Just east of the South Holland village of Zevenhuizen (municipality of Zuidplas), a new high-voltage substation is under construction. This 150 kV installation will relieve grid congestion in the region for TenneT, Liander and Stedin. Construction consortium SC&M, a collaboration between Croonwolter&dros and Mobilis, is simultaneously building a new 150 kV substation for TenneT at the Bleiswijk 380 kV substation. Three new underground high-voltage circuits with three cables each will connect the two substations. Prefabrication and standardization play an important role: dozens of similar projects are to be realized in the Netherlands in the coming years.
Located in the armpit of the N219 and the A12 national highway, the station looks as if the high voltage could go right up. "Appearances are deceptive," corrects Denis Walraven, Project Manager for Mobilis TBI. "That will be the end of 2025. We are keeping the same pace in the construction of the two stations and the new cable link, and eventually it should be ready at the same time. They also fall under the same project organization. Stedin and Liander are building their own transformer station on this site for conversion to 20 kV."
This new station will secure the electricity supply for Zevenhuizen, Waddinxveen, Lansingerland, Zoetermeer and Gouda for the future. Walraven: "Grid congestion in the Rotterdam-The Hague-Gouda triangle is high, so this region needs a bigger meter box. Existing customers cannot currently grow their capacity, new residential areas are being built, businesses and solar parks in the region cannot be connected, and greenhouse construction needs to be able to move away from fossil fuels. So the importance of this station is great. We are also facilitating two new customers who are making a big impact with 100 megawatt batteries across the A12. These are important steps for the energy transition."
Not surprisingly, there is a lot of interest in this project. Dirk van Reijendam, Tennet Project Manager for both Bleiswijk and Zevenhuizen substations: "It's getting a lot of attention. This is partly because it is close to The Hague. We recently had Minister Sophie Hermans of Climate and Green Growth visit here and the national opening of the Construction Day was also organized at this site. We particularly enjoy building this high-voltage substation together and thus being able to contribute to energy transition. It is exciting at times. From design to completion you have to work together and you are dependent on suppliers. That's why we took a very structured approach to procurement and opted for prefabricated and standardized solutions wherever possible. This is necessary because TenneT is building dozens of new substations over the next ten years and a large part of the existing substations will be replaced or expanded. SC&M is one of the selected parties within a framework contract to carry this out."
Together with Croonwolter&dros, Mobilis has already carried out a number of projects for TenneT. The momentum is now well underway. "On the day of the official first pile, the last of the 881 piles went into the ground," Van Reijendam reports with satisfaction. "These form the basis for the nineteen electricity fields, where power is distributed to the various customers. To give the steel structures of the electricity fields a solid foundation, we use Mobriq, a modular concrete system. These are precast beams of six tons each that allow us to quickly and cost-effectively construct the foundation for the superstructure."
Mobriq grew out of the SC&M collaboration, with the goal of speeding up the design and construction of power fields. Walraven: "With Mobriq beams that we place and pour onto the foundation in a standardized way, a crane lays a field in two days. The system was developed in previous projects and obviously tested against the applicable requirements. So we can use Mobriq on follow-up projects without any problems. Ideally, I would like to make the blocks from geopolymer concrete, but that requires a little more proof that it meets all the requirements. This plant must first provide power for at least forty years before we will change the foundation again."
Standardization and modularity was also the common thread for the steel superstructure (Esystruct) on which the insulators and aluminum conductors are mounted. Van Reijendam: "That looks like a meccano box with prefabricated uprights and beams. We are constantly learning to make this construction kit lighter, cheaper, more uniform and more sustainable. That applies equally to the logistical puzzle. Piling, placing beams, steel on top, the electrical assembly, you want to set this up in the smoothest running train possible. Adding an extra field for a battery, as in Zevenhuizen, is almost copy paste, since such a field is very similar to the ones we are already building. Some spare fields are built for future demand. Adding a field once the power is on is not easy."
The highest point of high-voltage substation Zevenhuizen was reached with the installation of the 24-meter-high lightning rods. "This facility must keep lightning away from the live parts," Walraven said. "Height and positioning are such that they capture lightning within a certain radius and discharge it to the ground network. This ground network is laid under the entire field. All the components in the switchyard are connected to this with their reinforcement." TenneT's central service building houses the various central functions. Walraven: "Then you have to think of the station safety devices, low-voltage power supplies and links to TenneT's national telecommunications network. This allows them to monitor the control and measurement values and control the substation, because this substation is basically unmanned. The building is very functional and has a high computer floor to accommodate all the cabling."
Next to TenneT's substation are the substations of Stedin and Liander. Van Reijendam points out the differences in elaboration: "They will have exactly the same transformers that convert 150 kV to 20 kV. Yet one chooses to build entirely above ground and the other makes a basement building. Within TenneT we are working hard - together with our suppliers - to standardize our building systems as much as possible. I am a great advocate of this. It helps us to build the energy transition even faster."