Successful preliminary trials for an islanding electrical switching of the Lérins Islands

The ambition of this part of the Nice Smart Valley project is to ensure the electricity supply of the isles being disconnected from the grid without using gensets. This is mainly done in emergency mode, in case of problem on the submarine cable which is the only connection to the main grid.
To validate the good behaviour of the systems to be implemented, some simulations have been requested.

From theory to practice
This is a first with so many constraints due to the lengths of submarine and buried cables on a Medium Voltage (MV) network. An initial modelling carried out by Socomec with the University of Padua led to the definition of the performance of the products to be used for the experiment.

A series of tests has then been realised on those products in order to validate the good behaviour of the systems before there on-site installation. Those tests have been conducted at EDF research lab, Concept Grid, on an installation sized at ¼ from the Lerins Islands one. The first batch of tests concerned the blackstart and they aimed at checking the ability of the storage system to recharge a part of the HTA grid disconnected from the main grid. A key point of this function is the ability of the storage system to magnetise the 5 transformers of the MV/LV posts that represent an installed power of 10 times the conversion power. The conformity of the storage system to Enedis’ rigorous protection plan was also check. Concretely, by detecting electrical faults on both the low and medium voltage networks, and by stopping the storage system when that occurs, we ensure that there is no danger for goods and people. The system was then qualified to do a programmed islanding without notice from the customer. In this case the system is piloted to go to islanding mode, for example to anticipate a maintenance, which it does with no service interruption. Once islanded, we checked the quality of the energy supplied by the storage system and its ability to pilot the local renewable energy production to ensure balance between consumption and production.

Those tests enabled the qualification of the solution’s robustness and the improvement of some performances.

Next steps in the project …
A first successful 15 minutes islanding of the islands has been made middle of March! This really gives us confidence for the last test phase that’s going to take place, among which we’ll test the synchronization to the grid, and of course for the entire commissioning of the Lérins islands.