Onsite PD Testing of Cast-Resin Transformers Installed in Wind Farms

November 18, 2021

As part of the energy transition and the associated development of renewable energies, the number of installed dry-type transformers is increasing in the medium voltage power grid. Dry-type power transformers are often installed in wind turbine nacelles, industrial sites as well as in marine and civil applications. Therefore, the importance of the condition assessment of these units increases as well.

The assessment of the insulation condition is based on an induced voltage test in combination with a partial discharge measurement. The CPC 100 is used in combination with the step-up transformer MTR2 to generate up to 800 V at the transformer’s LV terminals. Due to the single-phase injection, the power intake is reduced, and an individual evaluation of each coil becomes possible. By using up to three synchronized CPC 100, transformers with power ratings of up to 15 – 20 MVA can be energized.

On the HV terminals, the MPD 800 system is connected to record the PD activity of the individual coils. In contrast to laboratory measurements under controlled conditions, an increased level of interference due to rotating machinery, power electronics, and other consumers can be expected on site. Different filtering and gating techniques of the MPD 800 system allow performing sensitive PD measurements even in the presence of high interferences.


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