Megger ADX15, User Manual

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Surge Testing with Partial Discharge
Partial discharge testing is an optional feature on the ADX. Contact Megger Baker Instruments support for information
on adding the feature to your tester.
NOTE: PD can occur from test leads to ground, or from lead to lead. Keeping test leads off of the floor
and separated from each other can mitigate some issues that can affect PD test results.
Surge testing with the ADX can include partial discharge (PD) detection. PD testing detects the discharge of localized
ionic charge build-up within voids in the insulation system. This charge build-up is present due to the high electrostatic
charge associated with high-voltage transients stimulated by the surge pulse.
Partial discharge does not result in a full
conductor-to-conductor current flow.
These discharges can ionize gasses within insulation voids, forming ozone and nitric acid, which will damage insulation
over time.
Partial discharge testing relies on the accurate detection of four key metrics:
„ PDIV—partial discharge inception voltage.
„ RPDIV—repetitive partial discharge inception voltage.
„ RPDEV—repetitive partial discharge extinction voltage.
„ PDEV—partial discharge extinction voltage.
The ADX uses two parameters to monitor PD:
„ PD Threshold—the amplitude at which a high-frequency transient (PD Event) is counted towards the PD Event
Limit.
„ PD Event Limit—the cumulative number of PD Events during each surge pulse required to constitute a PD surge
pulse. When the number of PD Events exceeds this limit, a PD surge pulse is detected.
These parameters are defined in the active test configuration assigned to an asset.
As test voltage increases, PDIV is detected and recorded the first time that a PD Event Limit is reached or exceeded.
As voltage continues to increase, when PD is present, PD events tend to increase and are deemed repetitive when more
than 50% of consecutive surge pulses contain PD. RPDIV is recorded the first time that this repetition occurs.
Fig 112: Simplified representation of PD event detection elements. While these metrics are not usually
symmetrical, PD events typically occur in a nearly symmetrical fashion.
As voltage decreases, PD events tend to decrease. RPDEV is recorded the last time that more than 50% of consecutive
surge pulses contain PD. When PD events cease, the voltage of the last PD event is recorded as PDEV.
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Surge Testing with Partial Discharge