Upgrading TenneT's 150kV substation makes Amsterdam's energy supply safer

‘Crownstones ’ is the name of the project, which must be completed by mid-2024. The joking working title conceals a complex operation in which high voltage mains components (primary components) are replaced. Still, the tension is already gone for Prysmian Group. The new HS cables and terminals that it mounted for the substation function well. This was evident from the last high-voltage test on 1 June. The conversion with moving the pre-assembled cable systems to the switch garden is indeed the next major challenge. But construction company A.Hak does that, under the coordination of Qirion and with supervision of the cable systems of Prysmian Group.

End of technical life

The project is part of a multi-year strategy of TenneT, manager of the Dutch high-voltage grid. Much of that network reaches the end of the technical life. Replacement and modernization are necessary to continue to guarantee high security of supply (99.9% and more). In this context, the upgrading of the 150kV substation NDK150 (Noord Klaprozenweg ) in Amsterdam is current. “It is a fairly critical station because it supplies power to both the city center of Amsterdam and Amsterdam North”, explains Senior Site Manager Michaël van den Puttelaar on behalf of the coordinating party Qirion.

Three crown stones and VNB backup

NDK150 ( North Poppy Road ) is a substation that is fed by three connections from substation HW150 ( Hemweg ). From NDK150, three connections are forwarded to substation HK150 ( Hoogte Kadijk ) and three transformer connections to NDP50 ( North Papaverweg ).  The compounds of HW150 and HK150 are linked together ( the ‘ Crownstone ’ ), with a branch to NDP50. This will take the 150kV rail out of operation and make room for TenneT available to build a new twin-GIS installation. The new station replaces the old station, has more switching fields and thus contributes to the Amsterdam energy transition.

Three ‘ crowns ’ or coupled connections are required to replace the substation. Each crown stone includes two cable systems with two parallel terminals per phase, a total of six cable systems with 36 final closures. In addition, a temporary emergency device of two cable systems with 12 end closures is provided in advance to act as a replacement backup for the other two power cables whenever one line is switched off. For example, during the conversion of each crown stone, the return time can be minimized if the VNB is withdrawn.

Complete HS cable systems

Prysmian Group was commissioned by Reddyn, a joint venture of TenneT and Liander, to realize the eight new cable systems. “ Prysmian Group is a preferred supplier from TenneT for supplying and assembling 150kV ”, explains Van den Puttelaar. “ We always work well together. ” The order includes both the supply of 1,555 meter high voltage cable ( type 1200 mm2 Alrm ), 48 end closures ( type OTC-170-X ), the supervision of cable laying, mounting the terminals on the high-voltage cables, as performing necessary Site Acceptance Test high-voltage tests. Qirion is responsible for ultimately installing and connecting the cable systems in the switch garden during conversion into crown stones.

Unique pre-assembly

It is precisely the assembly of the closing points that distinguishes this work from other works, according to Site Manager HS projects Danny Bisessar of Prysmian Group. “ Usually such a replacement operation takes place directly in the switching garden. ” However, working under power lines is a safety risk for technicians. “ To limit that, the circuits or lines must be switched off and we do the mounting outside the switching garden, in the green field. ” TenneT wants to minimize this interruption, the so-called Provided Non-Availability or VNB. It has therefore been decided to have the new cable connections at ground level pre-assembled on the site next to the switching field. As a result, the required VNB period for the conversion is much shorter and the risk of run-out is smaller.

Transport and assembly

The entire replacement operation takes place in three phases, the first two of which are completed. In the first phase, Prysmian Group organized the transport of the cables and empty reels to the location respectively. Reddyn moved the reels, determined the final cable lengths, cut the cables to length and supplied them to the technicians of Prysmian Group. Everything under supervision on the cable of Prysmian Group. In the second phase, Prysmian Group mounted all end closures on the cables in the green field and performed the SAT for delivery per cable system. Due to the limited space in the final location for the crown stones after the conversion, the distance between the two parallel terminals per phase is also limited. OTC-170-X final closure is ideally suited for such tight spaces and has therefore been proposed and applied by Prysmian Group.

Big challenge

According to Van den Puttelaar, the biggest challenge is in the third phase or the conversion with moving the cable systems to the switching field. “ There is little space and the switching field is next to it, but because of the long cables, up to 110 meters, we have to maneuver around it. We have not done that before and that is why we carry out these activities together with construction company A.Hak. We must support the HS cable well and prevent the angle and position of the end closures on the cable from deviating. Because Prysmian Group has a lot of experience with the installation of cable systems, we have her, as an extra assignment, asked to advise us and to supervise the cable systems during that movement ”.

Good cooperation

The first crown stone in the transition garden is made in October. In addition, Qirion will move the cable systems, place the end closures on the steel foundation and connect the grounding cables. Prior to installing each crown stone, Qirion will place the VNB return backup emergency ( ver ). The completion of the entire work is scheduled for the summer of 2024. Van den Puttelaar is confident that the planning will be achieved, thanks in part to the collaboration with Prysmian Group and A.Hak. “We are very happy with the expertise and knowledge of Prysmian Group. The collaboration is fine, there are no problems and the working atmosphere is good. With the new installation, which will last for at least 40 years, the energy supply has been secured and no faults will occur.”