Distinguishing Between Phase to Ground, Phase to Phase and Cross-Coupled PD Signals in Stator Windings

Published Jun 7th, 2022 EIC 2021 - M. Sasic, H. Sedding, G. Stone

Abstract – Partial discharge (PD) detection in stator windings is widely used to assess the condition of the electrical insulation. When the winding is excited by 3-phase AC voltage, PD current pulses can occur between each phase and ground (i.e. within the stator slot and just outside of the same slot). PD can also occur in the endwinding region, driven by the phase to phase voltage. In addition, PD occurring in one phase often induces a “crosscoupled” signal into another phase, presumably due to the capacitance between phases in the endwinding region. These three “sources” of pulses can complicate the phase-resolved PD (PRPD) plots from each phase. Although some methods to separate these three types of pulses from one another have been proposed using post-data acquisition processing – they still require considerable expertise to separate them reliably. In this paper, experiments are conducted on stator winding models to identify the characteristics of the phase to ground, phase to phase and cross-coupled PD signals, in order to separate the sources in real time. Such separation is important, since PD in the endwinding is often much easier to repair than PD occurring with stator slots.


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