Study on the applicability of microstrip circular antennas in partial discharges detection in power transformers

The degradation of transformer's internal insulation system can be monitored by partial discharges activity. Among the supervising systems, the use of ultra high frequency (UHF) antennas attached on transformer's tank is highlighted. The UHF microstrip antennas can be used on this task and provide some interesting features, such as, low cost, ease of manufacturing and installation on several facilities. However, the microstrip antennas have a narrow band. The main objective of this work is to analyze the applicability of a microstrip circular antenna on detection of partial discharges in power transformers. For this purpose, a truncated ground plane technique for bandwidth optimization was applied. The manufactured antenna reached a high sensitivity for the partial discharges detection, showing mean gainvalue higher than 2 dB on the frequency range analyzed, as well return losses lower than −10 dB.