Partial Discharge Test: What the Test Confirms
Reviewed by the Fengguang engineering team · Last updated 11 Nov 2026
Partial Discharge Test checks insulation defects under high voltage. The result confirms the insulation is free of harmful discharges; read it against the approved datasheet and the applicable standard.
What the test checks
The test covers insulation defects under high voltage. It is performed under defined conditions, and the result is compared with the guaranteed value or the standard limit.
How to read the result
Check the serial number, test date, reference temperature, test standard and the measured value. A pass close to the tolerance limit should be discussed, not ignored.
What to ask the supplier
Ask for the test report, the reference conditions, the acceptance criteria and whether the test is routine, type or special. For critical projects, witness the test and agree the schedule before production.
Routine, type and special tests
A routine test is performed on every unit. A type test is performed on a representative design. A special test is agreed for a specific project. The quotation should state which category each test belongs to.
Common mistakes
Accepting a report without the serial number, ignoring the reference temperature, or treating a type-test report as evidence for a different rating. Always match the report to the unit and the approved design.
| Item | What to confirm |
|---|---|
| Test | partial discharge |
| Conditions | Temperature, voltage, current |
| Result | Measured value vs guaranteed |
| Report | Serial number and date |
| Acceptance | Standard and tolerance |
FAQ
Is partial discharge routine or type?
It depends on the test and the project specification. Confirm whether it is performed on every unit or on a representative design.
Can I witness the test?
Yes, subject to agreement. The test schedule and acceptance criteria should be fixed before production.
What if the result is outside tolerance?
The unit should be investigated and re-tested. Do not accept a report that does not match the guaranteed values.
How often should the test be repeated?
Routine tests are performed before shipment. After commissioning, periodic checks depend on the asset criticality and the operator's maintenance policy.
Related pages
Need this applied to a project?
Send the application, voltage class and site conditions through the inquiry form. The team will check the transformer family and the document scope.
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