In this paper, the design and development of a bio-inspired UHF sensor for partial discharge detection in power transformers is presented. The UHF sensor was developed for external use in dielectric windows of power transformers. For this purpose, a microstrip antenna was designed with a radiating element shape based on the leaf of the Jatropha mollissima (Pohl) Baill plant. Then, an epoxy coating and an aluminium enclosure were developed to protect the antenna against corrosion and to provide mechanical support, external noise immunity, and a lifetime compatibility with power transformers. In order to verify the electrical parameters of the developed sensor, measurements of the gain and the reflection coefficient were performed in an anechoic chamber. Lastly, the antenna sensitivity for denominated partial discharge (PD) detection was compared with the IEC 60270 standard method. For this purpose, simultaneous tests were carried out in a partial discharge generator setup, composed of an oil cell with needle-plane electrodes. The experimental tests demonstrated the effectiveness of the sensor for detecting PD signals with apparent charge values higher than 35 pC.

This paper presents an algorithm for the localisation of partial discharge (PD) sources in power transformers based on the electromagnetic waves radiated by a PD pulse. The proposed algorithm is more accurate than existing methods, since it considers the effects of the reflection, refractions and diffractions undergone by the ultra-high frequency (UHF) signal within the equipment tank. The proposed method uses computational simulations of the electromagnetic waves generated by PD, and obtains the time delay of the signal between each point in the 3D space and the UHF sensors. The calculated signals can be compared with the signals measured in the field, so that the position of the PD source can be located based on the best correlation between the simulated propagation delay and the measured data. The equations used in the proposed method are defined as a 3D optimisation problem, so that the binary particle swarm optimisation algorithm can be used. To test and demonstrate the proposed algorithm, computational simulations were performed. The solutions were sufficient to identify not only the occurrence of defects, but also the winding and the region (top, centre or base) in which the defect occurred. In all cases, an accuracy of greater than 15 cm was obtained for the location, in a 180 MVA three-phase transformer.

<p class="Normal1">The use of UHF sensors in high voltage electrical equipment for monitoring its insulation system is widely used. In order to improve these sensors,we present an analysis of different types of dielectric materials that can be used as physical coating and shield, which can enhance the electromagnetic characteristics of UHF microstrip sensors applied to the detection of partial discharges in performance transformers. The materials used as coating were glass, silicone, FR4, Teflon, and acrylic. In order to do so,, HFSS software simulations for the development of analyzes on two UHF microstrip antennas were performed. From the analyzes performed, it was verified the improvement of the reflection coefficient and the gain of the UHF sensor recorded the materials used to demonstrate the practical application. In addition to that, we also had simulations of a typical electromagnetic shield applied in conjunction with the sensor to demonstrate that the shield is still displayed in the design stages and is of great relevance. In order to underpin the data obtained from the simulations, the real models of UHF sensors were applied and tested in the laboratory.</p>