Power failure at CERN Meyrin site



The power failure, which occured at 7:47 on the morning of Saturday 29 July, was caused by a short-circuit in a 66 kV substation on the Meyrin site. The automatic reconfiguration of the network did not work as planned for a number of reasons, all of which are now well understood. As a result all the normal power networks on the Meyrin site, for the SPS and the LHC general services, were down.

The secured power supply on the Meyrin site is provided by a set of three diesel motor driven power generators. All three diesel engines started correctly, but only one power generator could be correctly engaged. The single power generator's diesel motor ran for 45 minutes but was stopped automatically due to a mechanical fault. The reasons for these failures are being investigated. At that point, the Meyrin site and LHC Point 1 did not have a secured power network. The secured power networks for all the other LHC points worked as expected with their local diesel generators. The normal power network for the SPS and LHC general services was re-established at 9:45 and on the Meyrin site, the different networks restarted in sequence from 13:23 but without the standard diesel backup.

The diesel backup for the secured power network for LHC Point 1 and the Meyrin site was re-established on Monday at 17:00.

The successive failures of the normal and secured power networks on the CERN Meyrin site on the morning of Saturday 29 July, resulting from unrelated causes, clearly reveal flaws in the functioning of equipment which is designed to guarantee users a permanent supply of electrical power. Once a thorough technical analysis has been completed and the necessary improvements have been made, further tests of the full power network will be urgently performed by the TS Group responsible.