Battery storage container destroyed by fire during commissioning at Perles-et-Castelet substation

What happened

During acceptance testing of a newly installed hybrid battery and supercapacitor storage unit at the Perles-et-Castelet RTE transformer substation in Perles-et-Castelet, Ariège, France, operated and owned by RTE, with the storage system supplied by Ingeteam as manufacturer and integrator, temperature and smoke alarms activated shortly after the equipment was energised. Personnel evacuated the control room as smoke emerged from one of two stacked containers. Around 45 minutes later, an overpressure event blew open the container doors and a fire broke out, ultimately destroying the storage container despite an extended firefighting response.

Investigation established that one battery rack suddenly discharged into an adjacent rack, with the resulting current flowing only through part of the second rack. Insulation resistance in the first rack had fallen close to short-circuit levels. Investigators proposed that a failed electrical connection contacting the rack's metal frame, combined with an insulation fault on a busbar linking a module to its protection unit, may have caused an electric arc upstream of a fuse.

Contributing factors

Investigators identified a probable insulation fault at electrical connections passing through the battery rack support frame, potentially combined with a failed electrical connection contacting the metal frame, which may have produced an electric arc not cleared by the fuse protection. The precise root cause of the insulation fault itself could not be determined.

Lessons learned

1. Battery rack insulation resistance must be monitored continuously at module level, as a sudden drop to short-circuit levels allowed rack-to-rack discharge.
2. Electrical connections through metal rack frames require extra design checks and inspection, since a fault here produced an arc that fuses did not clear.
3. Fire protection and isolation plans for BESS during commissioning must allow for rapid energy isolation, as the container was destroyed despite extended firefighting.

More lessons on detection and monitoring, electrical protection and isolation, fire suppression and firefighting, from every incident on the register.

Not yet known

• Battery and supercapacitor system model and age
• Duration of site downtime
• Cost of the damage and replacement

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Source

epri.box.com