Propagation feature of partial discharge UHF signal diffusing from GIS pouring aperture

It is a novel method to detect partial discharge of GIS by detecting the UHF electromagnetic wave signal diffusing from the pouring aperture in the insulator containing iron hoop. In contrast with the feature of UHF electromagnetic diffusing from the bare insulator without iron hoop, UHF electromagnetic wave diffusing from pouring aperture is undiscovered due to the tiny dimension and special configuration. In this paper, propagation feature of the UHF electromagnetic wave through the pouring aperture was analyzed by using the theory of pore electromagnetic leakage and it is simulated based on the finite difference time domain method. The conclusion is that the orientation of electric field principal component of UHF signal from the aperture is parallel to the short edge of aperture. The primary frequency range is concentrated from 0.8 to 2GHz. In addition, rangeability of the signal caused by the change of the long edge is much higher than the rangeability of the signal caused by the change of short edge.