Transformer Oil: Handling, Testing and Common Mistakes
Oil quality can degrade between the refinery certificate and the transformer. Storage, sampling and filling procedure matter as much as the initial test.
A transformer oil certificate describes the oil at the point of testing, not necessarily at the point of filling. Moisture ingress and particle contamination during storage and handling are common causes of failed commissioning tests.
Store it properly
Drums should be stored under cover, with bungs tight and drums not directly on the ground. Bulk oil should be kept in clean, dedicated tanks with breathers. Avoid transferring oil between containers that have held other products.
Sample before filling
Test breakdown voltage, moisture and acidity before filling. If the oil has been stored for a long period or transported through humid conditions, a dielectric dissipation factor test adds useful information.
Control the filling environment
Filter and degas the oil, use clean hoses and avoid open transfer. Measure moisture after filling and again after the transformer has stabilized.
Keep the records
Record the oil batch, test results, filling date and quantities for each unit. If a warranty or insurance claim arises, that record is the evidence trail.
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