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 up to two kilometers. 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.
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 in laborious and time-consuming procedures. This is particularly true in densely populated regions such as Germany.
For 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 needed, most of which are to be installed as underground cable. The main requirement is to install the cables at a shallow depth and at rigidly defined small distances apart with high precision over the greatest possible distances (up to 2 km).
In the area of non-accessible diameters for the individual installation of underground cables, until now no trenchless construction method has met all the criteria in terms of cost-effectiveness, safety, security and construction time. With the E-Power Pipe® technology, Herrenknecht has developed a new method that closes this gap.
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.
The fully remote-controlled AVNS350XB is equipped with a jet pump as the slurry pump as well as a hydraulic unit integrated into the tunnelling machine and improved control and navigation systems. The use of jet pump materials handling for the excavated material means it is now possible to achieve drives up to 20 times longer than previously in the small diameter range – that means drives of up to 2,000 meters with a shallow installation depth of 1.5 meters. With high precision the machine follows the planned alignment and can quickly and safely cross under existing infrastructure such as pipelines, roads, railways or smaller bodies of water.
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 fed into the launch shaft via the jacking frame. After installation of the protective 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.
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.
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 protective pipe was retracted demonstrated the efficiency of the method during the pilot project already.
The development of the method received funding from the Federal Ministry of Economics and Energy (BMWi research product IBoTec) and was carried out by Herrenknecht in cooperation with Amprion GmbH and with RWTH Aachen.
Our innovative E-Power Pipe® method receives the Environmental Technology Award:
E-Power Pipe® wins bauma innovation award 2019:
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