What Is a Transformer Oil Breakdown Voltage (BDV) Test?
Quick answer — The breakdown voltage (BDV) test measures the dielectric strength of the insulating oil by applying a rising AC voltage across a small gap until the oil breaks down. A low BDV indicates moisture, contamination or particles in the oil, which lower its ability to withstand voltage. It is a routine, fast oil-condition test.
What is an oil breakdown voltage (BDV) test?
How it is done
A sample of oil is placed in a test cell with two electrodes a fixed distance apart, and the voltage is raised until a breakdown (spark) occurs. The average of several tests gives the BDV.
What it indicates
A high BDV shows a strong, clean oil; a low BDV points to water, particles or contamination. It is usually combined with moisture and acidity tests.
What happens next
A low BDV often means the oil should be filtered or regenerated, or the source of contamination found. It is checked at commissioning and on a periodic test cycle.
References & standards
- IEC 60156 (insulating liquids)
- IEC 60296 (oil)
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
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Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.
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