UHF Measurement of Partial Discharge on Stator Bars Using Patch Antennas

Compared with other methods, there is limited research on the measurement of partial discharges (PD) in rotating machine windings using antenna-based UHF techniques. In this work, to investigate the value of measuring winding PD at higher frequencies, we designed and fabricated three patch antennas operating at 900, 1500, and 2450 MHz. The antennas are used to perform UHF PD measurements on single rotating machine bars rated at 13.8 kV. Measurements were performed in a laboratory with the specimens placed in grounded dummy stator slots. PD was produced by over-stressing the test specimens with a PD-free high voltage test set, and also by shorting out stress control region(s) using semi-conductive tape. The UHF PRPD patterns were compared to those from measurements on the same specimen with a VHF commercial instrument. It was clearly shown that PD can be measured with UHF patch antennas, despite some disagreement between UHF and VHF PRPD patterns.