A Winding-Core High-Frequency Equivalent Circuit Model for Exactly Simulating Partial Discharge Signals Propagation in Transformer

Wideband partial discharge (PD) detection, with its high bandwidth and strong anti-interference capabilities, is an inevitable trend in the development of discharge detection technology. However, the intricate propagation paths and attenuation patterns of high-frequency signals pose challenges for wideband detection of PD, especially in converter transformers. To study the transient response of transformer windings to wideband PD signals, equivalent circuit model is an excellent method. However, conventional equivalent circuit model generally only applies to frequency below 1 MHz. For converter transformers, this equivalent circuit model is insufficient due to strong interference exiting in such frequency band. To solve the problems, this article proposes a winding-core high-frequency equivalent circuit model. Multiple RLC parallel resonant units are added to the circuit model of the interleaved winding, and a transverse capacitance between the high-voltage (HV) winding and the core yoke is also included in the model. Experimental tests on a transformer demonstrate that the improved model can accurately simulate the impedance characteristics of windings up to a frequency of 10 MHz. Compared to the conventional model, the improved model significantly enhances the similarity between simulated signals and measured signals. It can accurately characterize the attenuation of different frequency components within the 10 MHz range, addressing the challenge conventional model faces in simulating signals at the core grounding point.