Enhanced bowtie UHF antenna for detecting partial discharge in gas insulated substation

UHF method to detect partial discharge (PD) phenomenon has been proven to be an effective way. Many types of UHF antenna have been developed in order to achieve a better sensitivity and accuracy in certain bandwidth (300 MHz-3.0 GHz) for detecting the ultra-high frequencies generated by partial discharge. Bowtie antenna is proven to be sensitive, accurate and easily designed and fabricated. This paper focuses on the enhancement of bowtie antenna to achieve better performance in detecting partial discharge using UHF method. Characteristics of antenna both on the simulation result prior to the fabrication and measurement using a network analyzer show the good agreement. Experiment was carried out in a gas insulated switchgear (GIS) model with a protrusion on the conductor as PD source and antenna located at different positions with applied voltage range from 20-25 kV. EM wave intensity and frequency captured by antenna were observed. The relation between the distances of PD source to antenna, either from one spacer aperture to others, or distance from one spacer aperture were investigated. Antenna mounted 55 cm from the closest spacer aperture to the PD source can still detect EM wave intensity very well. The lowest EM wave peak envelope intensity measured at 30.03 mV from the same spacer aperture compared to 1.952 mV peak-peak EM wave intensity from internal GIS UHF sensor demonstrates a sufficient sensitivity performance.