Research on the electrical resonance characteristics of power transformer windings

Abstract

When a power transformer subjected to transient over-voltages containing different harmonic components, the frequency components of over-voltages are coupled with the inherent electrical frequency of the transformer winding, which can induce high-amplitude resonant over-voltages in the winding and thus lead to transformer insulation failures. To analyze the electrical resonance characteristics of transformer windings, this paper establishes an equivalent model of transformer windings with reference to the actual transformer structure, and calculates the time-domain and frequency-domain distributions of transformer winding voltages. Furthermore, a test model of a real three-phase transformer is constructed, with measurement wires embedded at different positions of the windings. Experimental tests are conducted to investigate the electrical resonance characteristics of the transformer windings, verifying the effectiveness of the established equivalent model. Finally, based on the equivalent model, the effects of winding structure, number of turns per disk, wire thickness, and oil duct width on the winding resonance characteristics are analyzed.