Partial discharge (PD) are electrical discharges localized in the dielectric insulation, limited only to a part of the dielectric material.
The Partial Discharge test is the most effective system for assessing the quality of the insulation of a winding, by verifying the absence or presence of partial discharge (PD) and at what voltage these begin to manifest themselves. Download the brochure for more informations. Discover more about partial discharge in production.
The Partial Discharge test is the only system to identify insulation losses between the coils of the same winding. Adjustable voltage up to 4KV. It allows identifying potential coil defects, which over time could cause the failure of the DUT. The detection is entrusted to appropriate software filtering operated on the signal returned by the SURGE. It can be performed during the surge test or, depending on different objectives, during the electrical stiffness test.
The detection can be performed during the SURGE test or, with different objectives, during the dielectric strength test.
The Partial Discharge test performed during the SURGE test allows evaluating the discharge phenomena between coils, while the test performed using the circuits used to measure the dielectric strength allows identifying defects in the insulators.
The machine is equipped with a sensor connected to the coil under test, which can measure the current flowing in the high voltage conductor: the partial discharge test consists in the localization of small currents resulting from micro-discharges. The current sensor must be able to discriminate between the large value currents, those of the SURGE pulse, and those of small value resulting from micro-discharges without saturation: to achieve this goal, Risatti uses a current sensor with an adequate passband. The signal is then digitized and sent to the PC.
The measurement software performs digital filtering and provides the result in the form of a graph that shows the significant components of the signal: those resulting from micro-discharges. The evaluation of the detected micro-discharge level consists of a number obtained from the sum of the pulses measured over a certain period of time.
The measured value is then associated with the voltage value applied to the piece at that particular moment: a resulting graph gives an idea of the voltage at which the discharges occur, and, therefore, it is possible to evaluate PDIV and PDEV levels.
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