Elliptical UHF sensor for partial discharge detection

In this article, simplified geometries for microstrip antennas were evaluated and optimized, to select one appropriate geometry, aiming for its application of partial discharge (PD) detection, as a UHF sensor. To improve the performance of the proposed antenna, cascaded frequency selective surfaces (FSS), using double square loops as a unit cell element, were designed and evaluated. Antenna reflection coefficient measurements without and with the integrated FSS were performed and compared with simulated results. The results show that the insertion of the FSSs did not impact the operational bandwidth of the antenna, which comprises 100% of the characteristic frequency range, of the PD activity (300–1500 MHz). The insertion of the FSSs resulted in an average gain of 4 dBi, concerning the isolated antenna, increasing the sensitivity for PD detection, within the proposed frequency range. We evaluated the PD detection of the structure through measurements in three devices, a bar of a hydro generator, an oil tank with electrodes in the flat-tip configuration, and a potential transformer (PT). The proposed UHF sensor for PD detection could detect PD activity in all three scenarios and for levels lower than 10 mV.