Simulation Study on UHF Signal Propagation Characteristics of Pouring Hole of Basin-Type Insulator in GIS

Detecting partial discharge in GIS is crucial for identifying insulation defects and improving maintenance efficiency. Conventional detection methods are insufficient to detect the internal partial discharge UHF signal in the absence of a built-in UHF sensor. Thus, detecting the UHF signal radiated from the pouring hole of the basin-type insulator is the only way to detect partial discharge in GIS by UHF technology. However, this method presents a key challenge in field verification of sensitivity of the online monitoring system for detecting partial discharge in GIS. To improve UHF detection systems and enhance detection sensitivity, this paper analyzes the characteristics of UHF signal propagation when transmitted through the pouring hole of basin-type insulators, using the theory of guided electromagnetic waves. The paper also simulates the propagation process of partial discharge UHF signals using the finite difference time-domain method, and analyzes the directivity and spectral characteristics of the electric field intensity at the pouring hole. Additionally, the paper examines the emission method of GIS external UHF electromagnetic waves and injects calibration signals through the metal-edged pouring hole on the basin-type insulator. Research findings indicate that the UHF signal's electric field is oriented along the short edge of the hole, and its main energy is concentrated between 1.9 and 2.2 GHz. The frequency spectrum trend of the sensor under internal partial discharge and external sensor injection signal is generally consistent, with external sensor injection resulting in a stronger high-frequency voltage signal compared to internal PD.