Explosion in a High-Voltage Transformer
At 11:15 pm, an explosion followed by fire occurred in the vicinity of the measurement transformer on an isolated 90,000 V electrical oil transformer at a plant manufacturing technical polymers. Plant personnel placed the installations in safe operating mode, while the backup line and 15,000 V transformer were activated, in coordination with the electric grid operator to keep the sites supply lines open. The risk of falling electrical cables led to closing the adjacent departmental highway, and the emergency crew installed a protective fire hose. A certified plant employee isolated the transformer in order to allow the sites responders to put out the fire using a powder extinguisher. The response was concluded at 2:30 am, with plant production resuming by the end of the night. The plant operator issued a press release. The cause of this accident was a hydrogen release and explosion, most likely triggered by entry of humidity into the transformer oil. Two hypotheses were forwarded to explain this humidity inflow: a poor quality steaming of absorbent paper, and/or a flawed oil replacement procedure.
Event Date
July 26, 2012
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The cause of this accident was a hydrogen release from oil (probably due to heating), ignition and explosion, most likely triggered by entry of humidity into the transformer oil. Two hypotheses were forwarded to explain this humidity inflow: a poor quality steaming of absorbent paper, and/or a flawed oil replacement procedure.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
High voltage Transformer, oil
Storage/Process Medium
Location Type
Location description
Industrial Area
Lessons Learned
Lessons Learned
Hydrogen and methane emissions from transformers oil is a phenomenon known since many years. Strategy for preventing and/or mitigating it are available in the scientific literature. The following generic recommendations can be issued: Regular inspections should be performed, by performing concentration measurements to ensure the absence of water in the oil (especially after a maintenance and any changes in the procedures). An automatic emergency safety shutdown system should be set up.
Event Nature
Emergency Action
Plant personnel placed the installations in safe operating mode, while the backup line and 15,000 V transformer were activated, in coordination with the electric grid operator to keep the sites supply lines open. A certified plant employee isolated the transformer in order to allow the sites responders to put out the fire using a powder extinguisher.
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
ARIA data base
event no. 41508
An overview of the cause of generation of gaseous hydrogen from oil can be found here:
R. Girgis and E. G. teNyenhuis
Hydrogen Gas Generation Due to Moderately Overheated Transformer Cores
IEEE Comets #i_44