Discharge Characteristics of Motion and Aggregation of Fiber Impurity Particles Based on Multiphysics Coupling

Addressing the issue of impurity particle precipitation and aggregation within existing converter transformers, which can trigger partial discharge or dielectric breakdown. This paper employs finite element simulation methods to establish a multi-physics field model of solid-liquid two-phase flow involving the mixing of impurity particles from dielectric barrier fibers with flowing insulating oil. The simulation investigates the movement and aggregation characteristics of fiber impurity particles under different voltage application times, flow rates, and voltage amplitudes. Additionally, an experimental platform for simulating oil flow circulation discharge is established to experimentally validate and analyze the aggregation of fiber impurities and their associated discharge characteristics. The analysis shows that under dielectric barrier conditions, fiber particles mainly aggregate in the central region of the electrode plate, with minimal aggregation at the plate edges. As the voltage application time increases, the fiber particles gradually form a "particle bridge," and after 600 seconds of continuous voltage application, the amplitude of discharge pulse currents and high-frequency currents increases significantly. At an electric field strength of 20 kV/cm and an oil flow velocity of 0.3 m/s, fiber particles almost do not aggregate between the electrodes, effectively improving the degradation of the electric field. When fiber particles aggregate in a uniform electric field and discharge, the energy spectra of the generated UHF signals, high-frequency CT signals, and pulse current signals are mainly distributed in the ranges of 0.01-0.3 GHz, 10-120 MHz, and 0.1-1.5 MHz with fluctuating amplitudes.