SPIE is realising parts of two 380-kV extra-high voltage lines on behalf of TenneT

Published on 27 August 2020

Braunschweig, 27 August 2020 – SPIE Deutschland & Zentraleuropa, the German subsidiary of SPIE group, the independent European leader in multi-technical services in the areas of energy and communications, was awarded several contracts by the transmission grid operator TenneT, for realising 64 kilometres of extra-high voltage lines in Germany. This involves four contract sections of the new 380-kV North-South power link from Wahle in Lower Saxony to Mecklar in North Hesse and two contract sections of the 380-kV line from Emden to Conneforde. The latter replaced a 220-kV line and is intended to bring wind energy securely to the consumer.

103 Masts for Wahle-Mecklar

The extra-high voltage line between the transformer station Wahle near Peine and the transformer station Mecklar near Bad Hersfeld will have a total length of 230 kilometres. This new line will improve the electricity supply grid from North to South, as well as provide regional power supplies for Southern Lower Saxony and North Hesse. It is one of TenneT’s biggest onshore projects. SPIE is completely realising the four commissioned contract sections. This includes project management, providing the required  infrastructure, building foundations, fitting the steel lattice masts with angular steel brackets using a mobile crane and finally the cable work, which involves the SPIE team with overhead cable fitters, who pull the electric lines from mast to mast.

The two contract sections SPIE was awarded in spring are located between the transformer station Lamspringe and the town of Einbeck in Lower Saxony. “In the two newly awarded contract sections with a total length of 24 kilometres, we are fitting 62 masts with heights ranging between 50 and 70 metres. This is equivalent to a total steel mass of around 4,150 tons”, says the responsible SPIE project manager Oliver Gurgel. The multi-technical service provider started work in April and the two sections are scheduled to be completed respectively in spring and in summer 2021.

SPIE must plan the execution precisely and nevertheless operate flexibly – because on approximately five kilometres of the planned transmission route between Lamspringe and Einbeck there are two existing 110-KV extra-high-voltage lines of Deutsche Bahn, which are only allowed to be disconnected from the grid on an alternating basis and only after agreement with the German Federal Railway Office (Eisenbahnbundesamt), in order to constantly maintain the power supply. “We are temporally laying these overhead cables, in order to put them back after the new masts have been completed. Here we operate very flexibly and continually coordinate with TenneT and Deutsche Bahn”, explains Oliver Gurgel. “During peak times up to 40 fitters will work simultaneously on the two sections.”

The work on the two contract sections of the same power line which were awarded in 2019, with a total length of 15 kilometres and with 41 masts to be built, is expected to be completed, respectively in October and at the turn of the year. The entire new extra-high voltage line is intended to be commissioned in 2024.

3,500 tons of steel for Emden-Conneforde

Between the Emden/Ost transformer station and the Conneforde transformer station, the 220-kV line which is currently used will be replaced by a more powerful 60 kilometre-long 380-kV extra-high-voltage line. The capacity of the current power line is no longer sufficient— amongst other things — to continue to secure the transmission of wind power from Lower Saxony to the consumer. The installation of the new power line is mainly oriented to the existing route and is divided into six contract sections, whereby SPIE is realising the contract sections three and four, with a total length of almost 25 kilometres. “We are realising temporary access roads, performing foundation work and planning and erecting 52 masts with a total weight of 3,500 tons of steel. The conductor cables are subsequently fitted. The new line is to be fitted with a bundle of four cables instead of the single cable on the existing line. This is approximately five times as heavy as the slightly thinner existing line. The transmission performance of the new line increases from 950 amperes to 3,600 amperes”, says the responsible SPIE project manager Frederik Prenzel. The fact that a power line already exists is a challenge. “Here our extensive know-how in these specific operations is a great help. We always use temporary installations, to avoid interrupting the current electricity flow. We also have to take into consideration soils in the region which are often wet and soft.” The completely new power line is to be connected to the grid at the end of 2021. “The dismantling of the old power line is subsequently part of the contract. This is scheduled to be completed in the summer of 2022”, noted Frederik Prenzel.

Decades of experience in realising overhead power lines

“We are pleased to perform these extensive services in the field of extra-high voltage lines for our long-standing client TenneT”, noted Ingo Kiene, Braunschweig Technical Site Manager in the High Voltage division of SPIE Deutschland & Zentraleuropa. “We have decades of experience and special know-how, for erecting extra-high voltage lines and high voltage overhead lines of up to 500 kV”, he continues. Extra-high voltage and high voltage overhead lines are just as individual as they are complex. A wide variety of country and company-specific standards combined with constant changes of network structures require comprehensive know-how and high flexibility. Here SPIE not only takes over the installation of new power lines but also the upgrade and replacement of mast struts and of conductor cables.