Forensic Investigation of a Collapsed Section of a 230 kV Transmission Line

摘要

In January 2014, a freezing fog weather event moved through an area in the state of Washington, near the Columbia River, affecting several utility lines and facilities. As frost began to accumulate on the structures and wires, the loads supported by the structures increased. A partial failure of the primary load supporting system for one section of a 230 kV transmission line was discovered by maintenance crews, and a temporary solution was implemented. Upon investigation the following day, it was discovered that the temporary solution had failed, and a 1.75-mile section of the line had collapsed. An engineering consultant was mobilized to investigate the collapse and determine the cause and mode of the failure. A review of the design details was also performed to determine if a design flaw contributed to the collapse. This paper discusses the forensic investigation process, the findings of the investigation, and the results of the detailed design review. Recommendations to avoid a similar collapse in the future are also presented. This paper is of international interest for all areas subject to similar ice loading situations. Readers will become familiar with the forensic investigation process and learn how to use the investigation results to develop proposed improvements to design criteria.