Most recently, Tratos has proudly assisted Manchester University by providing samples of its hybrid High-Temperature Low Sag (HTLS) overhead conductor to be used for the commissioning and initial trials on the small-scale test rig designed by Dr Konstantinos Kopsidas and his research team on the Engineering Campus of Manchester University.

The CEO of Tratos UK Ltd, Dr Maurizio Bragagni OBE, says: “I am proud of the people and the culture of innovation that Tratos, a British- Italian and world-renowned cable-making company, is instilling wherever it operates”.

The unique test rig, designed and developed by Dr Kopsidas, allows for testing a conductor’s capabilities; it aims to quantify the advantages of the new HTLS conductor technologies on increasing the power transfer capability of existing Over Head Lines (OHLs). The length of the conductor fitted into this initial test rig is 12.4m; the test rig has been designed to be capable of having complete control and monitoring of the sample of the overhead conductor during

  • Tension-sag trials
  • Temperature-sag trials
  • Vibration-tension trials
  • Vibration-temperature trials
  • as well as combinations of these.

The test rig is developed to quantify heat transfer mechanisms, particularly at critical low wind conditions (and DLR practices), the effect of radial slack aluminium conditions on vibrations, and the effect of attached hardware on small radial “expansion” of the conductor (bird caging). It is hoped to also subject the conductor to weather during these tests at a later date.

The test-rig capability will help verify and quantify HTLS conductors’ performance above and below the knee-point temperature, which is not usually considered within current standard practices.

The Tratos Cable

The cable supplied by Tratos uses 7xØ4,70mm hybrid carbon fibre rods as a stranded central core, jelly-filled, taped and protected by a sealed tight-fitting aluminium tube. Two layers of Thermal Resistant (TAL) aluminium-zirconium AT1 alloy wires in accordance with IEC 62004 are applied helically around this tube, the inner layer containing 17 wires Ø3,75mm and the outer layer containing 34 wires Ø3,75mm having an external diameter of 32.3 mm.

Weight 1,703 kg/m. Electrical resistance at 20oC 0,0583 Ω/km. Rated tensile strength of the conductor was 21,000 daN. Ultimate tensile strength of the core 18400 daN.

Figure 1. Tratos OHC-HV made with trapezoidal wires

Although the HTLS conductor supplied by Tratos is a design for which TERNA successfully installed over 42km in the San Pellegrino Pass in 2013, and Tratos have supplied other similar designs since then, it is well established that the deployment of the new HTLS conductor technologies is not proceeding at the expected pace. One of the reasons for this delay is the lack of long-term service experience.

The future

Long ago, in many countries across the world, the rapidly growing demand for electrical energy led the bodies responsible for electrical transmission systems to search for technical innovations. They are searching for ways will increase the amount of power transmitted, with improved efficiency, within tight budgetary constraints.

Nowadays, as a result of Russia’s invasion of Ukraine, the world is facing an unprecedented energy crisis. In the UK,  National Grid has warned that Britain could face three-hour planned power cuts to homes and businesses this winter.

Tratos is actively exploring ways to be in a position to offer a path to a more sustainable future for the energy supply. HTLS conductors based on the hybrid centre developed by Tratos are, in effect, a solution to the rising costs of electricity and looming power cuts. Tratos HTLS conductors increase the transmission capacity and reduce the power lost.

Back in 2017, in a case study on line losses and total annual energy savings using Tratos OHC-HV, Tratos researchers calculated that annual savings for three conductors overhead line was 88,339.00 €/km and annual savings for a single conductor at 29,446.41 €/km. In 2017, the researchers used the energy cost of 0.04 €/kWh. Imagine the savings nowadays when energy prices have skyrocketed! According to the latest data from the Department for Business, Energy, and Industrial Strategy, average UK electricity prices per kWh were around 18.9 p/kWh in 2021 but will be closer to 51 p/kWh(~0,6€) by the end of 2022, which is 15 times more expensive than in 2017.

Figure 2. Line loss VS ampacity without solar radiation

In addition to increased power transmission efficiency, the new hybrid load-bearing core can easily be modified to match installation conditions, desired current carrying capacity and geographical and climatic location. It allows an increased span with reduced sag, gives a greater margin of safety for wind and snow loads or can be used to replace existing designs of all metallic conductors with a conductor of reduced mass.

Figure 3. Examples of Tratos OHC-HV conductors

Always innovating, Tratos is researching ways to incorporate fibre optics in its designs and has also manufactured a conductor with three hybrid strength members and three tubular elements –ideal for incorporating fibres or other elements into the cable.

Also, the cost of copper and aluminium base metals has risen dramatically during the last years and is set to continue; traditional Overhead Conductors are becoming increasingly expensive and prone to theft. Empowered with intelligent anti-theft technology, Tratos overhead conductors include a considerably reduced carbon footprint during manufacture and resistance to vandalism due to their unusual structure. This structure makes it difficult to extract the aluminium, and the lack of copper in it makes it less appealing to potential thieves. The new Overhead Conductor has wide-ranging cost benefits as not only does it come at a lower price point, but in line with operational and end-of-life dismantling costs are reduced.

Even with this cost-benefit, the new Overhead Conductor retains high-performance levels, with the ability to meet increased power demands, seasonal power peaks and backup of faulty feeders, thus improving network flexibility.

Tratos will continue to cooperate with academic & research institutions by supplying additional lengths of its HTLS conductor for testing on other test apparatus. Testing different sizes of each type of conductor will also provide additional valuable information, which Tratos’ R&D team will use to bolster innovation and offer more solutions to its clients and society-wide. 

Image source: Courtesy of Tratos

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