Transformer has been stored in humid area or exposed to water
If a transformer has been stored deenergized in a humid area, the windings and insulation may absorb water decreasing the dielectric strength of the insulation. In worst cases the windings have been exposed directly to water or submerged in it. If a transformer has been exposed to any liquid, immediately denergize and remove from service.
| Check: | Solution: |
|---|---|
| If the transformer has been stored in a humid area, megger the transformer. | If the insulation ratings are lower than needed, consult the factory. Dry hot air may need to be directed over the transformer for 24 hours ore more. In some cases, the transformer may need to be baked in industrial ovens to sufficiently dry out. |
| If the transformer coil has been exposed to rain or other dripping water, megger the transformer. | Immediately remove from service. Since liquid water can shift, even a proper megger reading may not be sufficient. Consult the factory. Dry hot air may need to be directed over the transformer for 24 hours or more. In some cases, the transformer may need to be baked in industrial ovens to sufficiently dry out. |
| If the transformer has been exposed to a liquid other than water, please consult the factory. | Some chemicals may leave conductive or corrosive residue that weakens the insulation. In this case, the transformer may need to be repaired or replaced. |
| If the transformer coil has been submerged in water, consult the factory. | In this case, the transformer will usually need to be replaced or returned to the factory for evaluation and possible repair. |