We started the project by studying different planar inductor topologies to evaluate their characteristic parameters’ variation range upon approaching Fe- and Cu-based shield plates. The use of such materials can differently alter the electrical properties of planar inductors, such as the self-inductance, resonant frequency, resistance, and quality factor, which could be useful in multiple devices, particularly in inductive sensing of partial discharge (PD) activities. To reach an optimal design, five different square topologies, including spiral, tapered, non-spiral, meander, and fractal, were constructed on a printed circuit board (PCB) and evaluated experimentally. Then, these were used as an electrically small-loop antenna sensor to detect PD signals through laboratory experiments. The proposed sensors, initially simulated with Ansys HFSS software, have a resonant frequency of about 100 MHz. Their detection capabilities for three types of partial discharges (i.e. corona, surface, and internal PDs) was evaluated and showed that the loop spiral antenna is the most suitable for detection of all three types of PD. Indeed, the results show a peak-to-peak damped sine wave voltage equal to 22.87 mV, 74.8 mV, and 79.72 mV, respectively, for corona, surface, and internal PDs, with a frequency spectrum showing a maximum at 42.19 MHz, 16.41 MHz, and 35.1 MHz, respectively. Afterwards, the performance of the proposed small-loop sensor was compared with that of the commercial high-frequency current transformer (HFCT) sensor. The results showed that the two sensors exhibit comparative sensitivity for the three types of PD. In conclusion, it could be confirmed that PCB-based spiral sensors appear to be a suitable and promising candidate for PD monitoring in high-voltage power apparatuses. Subsequently, we conducted an experimental investigation to assess its best orientation for corona partial discharge (PD) detection. Experimental tests showed that the best PD voltage detected was when the orientation was 90 degrees, with a main frequency of around 35 MHz. The obtained PRPD (phase-resolved partial discharge) patterns and the PD signal shapes were quite similar to those provided by a commercial HFCT sensor. All this study allowed us to fully understand the theme and then to write an exhaustive study of the state of the art of PD detection based on radiometric methods in different usable radio frequency bands (i.e. HF, VHF, and UHF). Accordingly, we proposed a new generic categorization approach based on the detected electromagnetic wave component (magnetic or electric fields) and pick-up location, either from free space or ground cable. Next, we focused on optimizing and quantifying performance during PD detection using on-chip integrated planar inductors. Therefore, we compare the performance of a large square spiral integrated inductor with areas varying from 0.5 × 0.5 mm2 up to 2.5 × 2.5 mm2 and an operating frequency of a few hundred MHz, integrated on four different types of silicon substrates. Measured and characterizations results show that the high-resistivity (HR) substrate with a trap-rich (TR) layer yields significantly better performance in terms of quality factor, resonant frequency, self-inductance, and PD detection capabilities than the HR or standard Si ones.
