Summary
Energizing a transformer without sufficient tests increases the risk of failures, damage and outages. Pre-energization tests validate condition, connections and technical evidence before commissioning.
Why test before energizing
Transport, assembly, storage or intervention can affect the transformer.
Tests make it possible to detect connection errors, insulation problems or anomalies before the equipment is put into operation.
Common tests
The TTR test verifies transformation ratio and taps. Winding resistance helps review continuity and internal connections.
Insulation resistance and tangent delta support dielectric diagnosis according to equipment type and voltage.
Documentary review
It is advisable to review nameplate, factory protocols, history, oil if applicable, connections, grounding and associated protections.
Documentation makes it possible to compare results and define acceptance criteria.
Report and decision
The report must record equipment, nameplate data, methods, results, photographs and recommendations.
If deviations exist, they must be resolved before energizing or actions must be defined with the owner.
Frequently asked questions
What is the TTR test?
It is the measurement of transformation ratio to verify taps, polarity and transformer consistency.
Is tangent delta always required?
It depends on transformer type, voltage, criticality and technical scope.
Is it useful for used transformers?
Yes, especially before re-energizing, moving or commissioning equipment with uncertain history.
Is a technical report delivered?
Yes, with results, evidence, observations and recommendations.
If you need technical support applied to this topic, review our transformer testing service.