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 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 (> 1 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.
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.
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 10 times longer than previously in the small diameter range – that means drives of more than 1,000 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.