In the Wahle-Mecklar pilot project of the project developer TenneT, Bohlen & Doyen used the “KaRoSch” cable pipe sled for the underground cabling section, a new Installation technology for power cables, and thus achieved a significant increase in efficiency: an up to 25% higher Installation speed, increased occupational safety and a significant reduction in resource consumption.
The energy transition requires new power lines. For this reason, the grid in the middle of Germany is being reinforced from north to south. The almost 230 km long connection leads from the Wahle substation, between Peine and Braunschweig, to the Mecklar substation near Bad Hersfeld in Hesse. One of the special features of this project: Wahle-Mecklar is one of four pilot projects in the alternating current sector that are legally permitted to use underground cables on certain sections. Geographically, the sixth construction lot of section C is located between Hetjershausen and Olenhusen near Göttingen. One of the two underground cable sections of the Wahle-Mecklar line is being built here over approx. 5.5 km, and Bohlen & Doyen used its new KaRoSch on the Göttingen section.
The construction of transmission networks often includes long sections in which the underground cables are drawn into protective pipe systems. For the implementation, heavy construction equipment for earthmoving, pipe handling and water management is traditionally required, and large quantities of construction and auxiliary materials are consumed. Therefore, in cable line construction, continuous efforts are made to make the construction process more efficient through new and further developments of construction machinery and techniques.
In addition to efficiency, Bohlen & Doyen also focused on developing and implementing economic and sustainable construction methods for the construction of transmission networks. The aim for the implementation of the protective pipe Installation in the Wahle-Mecklar project, section C6, was to accelerate and simplify the work steps in the process of protective pipe Installation under the aspects mentioned.
For this purpose, the cable pipe sled called “KaRoSch,” which was newly developed by Bohlen & Doyen and manufactured in-house, was used for the first time on this pilot section near Göttingen.
This Installation sled enables a combination of a total of eight work steps, some of which previously had to be carried out without mechanical assistance, i.e. with laborious and physically demanding manual work. For example, the conventionally produced lower pipe bedding, which is conventionally installed true to profile using a delta loader with a mini-grader, is completely unnecessary thanks to the sled. The skilled workers in the pipe trench, who are required for laying the pipes and aligning and positioning the pipe strings along the templates in conventional Installation technology, can also be used elsewhere thanks to the Installation innovation.
The introduction of the bedding material and the compaction using vibratory plates are further work steps that are carried out in one work step by using the Ka- RoSch. This means that there are no more people in the pipe trench to carry out work during the Installation process. This means a significant improvement both in terms of the occupational safety of the colleagues in the pipe trench and in terms of personnel and equipment costs.
The KaRoSch also offers significant advantages in terms of environmental compatibility and resource conservation. Compared to the usual open construction method, the period during which the pipe trench is open is reduced to a few minutes. Depending on the prevailing soil conditions, water management can be minimized or completely eliminated. By adapting the trench profile to the KaRoSch geometry and the technology installed in the sled, considerable quantities of bedding material (up to 20%) can be saved.
In addition to the modified trench geometry, the profile extraction plates and the arrangement of the compaction unit ensure that no excess bedding material is introduced. Thanks to state-of-the-art technology, the compaction unit is operated by rechargeable batteries. The always only short sequential use ensures that the devices can usually be operated for a full working day. Thus, no exhaust gases are generated for the direct sled use itself. In addition, the risk of environmental damage in the event of a possible accident is eliminated, as no water- or soil-endangering operating materials are required for the technology.
Overall, the impact on nature can be significantly reduced by reducing the amount of excavation as a result of minimizing the trench cross-section, by the short opening time of the trench and by the optimally coordinated technology in the process with the KaRoSch.
With the development and use of the new KaRoSch cable and pipe sled, an efficient Installation system was successfully developed, designed, manufactured and used in the project at Bohlen & Doyen Bau GmbH. With the simulations of the processes and the previous test with comprehensive documentation, the application of the device could be optimized. The use on the construction site then showed that an optimally coordinated preparation of the individual work steps is fundamental for a successful application of the KaRoSch. In this context, the functioning of the logistics chain for the delivery of the bedding material plays a key role in particular.
The KaRoSch offers its advantages particularly on predominantly straight route sections without crossing obstacles. Compared to the conventional Installation method, an up to 25% higher Installation speed can be achieved with the KaRoSch. This can be attributed to the simultaneous Installation of the six pipes, the ease of conversion and, above all, the integration of the compaction technology. It was particularly important for the project developer TenneT to be able to use the KaRoSch on slopes that made the standard trench of the open Installation method impossible, or in very moist soil structures, which makes extensive water management, as would be necessary in the open cable trench, obsolete.
In the course of the execution work, many findings were gained for a partial further optimization of the KaRoSch. This enables Bohlen & Doyen to further develop this system for future applications such as also for other bedding materials and pipes.
egeplast
Power Protect PE
Protective pipes for high and extra-high voltage cables with a low-friction inner layer and individual marking.
UV-resistant signal color layer
Solid wall or co-extruded, optionally with stripes
Inspection-friendly inner layer: optionally highly slidable or abrasion-resistant
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