documented, they can teach engineers how to become better designers. In 2025, EPRI aims to add multiple case studies to its current guide on documented failures related to how structures have failed in the past and how future generations of engineers may use this information to achieve more resilient designs.

Quantification of Transverse Cascading Loads. Although EPRI and other institutions in the transmission industry have conducted research into longitudinal cascading events, transverse cascading loads remain a knowledge gap. EPRI aims to build and operate a transverse cascading test line to quantify loads experienced by structures during these events and ultimately help engineers design against them. In 2025, EPRI aims to design a test line and develop a research methodology for transverse cascades to then execute upon in subsequent years.

Impact of Soil Investigation Frequency on Design Reliability. Engineering practices with regard to soil investigation frequency for transmission line projects vary widely. Every foundation that is designed and installed without an adequate soil investigation presents risk to a utility. In 2025, EPRI aims to complete a study to correlate the impact of soil investigation frequency on foundation design reliability.

Rapid Response Emergency Tower. The Rapid Response Emergency Tower is performed under EPRI’s Technology Innovation Program, in support of P35.008. In 2025, EPRI aims to demonstrate the operation of the completed emergency restoration system and to document improvements to the prototype.

Live Working Reference Guide (Tan Book): This is a comprehensive technical resource on live working, including deenergized work, North American and international standards, and fundamentals and principles related to live working tools, equipment, methods, and training resources. The guide is designed to be used by utility personnel engaged in all aspects of live work, from transmission maintenance managers and supervisors to line workers. A new version of the guide is published each year, including new or revised content based on input from project members.

Live Working Rope Testing and Evaluation: Dielectric ropes are used in live work along with rigid insulating tools. Currently available live working ropes have several advantages and disadvantages. An updated research plan intends to evaluate the electrical and mechanical performance of new rope designs coming to market as well as aged ropes. Testing has been performed according to existing standards but also based on “real-world” conditions. In 2025, EPRI intends to publish a technical update detailing results of electrical testing of synthetic ropes used in stringing operations in “real-world” conditions, such as exposure to fog.

Evaluation of Portable Rope Testing Devices: Devices known as dielectric rope testers are used to determine if the dielectric characteristic of the rope is safe for contact with energized lines. This task intends to identify the commercially available rope testers and conduct tests to evaluate their performance. In 2025, results from the testing of commercially available detectors are intended to be presented in a report.

Minimum Approach Distance Calculator (Software): This desktop software tool calculates and illustrates the minimum approach distance (MAD) for phase-to-ground and phase-to-phase clearances based on the Institute of Electrical and Electronics Engineers standard IEEE-516 and The International Electrotechnical Commission standard IEC-61472 formula for utility-specific structures using line components and dimensions for that structure’s location. In 2025, EPRI intends to update the software with new realistic features, continue updating the insulator model builder, and initiate the structure model builder. This new module is envisioned to enable users to create their custom structures, including features such as underbuilt conductors, braced pole configurations, and asymmetric crossarms.

Temporary Protective Grounding Rating Calculator (Software): This calculator is intended to quickly calculate the parameters for sizing temporary protective ground cable based on thermal constraints. This software calculates maximum clearing time, maximum current, temperature, and associated cable cross-section according to ASTM standard. In 2025, EPRI intends to update the software.

Understanding Insulating Tool Flashovers at Normal AC Voltages: This multi-year task supports and complements industry and member problem-solving efforts related to past industry insulating tool flashovers at normal ac system voltages by investigating the incidents and developing and performing laboratory tests based on hypotheses and/or numerical models to evaluate them as viable flashover mechanisms.

This research is part of a broader research effort that intends to investigate degradation and failure modes of insulating tools, research new materials to enhance tool performance, develop/search for new tool testing and inspection technologies, and develop reference and training materials that enhance worker safety in the use, inspection, testing, and care of insulating tools used in live work. In 2025, EPRI intends to verify the validity of the finite element modeling developed in 2023 and 2024 by means of small-scale testing.

Conductive Suit Evaluation: This task aims to update and expand the investigation of conductive suits performed in 1995. It seeks to verify the electrical performance of conductive suits available on the market, including shielding efficiency, current carrying capacity, and electric resistance degradation because of washing cycles. In 2025, EPRI intends to expand the investigation and test conductive suits from two additional manufacturers. Results from the testing of the conductive suits performed in 2024 and 2025 are intended to be presented in a report.

Understanding Effects of High Temperature on Insulating Tools: This multi-year task seeks to identify mechanical and electrical effects on insulating tools, such as hot sticks and ropes, caused by contact exposure with conductors operating at high temperatures. This task is important because utilities have replaced conventional aluminum conductor steel reinforced (ACSR) for high temperature, low sag (HTLS) conductors to operate at temperatures up to 250°C.

Multi-Stress Aging Tests: For more than two decades, EPRI’s multi-stress aging chamber has provided utilities with timely information about the performance of polymer insulators in less time than from in-service experience alone. As such, the chamber continues to be an asset to utility members. As some components are removed for evaluation, EPRI intends to add designs into the available space to represent the industry direction.

Small-Scale Degradation Tests: EPRI has developed several small-scale degradation tests that have proven repeatable, reproducible, and relevant to assessing an insulator’s performance to specific in-service degradation. EPRI has continued expanding the number of small-scale tests focused on different in-service issues. As new materials are developed, these tests are performed to provide members with performance guidance. EPRI continues to refine the test methods and tools as data are collected and technology becomes more advanced.

E-Field Modeling Software: Because electric fields are a critical factor in the service life of polymer insulators, this software helps calculate the electric field on new or existing insulator designs so utilities can determine the need for corona rings. EPRI continually works with user feedback to keep this tool relevant and easy to use.

Polymer Insulator Population Assessment (PIPA): This population assessment web-based software determines the potential condition and failure risk of in-service populations of insulators. Members can use this tool to quickly understand which population of insulators is prone to degradation. EPRI continues to work on improving accessibility for the user and refining the algorithms based on new data.

Insulator Reference Book: This book is a comprehensive reference guide that provides state-of-the-art information on insulator selection, inspection, and maintenance. There has been new development in contamination research that can enhance the existing information in the book.

ADSS Application: A web-based software tool to help users understand the electric field influence of high-voltage transmission lines on all-dielectric self-supporting (ADSS) installations. EPRI continues to work on improving accessibility for the user.

Handling Tests: These tests are being developed as a supplement to performance tests. They are intended to identify polymer insulators that, in addition to meeting in-service performance needs, resist handling damage. EPRI intends to develop a test protocol based on the several years of test development.

Nondestructive Weathershed Bonding Assessment: This task intends to evaluate a combination of ultrasound technology and nondestructive stress application to reveal poor weathershed bonding in polymer insulators. EPRI intends to expand the data set across multiple makes and designs to verify the test method.

Porcelain and Glass Insulator Vintage Guide: Much of the industry has a history of using porcelain insulators; therefore, assessing and managing these aging populations will be required for many years. However, test data alone are just one component of deciding the end of life. In addition, the use of glass insulators is increasing. This task plans to develop guidance combining the necessary information in a guide to help utilities assess failure risk and determine when population replacement is required based on make and vintage of insulators.

Evaluation of the Performance of RTV-Coated Insulators: Manufactured RTV-coated glass insulators are relatively new to the market and have limited worldwide experience. This task intends to evaluate how RTV coatings perform in various service environments. EPRI plans to perform various short-term and monitor long-term testing to assess coating performance in 2025.

Glass Insulator Failure Studies: Glass insulators have recently become more common across the industry. As more are being used, reports on shattering may increase. Having tools to understand the cause of the shattering can decrease time to issue resolution. EPRI intends to build on existing data to develop methods to determine how glass insulators are failing.

E-Field Modeling Software Update: As RTV silicone-coated glass insulators emerge in the market, controlling corona to reduce degradation of the RTV becomes essential. This tool can help calculate the electric field stress along an insulator string to determine if grading devices are needed. EPRI continually works with user feedback to keep this tool relevant and easy to use.

Insulator Reference Book: A comprehensive reference guide that provides state-of-the-art information on insulator selection, inspection, and maintenance. In 2025, EPRI intends to refresh the information with the latest research results. There has been new development in contamination research that can enhance the existing information in the book.

Applying Novel and Emerging Technologies: There are many providers in the grid-enhancing technologies (GETs) space. EPRI routinely identifies the newest technologies and updates to existing technologies to increase member awareness. Information is captured in EPRI guidebooks and presented during annual meetings. In 2025, EPRI plans to add a technical report to “demystify” the array of dynamic line rating (DLR) technologies, discuss what makes them different, and describe the inherent strengths and weaknesses of their approaches.

Grid-Enhancing Technologies (GETs) Field Trials: In some cases, utilities may wish to pilot an emerging technology, such as DLR sensors, to get hands-on experience with the new tools and practices. EPRI collaborates with members to provide guidance, capture lessons learned, and provide data needed to conduct performance evaluations. The findings are brought back to members via presentations by the host utility and technical reports. This allows utilities to understand the potential benefits as well as the barriers to adoption.

Radial Conductor Temperatures and Ratings: Because of the fundamental properties of heat transfer, transmission conductors are hotter at the core than at the outer surface. The increased core heat can lead to line sag being greater than projected in software tools. A combination of literature review, modeling, and lab testing can be used to establish correction factors to prevent utilities from exceeding clearance requirements or identifying the required ampacity derates if no action is taken.

Acceptance of Increased Power Flow (IPF) Projects: 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, electromagnetic fields, and cybersecurity to aid engineers in identifying “least regrets” options when considering upgrades to existing lines. The primary focus in 2025 will be mapping ambient adjusted rating (AAR) and DLR technologies to the relevant communcation and cybersecurity considerations.

Increased Power Flow and Limiting Components: As part of this task, EPRI plans to work with utilities and technology providers to identify case studies where lines have been uprated. An update to the Recent Increased Transmission Line Utilization Projects report is planned for 2025. This report includes case studies that have implemented uprating solutions such as coated conductors, voltage upgrades, reconductoring, and DLR to provide real-world lessons learned and decision-making processes from around the world. Utilities may use these findings to better understand where limiting components are within the system and the potential capacity increases available.

Evaluation of Methods and 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. Guidance is provided for ratings standards such as IEEE Std 738, FERC Order 881, and NERC FAC-008. In addition, updates to the Increased Powerflow Guidebook (The Platinum Book)—which addresses standards and regulations for rating overhead lines, underground cables, transformers, and substation components—is planned for 2025.

Weather Models and Forecasted Ratings: As utilities begin to apply AAR and FERC Order 881, there will be initial lessons learned. As part of this task, EPRI will work with utilities to capture their initial experiences, any unexptected issues, and workflow improvements that are made around handling data needed for ratings development.

Conductor Characteristics for Ratings (emissivity and absoptivity testing): EPRI offers conductor testing for emissivity and absorptivity on an ongoing basis. Using measured values improves the accuracy of ratings, light detecting and ranging (LiDAR) scans, and infrared (IR) inspections. Periodic reports share industrywide findings; however, utilities can provide samples and receive their specific results at any time.

Evaluation of the Effect of Emissivity on Conductor-Connector Thermal Performance: This task intends to undertake research to understand the thermal effects of having a high-emissivity surface on conductor-connector systems. A high-emissivity coating will be applied to aged conductor and new connectors to evaluate their performance and durability. At the end of the thermal cycling, the thermal profiles of the high-emissivity connectors are planned to be compared to noncoated conductor-connector systems. Mechanical tests may also be performed to determine the residual strength after the thermal mechanical cycling.

HTC Matrix Software Tool for Evaluating High-Temperature Operations: The High-Temperature Conductor (HTC) Matrix was developed as a repository for all the high-temperature overhead conductor research conducted by EPRI. The HTC Matrix includes several calculators. For 2025, the intent is to update the software for improved usability and accessibility as well as transfer one calculator to the web-based platform.

Guide for High-Temperature Operation: This task intends to update the guide developed to assist utilities in safely operating lines at higher temperatures. Each year, a new chapter could be added or an existing chapter updated. In 2025, case studies from utilities are expected to be collected and published.

Evaluating Connectors at High Temperature: A variety of overhead transmission connectors are used, including quadrant clamps, preformed wraparound connectors, and compression connectors. In addition, new single-stage compression connector designs are entering the market. This task intends to evaluate the performance of these connectors operating at elevated temperatures. In 2025, we anticipate continuing our research into the effects of high-temperature operation on bolted connectors.

Corrosion at Elevated Temperatures: Corrosion rates increase at elevated temperatures; however, those rates have not been quantified. This task sets out to understand the increase in corrosion rate with elevated temperature. In 2025, the plan is to continue work on the development of equations to model corrosion rates at elevated temperatures.

High-Temperature Effects on Conventional Conductor-Connector Systems: This task sets out to understand the degradation mechanisms of conventional conductor-connector systems, such as copper, all aluminum conductor (AAC), all aluminum alloy conductor (AAAC), aluminum conductor alloy reinforced (ACAR), and aluminum conductor steel reinforced (ACSR). In 2025, the project aims to develop equations representing the annealing behavior of copper using the results obtained from the 2024 empirically obtained data.

Radial Conductor Temperatures and Ratings: Because of the fundamental properties of heat transfer, transmission conductors are hotter at the core than at the outer surface. The increased core heat can lead to line sag being greater than projected in software tools. A combination of literature review, modeling, and lab testing can be used to establish correction factors to prevent utilities from exceeding clearance requirements or identifying the required ampacity derates if no action is taken.

Guidelines for the Installation of Advanced Conductors: Generally, composite core conductors have different handling and installation requirements than traditional steel core conductors. Typical line installation crews are not as familiar with the HTLS installation requirements compared with the traditional ACSR conductors. Most of the premature HTLS failures have occurred because of improper installation practices. This task intends to compile best practice guidelines based on manufacturer recommendations and utility experiences.

Inspection of Advanced Conductors: Composite core conductors generally are more fragile than traditional conductors. There may be a need to evaluate the condition of conductors after installation, impact events, or extreme weather. In addition, as many lines using advanced conductors start to age, there is a need to inspect and assess the core condition. In 2025, this task intends to further evaluate the inspection technologies tested in 2024.

Qualification Testing of Carbon Core Conductors: Because carbon core advanced conductors have only recently been developed, there is a lack of information on how utilities can qualify them for application on their transmission systems. In 2025, this task intends to test and document the results of a TS carbon core conductor. This information can be used by utilities to properly evaluate these advanced conductors.

Identification of Best Practices for the Maintenance of Advanced Conductors: Advanced conductors can operate at temperatures greater than 150°C. These temperatures could pose a risk for utility workers and the tools they use. This task intends to evaluate the effects of high temperature on workers and the tools they use as well as investigate the effects of tools on the conductors.

Environmental Effects Impact on the Performance of Advanced Conductors: This task intends to investigate how exposure to various environmental factors might affect the electrical and mechanical performance of HTLS conductors—specifically, non-steel-core HTLS conductors. The factors intended to be evaluated include fire, tree falls, hurricanes, and tornadoes.

Development of a Guide to Safe Design Tension for ACSS Conductor: Determining a safe conductor tension is a multi-faceted problem that requires understanding of the self-damping performance and fretting fatigue endurance of a conductor. This initiative, which is a collaborative effort with P35.007, is focused on helping solve this problem initially for ACSS conductor because its self-damping and fatigue properties vary significantly from those of ACSR conductor. In 2025, full-scale vibration testing of an advanced conductor is planned.

Evaluation of Field-Aged Conductors and Connectors: This task intends to provide an update on the results of evaluations performed on aged HTLS conductors. Through this evaluation, it is envisioned that a better understanding of the aging impact on the electrical and mechanical performance of these conductors may be obtained. In 2025, a report detailing these evaluations is intended to be updated.

Development of Guidelines for the Specification, Selection, and Application of Advanced Conductors: This task develops a guide (which is intended to be updated each year) to assist utilities in the proper selection and application of advanced conductors. The following information is intended to be included:

• Field and test experiences with different advanced conductors

• Application case studies

• Documentation and characterization of various types of conductors

• Review and development of technical specifications of the different advanced conductor types

• Review of the various standards associated with advanced conductors

Quick Break Whip Device Testing: This task intends to develop guidelines and determine, through laboratory testing, the performance and current handling of quick break whip arc interrupting devices. Because there is currently no test methodology for evaluating quick break whips, this research is intended to advance the knowledge and understanding of laboratory evaluation of these devices. In 2025, EPRI intends to focus on the electrical and mechanical endurance of different whip manufacturers.

Inspection and Maintenance Considerations for Line Switches: This task investigates the use and application of existing, new, and emerging technologies for inspecting, assessing, and monitoring the health conditions of line switches. The information obtained is intended to be compiled into a comprehensive guide to form the basis for understanding components, inspection, and monitoring techniques. Technologies such as unmanned aerial systems, testers, and sensors are intended to be explored. In 2025, EPRI intends to work on additional detailed inspection procedures for specific components and include new line switch models in electronic form for the inspection of line switches.

Transmission Line Switch Vintage Guide: This task aims to develop a comprehensive technical resource intended to provide guidance and strategies on procedures to assess the condition of transmission line switches in service by model and vintage. For that, underlying failure and degradation modes and mechanisms have been identified and catalogued by component to help estimate life expectancy and required maintenance actions. In addition, this task assists utilities in the performance of root cause and failure analyses. In 2025, EPRI aims to include results of additional forensic investigations and compile case studies provided by utilities.

Catalog of Component Degradation Modes: This task seeks to catalog degradation modes of line switch components from different manufacturers. The information will be gathered through findings from forensic investigations and utility reports and organized in the Transmission Resource Center (TRC) website.

Practical Installation Guide of Line Switches: This task intends to provide the technical basis and guidelines to support field engineers and technical staff with information regarding component specification, design, installation, and commissioning protocols of new equipment, as learned through best practices. In 2025, EPRI intends to include technical information about line switches with permanent bypass capabilities and initiate design templates for different switch manufacturers.

Motorized Switches Evaluation: This task seeks to gain a better understanding of the functionality of and inspection techniques required for motorized switches compared to manually operated switches. Possible topics include the additional components needed for motorization such as batteries, supervisory control and data acquisition (SCADA) systems, and alternatives of power supply. Findings from this task are anticipated to be shared through the Inspection and Maintenance Guide and the Line Switch Vintage Guide technical updates.

HVDC Line Design Guide: This task, updated each year, collects relevant information on HVDC line designs from various completed HVDC research tasks. Topics will include design aspects pertinent to HVDC and will identify areas of design that are similar between dc and ac.

Anomalous HVDC Flashovers: Unknown flashover events have occurred on several HVDC lines around the world. This task is intended to document the various cases of unknown flashovers and analyze the data to determine trends that could identify possible causes of these events.

Live-Line Tool Testing: This task intends to test live-line tools under HVDC conditions. The plan is to investigate the effects of space charge and corona to determine their impact on flashover performance and voltage distribution along the length of the tool. Work might also be performed to determine the accuracy of voltage detection devices under HVDC conditions.

Insulator Dimensioning for Contaminated Environments: Contamination is the main driver for insulation coordination of HVDC lines. Contamination performance of dc is vastly different from that of ac. This task intends to determine the latest state of the science in HVDC insulator dimensioning for contaminated environments. Testing and long-term aging of insulator materials may also be performed.

HVDC Reference Book (The Olive Book): An electronic version of the updated HVDC reference book will be made available to project funders. This reference book, updated each year, contains information on overhead lines and converter stations.

HVDC Electrical Effects Module in TLWorkstation: Based on the results and data obtained from the reduced-scale, full-scale, and operational line measurements, the existing algorithms used in the EPRI TLWorkstation software tool are intended to be updated and the user interface improved.

HVDC Transmission Line Reference Guide: This task intends to update the Overhead Line HVDC reference book, which was previously published by EPRI in the early 1990s. This document details the design characteristics of existing lines and describes the testing conducted and results obtained in determining the corona and electric field characteristics of HVDC transmission lines.