Smoke and a fire occurred as the result of overheating and a short circuit/arc flash in a dry-type high-voltage transformer in the utilities area on the lower deck of the gas production platform.
This facility is part of the Åsgard field in the central Norwegian Sea. Operated by Equinor, the field came on stream in 1999.
Direct and underlying causes
The PSA investigation has concluded that the direct cause of the fire was a short circuit/arc flash resulting from impairments to and/or degradation in the winding insulation over time.
Underlying causes of the breakdown are thought to be the following.
- Accelerated degradation of winding insulation at the fault site as a result of overheating.
- Local failure and partial discharges because of transient surges from the 11 kV switchboard.
- Possible problems with the special configuration of the system for direct electric flowline heating could have contributed over time to internal impairments in the transformer.
Actual and potential consequences
Nobody was injured, but the incident caused a transformer breakdown and consequent loss of production.
In the PSA’s view, the fire in the transformer room did not have a major accident potential. The room has been designed to withstand fire, while little flammable material is present in the area. As a result, the fire is unlikely to have spread beyond it.
Had there been personnel in the room when the short circuit/arc flash occurred, they are unlikely to have been directly exposed except to noise and possible smoke during the seconds it takes to leave the room.
The investigation has identified one nonconformity related to:
- following up and learning from incidents.
It has furthermore identified two conditions which have been categorised as improvement points:
- door impaired A-60 firewall.
What happens now?
The PSA has asked Equinor to explain how the nonconformity will be tackled, and to provide its assessment of the improvement points which were observed.