Executive Summary
Fjellnett AS is a regional power distribution company operating in Nord Gudbrandsdalen, Norway, managing over 1,274 km of high-voltage lines and serving more than 14,500 metering points across five municipalities including Lom, Vågå, Sel, Lesja, and Dovre.
During winter, de-energized lines run cold, accumulating ice that, combined with crosswinds, triggers violent low-frequency oscillations known as galloping, causing conductors to whip and ultimately break. The root cause had gone unidentified for years.
Sentrisense deployed its OHL monitoring technology across three phases of a critical span, capturing vibration and weather data from December 2023 to March 2024. The analysis revealed that the installed dampers were inadequately designed for the site's icing conditions, a finding that directly led to a fix that eliminated the problem.
The Challenge
Fjellnett's lines in the mountainous Gudbrandsdalen valley are de-energized during winter, leaving conductors cold and highly susceptible to ice accumulation. With no current flowing through them, the lines drop to ambient temperature, and the conditions in this region are extreme: temperatures remained below 0°C during 98% of the winter, reaching lows of -28.7°C.
The main objective was to determine the factors linked to the fall of power lines installed in Norway. Due to the harsh winter environment, the utility suspected that severe weather and physical stressors were contributing to the mechanical failure of their infrastructure, but they needed precise data to diagnose the root cause.
The Sentrisense Solution
To investigate this issue, Sentrisense deployed its novel technology for monitoring overhead power lines. Data collected from December 2023 to March 2024 was analyzed to detect events associated with high-energy vibrations and damaging power surges. The devices captured critical oscillation records, which were analyzed alongside local meteorological data to accurately map the conditions under which the line was operating.
Results
Acting on Sentrisense's findings, Fjellnett redesigned the dampers, and the conductor failures stopped. Beyond galloping, the monitoring also captured aeolian vibrations throughout the period.
The analysis was completed showing the motion alert system has a clear correlation with actual galloping events, demonstrating that the technology can support not only post-event analysis but also real-time intervention. Following the success of this deployment.
Following the trial, Mr. Asbjørn Vang of Fjellnett confirmed that the utility was highly satisfied with the results, noting that the data successfully validated their ongoing concerns regarding severe ice accumulation and line sagging.
Armed with the proof of high-energy galloping and excessive line weight, Fjellnett engaged SINTEF Energy Research for further mechanical evaluation. Leveraging the context provided by the Sentrisense trial, SINTEF discovered that the specific line clamps in use featured a design unsuitable for the extreme tension and galloping conditions present on that span.
As a direct result of the visibility provided by Sentrisense, Fjellnett was able to replace the inadequate hardware, proactively preventing future line failures and significantly improving the resilience of their grid.