Importance of bandwidth in PD measurement in operating motors and generators

If is well known that partial discharge (PD) events produce electromagnetic radiation with frequencies from de to sometimes hundreds of megahertz. Tn addition, in complex structures such as stator windings, the initial pulses are significantly distorted and attenuated as they propagate through a winding. The detection of the PD pulses needs to account for these effects. In particular, the bandwidth of the detection system will influence the sensitivity of the PD measurement as well as in what portions of the winding PD can be detected. This paper summarizes over 20 gears of research into these effects in stator windings, and discusses the implications for off-line and on-line PD testing, and the calibration of the PD quantities into apparent charge.