Reduction of the Background Noise for Partial Discharge Measurements in Transformer Test Circuits fed by Static Frequency Converters

摘要

As static frequency converters by default emit electromagnetic interference to a certain extent, partial discharge measurements in transformer test circuits fed by static frequency converters are affected by a high background noise level, if no appropriate measures are taken. In this paper the emergence and propagation of the common-mode noise are presented and possible solutions are discussed, introducing the application of a step-up transformer with static shielding layers. A laboratory setup was used to assess the spectral properties of disturbance emitted into a distribution transformer test circuit by a standard static frequency converter designed for drive applications. The impact of static shielding layers in the step-up transformer on the coupling between the winding systems was examined by a swept frequency response analysis. The feasible reduction of the background noise level for partial discharge measurements obtained by static shielding layers and additional measures was assessed experimentally.