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E-Power Pipe®

Method innovation for the secure and fast installation of cable protection pipes

With E-Power Pipe®, Herrenknecht has developed a new method to quickly and securely install small-diameter cable protection pipes underground with drive lengths of over a kilometer. The trenchless technology can be precisely controlled and used with only small overburdens, thus offering a ground-conserving alternative to the conventional open-cut method for high-voltage grid expansion.

High demand for new transmission grids

The expansion of power transmission grids and the construction of new trunk lines are typically carried out with overhead lines. For this the time and budget plans of the authorities and planners often have to be adapted to the demands of local residents and property owners. This is particularly true in densely populated regions such as Germany.

In accordance with the grid expansion planned in Germany (Grid Development Plan Power 2030, version 2017, 2nd draft), around 2,400 kilometers of new high-voltage direct-current transmission lines (HVDC) are required, most of which are to be installed as underground cable. The main requirement is to lay the cables at a shallow depth and at rigidly defined small distances apart with high precision over the greatest possible distances (> 1 km).

In the area of non-accessible diameters for the individual laying of underground cables, until now no trenchless construction method has met all the criteria in terms of economy, security and construction time. With the E-Power Pipe® technology, Herrenknecht has developed a new method that closes this gap.

Newly developed machine technology

E-Power Pipe® combines and further develops the proven horizontal directional drilling (HDD) and AVN or Direct Pipe® drilling technologies. The centerpiece is the newly developed AVNS350XB tunnel boring machine developed by Herrenknecht with an excavation diameter of 505 millimeters.

New development for E-Power Pipe®: AVNS350XB with jet pump as slurry pump, a hydraulic unit integrated in the TBM and improved control and navigation systems

The fully remote-controlled AVNS350XB is equipped with a jet pump as slurry pump as well as a hydraulic unit integrated into the tunnelling machine and improved control and navigation systems. Thanks to the jet pump for handling of the excavated material it is now possible to achieve up to 10 times longer drive lengths in the small diameter range than before - this means tunnel lengths of more than 1,000 meters at a shallow installation depth of 1.5 meters. The machine adheres to the planned alignment with high precision and can cross existing infrastructure such as pipelines, roads, railways or smaller bodies of water securely and quickly.

Two-stage installation process

At the starting point a jacking frame is installed, with the feed force of which the jacking pipes and the TBM are pushed along the specified route in the direction of the target point. The borehole remains securely supported by the machine and the jacking pipes the whole time. After breakthrough at the target point, the pipe jacking machine is separated from the jacking pipes. Subsequently, the prefabricated cable protection pipe is connected to the jacking pipes still located in the borehole and pulled back to the launch shaft via the jacking frame.

After installation of the protection pipe, the E-Power Pipe® mission is complete. In a second step, final insertion of the underground cable is carried out by suitably specialized companies.

E-Power Pipe® quickly and securely installs cable protection pipes for the subsequent installation of high-voltage cables.

The method innovation involved the development of new, extended jacking pipes that allow a practically continuous advance. Herrenknecht developed an appropriate jacking frame especially for these jacking pipes with a 10 meter stroke and a thrust force of 350 tonnes. By rotating it 180° in the launch shaft it can also handle the retraction of the cable protection pipe and thus takes on a double function.

Successful breakthrough in Borken: E-Power Pipe® demonstrated its capabilities in spring 2017 during a pilot project in North Rhine-Westphalia

Successful pilot project

E-Power Pipe® was presented for the first time in December 2016 to representatives from the construction industry, engineering firms, network operators and politics. In the spring of 2017, together with Amprion GmbH, a leading transmission grid operator in Europe, and RWTH Aachen, Herrenknecht demonstrated the performance of E-Power Pipe® with a successful pilot project in Borken (North Rhine-Westphalia).

Three parallel holes with a length of 300 meters at a shallow depth were bored for the installation of HDPE pipes for later cable insertion. Best performances of up to 126 meters advance per day during pilot drilling and 266 meters per day when the protection pipe was retracted demonstrated the efficiency of the method during the pilot project already.

  • Method for the trenchless installation of protection pipes for underground cables
  • Technology combination of pipe jacking (microtunnelling) and horizontal directional drilling
  • Drive length: over 1,000 meters
  • Installation depth: min. 1.5 meters
  • Newly developed machine type AVNS350XB with jet pump, integrated hydraulic unit and improved control and navigation

+ Low impact on environment and local residents, no complicated and time-consuming recultivation measures required
+ Fast and secure creation of the borehole and product pipe insertion
+ Fully remote-controlled TBM
+ No heavy equipment between connection points
+ Borehole support by machine and jacking pipes at all times
+ Tunnelling under groundwater possible


The development of the method was funded by the Federal Ministry of Economics and Energy (BMWi research project IBoTec) and carried out by Herrenknecht in cooperation with Amprion GmbH and with RWTH Aachen.

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