Switchgear breaker misconfiguration causes data centre power outage in Stockholm
Aug 2024Published 12 Oct 2026Responsible editor: Chief Editor
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Companies named in this entry: GleSYS
What happened
On 12 August 2024, GleSYS AB was carrying out planned maintenance at its VBDC data centre in Stockholm, Sweden. The work involved installing one of two new uninterruptible power supply (UPS) units with new switchgear, and retiring the previous UPS system. Backup generators were started at 08:20 as a precaution. At 20:42, while technicians moved the load from the old system to the new UPS, the main power circuit from the UPS tripped in the new switchgear within 10 seconds.
This caused loss of critical load in Zones 2 and 3 of the data centre. Power was restored at 20:44. Three racks had partial power because PDU fuses had tripped, and these were corrected. One rack needed customer attention. Staff found that the maximum current settings on the outgoing breakers in the new switchgear had been set too low. The new UPS and switchboard were confirmed to be operating correctly at 21:22.
Contributing factors
The operator's report says the circuit breaker in the new switchgear was configured to its minimum value instead of its maximum value. The operator says multiple levels of checks should have caught this, and that its subcontractors and vendors had not yet explained how it happened. The site was running on a single UPS at the time of the transfer. The operator's status page showed the maintenance window as complete at 17:00, although work was still under way, which gave customers misleading information.
Lessons learned
- Check protection and breaker settings against the design values, with an independent second check, before transferring load to new switchgear.
- Treat the transfer of load to new UPS equipment as a high-risk step, with a rollback plan and staff ready before it begins.
- Tie status page updates to verified completion of work rather than automated timers, so customers receive accurate information during maintenance.
More lessons on electrical protection and isolation, outages, backup supply and restoration, from every incident on the register.
Source
Published 2026-10-12. Written from public reporting. Descriptive, not investigative. See the data accuracy disclaimer.
