What Is a Partial Discharge (PD) Test?
Quick answer — A partial discharge (PD) test measures the small, localised discharges that occur in a void or defect in the insulation when a high voltage is applied, and reports the PD magnitude and inception/extinction voltage. A low/no PD indicates a void-free insulation; a high PD points to a defect. It is a type and routine test (and done by monitoring) that verifies the insulation is free of a harmful PD source.
What is a partial discharge test on a transformer?
What it measures
It applies a voltage (often above normal and at a test level) and detects the PD pulses, giving a charge magnitude (in pC) and the inception and extinction voltage.
What it indicates
A low or no PD at the test level is good; a high PD or a low inception voltage indicates a void, delamination or contaminant that will erode the insulation.
When it is done
It is a routine/type test and is also used online (via sensors) to detect a developing PD source in service.
References & standards
- IEC 60270 (PD measurement)
- IEC 60076-3
Related
Related manufacturers
Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp
Related components
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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