Impact of velocity on partial discharge characteristics of moving metal particles in transformer oil using UHF technique

Metal particle contamination can cause partial discharge (PD) and seriously degrade the withstand voltage of transformer oil. The moving metal particles, which display PD characteristics that differ from those of free particles, perform complex movements within the transformer oil duct under the force of a submerged pump. This study analyzed the Φ-U-N diagram and measured the inception voltage, number, and amplitude of PD under different supply voltages. The influence of flow velocity on the characteristic parameters of PD was examined. The forces of charged metal particles were analyzed, and the trajectories were simulated in an oil duct under different flow velocities. As the supply voltage was increased, the number and amplitude of PD increased, whereas the shape of the Φ-U-N diagram remained the same. As the flow velocity was increased, the inception voltage of PD increased, but the number and amplitude of PD decreased. The ΦU-N diagram demonstrated slight changes under different flow velocities. Overall, an increase in flow velocity reduces PD possibly because of particle oscillation within the system.

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