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Partial Discharge Testing for Power Transformers

Condition assessment solutions and on-line diagnostic testing services for power transformers.

Insulation deterioration is a frequent cause of transformer failure. But failure can be predicted if transformer aging is monitored.

Diagnostics and Condition Assessment


Techniques have been developed to help utilities evaluate the condition of their transformer assets. These methods include: Dissolved Gas Analysis (DGA), moisture analysis and other oil tests, Furfural, Frequency Response Analysis (FRA), Recovery Voltage Measurement (RVM), Power Factor measurement, Partial Discharge, Insulation resistance and Polarization Index.

Partial Discharge (PD) can be measured off-line using a high voltage power source, or on-line as the transformer is energized—under load or no-load.

Value of Partial Discharge Testing for Power Transformers


PD measurement is a fundamental tool used to assess the condition of oil-filled or cast resin power transformers. This unique on-line method can directly assess the solid insulation of power transformers and detect the deterioration of inter-turn insulation, disks insulation, HV to LV insulation, tap changer, and bushing.

PD measurements also offer insight into the presence of harmful defects that can compromise transformer insulation.

On-line Partial Discharge Monitoring by Kinectrics
Kinectrics offers a variety of off-line and on-line non-destructive testing techniques for power transformers, including on-line Partial Discharge, DGA, moisture test, Frequency Response Analysis, and bushing testing for small and large generation, and transmission class power transformers.
Combined with other techniques, PD measurement can fully evaluate power transformer condition and effectively detect insulation problems before catastrophic failures occur.
Kinectrics offers an on-line PD assessment method that combines both acoustic and electrical detectors.  A database and grading system is used that contains data from both the main tank, as well as tap changers.
Kinectrics’ acoustic location technique is based on IEEE Std C57.127™-2007, “IEEE Guide for the Detection and Location of Acoustic Emissions from Partial Discharges in Oil-Immersed Power Transformers and Reactors”. This system is ideal for on-line monitoring of critical transformers.
Besides acoustic measurement, an electrical tool for on-line diagnostics is offered by Kinectrics via bushing tap. Kinectrics is able to provide adapters for different types of tap.
If the transformer does not have capacitive taps, High Frequency Current Transformers (HFCT) can be effectively employed. The HFCT is wrapped around one (or more) grounding connection(s) of the transformer. The acquisition philosophy provides efficient noise rejection in most cases without adding any suppression device.
Data download can be accomplished by a walk-up attachment (plugging in a notebook computer via its standard Ethernet port), through an automated remote interface, either via Ethernet; optional wireless Ethernet; Internet; or telephone modem to a remote control and data processing station.
If the transformer is also equipped with a DGA (Dissolved Gas Analysis) permanent monitoring system, this may be interfaced with the PD monitoring system to utilize all the best diagnostic capabilities.
On-line Testing—No Need for Outage
The main advantage of the acoustic and electrical measurement offered by Kinectrics is that there is no need for transformer outage. The measurement can be conducted even if the transformer is just energized and whether under load or not.
Off-line PD testing may be applicable depending on the size of the transformer. In this case an external 3-phase source feeds the transformer during the test period.