TenneT operates more than thirty 155 kV and 220 kV AC submarine cable platform grid connections in the North Sea off the German and Dutch coasts which transport renewable energy from offshore wind farms to the mainland. Over the past 15 years, numerous different cable types with different conductor cross-sections and from various cable manufacturers have been used for the submarine cable connections. To enable repairs for any cable faults that may occur, spare cables, repair joints and spare parts specific to the cable used must be kept in stock for each specific connection. This requires a lot of storage space, and material handling is extremely complex and time-consuming.
Safety when damage occurs, with simplified inventory management
To minimise storage and material handling complexity, and at the same time be optimally equipped to execute a repair, TenneT approached PFISTERER to develop a universal repair joint. It allows different cables to be connected, regardless of the cable manufacturer, materials used and conductor cross-section. As a result, submarine cable faults can be repaired quickly and efficiently. “The universal design means we can use a single repair joint for all submarine cables with a minimal need for spare parts. This means that we can significantly improve our inventory management and are well prepared to deal with any damage that occurs,” says Dirk Hansen, project manager for cable repairs at TenneT.
The universal submarine cable repair solution up to 170 kV from PFISTERER
The solution is based on the pluggable epoxy resin joint up to 170 kV from PFISTERER’s Connex product family. This technology is already in use on many offshore wind and oil platforms as a connection between the platform cables and the export cable. It is also widely used onshore by energy suppliers as a universal cable repair system. Aside from its compact and robust design, it is particularly attractive because it is quick and easy to install. To date, PFISTERER is the only manufacturer of pluggable epoxy resin joints up to 170 kV. “We are a pioneer in developing the world’s first repair concept for offshore AC submarine cable connections as a pluggable solution. Our epoxy resin joints are the key component. Thanks to their plug-in technology, they enable fast and efficient repairs to all different kinds of cables,” explains Vukašin Basara, Senior Product Manager and project manager for this project. In addition to the development and production of the repair joints, the contract scope includes type tests for mechanical and electrical product qualification. “As a pioneer in the offshore market, with the Connex product portfolio we have demonstrated how quick and simple it is to connect offshore platforms using pluggable high voltage cable accessories. Our aim now is to use this concept specifically for subsea applications,” says Vukašin Basara about the project.
Universal submarine cable repair joint up to 245 kV
In addition to the solution up to 170 kV, PFISTERER is also developing a universal repair joint up to 245 kV for TenneT. The concept envisages using the same components as for the 170 kV solution as far as possible. Here too, the focus is on a central joint body for all cable types that can connect different conductor cross-sections and geometries. This project for the development and prototype construction is scheduled for completion by the end of 2024.