Simulation Study on Spatial Distribution Characteristics of Partial Discharge UHF Signal in Transformer Outlet Device

The power transformer plays a critical role in power grid. In the case of extra-high and ultra-high voltage transformers, an indirect central outlet device is commonly employed. This device, however, poses a vulnerability to transformer insulation due to concentrated field strength. Consequently, it becomes imperative to investigate the detection of partial discharges (PD) in the outlet device. The ultra-high frequency (UHF) method is widely utilized for monitoring PD in electrical equipment due to its high sensitivity. This study focuses on accurately modeling the indirect outlet device and employs the time-domain finite difference simulation method to study signals characteristics associated with PD in the outlet device. The simulation results provide evidence that when PD takes place in the outlet device, the UHF signal effectively propagates into the external space through the oil channel between the casing and bushing. The location and magnitude of the PD have a significant influence on the time-domain waveform of the UHF signal.