Research on partial discharge detection through ultra high frequency signal diffusing from GIS pouring aperture

Detecting the UHF (Ultra-High Frequency) electromagnetic wave has been widely used in the measurement of various types of partial discharges in GIS (Gas Insulated Switchgear). A lot of insulators of GIS are surrounded by iron hoops in recent years, which can prevent electromagnetic wave from spreading out extremely. So it's difficult to detect the electromagnetic wave from the surface of the insulator. It is a new method to detect the electromagnetic wave diffusing from the pouring aperture in the iron hoop. However, propagation feature of UHF electromagnetic wave diffusing from pouring aperture is undiscovered due to the tiny dimension and special configuration. It's essential to develop an UHF transducer exclusively used in detecting UHF electromagnetic wave diffusing from pouring aperture. Propagation feature was simulated by FDTD (finite-difference-time-domain) method. The UHF transducer of dipole antenna was developed based on the software of CST (Computer Simulation Technology). Ultimately, detection sensibility and validity of the transducer was tested via an experimental platform of 110kV GIS. It is concluded that the electric field principal component of UHF electromagnetic wave diffusing from the pouring aperture is parallel to the short edge of pouring aperture. The primary frequency range is concentrated in 0.8-2GHz. The average equivalent height of the dipole antenna transducer achieves 8.1mm in the range of 0.8-2GHz. Partial discharge detecting sensitivity of the dipole antenna transducer detecting the partial discharge UHF signal can be lower than 25pC.