Overhead conductor line sag measurement

The Innovation Exchange programme is working alongside Scottish & Southern Electricity Networks Transmission (SSEN-T), the owner of north Scotland’s high voltage electricity assets. SSEN-T is looking to engage innovators that can help them solve the challenge of accurately detecting sagging overhead conductor cables in remote locations.


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Scottish & Southern Electricity Networks Transmission (SSEN-T) is looking to use open innovation to find potential solutions that can be developed to suit the conditions and needs of the challenge. Successful applicants will be given an opportunity to pitch their innovation to SSEN-T. Selected solution(s) will be trialled at key SSEN-T sites, with the possibility of further roll out if trials are successful.


Scottish & Southern Electricity Networks Transmission (SSEN-T) is the owner of the high voltage electricity assets in the north of Scotland, including the 132kV, 275kV and 400kV electricity network. Whilst operating in the north of Scotland, SSEN-T faces some of the most extreme weather conditions in the UK. During winter periods temperatures can drop as low as -30°C with wind speeds up to 110 mph. Such weather conditions can result in thick, dense ice forming on the overhead lines, causing them to sag under the weight of the accrued ice.

Recently a 132kV overhead line has been fitted with ACCC conductors, which are high-temperature low-sag conductors, however subsequent design studies have indicated that the conductor will sag to an unacceptable level due to ice build-up. This may present a hazard to third parties and/or require additional manpower as a result of potential outages. These conductors and transmission towers can be in very hard to access locations which may require a person walking long distances over difficult and often mountainous terrain to address issues.

The ideal operating height of such lines typically around is 6 - 7m above ground level, however under iced conditions ground clearance can reduce to as little as a few meters with the potential for serious issues to occur.

Ice build-up on conductors of sufficient weight to cause problematic sagging is thought to be unlikely, but a lack of records makes it difficult to accurately define the risk level and subsequent mitigation strategies. To control the risk, SSEN-T has previously installed an indirect monitoring system aimed at detecting weather conditions leading to ice build-up and sending a notice when these conditions are present. This system has proved unreliable, producing a high number of false alarms, requiring interpretation of photos to discern if a potential risk is occurring and therefore costing significant staff time. 

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