Universal Transition Joint 150kV for XLPE cable on the Belgian Grid

XLPE based 150 kV underground cable systems. Over the years, this population of cables has become quite diverse. Cables with different conductor sizes and materials, different metallic screen designs and a multiple of cable manufacturers have been installed over the last decades, leading to an important variety of XLPE based underground cable systems.

New installed cables are covered under warranty period for incidents. In this case, cable manufacturers organize repairs with qualified material. Today, more than 50 % of the 150 kV cable fleet (roughly 600 km in total), is not covered by warranty anymore. The amount of incidents/year on 150 kV will, based on the failure curve, increase to approximately 1,5 incidents by 2030 (increase of fleet cables out of warranty and increase failure rate due to ageing).

This has a big impact for the repair works on this population of cables, leading to important variety of spare parts (cables and accessories) and multiple cable suppliers for these interventions. Besides the spare parts themselves, also the management of these spare parts becomes quite time consuming and costly. Intervention on these cables is not only limited to repair works (repairs), also the requests for local rerouting of existing cables becomes more important, as well as the evolution of the grid where interventions on existing cables are more and more required such as, prolongation of existing cables, in-out connections of existing cables in a new substation, …

In 2021, the idea was launched to tender a project to develop and qualify a standard joint that can be used for repairs on XLPE insulated 150kV underground cables of different cable manufacturers, the Universal Transition Joint (UTJ). A European tender has been launched for this project with the aim to have a service level contract in place with a cable supplier for the delivery (after qualification) of the UTJ, the installation and spare part management.

From a stock management perspective, the UTJ delivers a substantial reduction in the number of unique components for joint reparation on 150 kV - by a factor of ten - and a notable decrease in strategic stock value of approximately 25%. This streamlining enhances operational flexibility and reduces complexity in procurement and inventory management.

The paper will describe more in details the existing needs with an overview of the existing population, the preferred solution, the tendering procedure, the selection of the material, the qualification process of the UTJ, the impact of the UTJ on the strategic stock and finally the implementation within the Belgian TSO and some future steps.