LS2 Report: renovation of the electrical infrastructure
Oct 15, 2019
You arrive at your office, switch on the lights and pick up the phone, while your computer hums into life. Without electricity, the scenario is slightly different... CERN’s electrical network is so reliable that we forget what’s going on behind the scenes.
The Laboratory’s electrical infrastructure – which plays an essential role in the excellent performance of our experiments and accelerators, and of all CERN facilities – is anything but trivial. In its nominal configuration, it comprises two substations (BE1 and BE2) with an input voltage of 400 kilovolts (kV), supplied by the French electrical grid. Downstream, these are connected to another substation that lowers the voltage to 66 kV. Part of this network supplies facilities several kilometres away (notably in the LHC), while the other undergoes a further conversion to 18 kV in order to supply the nearby Meyrin and Prévessin sites, as well as the SPS. To provide redundancy, CERN’s electrical infrastructure is also connected to the Swiss grid, ensuring that a reduced power supply continues in the event of a problem with the French grid or CERN’s internal network. The switchover to the Swiss grid happens automatically thanks to an “auto-transfer” system.
During LS2, due to the major renovation and maintenance work under way, CERN’s electrical network is working somewhat differently. “At the beginning of July, the BE1 input station was disconnected. We are now consolidating its protection system because, since this station dates from the 1970s, some of its equipment had reached the end of its life,” says Davide Bozzini, technical coordinator in the Electrical Engineering (EN-EL) group. During the course of the work, which should finish some time in November, the BE2 substation is therefore supplying the entire Laboratory alone.
In mid-September, Meyrin’s main substation, ME9, which has supplied the site with 18 kV since the 1960s, was “unplugged”. It is being completely renovated and should come back into operation at the end of April 2020. In parallel, the auto-transfer system will also be entirely renovated. While these two renovations are taking place, the connection to the Swiss grid has also had to be suspended. This enables the EN-EL group to carry out important work on the ME9 substation, but also deprives CERN’s general network of one of its sources, which could, in rare cases, lead to temporary power cuts*.
Major work is also under way on the SPS, where five of the seven 18 kV substations located at the seven SPS surface points are being renovated. Work on four of them required new buildings to be constructed, which meant that the EN-EL group could start work before LS2 began, while the accelerator was still running.
The EN-EL group is also working on the LHC Injectors Upgrade (LIU) project. “Our LIU activities are very varied, just like the needs of our clients,” says Davide Bozzini. “In the PS Booster and the PS, for example, we have replaced several electrical boards and low-voltage switch boxes dating from the 1970s, as well as the lighting systems, which were antiquated and have now been replaced with new radiation-resistant lights. The latter were developed by the EN-EL group in collaboration with manufacturers.”
Many other activities, notably maintenance, are also under way in preparation for future runs: maintenance of several hundred transformers and circuit breakers, replacement of the batteries of critical supply systems in the LHC, updating of network status control systems, etc. Currently, more than 200 people (personnel from CERN and from external companies) are working on the consolidation, maintenance and operation of CERN’s electrical infrastructure, on which depend all the activities carried out at the Laboratory.