An External UHF Miniaturized Compound Spiral Slot Antenna for Partial Discharge Detection in GIS

The ultra-high frequency (UHF) electromagnetic wave excited by partial discharge (PD) can leak from gas insulated switchgear (GIS), therefore the external UHF antenna can be selected to detect the electromagnetic wave and diagnose the internal PD in GIS. Based on the concept of conformal design, two kinds of basic structures of frequency-independent broadband antenna are selected and combined: planar equiangular spiral antenna and planar Archimedean spiral antenna, then an external planar compound spiral slot antenna with broadband and miniaturization was designed by extracting the key structural parameters to optimize the structure. The proposed antenna was firstly required to meet the structural requirements of miniaturization and low profile, and then the main working frequency band and gain of the antenna were determined. During the design process, the resistance value loaded at the end of the spiral structure of the antenna was selected through simulation to improve its low-frequency performance. Meanwhile, the metal shielding box was installed to make the antenna have single-side radiation and large gain, so as to be low profile. The results of simulation show that this antenna has the characteristics of large gain, high sensitivity and single-side radiation in UHF, of which structure and size meet the requirements of the external UHF antenna in GIS.