Steel structures for energy transition

High-voltage substations Zevenhuizen and Bleiswijk

High-voltage substation Zevenhuizen is one of the many projects where work is underway to increase the capacity of the Dutch electricity grid. The location is in the municipality of Zuidplas near the village of Zevenhuizen, in the armpit of the A12 and N219 motorways. Construction consortium SC&M, a collaboration between Croonwolter&dros and Mobilis, is building a new 150 kV high-voltage substation here for TenneT. The regional grid operators Liander and Stedin will connect to it. At the same time, the 380 kV substation in Bleiswijk will be expanded with a new 150 kV substation and both substations will be connected to three new underground high-voltage circuits. Steel supplier for both projects is Severfield De Haven, which has been active in the energy sector for decades.

TenneT is investing billions in the renewal and expansion of the high-voltage grid. To this end, hundreds of substations are being modified, replaced, expanded or newly built in a multi-year program. Nine contractors (combinations) have been selected in a framework agreement to carry this out. Severfield De Haven has been working for TenneT in the Netherlands for 25 years. First as Machinefabriek en Constructiebedrijf De Haven and since 2020 under the flag of Voortman Steel Group and since January 2024 as part of Severfield. Peter de Vreugd, project manager for Severfield De Haven, has been working for the steel builder for eighteen years now. "And I also have eighteen years of working experience with TenneT. We have already supplied a lot of steel for high-voltage projects and there is a lot more to come."

Dimensions

For high-voltage substation Zevenhuizen, Severfield De Haven supplied the superstructure on which the insulators and aluminum conductors are mounted, the secondary steel components such as supports and cable guides, and the 27-meter-high lightning conductors. "The heaviness of the station determines the stroke distances of the fields," De Vreugd explains. "The recently built 380 kV substation at Wijk aan Zee, the largest land-based substation in the Netherlands, has larger field strike distances than a medium-sized substation like the one at Zevenhuizen. In addition, Wijk aan Zee is subject to tougher wind load and corrosion resistance requirements (C5M, ed.)." 

Optimize design

The design of the steel structure of the high voltage station was made by SC&M. De Vreugd: "A party we have worked with many times before. We make the step from Final Design to Execution Design together, in order to optimize the design for practical feasibility, for example. Thinking along with and supporting clients is one of our strengths. High-voltage substations are construction kits with a lot of repetitions and you can gain a lot by standardization. You are constantly working to make that construction kit lighter, cheaper, more uniform, more durable and easier to assemble. That is a learning process that you go through with all the partners. Internally we now have a well-oiled machine: it starts with the supply of the semi-finished product and runs through pre-processing, assembly, welding and checks by the customer and ourselves. That culminates in the delivery to the finishers, where checks are again made on, for example, layer thicknesses."

Modular skids

In 2018, the steel company collaborated with SC&M to develop a standard design for AIS Stations. "This is a TenneT program in which 140 existing open air stations are replaced quickly, efficiently and safely," continued De Vreugd. "The design with modular standard building blocks, or skids, was approved in 2019 and implemented in two Proof of Concept projects. Since then, we have helped build hundreds of skids for various high-voltage substations in the Netherlands. It's a great system that allows you to replace a field at lightning speed, minimizing plant downtime."

The replacement and renewal task TenneT is currently rolling out is putting considerable pressure on the market. "That enormous volume requires a lot of people and equipment for implementation and puts pressure on the market," De Vreugd concludes. "I am therefore pleased with the new cooperation with first Voortman and now Severfield. This not only gives us even more knowledge to offer solutions to our customers, it has also given us more production capacity. That will come in handy in the coming years."