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2025 Research Plans

The research team is happy to share our plans for this year’s R&D. Thanks to all of our utility advisors that have given input throughout the planning process. We are excited to continue working together!

P37.101: Transformer Life Management
P37.102: Circuit Breaker Life Management and SF6 Management
P37.103: Protection and Control
P37.104: Substation Corrosion Management
P37.105: Balance of Substations: Batteries, Arresters and Ratings
P37.108: Gas Insulated Substations and Lines
P37.113: Polymer Bushing Life Management
P37.114: Substation Physical Security
P37.116: HVDC Converter Stations and Flexible Alternating Current Transmission System (FACTS) Devices
P37.117: Using Voltage and Current Measurements for Monitoring Asset Conditions

1 - P37.101: Transformer Life Management

Objective

Unique EPRI transformer research laboratories and expertise are feeding the development of new tools and knowledge to help substation owners anticipate and prevent failures in transformers, extend transformer life, retain key subject knowledge, and specify new diagnostic equipment with confidence. With the increasing need to maximize transformer assets while maintaining the highest levels of system reliability, management of aging power transformers has become a critical issue facing today’s substation owners. The objectives of this research are to provide accurate, rapid, and useful research results to help members better specify, operate, and maintain transformers. Results take the form of hardware, software, laboratory results, and guidebooks. Hardware prototypes are tested first in the laboratory and then piloted in utility substations, allowing for easy future adoption. Online monitoring technologies are thoroughly assessed using repeatable test protocols. The Power Transformer Guidebook (The Copper Book) is continually expanded and updated as a comprehensive reference guide that can be used by utility personnel responsible for all aspects of transformer operation, maintenance, procurement, and life-cycle management. The Copper Book is also used as the basis for regular EPRI technical training webinars.

Research Value

  • Reduced operations and maintenance (O&M) through improved specification of emerging condition monitoring techniques, based on solid facts and repeatable test protocols.
  • Third-party unbiased assessment of online monitoring technologies’ life-cycle costs to aid industry specification and interpretation.
  • Improved risk assessment of transformers, which translates into improved decision making on these critical assets.
  • Effective knowledge transfer through The Copper Book and regular technical webinars. The guidebook is a comprehensive collection of transformer knowledge designed specifically for utility owners and operators.
  • Novel technologies for continuous transformer dehydration—which, in turn, translates into reduced O&M and improved reliability.
  • Valuable guidance on the application and effective use of novel fluids for transformers.
  • Industry-standards-based loading methodologies for transformers and other equipment on the same circuit.

Planned 2025 Research

EPRI Power Transformer Guidebook (The Copper Book) 2025 update: Each year, EPRI publishes updates to The Copper Book to keep members up to date with the latest research, technology developments, and transformer standards. The guidebook has been written with the utility engineer and field staff as the audience and covers the entire range of topics from specification to end-of-life assessment. In 2025, two valuable additions will be made: first, deeper guidance on dissolved gas analysis (DGA) sampling based on EPRI laboratory testing; second, a growing list of quick reference, single-page summaries of key topics.

Technical webinars on the Transformer Guidebook: Multiple technical webinars based on sections in the Transformer Guidebook are hosted each year. The webinar material is published for continued and convenient future access. Topics are selected to accelerate learning on key topics in the Transformer Guidebook (The Copper Book).

Transformer online monitoring technologies: Laboratory testing to help members in specification development: The results from the 2025 research provide valuable assistance in transformer monitor specification, interpretation, and adoption. A full 138-kV EPRI research substation was commissioned and energized to support this research. EPRI laboratory test results are executed against a well-defined test protocol for online DGA monitors, online bushing monitors, online partial discharge (PD) monitors, and online temperature monitors. This unique approach allows for rapid answers on high-impact decisions that are then applied fleetwide in a utility.

Alternative fluids for transformers for increased ratings, extended service life, and reduced environmental impact: This research in 2025 intends to explore the characteristics that define the end of life for an ester fluid. With several years of use, many chemical and physical properties of ester fluids can change significantly from the starting values. In many cases, the values of different ester properties can surpass the limits set for mineral-based oils. Even with such property changes, many users continue to use the ester fluids, not knowing how detrimental the changes in fluid could be to the operation and health of their transformer. Using accelerated aging systems, beneficial guidance could be obtained on what changes to chemical and physical properties (such as acid number, fire point, and viscosity) mean to system operation and health. The goals of the results are twofold: first, to help set limits for acceptable operation of ester fluids; second, to help users decide when to perform a course of action on an ester fluid such as maintenance, a fluid change, and/or change the loading on the transformer.

Membrane technologies for online, low-maintenance dryout of transformers: Through several years of research, EPRI has developed a novel membrane-based system that continuously removes water from transformer oil online. The system removes water without the need to use replaceable cartridges or remove diagnostic dissolved gases, all while using minimal moving parts. A goal of the research in 2025 is to explore further enhancement of the water extraction through methods such as oil precooling and/or multiplexing internal technologies, while keeping the system size within the current footprint. In addition, it is intended that the condition of some components used in field systems will be examined to potentially devise ways to increase the ruggedness and resilience of future systems or retrofits or allows field personnel to easily replace certain components. Field pilots in utility substations will continue to validate the technology to strive for systems that can be deployed for multiple years with minimal or no maintenance.

New oil markers to aid power transformer diagnostics: In 2025, it is planned that the stability and dynamics of some newly identified oil markers by EPRI, and others in the literature, be explored. It is known that new marker compounds are generated in the presence of oil and/or paper under different stresses (that is, overheating, PD, arcing). However, the longevity and interaction dynamics of the new markers with other components and chemicals inside a transformer are not known well—or sometimes not known at all. Data collected from a unique online marker detection system deployed by EPRI aim to provide insights into new marker dynamics in a working transformer. It is also intended that further exploration into new marker dynamics will be performed. The results will provide the industry with enhanced value from oil samples—allowing greater insights into transformer condition.

Anticipated Deliverables

Deliverable Description Date
EPRI Power Transformer Guidebook (The Copper Book) 2025 update The 2025 EPRI Power Transformer Guidebook will include the latest updates based on ongoing research and industry advances and continue adding valuable single-page quick reference guides for key topics. December 2025
Technical webinars on the Transformer Guidebook Regular webinars are developed for project funders on key topics in the EPRI Power Transformer Guidebook. December 2025
Assessment of transformer online monitoring technologies to help members in specification development New self-calibrating online DGA technology and new bushing monitoring technologies will be added to the wide array of monitors under assessment. December 2025
Novel fluids for transformers Through well-defined test protocols, input from users, and emerging literature, the research looks to provide valuable guidance on the opportunities, uses, and challenges associated with alternative fluids. December 2025
Membrane technologies for online, low-maintenance dryout of transformers The 2025 research aims to explore enhancing unit water extraction efficiency. In addition, piloting of smaller and longer lasting units using solid-state Peltier technology plan to be performed. December 2025
New oil markers to aid power transformer diagnostics The 2025 results strive to enhance the value gained from oil samples through exploring the dynamics of newly identified health markers—allowing for greater insights into the transformer health condition. December 2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002026941 EPRI Power Transformer Guidebook (The Copper Book) 2023 Update The Copper Book is a comprehensive reference guide that can be used by utility personnel responsible for all aspects of transformer operation, maintenance, procurement, and life-cycle management. December 2023
3002026943 Assessment of transformer online monitoring technologies to help members in specification development Online monitor laboratory data that support functional specifications. December 2023
3002027003 Novel fluids for transformers Valuable insights on novel fluid aging, diagnostics, selection, and application. December 2023
3002027005 Membrane technologies for online, low-maintenance dryout of transformers Continued research on the novel membrane-based system. Additions with the Generation 2 design. December 2023
3002027008 New oil markers to aid power transformer diagnostics Initial understanding of the oil markers to understand transformer health conditions. December 2023

2 - P37.102: Circuit Breaker Life Management and SF6 Management

Objective

The life-cycle performance of a circuit breaker is determined by the performance and condition of its materials and components. Together, these characteristics drive the requirements for maintenance and refurbishment or replacement. However, there is limited quantifiable data on breaker materials and subsystem performance available to inform decisions and design cost-effective condition-based maintenance or replacement programs. Utility maintenance practices vary widely, as do manufacturers’ recommendations. This research addresses the need to develop information, techniques, and methodologies to support best practices in high-voltage circuit breaker life management. The methods developed for transmission classes may be adapted to medium-voltage (13.8–69 kV) breakers.

The objectives of the proposed research are to better understand circuit breaker operating stresses, underlying failure modes, and degradation patterns to provide utilities with knowledge and guidelines for selection, application, procurement, maintenance, and condition assessment and testing to ensure satisfactory circuit breaker life-cycle performance.

Through a multi-year research effort, it is anticipated that the project could result in:

  • Methods to assess the aging of gas-insulated switchgear (GIS) and circuit breaker components and subsystems, including identification of failure modes and degradation mechanisms
  • Innovative leak-sealing techniques for breakers and GIS and both SF6 and SF6 alternatives
  • Noninvasive condition assessment techniques
  • Assessment of diagnostic effectiveness of online monitoring as well as offline testing
  • Maintenance guidelines for select mechanisms
  • Reference books, guidelines, videos, field guides, and technology transfer workshops
  • Collaborative forums for sharing lessons learned and best practices

Research Value

Proposed research may help utilities reduce costs and improve reliability and availability by decreasing the potential for circuit breaker failures and increasing the effectiveness of circuit breaker maintenance.

Research results are expected to provide:

  • A quantitative understanding of aging and deterioration rates
  • Reduced unplanned expenses and increased benefits and value of planned work
  • A better understanding of the expected life of circuit breaker materials
  • Knowledge for developing enhanced cost-effective methods for implementing a condition-based maintenance and replacement approach
  • A technical basis to help assess and manage risks
  • Better controlled life-cycle costs and risks, which contribute to reduced operating costs
  • Improved reliability and quality of electric service by reducing unplanned outages and costs and improving customer satisfaction and service availability

Planned 2025 Research

Effect of Component Degradation on Circuit Breaker Operation intends to characterize possible consequences of degraded components on circuit breaker operation (for example, slow trip, abnormal mechanism wear, lubrication, compressor/pump failures) with the following:

  • Catalog failure reports and other information available from circuit breaker failure events and/or utility root cause analysis

  • Document industry practices in circuit breaker routine maintenance, diagnostic testing, and overhaul

  • Catalog utility experiences of using digital relays for circuit breaker diagnostics

Circuit Breaker Online Monitoring Effectiveness Assessment aims to develop and apply assessment metrics to various circuit breaker online monitors to determine which monitors and tests provide the most useful information. The objective is to provide information to assist in monitor application and specification.

  • Tasks in 2025 plan to:

  • Work with funders to identify specific circuit breaker monitors of the highest interest, and use publicly available information to perform systematic investigations to understand what capabilities are claimed, make comparisons, and assess their applicability

  • Perform tests in EPRI laboratories, when possible, to confirm that monitor measurements match comparable offline tests—for example, breaker timing

  • Document utility experiences with using online monitors

  • Maintain awareness by scouting commercially available and emerging technologies

Circuit Breakers Diagnostics Effectiveness Assessment intends to continue to assess the effectiveness of dynamic resistance measurements (DRM) and develop and apply metrics to assess the effectiveness of various additional circuit breaker diagnostic techniques. The objective is to provide utilities with guidance on the most informative and cost-effective procedures for nonintrusive diagnostics to support condition-based maintenance.

  • Tasks in 2025 plan to:

  • Better determine the relationship between DRM waveforms and contact condition and build a library for different circuit breaker interrupter models. The tests would rely on field-aged circuit breaker arcing contacts provided by utilities or by simulating defects using the circuit breaker in EPRI’s 138 kV substation laboratory.

  • Maintain awareness by scouting commercially available and emerging technologies.

  • Expand efficacy assessments to additional techniques, for example, X-rays, acoustics, and partial discharge.

New Markers for Circuit Breaker Dielectric Condition Assessment proposes to undertake a multi-year effort to research, develop, and apply new chemical markers that could assist in providing information for effective condition-based maintenance of oil-filled and SF6 circuit breakers. Initial focus will be on concept development. Future work may include methodology enhancement, prototyping, and additional experience gathering. Associated supplemental projects may be initiated to assist with field demonstrations and testing.

Leak Sealing for Circuit Breakers and Gas-Insulated Substations investigates methods that utilities can use to cost-effectively seal dielectric gas (SF6 and non-SF6) leaks. The emphasis is on identifying materials and techniques that can seal while maintaining equipment operating pressures and are easy for utility personnel to apply and remove. Novel techniques for sealing SF6 leaks on circuit breaker and gas insulated substation (GIS) component geometries at ground potential were developed, and three successful techniques identified in the laboratory are in field tests at eight utility sites. Tasks in 2025 plan to:

  • Continue monitoring the performance of the field trials

  • Develop application guides and “how-to” videos for techniques that are successful in the field and make them available through the Transmission Resource Center (TRC): Circuit Breaker Life Management

  • Continue investigations to find sealants that cure at lower temperatures

  • Scout innovative methods used by other industries and investigate whether they can be used for sealing breaker and GIS leaks

  • Develop techniques for additional geometries, for example, the bushing flange interface; some of these new geometries may not be at ground potential

  • Investigate scaling application of existing techniques to larger flange diameters

  • Initiate a new effort to investigate:

    • Challenges that may be encountered in sealing leaks of SF6 alternatives
    • Applying techniques successful in sealing SF6 to SF6 alternative gases

Circuit Breaker Reference Guide. There are plans to continue developing a comprehensive reference on circuit breaker procurement, operation, maintenance, and life-cycle management to serve as a resource for less experienced personnel. The goal is to develop a guide that provides information on fundamental design descriptions, operation, selection, and application principles, maintenance, monitoring, and replacement and captures the knowledge of leading circuit breaker experts. To date, nine sections have been written, including sections on circuit breaker installation, diagnostics, problem and failure investigation, lubrication, pump and compressor maintenance, specifications and procurement, and interrupter cleaning. New works aims to:

  • Develop guidance material for performing factory visits and design reviews for SF6 circuit breakers

  • Develop content on emerging circuit breaker technologies such as non-SF6 circuit breaker technologies

  • Develop content on handling SF6 and SF6 alternatives

Technical Webinars on the Circuit Breaker Guidebook intends to develop and host a series of technical webinars based on sections in the Circuit Breaker Guidebook. Content will be selected to accelerate learning on key topics in the Circuit Breaker Guidebook for those with less circuit breaker experience. Webinar material will be published for continued and convenient future access.

Circuit Breaker Mechanism Maintenance Guides. Maintenance supplements written for specific breaker models serve as training tools and guidance for proper mechanism field disassembly, cleaning, lubrication, and reassembly. Gaining importance as experienced personnel retire, the guides communicate information in step-by-step illustrated tasks, cover material not included in manufacturers’ instruction manuals, can be readily incorporated in a utility’s maintenance procedure, and have been developed for 11 models. The intent is to expand the library with new guides annually. Model selections will be prioritized based on advice from the task force.

HVCB Life Management Workshop proposes an annual workshop that will include tutorials on the material contained in the project’s products, presentations on utility experiences, and examples of the application of the project’s results.

Anticipated Deliverables

Deliverable Date
Technical Update: Effect of Component Degradation on Circuit Breaker Operation 12/31/2025
Technical Update: Circuit Breaker Online Monitoring Assessment 12/31/2025
Technical Update: Circuit Breaker Diagnostics Efficacy Assessment 12/31/2025
Technical Brief: New Markers for Circuit Breaker Dielectric Assessment 12/31/2025
Technical Update: Leak Sealing for SF6 Circuit Breakers and Gas Insulated Substations 12/31/2025
Videos: Applying Leak Sealing for SF6 Circuit Breakers and Gas Insulated Substations 12/31/2025
Technical Brief: Leak Sealing for Non-SF6 Circuit Breakers and Gas Insulated Substations 12/31/2025
Technical Update: Circuit Breaker Reference Guide 12/31/2025
Tech Transfer: Technical Webinars on the Circuit Breaker Guidebook 12/31/2025
Technical Update: Circuit Breaker Mechanism Maintenance Guides 12/31/2025
Tech Transfer: HVCB Life Management Workshop 12/31/2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002027034 Circuit Breaker Mechanism Maintenance Guides - 2023 Presents mechanism-specific maintenance and lubrication instructions for nine models of high-voltage circuit breakers. The instructions are meant to supplement manufacturers’ instruction books and describe tasks beyond routine maintenance to extend the reliable operation of each mechanism type with limited disassembly. December 2023
3002027018 Novel SF6 Leak Sealing Techniques Documents test plans and results of small-scale laboratory tests for sealing leaks from breaker/GIS components that are at ground potential (threaded fittings, bus flanges, and porous welds on buswork). Identifies promising materials and repair techniques for full-scale laboratory and controlled field testing. December 2023

3 - P37.103: Protection and Control

Objective

Utilities face the challenge of managing the performance and reliability of multi-generation protection and control (P&C) assets accompanied by tighter regulations and resource limitations. New technologies and automation tools provide utilities with tremendous opportunities to advance new P&C designs.

By developing application guides, evaluating new technologies, and conducting technology transfer, the project aims to assist members in:

  • Reducing the risk of protection system misoperation by establishing systematic configuration management processes that can seamlessly integrate protection data, streamline setting change management processes, and automate relay settings verification
  • Lowering costs and improving protection reliability by advancing condition-based protection system maintenance programs
  • Advancing new P&C designs by embracing fiber-optic communications and digital substation technologies
  • Knowledge preparation and field deployment of IEC 61850 standard and technologies

Research Value

  • Improve relay setting management by applying configuration management guidance and automation technologies.
  • Increase protection system reliability by reducing human errors, preventing relay misoperation, and detecting hidden failures.
  • Reduce costs and improve safety, storm -hardening, and grid resilience by advancing new designs and embracing digital substation technologies.

Planned 2025 Research

  • Life-Cycle Management of Relay Settings: Configuration Management Guidelines and Effective Practices. Many utilities face challenges in managing the consistency, conformance, and accuracy of large volumes of relay settings for meeting reliability and regulatory requirements. The growing complexity of digital relay technologies, tighter compliance requirements, and increasing concerns with setting-error-caused relay misoperation drive utilities to identify applicable research on systematic approaches and automated tools for improved relay-setting data management. Configuration management (CM) is a proven methodology that addresses requirements, controls changes, and maintains facility configuration throughout a system’s life cycle. A well-established configuration management system, when applied to a P&C asset, can help ensure that relay settings and changes to that information are systematically identified, approved, verified, and recorded in sufficient detail throughout the life cycle of P&C assets.

  • Application Guide for Relay Firmware Change Management. Upgrading relay firmware not only impacts relay functionality but also introduces compatibility issues with other components in P&C systems. Previously, a common practice for utilities was to freeze relay firmware versions through standardization of P&C design. However, with tighter regulation on security patch management, new approaches and application guidance are needed for utilities to keep relay firmware up to date while maintaining the integrity and reliability of P&C systems.

  • Life-Cycle Management of Relay Settings: Tools Assessment. Traditional tools for creating and managing relay settings have led to many disconnected data repositories, applications, and environments. Meanwhile, there are growing business needs for stakeholders across a utility organization to inquire and exchange accurate setting information to support engineering, planning, field service and compliance. Assessing and analyzing commercially available software can help answer these questions: What tools can provide the Single Source of Truth for managing relay settings across different applications? What tools can help automate setting data exchange, verification, and documentation?

  • Application Guidelines for Protection System Maintenance. The reliability of P&C systems relies on well-established asset maintenance programs. The challenges utilities face today include difficulty in scheduling outages, stretched resources, and the growing complexity of relay technologies. The research aims to address these challenges by evaluating new monitoring technologies and advancing condition-based maintenance (CBM) programs. The research results might provide utilities with application guidance that can be used in engineering standards and design specifications for creating effective CBM programs and reducing the costs associated with time-based maintenance (TBM) programs. The benefits of combining CBM and TBM in maintenance programs include reducing the cost and outage requirements of TBM, expanding maintenance intervals based on NERC PRC-005, detecting hidden failures at once, and triggering a maintenance action when it is truly needed.

  • Evaluation of Protective Relay Performance Under Power Swings: Lab Testing and Research Findings. Stable power swings can cause unwanted operations of protective relays and consequently compromise power system reliability. The NERC PRC-026 standard requires that utilities take necessary actions to prevent transmission protection misoperation during stable power swings at non-fault condition. Through power swing simulation and lab testing, the EPRI research plans to evaluate the performance of transmission protective relays under stable power swings with various fault or non-fault conditions. The research may provide members with new discoveries about power swing dynamics, the state-of-the-art power swing detection and blocking technologies, and potential impacts of power swings on the transmission protection relays. The outcomes of the research may assist utilities in specification, engineering, and application of relaying technologies to improve the reliability of protection systems subject to the NERC PRC-026 standard.

  • Technology Transfer Workshop: IEC 61850 Standard and New P&C Designs: The International Electrotechnical Commission (IEC) 61850 standard facilitates substation automation and enables equipment interoperability through a common data format. There is growing interest from utilities to explore the IEC 61850 standard and associated digital substation technologies, for to advanceing new P&C designs that promise to improve safety and reliability, reduce costs, enable interoperability and condition monitoring, and strengthen grid resiliency.

    The technology transfer workshop will provide members with knowledge preparation and new insights on:

    • IEC 61850 standard and digital substation architectures
    • New technologies for resilient communication networks
    • New P&C applications using the Generic Object-Oriented Substation Event (GOOSE) message
    • Emerging process bus technologies and new P&C applications using sampled value
    • New technologies and industry standards for precision time synchronization

    The workshop, held in collaboration with relevant EPRI research programs and industry stakeholders, aims to keep members abreast of the latest technologies and industry standards, provide a forum for members to share success stories and lessons learned, and prepare members for field deployment through EPRI technology transfer.

Anticipated Deliverables

Deliverable Description Date
Life Cycle Management of Relay Settings: Configuration Management Guidelines and Effective Practices (2025 update) Provides research on effective relay-setting management processes by applying the configuration management guiding principles. December 2025
Application Guide for Relay Firmware Change Management (2025 update) Documents effective methods for evaluation, impact analysis, testing, and implementation of relay firmware revisions. December 2025
Life-Cycle Management of Relay Settings: Tools Assessment (2025 update) Documents the research findings in evaluation of commercially available relay-setting management tools. December 2025
Application Guidelines for Protection System Maintenance (2025 update) Explores new self-monitoring technologies for advancing condition-based protection system maintenance programs. December 2025
Evaluation of Protective Relay Performance Under Power Swings: Lab Testing and Research Findings (2025 update) Describes lab testing to evaluate the performance of protective relays to reduce the risk of protection system misoperation in response to power swings. December 2025
Technology Transfer Workshop: IEC 61850 Standard and New P&C Designs (workshop) Provides knowledge preparation, project experience sharing, and hands-on lessons from emerging P&C technologies. December 2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002027041 Life-Cycle Management of Relay Settings: Configuration Management Guidelines and Effective Practices Applying configuration management guiding principles to the processes of effective management of relay settings in P&C systems December 2023
3002027057 Application Guide to Relay Firmware Change Management Guidance and effective processes for management of relay firmware changes December 2023

4 - P37.104: Substation Corrosion Management

Objective

All assets within a substation are subject to degradation and have maintenance programs to extend the service life or a replacement scheduled. This project provides guidance in understanding the degradation rates of assets in soil and atmospheric exposure, how to select the appropriate corrective action, and how to ensure that the corrective action is aligned with the environment.

Ground grid integrity is a critical factor governing the safety and reliability of a substation or switchyard. Copper is the typical material used in the construction of a ground grid because of its corrosion resistance in most soil series. Degradation of the grid, however, can still occur when this material is present. A few possible reasons are application outside the design specifications, chemically incompatible soils, or the presence of stray current. These tasks help understand what existing tools or techniques can identify locations within the ground grid that do not meet the design specifications and represent risk to the utility.

The objective of this project is to understand how substation assets degrade in soil and atmospheric exposure and where this represents risk to the utility. This is achieved through:

  • Evaluating existing, new, and emerging inspection technologies to understand the limitations and benefits so that utilities can select these tools based on the construction specifications
  • Determining corrosivity levels of the soil series at a substation so that engineers can select the appropriate materials for the ground grid designs, foundations, and tank bottoms
  • Determining corrosivity levels of the soil series at a substation so that maintenance personnel understand when to inspect and maintain the ground grid and other substation assets
  • Defining corrosion control options and providing guidance for the appropriate mitigation methods for substation assets in soil exposure

Research Value

This research can provide the following value:

  • Provide guidance to asset management teams for life-cycle decisions
  • Develop processes and training for inspection and maintenance operations
  • Optimize maintenance budgets through population assessment (targeted inspections) and predictive maintenance of ground grids
  • Develop guidelines for material selection and application to reduce theft of grounding system conductors and optimize corrosion control
  • Help understand and manage risks through prioritized inspections
  • Improve worker and public safety by proactively identifying areas of ground grid degradation
  • Assess the potential of a cathodic protection system to detect ground grid theft

Planned 2025 Research

Each research task in 2025 is designed to provide value to the funding utility, and each task has a different level of complexity. Some tasks may require more time to mature, and, in some instances, the results are incorporated into future work. Therefore, the research approach for understanding corrosion on substation assets is categorized by short-, medium-, and long-term research for the reader to understand its value.

Short-Term Research:

Refinement of Impressed Current Cathodic Protection for Corrosion Control on Ground Grids: Cathodic protection (CP) is one of the primary corrosion control methods for managing degradation of ground grids because of soil exposure. When applied properly, CP may also offset the effects of stray and circulating currents because of connectivity to the transmission lines and operation of the substation equipment. A temporary CP system was installed at EPRI’s Lenox, Massachusetts laboratory in 2020, and the resulting voltage gradients were plotted to show locations where the protection was insufficient and discharge locations remained.
In 2021 and 2022, the process was refined by adding new equipment to level the potentials throughout the Lenox substation and eliminate discharge locations. The findings are that CP systems must be carefully designed to eliminate additional circulating currents. In 2025, research will focus on the development of a web app supporting cathodic protection design, installation, and maintenance operations.

Corrosion Due to AC and DC Stray and Circulating Currents: The effects and severity of alternating current (ac) corrosion coupled with direct current (dc) stray currents have been studied and quantified in previous research. This task explores the methods to screen and quantify the effects as well as the mitigation options for these corrosion-related issues. Mapping circulating currents allows engineers to understand where problematic locations exist within the substation. This makes the design of a corrosion control system much more effective and cost-efficient.

Research in 2025 will continue to focus on modeling induced voltages and resulting stray circulating currents. This is anticipated to augment the existing metrics for the GIS models that have been developed and are being validated.

Field Guides: A field guide is a pocket reference book that allows personnel to identify, quantify, and prescribe a corrective action based on illustrations depicting levels of corrosion severity.

Medium-Term Research:

Sensor Development to Discriminate Between Localized, General, and Stray Current Corrosion: Corrosion depends on environmental factors, such as moisture, temperature, pH, and stray or circulating currents. To understand and delineate between the many types of corrosion, EPRI has developed a sensor array that helps researchers and asset managers identify and quantify the severity of each type of corrosion. The array’s capabilities were expanded in past years to measure atmospheric weather patterns to correlate those factors with changes in subgrade corrosion. Ongoing research is focused on analyzing large data sets from these individual sensors in the array to further our understanding of diurnal changes in corrosion activity for substation assets exposed to soil.

Atmospheric Corrosivity Maps: Atmospheric Corrosion in Substations: Environments can vary within a substation because of energized equipment, proximity to a generation plant, and topography at the site. This makes forecasting for maintenance operations because of atmospheric corrosion within a substation a challenge. Having corrosion rates for steel, zinc, and aluminum within a substation allows asset managers to understand and forecast for maintenance and replacements.

Atmospheric Corrosivity Maps: Voltage Gradient Mapping: Corrosion severity may be understood by measuring the potential of a metal in soil exposure. This is useful when reviewing a copper grounding system to determine if the grid is picking up or discharging corrosion current. Creating a voltage gradient map allows visualization of the equipotential lines within a substation and refinement of the locations requiring further investigation.

Long=Term Research:

Evaluation of Ground Grid Inspection Technologies: Four inspection technologies for ground grids have been evaluated at EPRI’s 138-kV substation. Each tool has performance metrics evaluated and will be deployed at a utility’s service territory to evaluate operational limits and performance in the field. The goal is to understand the benefits and limitations for each technology, which will allow a utility to select the technique or technology that is appropriate for their specifications. Additional inspection technologies will be identified and evaluated, and the results will be published for inclusion along with the three-tiered inspection process in the Ground Grid Corrosion Management Guidelines.

Subgrade Corrosion on Ground Grids: This task is an overview of all the new learning in the form of guidelines for ground grid corrosion. This includes inspection, assessment, and mitigation techniques and technologies that may be studied and implemented by utility personnel.

Subgrade Corrosion in Substations: Corrosion is not limited to ground grids but is also seen in tank bottoms, foundations, underground piping, and communications assets. The objective of this task is to develop a suite of inspection tools or technologies and best-in-class methods to mitigate or arrest corrosion on these assets.

Corrosion and Corrosion Control Workshop: Held every two years, this workshop provides both theory and practical experience in understanding corrosion and how to assess and implement various types of corrosion control technologies. The workshop is designed to support asset managers, engineers, maintenance managers, and field crews in gaining practical knowledge for extending the service life of their assets.

Corrosion Management Guidebook: Guidance on corrosion management is needed for all areas of power delivery. This guidebook contains asset management information for inspection, assessment, mitigation, and remediation for all departments within a utility. The guidebook contains the fundamentals of corrosion, guidance for inspection and assessment, and an understanding of mitigation methods that align with the environment.

Anticipated Deliverables

Deliverable Date
Stray and Circulating Current Corrosion Control December 31, 2025
Atmospheric Corrosion in Substations December 31, 2025
Monitoring Ground Grid Performance at Corrosion Discharge Locations December 31, 2025
Identifying Corrosion Locations Through Equipotential Line Mapping December 31, 2025
Corrosion Management Reference Book December 31, 2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002021374 Ground Grid Protection Methods: Cathodic Protection Changes with Increased Impedance Refines the efficacy of a cathodic protection system as segments of a ground grid are removed from operation. December 2021
3002024603 Evaluation of Ground Grid Inspection Technologies This deliverable continues the evaluation of new and emerging inspection technologies but also begins development of a training module for early career engineers, technicians, and field crews. December 2022
3002027081 Workshop for Corrosion Fundamentals and Corrosion Control This course is designed to support all departments within transmission and distribution and allow an understanding of how to extend the service life of their assets. December 2023
TBD Field Guide: IAM of Substation Ground Grids Substation Ground Grid Inspection and Assessment Field Guide. December 2024

5 - P37.105: Balance of Substations: Batteries, Arresters and Ratings

Objective

The project objective is to determine how to optimize the maintenance of various substation assets and maximize their service lives. Equipment under test varies by project year. Research focuses on equipment that is not typically designated as a major asset but still affects the reliability, safety, and longevity of substations. Examples of such assets include battery banks, disconnect switches, instrument transformers, and surge arresters.

Research Value

This research can provide the following value:

  • Provide guidance regarding asset life cycles, including specific assets such as monitoring of surge arresters and battery systems
  • De-risk novel technologies associated with asset inspection, monitoring, and assessment via robotics
  • Support utilities in making informed decisions about substation ratings, including improved thermal models to optimize power output and guidance for applying this information in overall transmission system ratings

Planned 2025 Research

Continue development of surge arrester sensor to monitor pending arrester failure: This multi-year task evaluates the long-term durability of EPRI’s surge arrester failure sensor. The approach involves the monitoring of new, aged, and failing arresters in the controlled, 138-kV research substation environment to increase the sensor’s data set for future analysis. This allows for examination of the impacts of a substation environment on sensor performance while enabling easy access to the sensors if problems occur.

Assess performance of battery monitoring systems: Assess battery monitoring systems from several manufacturers. Use bench testing and battery emulators to create repeatable test plans that allow for comparison between systems that may otherwise require different battery chemistries or configurations.

Evaluate robot chassis for applicability to substation inspection: This research explores the feasibility of autonomous mobile robots for substation inspections, investigating their potential to complement human inspectors, be shared across substations, operate with minimal supervision, be portable, and ultimately determine if they currently complement or supplement human inspectors for improved efficiency, safety, and reliability in substation inspections. This task expands on work from 2024 by evaluating additional technologies.

Issue updates to EPRI’s Increased Power Flow Guidebook for 2025: This effort advises utilities on how to calculate and apply ampacity ratings to substation equipment, pursuant to NERC requirements and FERC Order 881, which shifts the industry from ambient adjusted ratings that vary with air temperature to dynamic line ratings (DLRs) that vary with wind speed. In addition to applying DLRs to bus ratings, the new designations may result in the most limiting series element designation applying to station equipment, instead of the transmission line, for many circuits in 2025.

Anticipated Deliverables

Deliverable Date
Robotics Assisting Electrical Substation Inspectors (Technical Update) December 31, 2025
Insights and Considerations from Substation Battery Monitoring System Evaluation and Testing (Technical Update) December 31, 2025
EPRI Increased Power Flow Guidebook—2025: Increasing Power Flow in Lines, Cables, and Substations (Technical Update) December 31, 2025
Transmission Ratings Workstation: 2025 (Software) December 31, 2025
Arrester Condition and Failure Monitoring December 31, 2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002027110 Insights and Considerations from Substation Battery Monitoring System Evaluation and Testing Report describing work performed by EPRI to evaluate various battery monitoring systems through 2023 December 2023
3002027105 Transmission Rating Workstation (TRW) STLoad 2023 2023 software release of Transmission Ratings Workstation for performing rating studies and evaluating and optimizing static ratings, real-time ratings, and forecasted ratings for transmission equipment and entire circuits December 2023
3002027331 Increased Power Flow Guidebook (The Platinum Book) Technical reference book that accompanies the Transmission Rating Workstation STLoad software December 2023
3002027114 Arrester Condition and Failure Monitoring Description of the development of the arrester monitor, laboratory test results, and results from two field demonstrations through 2023 December 2023

6 - P37.108: Gas Insulated Substations and Lines

Objective

Gas insulated substations (GIS) and gas insulated lines (GIL) offer many benefits, including compact size, modularity, physical security, and protection from pollution and harsh environments. They also present unique challenges in how to reduce SF6 emissions and effectively detect and locate defects. EPRI research is addressing this need through laboratory tests on representative defects. The value provided will be practical and well-informed guidance on GIS and GIL application, use, and management. The GIS and GIL research is focused on two key areas: SF6 alternatives and condition monitoring of GIS/GIL systems.

Because GIS and GIL use large volumes of SF6, it is important to understand the upcoming technologies and dielectrics that offer reductions in that usage. EPRI has a GIS laboratory that is being used to answer key open issues. The research will also report on the latest field applications and trends in the industry.

The second important focus is on GIS condition monitoring and leak detection. There are various existing and emerging techniques, including ultra-high frequency (UHF), acoustic emission, and SF6 gas analysis. Each has unique merits in defect detection. To better assess each approach, EPRI has built and commissioned a full-scale GIS laboratory. The facility allows EPRI to introduce a range of defects into GIS components and explore the performance of each approach. The effectiveness of each technology to reject external noise will also be quantified. The results will guide the industry in the specification, interpretation, and adoption of technologies.

Research Value

The research aims to provide value in the following key areas:

  • Guidance on SF6 alternatives
  • Reduced SF6 emissions through improved leak detection
  • Lowered maintenance cost of GIS and GIL through improved diagnostics
  • Improved reliability of electric service through better reliability and availability

Planned 2025 Research

The approach in 2025 will be to conduct laboratory testing on GIS and to research field applications and industry trends. Results each year add to the EPRI GIS/GIL Guidebook. The following activities will be conducted to support the objectives:

Emerging issues with new GIS and GIL technologies: The first goal of the 2025 research is to provide further valuable and practical insights into the continually growing topic of using C4-fluoronitrile mixtures or clean air as insulation gases instead of SF6. The focus of this portion of the research is to explore the new technologies/equipment that use alternative insulating gases to SF6 and to probe issues and considerations for gas handling, analysis, safety, and reclaiming/recycling.

A second goal of this research is to further explore the use of vacuum technologies for arc interruption. Elucidating issues such as understanding high-frequency transients that can occur at elevated voltages is a primary objective of this research portion.

The third aim of this research stream spans all three alternative SF6 technologies. With the implementation of new insulating technologies, independent of the composition, the ability to detect wear of internal components noninvasively is of high importance to users. Evaluating new detection technologies, detection techniques previously used for SF6-based systems, and/or mechanical wear detection techniques used for other gas systems to determine physical system condition is planned.

The findings of this work are intended to guide the industry on how to best respond to the ever-increasing pressures to reduce SF6 emissions and usage.

EPRI Guidebook on GIS and GIL – 2025 update: Under this task in 2025, EPRI plans to use its GIS laboratory to introduce classically observed SF6 (and C4-fluoronitrile) leaks and defects in components and reproduce abnormalities observed by users on equipment in the field. Systematically standardizing an assessment of the technologies, to observe detriments accurately and precisely in live GIS, is planned to be the focus. The findings from this work will help the industry with specification and interpretation of deficiencies and irregularities.

Anticipated Deliverables

Deliverable Description Date
Emerging issues with new GIS and GIL technologies EPRI research results and industry trends and lessons learned December 31, 2025
EPRI Guidebook on GIS and GIL – 2025 Update Practical and well-informed guidance on GIS and GIL leak detection and condition monitoring December 31, 2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002027117 GIS and GIL EPRI Guidebook – 2023 Edition This guidebook is updated each year to include the latest research. In 2022, chapters were added on SF6 leak detection. December 2023
3002027120 SF6 Alternatives: Industry Status Update for 2023 A status update of the current state of the industry when it comes to progression and availability of SF6 alternatives. December 2023

7 - P37.113: Polymer Bushing Life Management

Objective

The reliability and availability of a utility’s power transformers depend highly on the condition and performance of transformer components such as bushings. Today, as much as 20% of transformer failures could be related to bushing issues. Polymer bushings offer an attractive alternative to traditional oil-impregnated paper bushings with porcelain exteriors. However, there is not a significant body of experience with these newer bushing technologies. In particular, the longevity and reliability of dry-type bushings are a significant unknown. A portion of the work proposed under this effort aims to understand some of the unknown information surrounding the application of polymer bushings through long-term testing under simulated field conditions and climate extremes. Any concerns identified in this long-term testing can then be studied with more targeted research.

This project also aims to produce guidelines on selection, application, operation, and diagnostics for these new technologies based on research to date and the aggregate shared experience of funding members to aide with adoption of technology.

The research is structured to specific uncertainties surrounding polymer bushings by performing a mix of long- and medium-term laboratory experiments, as well as data collection to extract insights in the short term:

  • How do polymer bushings perform under extreme environmental conditions and operating stresses (electrical, thermal, and mechanical)?
  • How would the polymer bushings be affected by overloading, and does this require different specification and/or operating practices?
  • Are present monitoring and diagnostic test methods sufficiently effective for assessing the condition of polymer bushings?
  • Are there unique operating or maintenance concerns with polymer bushings?
  • Can we identify prevalent failure modes or emerging reliability issues earlier to mitigate concerns with widespread adoption?

Research Value

The core value that this research aims to provide includes:

  • Greater confidence in the adoption of polymer bushings
  • A sound technical basis for decisions when specifying, operating, and maintaining new polymer bushing technologies
  • Lower life-cycle risks and costs to improve reliability and affordability
  • Help in assessing and managing risks through early insights gleaned from laboratory testing and field experience
  • Better understanding of the efficacy of various monitor and diagnostic test technologies applied to polymer bushings

Planned 2025 Research

  • Performance of polymer bushings under extreme environmental conditions and operating stresses: In a full-scale setting, EPRI intends to conduct long-term bushing testing of polymer bushings under a range of environmental and operating stresses. The 138-kV research substation in Lenox, MAassachusetts affords the opportunity for convenient outdoor testing under a wide range of ambient temperatures and precipitation types. In addition, an installed rain spray equipment is available to simulate wet climates. The bushings can be simultaneously energized to rated voltage while circulating currents up to, and in excess of, rated current. This is a continuation of a test program that commenced in 2019 and is ongoing.

  • Guidelines on specification and maintenance of polymer bushings: Work will continue to incorporate the distilled learnings and insights developed through this research and through the combined operating experience of participating utilities into a series of guidelines on application, installation, operation, maintenance, and diagnostics of polymer bushings.

  • Targeted testing of specific concerns: The full-scale testing in the 138-kV research substation is necessarily a long-term task. To accelerate learnings, and to provide actionable information on specific areas of concern, —such as sensitivity to overloading or exposure to high mechanical stresses, —EPRI intends to perform specific, targeted tests to address concerns identified by participating members. In 2024, research plans include an investigation to better understand sensitivity to overload. In 2025, a potential targeted investigation might involve laboratory-investigation of bushing reliability when exposed to high cantilever forces that might be experienced under through-fault conditions.

  • Analysis of the reliability and performance experience of polymer bushings: This task will provide the results of a broader statistical study to classify the reliability, performance, and life expectancy of polymer bushings utilizing using voluntary contributions of data and field experience from interested members.

Anticipated Deliverables

Deliverable Date
Performance of Polymer Bushings Under Extreme Environmental Conditions – Technical Update Report documenting 2024 test results of polymer bushings tested in the 138-kV research substation in Lenox, Massachusetts December 31, 2025
Guidelines on Specification and Maintenance of Polymer Bushings – Technical Update Report documenting industry guidance and best practices on applications, operation, and diagnostics of polymer bushings December 31, 2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002027124 Guidelines on Specification and Maintenance of Polymer Bushings: 2023 Update Updated version of Polymer Bushing Guidelines December 2023
3002027125 Performance of Dry Bushings Under Extreme Environmental Conditions: 2023 Update Testing and monitoring results of polymer bushings tested in the 138-kV yard in Lenox, Massachusetts in 2023 December 2023

8 - P37.114: Substation Physical Security

Objective

The energy sector’s assets, systems, and networks are so vital that their incapacitation or destruction could have a debilitating effect on national security, the economy, and/or employee and public health and safety. Other vital industry sectors (for example, water, banking, and transportation) depend on safe, reliable electricity.

Two types of threats exist for transmission and substation assets, including natural threats and man-made threats. Natural threats can include tornadoes, hurricanes, earthquakes, wildfires, and geomagnetic disturbances. Man-made threats can include vandalism, theft, drone attacks, sabotage, and cyberattacks.

Emerging technologies may exist that could enhance situational awareness and asset protection. This research seeks to enhance resilience and reduce the potential of disruptions in substations through a better understanding of physical security events and the efficacy of mitigation and response options. EPRI regularly collaborates with industry, government, academia, and others to share and leverage knowledge and resources and avoid duplication of efforts. EPRI’s research and development (R&D) intends to identify, evaluate, or develop better ways to detect, deter, and respond against these threats.

Research Value

The intent of this project is to continue a multi-year, multi-layered approach to improve security. The project focus is on these key tasks:

  • Intrusion Detection Devices: Because many substations are unmanned, there can be a need to use technology to detect intrusions into the substation. There are numerous detection devices on the market. EPRI aims to provide third-party objective testing of those devices and applicability in the substation by repeatable evaluation in EPRI’s 138 kV research substation.

  • Robotics Technologies: Automated or teleoperated robotics hold significant potential to increase situational awareness during physical security events. This research aims to create laboratory tests using security scenarios and evaluate the effectiveness of robotic systems to increase situational awareness, decrease response times, and decrease risks during the simulated events. The result of this research is to further understand how robotics can assist in the unmanned substations.

  • Uncrewed aircraft systems (UAS) Detection Technologies: UAS present security risks to substations, from either malicious or unintended operations. This research explores technologies that could detect unauthorized UAS operations around substations. Research objectives include understanding detection effectiveness in substation environments as well as potential unintended consequences. There is already a body of research for counter-UAS technologies. However, the field is rapidly expanding, and the research must stay at the forefront.

Planned 2025 Research

The importance of safe and reliable electricity as a critical resource for the public good cannot be overstated. The benefits of EPRI’s work in this area may include:

  • Improving the resilience and protection of critical infrastructure
  • Leveraging R&D on cross-cutting topics, such as ballistics, intrusion detection, and insider threats
  • Establishing a technical basis to enhance security and decision making
  • Detecting and deterring threats for a substation
  • Increasing understanding of the component vulnerability to physical attacks
  • Increasing understanding of the effectiveness of protective, defensive, and recovery technologies
  • Understanding the impact of various mitigation and hardening solutions on day-to-day operations
  • Protecting public and employee health and safety

Anticipated Deliverables

Deliverable Date
Intrusion Detection Devices in Substations – Technical Update – Furthering research on the detection devices in the substation and increasing situational awareness December 2025
Robotics for Physical Security Assets – Next Steps in Research – Furthering research for robotics in decreasing manned tasks for substations December 2025
UAS Detection Technologies – Current start of the technology and assessments of new technologies December 2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002025362 Applying Robots to Improve Physical Security at Utility Sites: Updated Evaluation Results Understanding and research of robotics in assessing the physical security of the substation December 2022
3002028197 Compendium of 2014–2021 EPRI Ballistic and Blast Testing Technical Reports Compendium of all EPRI ballistics testing for transmission and substation (T&S) assets December 2023

9 - P37.116: HVDC Converter Stations and Flexible Alternating Current Transmission System (FACTS) Devices

Objective

This project assesses and evaluates high-voltage direct current (HVDC) and flexible alternating current transmission systems (FACTS) technologies. HVDC and FACTS technologies offer options to increase the transmission capacity of existing lines. A dc transmission system also provides an effective alternative for integrating renewable resources, increasing the overall power system reliability, and transferring bulk power.

Significant advancements in HVDC and FACTS technologies have been made in recent years—for example, the development of voltage-source converter (VSC) technology. As HVDC transmission systems and FACTS are planned, built, and refurbished, it is important that the power industry has access to the latest technologies and options to make proper decisions. Guidelines are needed to match applications with available approaches and to guide utilities in the selection between an ac or dc system. Research is also needed to address the challenges with and reduce the costs of HVDC and FACTS controllers, which will increase their applications. In addition, applications of HVDC and FACTS for renewable integration and smart transmission grids must be studied.

EPRI conducts investigations and develops reference materials that capture and consolidate the experience and knowledge of the industry on HVDC and FACTS technologies. EPRI continues to build a comprehensive library of information on HVDC and FACTS technologies to inform technology application and management.

The objectives of this project are to:

  • Provide state-of-the-art information on HVDC and FACTS technologies.
  • Assist members in selecting proper options for renewables integration, increased capacity, and other applications
  • Identify new applications and opportunities to reduce costs for HVDC and FACTS
  • Develop operational, maintenance, and replacement strategies for HVDC and FACTS
  • Identify and conduct research to address knowledge gaps

Research Value

The project can provide the following benefits:

  • Research results to help with the construction and operation of cost-effective HVDC and FACTS infrastructures
  • Data to help in selecting an optimal option (HVDC or HVAC with FACTS) for members’ utility systems
  • A comprehensive and current resource for members to keep abreast of HVDC and FACTS technologies
  • Increased overall system controllability, stability, and reliability by using HVDC and FACTS
  • Newly developed concepts, such as dc grids and dc circuit breakers to support a smart grid

Planned 2025 Research

This project seeks to enhance knowledge of HVDC and FACTS technologies in the following ways:

Novel Concepts for DC Circuit Breakers and DC-DC Transformers: In previous years, a new, innovative tri-pole concept was developed to maximize the power transfer capability of ac-to-dc line conversions. Another new concept—transformerless voltage source converters—was studied, and the results were documented. The operational challenges of dc grids and the requirements for dc circuit breakers and dc-dc transformers were studied in 2016. In 2017, new VSC concepts on full-bridge modular multilevel converters and cascaded converters (half-bridge and full-bridge modules in the same converter) were studied. In 2018, compact dc converter stations were studied using simulations. In 2019, single-arm modular multilevel converter concepts were studied, and a prototype of the new concepts in a lab environment was developed in 2020. In 2020, a novel VSC concept with dc fault-current-blocking capability was studied, and prototype development in a lab environment was performed in 2021. In 2022, the state of the art of dc circuit breakers—including hybrid-type (mechanical plus solid state) breakers and dc-dc transformers—was documented. In 2025, different possible VSC topologies such as alternate arm converter for fault current limiting will be documented. In addition, new dc circuit breaker concepts and dc-dc transformer concepts will be explored in future years. Other new VSC concepts are being identified and developed. Some of these new concepts might be demonstrated at utility sites using supplemental funding. The study of each topic is prioritized with guidance from the members and the industry.

Best Practices for Operation, Maintenance, and Refurbishment for Life Extension of FACTS Controllers – SVC and STATCOM Life Extension Guidelines: This task systematically identifies needs in the operation, maintenance, and replacement of FACTS controllers. Initially, utilities with existing FACTS controllers might be surveyed to understand the existing maintenance and operation practices, and their needs documented and prioritized. Based on the survey results, best practices for operation and maintenance as well as replacement strategies may be developed. Plug-and-play components, which are vendor-independent, are necessary to facilitate upgrades of FACTS controllers. The requirements for plug-and-play components and potential components that could be plug-and-play may also be identified. Life extension guidelines for FACTS controllers—such as SVC, static synchronous compensator (STATCOM), static synchronous series compensator (SSSC), and unified power flow controller (UPFC)—will be developed in future years.

Performance and Cost Comparison of FACTS Controllers: In 2018, utility surveys were conducted to understand the operation and maintenance of some of the FACTS controllers, and the best practices were documented. In 2019, FACTS valve cooling system life assessment studies were conducted with utility surveys using practical applications. In 2019, novel control strategies were developed to operate a STATCOM as an active filter to absorb system harmonics. In 2020, a comparative study on the performance and costs of thyristor-controlled series capacitors (TCSCs) and SSSCs was started; it was completed in 2021. Comparison of the performance and costs of other FACTS controllers—such as SVC, STATCOM, and synchronous condensers—was started in 2021 and completed in 2022. In 2023, EPRI compared the performance and costs of UPFCs, interline power flow controllers (IPFCs), and other FACTS controllers. In 2024, the application of STATCOM with energy storage was studied and documented. A FACTS Application Guide, which includes all FACTS controllers, was developed in 2024. Several case studies will be developed with different FACTS device applications for power grids, including renewable applications in 2025 and beyond.

HVDC & FACTS Technology Watch Newsletter: To foster new opportunities in the HVDC and FACTS areas and disseminate technical developments in a timely manner, HVDC & FACTS Technology Watch is published annually. The newsletter reports on current and new HVDC and FACTS installations around the world as well as the latest developments in HVDC and FACTS technologies.

HVDC & FACTS Conference and Workshop: An HVDC & FACTS conference or a workshop is organized in alternating years, and a workshop is expected to be held in 2025. The conferences provide a forum for members to learn, gain, and share experience with other utilities and for suppliers to present their latest technology to members. The workshops vary in scope from HVDC and FACTS basics to specialized topics, such as modular multilevel VSCs.

Updated HVDC Reference Book: Information is being developed for the HVDC Reference Book (also known as The Olive Book). The updates incorporate new developments and experiences and assist users in specifying HVDC system components, designing overhead lines, and assessing existing HVDC systems for life extension options. In 2020, EPRI updated the chapter on HVDC overhead lines; in 2021, EPRI updated the chapter on HVDC cables. In 2022, EPRI updated the chapter on VSC-based dc transmission. In 2023, all the chapters were edited and updated with the latest information; hard copies of the HVDC Reference Book were published in March 2024. In 2024, EPRI updated the chapters on converter cost estimates. In 2025, EPRI plans to update HVDC cables and VSC chapters with the latest technical information. The electrical effects chapter with the latest information obtained from testing will be updated in future years.

Anticipated Deliverables

Deliverable Description Date
Novel VSC Topologies for Fault Current Limitation Different voltage source converter topologies and their applications for renewable integration and dc grids will be documented with the goal of limiting dc line fault currents. December 31, 2025
Performance and Cost Comparison of FACTS Controllers – TCSC, SSSC, SVC, STATCOM, UPFC, IPFC, and Synchronous Condenser (Technical Update) – Case Studies Case studies will be developed for the application of TCSC, SSSC, SVC, STATCOM, UPFC, IPFC, and synchronous condensers for increasing transmission capacity. December 31, 2025
Best Practices for Operation, Maintenance, and Refurbishment for Life Extension of FACTS Controllers – SVC and STATCOM Life Extension Guidelines Develop life extension guidelines and techniques to improve operation, maintenance, and refurbishment of SVCs and STATCOMs. December 31, 2025
HVDC & FACTS Technology Watch Newsletter (Technical Resource) The newsletter provides updates on recent HVDC and FACTS projects and new technologies. December 31, 2025
HVDC & FACTS Workshop The workshop provides training to utility engineers on specific HVDC and FACTS topics prioritized by the advisors. December 31, 2025
Updated HVDC Reference Book – The Olive Book (Technical Update) Update the chapters on HVDC cables and VSC converters with the latest information. December 31, 2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002027330 EPRI HVDC Transmission Reference Book: 2023 Edition EPRI HVDC Transmission Reference Book (The Olive Book) is a state-of-the-art guidebook that provides transmission companies with a comprehensive, single source of technical information and guidance for designing, building, operating, and extending the life of HVDC transmission systems. December 2023 - Hardcopy: March 2024
3002027143 Technical Performance and Cost Comparison of FACTS Controllers: Unified Power Flow Controller (UPFC) and Interline Power Flow Controller (IPFC) A comparative study of the technical performance and cost comparison of UPFC and IPFC with other FACTS controllers for increased transmission capacity on existing ac lines. December 2023
3002024631 Novel Concepts for DC Circuit Breakers and DC-DC Transformers The state-of-the-art topologies for DC circuit breakers including mechanical, solid-state, and hybrid topologies were documented. Several proposed DC-DC transformer concepts were also documented. December 2022
3002024629 Technical Performance and Cost Comparison of SVC, STATCOM, and Synchronous Condenser A comparative study of the technical performance and cost comparison of the shunt FACTS controllers – SVC and STACOM as well as non-FACTS controller – Synchronous Condenser was documented for making decisions on increasing transmission capacity on the existing assets. April 2022
3002021402 Novel Voltage Source Converter Topology with Fault Current Blocking Capability A novel concept was developed replacing the diodes with thyristors in a half-bridge module of a voltage source converter to block fault currents coming from AC system for DC line faults as a prototype in a lab environment, and the operation was demonstrated successfully. June 2021
3002021404 Technical and Operational Comparison of series FACTS controllers – TCSC and SSSC A comparative study of the performance and cost of the TCSC and SSSC was documented for making decisions on increasing transmission capacity. July 2021
3002019243 Single Arm Modular Multilevel Voltage Source Converter Concepts – Prototype Development A voltage source converter was developed with a single arm only (instead of three arms) as a prototype in a lab environment, and the operation was demonstrated successfully. May 2020
3002019241 HVDC & FACTS Workshop An HVDC & FACTS technology update workshop was provided by WebEx, which was well-attended by more than 80 utility engineers. November 2020
  • P35.019: HVDC Lines
  • P36.008: HVDC Cable and HVAC Submarine Cable Systems
  • P40.E: HVDC Planning

10 - P37.117: Using Voltage and Current Measurements for Monitoring Asset Conditions

Objective

The project objective is to effectively use existing data streams of voltage and current to evaluate substation equipment health. The focus of this project is on voltage and current signals that are already being measured for other functions (i.e. protection, control, metering) and readily available in many substations, without the need for additional sensors specific to asset health monitoring. Research interests include improved understanding of online voltage and current waveforms as indicators of asset health, evaluation of the effectiveness of commercial solutions, and development of novel techniques.

Research Value

The project can provide the following benefits:

  • Improved risk assessment of substation assets using minimal quantities and types of data
  • Reduced operation and maintenance (O&M) cost for monitoring major substation equipment health
  • Increased reliability of power supply through early warning of asset failures
  • Enhanced safety by reducing unexpected catastrophic equipment failure

Planned 2025 Research

This project seeks to enhance knowledge of HVDC and FACTS technologies in the following ways:

Evaluate capacitively coupled voltage transformer (CCVT) signals across CCVT degradation: This project intends to catalog CCVT failure signatures to link incipient CCVT failure to various voltage waveforms. Research may be performed on a combination of CCVT computer models and some quantity of physical CCVT assets, depending on the level of member engagement. The project intends to stress CCVTs to push them toward failure through thermal cycling, with additional waveform data collected and compared to baseline. The forensic examination of failed CCVTs may identify which CCVT component failure was the primary cause of degradation, possibly offering a link between waveforms and specific component degradation. The intention of this task is to improve our understanding of the complexities of CCVT failure, gather data for future development of CCVT failure detection algorithms, and enhance EPRI’s skill set of CCVT forensic analyses for member applications.

Evaluate link between voltage/current data and state-of-the-art transformer failure indication techniques: This research constitutes a review of literature to examine what transformer failure detection techniques or algorithms have been proposed but not yet developed into commercial technologies. The intent of this task is to identify which methods may be most promising to transition from a theoretical space to more applied evaluation in a substation test bench or controlled high-voltage field deployment by EPRI and its members near term.

Anticipated Deliverables

Deliverable Date
Evaluation of CCVT Secondary Voltage Recordings During CCVT Failure (Technical Report) December 31, 2025
Methods to Evaluate Large Power Transformer Health Using Online Voltage and Current Measurements (Technical Report) December 31, 2025

Past EPRI Research on Topic

Product ID Title Description Published Date
3002027137 Testing and Lessons Learned on Using Voltages and Currents: Key Transformer Parameters This technical update provides updated results of laboratory tests from the EPRI 138-kV research substation and Charlotte-based lab test plans to evaluate ABB Hitachi’s transformer analyzer. December 2023
3002027138 Using Voltages and Currents: Applicable Assets This report is a review of literature to determine which substation assets are likely candidates for health monitoring using voltage and current signals. December 2023
3002024635 Using Existing Voltages and Currents in Substations for Transformer Diagnostics: 2022 Update This deliverable provides the results of laboratory tests from the EPRI 138-kV research substation to evaluate ABB Hitachi’s transformer analyzer. December 2022
3002021406 Using Existing Voltages and Currents in Substations for Transformer Diagnostics This technical report describes the installation of the voltage and current system in Lenox to monitor the key transformer parameters from Hitachi Energy. December 2021