P35.008: Line Resiliency
Objective
Overhead line failures have significant negative consequences for both utilities and the general public, resulting in line resiliency being of critical importance to utilities. Ensuring resiliency is especially challenging with a steadily aging grid and climate change. Recent statistical data points to a consistent and sustained increase in the average number of weather-related outages 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.
The objectives of this project are to provide guidance on how to increase overhead line resiliency through the hardening of new and existing lines and, when failures do occur, to limit and contain the extent of damage.
Research Value
- Significant resilience may be obtained from this research through the correct application of technologies, tools, and design techniques to reduce or avoid unintended structural, mechanical, and geotechnical failures.
- Guidance is provided on how intelligent hardening for both new and existing assets may be achieved.
- Knowledge may be gained relating to grid sensitivities and modes of failure, and improved accuracy in the quantification of probability and uncertain load events.
- Emergency restoration capability may be enhanced though access to improved restoration strategies.
Approach
In 2026, EPRI aims to enhance transmission line resiliency by performing the following tasks:
Quantify Transverse Cascading Loads: While EPRI and other institutions in the transmission industry have conducted research into longitudinal cascading events, transverse cascading loads remains a knowledge gap. EPRI aims to build and operate a transverse cascading test line to quantify loads experienced by structures during these events and ultimately help engineers design against them. In 2026, EPRI aims to install a test line and perform exploratory tests to simulate transverse cascades to then execute upon in subsequent years.
Develop Design Guidance to Prevent Phase-to-Phase Flashover Resulting from Asynchronous Conductor Movement: When spans are long or phases are horizontally compacted, utilities have experienced phase-to-phase flashovers during gusty wind conditions. There is very little guidance on how this problem should be avoided. EPRI aims to vet previously proposed design techniques and will examine past wind tunnel research and climate data to determine an appropriate design technique to prevent phase-to-phase flashovers.
Produce Enhanced Climate Risk Maps: Significant value can be obtained by exploring climate data as it relates to weather events impacting the structural and electrical reliability of overhead lines. EPRI intends to leverage new and existing climate data to produce a range of enhanced climate risk maps for specific weather events.
Derive Lessons from Failure: With every structural or mechanical failure event, there is a potentially valuable lesson to be learned by line design engineers. Very often the events leading to failure are often multi-dimensional. When the root causes and possible preventative actions from these events are documented, they can teach engineers how to become better designers. In 2026, EPRI aims to add multiple case studies to its current guide on documented failures related to how structures have failed in the past and how future generations of engineers may use this information to achieve more resilient designs.
Rapid Response Emergency Tower: The Rapid Response Emergency Tower was developed under EPRI’s Technology Innovation Program in support of project 35.008. In 2026, EPRI aims to compile instruction manuals and finite element modeling (FEM) models for various configurations in order to facilitate applications to various restoration scenarios.
Host a “Design for Extreme Environments” Workshop: EPRI has interacted with utilities that operate transmission assets in extremely corrosive environments. There is potential value in understanding the performance of hardware, structures, and components subjected to such conditions. EPRI plans to host a workshop/information sharing session in collaboration with P35.002 (Conductor, Shield Wire, and Hardware Corrosion) and P35.003 (Structure and Foundation Corrosion Management), to facilitate mutual understanding of potentially useful countermeasures for extreme environments.
Provide Tools and Resources on the Transmission Resource Center: The following calculators, tools, result summaries, and references are planned to be available on the Resiliency Transmission Resource Center:
| Resource Title | Resource Type |
|---|---|
| Dynamic Impact Load Testing – 2023 Results | Results Summary |
| Learning from Failure – Case Studies in ImprovedEngineering | Results Summary |
| EPRI White Paper on Overhead Line Resiliency | Reference |
Anticipated Deliverables
| Product Name | Deliverable Type |
|---|---|
| Quantification of TransverseCascading Loads: 2025 Edition | Technical Update |
| Electrical Reliability: Designfor Asynchronous Conductor Movement | Technical Update |
| Fundamental Research IntoClimate Impacts That Matter | Technical Update |
| Learning from Failure - CaseStudies in Improved Engineering | Technical Update |
| Rapid Response Emergency Tower | Technical Update |
| Workshop - Design for ExtremeEnvironments | Workshop |
Past EPRI Work on Topic
| Product ID | Title | Description | Published Date |
|---|---|---|---|
| 3002029585 | Practical Determination of Dynamic Load Impact Factors | EPRI constructed a unique test facility to enable extensive evaluation of multiple factors that affect broken conductor load magnitudes. Empirical data from the facility enabled the calibration of an accurate dynamic FEM model and the compilation of a simplified algorithm to quantify the magnitude of broken conductor loads unique to a transmission line application. | Nov. 2024 |
| 3002027006 | Tools and Solutions for Effective Emergency Line Restoration | This extensive report covers a wide range of emergency restoration systems, effective restoration strategy, emergency restoration training, and tools useful for emergency repairs on transmission systems. full stop | Dec. 2023 |