Optimisation of built-in UHF conical monopole antenna sensors for partial discharge detection in high voltage switchgear

In this paper, a built-in antenna sensor for wide-band based on a classic conical monopole antenna is proposed to detect partial discharge(PD) in 600MHz-1.2GHz. The antenna is modeled by CST Microwave Studio to yield good performance in the frequency range of interest. The large ground plate of the classic conical monopole antenna is replaced by a concentric cylindrical block, which reduces the area of the cross-section of the ground plate and realizes the miniaturization of antenna. By appropriately choosing the gap distance between the cone and cylindrical block, cone length and the diameter of the concentric cylindrical block, the performance of wide bandwidth, omnidirectional radiation patterns and good gain are acquired. A vector network analyzer(VNA) is used to test the return loss of the conical antenna, and the test results are consistent with the simulation results (standing wave ratio of less than 2.5). Finally, an experimental platform is set up in the laboratory and typical partial discharge defects are set. The proposed UHF monopole antenna is fabricated and tested. Detection impedance, transient earth voltages(TEV) and UHF are used for PD detection simultaneously with the aim to validate the effectiveness of the antenna and the experimental results demonstrate that the proposed UHF antenna appeared to be suitable for PD detection.