Electromagnetic Radiation Characteristics of PD in Inverter-fed Motor Inter-Turn Insulation

Ultra-high-frequency (UHF) antenna sensors are commonly used for the detection of partial discharge (PD) signals which are helpful to diagnose the insulation performance of inverter-fed motor. It is possible to reliably detect PD activity through analysis in the frequency domain with high pass filtering, however, it is unclear whether the frequency content of the signals gathered is typical of the discharge. In this paper, the resonant frequency of the single-point cross-insulated sample as a dipole antenna is simulated, and the radiation characteristics of the Sample Antenna (SA) with different lengths are analyzed. The PD detection platform for single-point cross-sample is built with a wide-band antenna (0.5-2 GHz Archimedes helical antenna). The PD signals in the frequency domain are analyzed. The results show that the Resonant Frequency (RF) of sample antenna and the frequency domain of PD signal (SF) move to low frequency with the increase of sample length. The RF of the 10 cm sample antenna is 2.3 GHz, but the SF is missing seriously, and the amplitude in time domain decreases significantly. It can be concluded that the structural parameters of the antenna determine the radiation characteristics of the antenna. As an antenna, the structure of the SA affects the time-frequency characteristics of PD signals.