Objective
Inspection, assessment, and maintenance of overhead transmission systems is vital for the safe, reliable, and efficient delivery of power. Not only is the overhead transmission infrastructure aging, but there is an increased demand for power delivery and an increase in severe weather events. This situation places an even greater importance on understanding the condition of overhead transmission assets and making timely repairs or replacements.
Additionally, inspection, assessment, and maintenance activities for an entire system are expensive. Utilities are evaluating ways to make these activities more efficient while maintaining their effectiveness.
This project aims to provide:
- Comprehensive guidance for inspecting and assessing overhead transmission assets
- Best practices and lessons learned from utilities
- Evaluations of the effectiveness of new and emerging inspection technologies and methodologies
Research Value
EPRI intends to leverage its more than fifty years of research in overhead transmission assets, relationships with more than fifty utilities, subject matter experts, and laboratory resources to collate relevant information and evaluate technologies to provide its members with the capability to:
- Enhance the effectiveness of inspection and assessment processes
- Provide a robust technical foundation for informed decision making
- Assist in assessing and managing risks related to the condition of overhead transmission line components
- Maintain or reduce life-cycle costs, contributing to affordable electric rates
- Improve worker and public safety by detecting high-risk components before they fail
Approach
The objectives of this project are planned to be achieved by performing the following tasks:
Update the Inspection and Assessment Reference Book (The Yellow Book): This reference book is intended to be an evolving resource designed to become a single living repository of information on the inspection and assessment of overhead transmission lines. In 2026, EPRI intends to make updates in the reference book related to use of unmanned aerial vehicles for inspection of overhead transmission systems as well as new and emerging inspection technologies.
Update Inspection Field Guides: EPRI’s field guides provide 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 what actions to take. In 2026, EPRI intends to update the media content and update conditions assessment to reflect the most recent learnings and improve the accessibility and relevance of the guides.
Evaluate New and Emerging Inspection Technologies: This task focuses on inventorying and evaluating the efficacy, practicality, and application of new and emerging inspection technologies. EPRI plans to monitor all new technologies on its Tech Radar website as well as evaluate the early fault detection (EFD) technology developed by IND.T which utilizes radio frequency sensors and advanced analysis to detect and locate failing assets.
Develop Training Database for Artificial Intelligence Image Processing: Utilizing artificial intelligence (AI) to accelerate the processing of images from visual inspections is one method to increase the efficiency and decrease the cost of inspection of overhead transmission systems. One of the challenges with AI image processing is the lack of good data to train models. EPRI plans to gather and classify as many overhead transmission inspection images and datasets as possible to aid the training of AI models.
Develop an Asset Reliability & Availability Model: This task focuses on the development of an Asset Reliability and Availability Model for overhead transmission lines with a specific focus on the selection of appropriate maintenance regimes. Many utilities face the challenges of aging infrastructure and how best to handle the end of life of these assets. This model aims to use historic data as well as various other utility inputs to guide users to a selection of an appropriate maintenance practice per asset.
Host an Inspection, Assessment, and Maintenance Workshop: This task is aimed at enhancing the knowledge and skills of professionals involved in the inspection and maintenance of overhead transmission systems. This workshop will provide participants with insights into best practices, emerging technologies, and methodologies for effective assessment and maintenance of transmission assets. By bringing together industry experts and utility representatives, the workshop will facilitate discussions on challenges faced in the field, share lessons learned from past experiences, and promote collaboration among utilities to improve overall safety and reliability in power delivery. Participants can expect to gain valuable information that will aid in making informed decisions regarding their inspection and maintenance strategies.
Provide Tools and Resources on the Transmission Resource Center: The following calculators, tools, result summaries, and references are planned to be available on the Inspection and Assessment Transmission Resource Center:
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The Inspection and Assessment Reference Book (The Yellow Book)
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Overhead Transmission Line Asset Management Model
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Assessing the BATCAM’s Ability to Detect Corona
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Transmission Inspection Practices and Information Management
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Selecting Effective Inspection and Assessment Methods and Technologies
Anticipated Deliverables
| Deliverable | Deliverable Type |
|---|---|
| Inspection and AssessmentReference Book (The Yellow Book) | Reference Book |
| Daytime Discharge Inspectionof Transmission and Distribution Overhead Lines | Field Guide |
| Inspection of Conductors forOverhead Transmission Lines | Field Guide |
| Inspection of TransmissionLine Grounding Systems | Field Guide |
| Visual Inspection of Polymer Insulators | Field Guide |
| Visual Inspection ofPorcelain and Glass Disc Insulators | Field Guide |
| Visual Inspection of SteelStructures | Field Guide |
| Visual Inspection of WoodStructures | Field Guide |
| Inspection ofTransmission Line Foundations | Field Guide |
| Inspection, Maintenance, andTroubleshooting of Sacrificial Anode Cathodic Protection Systems forTransmission Line Structures | Field Guide |
| Visual Inspection of AvianIssues on Transmission and Distribution Structures | Field Guide |
| Corona Rings for PolymerInsulators | Field Guide |
| Tier 1, Above- and Below-GradeCorrosion Assessment of Weathering Steel Transmission Structures | Field Guide |
| Construction and Inspectionof Compression Connectors for Overhead Transmission Lines | Field Guide |
| Infrared Thermography forOverhead Transmission Lines | Field Guide |
| Transmission Line AerialMarking & Lightning | Field Guide |
| Live Working Rope | Field Guide |
| Corrosion Assessment ofWeathering Steel Transmission Structures | Field Guide |
| Evaluation of New andEmerging Inspection Technologies | Technical Update Report |
| Inspection, Assessment, andMaintenance Workshop | Workshop |
Past EPRPI Work on Topic
| Product ID | Title | Description | Published Date |
|---|---|---|---|
| 3002029552 | Evaluation of Insulator In-ServiceInspection Tool | Evaluation of PositronInsulator Testers | 2024 |
| 3002021459 | State of the Art ofProcessing Inspection Imagery | Summarizes the currentcapability and use of image processing for transmission line inspections. | 2021 |
| 3002018881 | Utility Inspection andAssessment Practices | Summarizes the latestinspection and assessment practices around the industry. | 2020 |