Overview & Events
Objective (The Why)
Recent statistical data points to a consistent and sustained increase in the average number of weather-related outages in the USA. Worldwide, continued significant impacts from storm events place a clear emphasis on the need for increased resiliency in power systems. Not only do overhead lines need to be structurally resilient, but utilities need the ability to respond quickly and effectively to restore damage following extreme weather events. This unfavorable trend has raised the question of how both existing and new lines can be hardened to provide additional resiliency in the network, and where failures do occur, to limit and contain the extent of damage.
In addition, since some proportion of overhead line failures can still occur due to exceeding design conditions under extreme events or material degradation, the question is raised: What existing and emerging restoration systems are available, and how can these be effectively incorporated into an integrated restoration strategy that seeks to maximize cross-departmental integration to result in the lowest possible response time? How can utilities create and grow internal emergency response capability and achieve continually improved emergency response times?
The objectives of this project are to enhance transmission line resiliency by:
- Seeking to develop new design approaches and tools to achieve hardened overhead lines in both new and existing assets.
- Provide guidance on the application, design, and effective use of emergency structures, restoration strategies, and emergency preparedness across the full range of transmission voltages.
Research Value
The project provides utilities the ability to identify potential weaknesses in existing overhead lines, and it equips engineers with practical, implementable solutions to achieve line hardening and enhanced resiliency.
By applying more effective restoration strategies, transmission asset owners will be able to reduce outage times and effectively respond to extreme events when they do occur.
This project may have the following impacts:
- Identification of weak spots in overhead lines
- Strengthening of specific areas to eliminate; reduce weaker areas
- Reduced restoration times following extreme events
- Improves intra- and inter-utility coordination during extreme events
- Enables accurate quantification of high-impact load events
Approach (The How)
Tasks addressed in this project include:
Learning from Failure - Case Studies in Improved Engineering: With every structural or mechanical failure event, there is a potentially valuable lesson to be learnt 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 often multi-dimensional and not the result of a single point of discrepancy. When the root causes and possible preventative actions from these events are documented, they can increase system resiliency and improve design skills of future line designers. EPRI aims to add multiple case studies to this guide, and actively seeks utility participation to expand on the list of case studies.
Tools and Solutions for Effective Emergency Line Restoration: The ability to restore lines rapidly is an is important facet of overhead line resiliency. This task intends to build on the previous research by exploring specific tools and solutions that may be useful in emergency restoration. This research will provide specific and detailed information to enable utilities to assemble and organize their own emergency solutions.
In 2023, EPRI added a detailed design for a wood pole bypass to the existing emergency restoration guide.
Practical Determination of Dynamic Load Impact Factors: Although significant research has been conducted to determine the response of support structures from impact load events, the quantification of case-specific impact load factors is typically beyond the scope of most overhead line design codes. This research aims to enable line designers to quantify case-specific impact load factors following a broken conductor event accurately and easily. This research will incorporate line variables including span length, conductor type, installed tension, insulation type, insulator length, and structure flexibility.
In 2024, EPRI will continue to conduct full-scale experiments, supplemented by finite element modeling to produce a methodology for simpler dynamic impact load determination
Evaluation of the Effect of Seasonal Moisture Variation on Helical Foundation System’s Reliability : Several utilities have experienced helical foundation failures on their systems. One contributing factor is seasonal moisture variations in the soil surrounding the helical anchors leading to a reduction in the anchor capacity and ultimately decreased reliability. In 2023, EPRI conducted a literature review on the topic of soil seasonal moisture variation and its effect on foundation reliability. EPRI plans to determine if there is a need for fundamental research related to this topic. This research would result in design recommendations for engineers to maintain high reliability for helical foundation systems in the face of soil seasonal moisture variations.
Rapid Response Emergency Tower
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Project goal is to build and demonstrate a rapid restoration structure suitable up to 500kV and capable of deployment in 2-3 hours
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Proposed tower is modifiable for a tangent, running angle, or dead-end configuration
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Innovation includes design of the tower’s shipping container which includes all required material for construction
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Construction possible via crane or helicopter
Rapid Emergency Restoration Concept for 220-500kV Transmission Lines
Engagement Opportunities
| Meeting | Scheduled Date |
Location |
Information |
|---|---|---|---|
| Overhead Line Design Task Force | February 19-22 (In-person), February 26-29 (Virtual) | Charlotte, NC | Meeting Materials |
| EPRI R&D Project Update Webcast: P35.005 Composite Structures, P35.007 Line Design, P35.008 Increasing Line Resiliency | May 30: 11:00am - 12:30pm ET | Webcast | Meeting Materials |
| Overhead Transmission 2025 ARP Rollout #1 | June 12: 11:00am - 12:30pm ET | Webcast | Meeting Materials |
| Overhead Transmission 2025 ARP Rollout #2 | July 16: 2:00pm - 3:30pm ET | Webcast | Meeting Materials |
| Overhead Line Design Task Force | August 19-21 (In-person) / August 26-29 (Virtual) | Charlotte, NC | Meeting Materials |
| EPRI Overhead Transmission (Program 35) New Supplemental Launch Webcast | October 8 : 1:00pm - 2:00pm ET | Webcast | Meeting Materials |
| EPRI End of Year Webcast: P35.005 Composite Structures, P35.007 Line Design, P35.008 Increasing Line Resiliency | November 14 : 11:00am - 12:00pm ET | Webcast | Webcast Information |
| Overhead Line Design Task Force - March 2025 | March 10-13 (In-person) / March17-20 (Virtual) | Charlotte, NC | Register Here |