Impact of Ice and Wind on Overhead Power Lines

The White Paper discusses a monitored winter test of three conductor systems, including bare conductors, covered conductors, and spacer cable systems. This test was conducted in regions prone to severe winter weather, such as the northeastern United States, where ice storms are common. The study evaluated how each conductor type performed under the combined stresses of freezing rain, wind, and ice accumulation. The test data showed that spacer cable systems, which use messenger-supported spacers to separate electrical and mechanical functions, demonstrated improved resilience compared to traditional bare or covered conductor systems. These findings are relevant for engineers designing overhead lines in regions with high exposure to ice and wind loads. [1]

The paper emphasizes the importance of assessing the complete line, including poles, brackets, and foundations, rather than focusing on a single component. This approach is particularly important in regions with a history of severe ice storms, such as parts of Canada and the northern United States. The White Paper outlines documented limits of traditional overhead line designs, noting that moderate wind speeds on heavily iced lines can govern the overall design and increase the risk of failure. Engineers are advised to use monitored severe-weather test data to compare tension changes in different conductor systems and to ensure that the full load path of each structure is evaluated for resilience and safety during extreme weather events. [1]

Ice storms cause long outages because several exposures act together. Ice adds weight to conductors, hardware, and structures, increasing the mechanical load on the system. This is supported by evidence from a white paper published by IEEE Spectrum, which explains how freezing rain, rime ice, and wet snow contribute to the overall burden on overhead distribution lines. The combined weight of ice and the altered shape of conductors in the wind create additional stress, which can lead to failures if not properly managed. The paper highlights the need for engineers to assess the complete line rather than individual components to ensure resilience. [1]

Wind pushes on the larger iced surface, increasing the load on conductors and contributing to potential failures. This is further complicated by the impact of trees and limbs bending into the line, which adds uneven load and impact. According to the white paper, these combined factors can lead to conductor galloping and loss of clearance, increasing the risk of outages. The paper reviews monitored winter test data of three conductor systems, showing how different configurations respond to ice and wind loads. It also summarizes utility records from a major regional ice storm, such as the December 2008 Northeast ice storm, which provides insights into circuit availability and restoration times. [1]

The white paper emphasizes the importance of assessing the full load path of poles, brackets, and foundations when planning for ice and wind exposure. It also outlines how to compare options at the corridor level and apply energized-line safety rules during restoration efforts. The paper explains that a messenger-supported spacer cable can separate the electrical function of covered conductors from the main mechanical load path, improving resilience. These findings are based on a detailed analysis of how various factors interact during ice storms, as documented in utility records and monitored test data. [1]

Sources

IEEE Spectrum

Prepared with AI assistance from the cited sources.