When a transformer requires attention, oil testing is almost always the first step. A properly collected oil sample can provide valuable insight into the transformer’s internal condition, identify developing faults and help determine whether additional investigation is necessary.
Laboratory diagnostics and field testing provide different types of information. Based on the oil test results, operating history and condition of the equipment, on-site electrical testing or inspection may be recommended to develop a more complete understanding of the transformer’s condition. In the event of an unplanned outage or other urgent concern, however, an immediate field evaluation may be required.
Transformer Oil Testing
Transformer oil testing can reveal developing internal conditions without opening the equipment or removing it from service. It is often the best first step for:
- Routine condition monitoring
- Establishing baseline results
- Evaluating aging or critical equipment
- Investigating gradual changes
- Reviewing equipment before planned maintenance
- Monitoring a transformer after an unusual operating event
Dissolved Gas Analysis can identify gases associated with overheating, partial discharge and electrical faults. Fluid-quality testing evaluates characteristics such as moisture, acidity and dielectric strength, while furan analysis provides information about paper-insulation condition.
Trending these results over time can help identify changes early and guide maintenance decisions.
On-Site Transformer Inspection
Field inspection may be needed first when there is an immediate physical or operational concern, including:
- An active oil leak
- Visible component damage
- Abnormal noise, vibration or odor
- Evidence of overheating
- A cooling-system problem
- A sudden performance change
- A recent fault or protection-system operation
An on-site inspection allows technicians to assess the equipment directly and determine whether oil sampling, electrical testing or repairs are needed.
When Electrical Testing Is Needed
Oil diagnostics cannot directly evaluate every electrical and mechanical component. Field testing may be required when there are concerns about windings, bushings, insulation integrity or possible internal movement.
Testing may include turns ratio, winding resistance, insulation resistance, power factor, excitation current and Sweep Frequency Response Analysis. Electrical testing is also commonly performed following installation, relocation, repair or a system fault.
When Both Approaches Are Necessary
Abnormal oil results may lead to field inspection or electrical testing. Likewise, an on-site concern may prompt laboratory analysis to determine whether internal stress or insulation deterioration has occurred.
Combining oil-test results, electrical data, operating history and physical observations provides a stronger basis for deciding whether the transformer should be monitored, maintained or repaired.
One Team From Diagnosis to Action
MVA provides transformer oil testing, expert interpretation, on-site inspections, electrical testing, maintenance and repairs. Whether the process begins in the laboratory or at the transformer, our teams work together to identify concerns and determine the appropriate next steps.