Conneforde–Cloppenburg–Merzen: Construction of a 380-kV Extra-High-Voltage-Line

The new route will replace the existing grid section between Conneforde and Cloppenburg and, for the first time, create a direct connection to Merzen. This will significantly increase transmission capacity, particularly for transporting large volumes of wind energy from onshore and offshore facilities in northern Germany to consumption centres in the south.

The project is designated a high-priority measure in the Federal Requirements Plan Act. Project development and planning started in 2015. Construction began in 2023 and is scheduled for completion in 2026. Once commissioned, the existing 220-kV line between Conneforde and Cloppenburg will be dismantled.

TenneT TSO GmbH has entrusted CDM Smith with the comprehensive support of this complex infrastructure project. Within the framework of an EPCM contract (Engineering, Procurement and Construction Management), we are responsible for all planning, supervisory, coordination and management services required for successful delivery.

Our Scope of Services includes:

• Project leadership and management

• Ensuring an efficient project process, including cost, schedule, risk and contract management

• Coordination and management of all planning and construction processes across all project phases

• Structural and object planning

• Permitting procedures and structural design

• Geotechnical investigations and foundation design

• Preparation of tender documents and procurement support

• Development and implementation of project-specific standards for ecological and soil management supervision

• Ecological and soil management supervision during construction

• Support with material procurement and quality assurance (construction logistics)

• Development and implementation of project-specific HSE standards (HSE coordination)

• Safety and health coordination

• Management and supervision of all construction activities, including schedule and cost control (construction coordination)

• On-site construction supervision, including quality assurance and tower inspections

In addition to the construction of around 100 km of the 380-kV extra-high-voltage-line, the project also includes a 4 km section of underground cable as well as the construction of two substations and one cable transition facility. For these components, CDM Smith is responsible for planning, coordination and construction supervision, drawing on our extensive experience in complex infrastructure projects and large-scale multidisciplinary developments.

A particular challenge is the comparatively short construction period in relation to the overall project scope. This is being achieved through the parallel execution of several project sections and by ensuring high availability of personnel and material resources during the core construction phase from 2023 to 2025.

Jörn Müller, Senior Project Manager

Why is Grid Expansion necessary?

With the expansion of renewable energy and wind farms in northern Germany, large amounts of electricity need to be transmitted to consumption centres in central and southern Germany. To keep the power grid stable and reliable despite the energy transition, new transmission lines are essential.

Which Type of Transmission Tower is Suitable?

In Germany, three main types of transmission towers are commonly used: single-level towers, “Donau” towers and barrel towers. The single-level tower has a relatively low height and is preferred in sensitive areas such as near residential neighbourhoods or airports. The “Donau” tower is particularly suited for double-circuit high-voltage lines and is therefore widely used. The barrel tower, with its slim design, offers advantages in challenging terrain, such as along motorways or forest edges. In this project, both “Donau” and barrel towers will be employed.