Active noise reduction for partial discharge measurement in the frequency domain

Two procedures are presented which perform noise reduction up to 50+ dB of partial discharge measurements (PDM) in real-time using the frequency domain and digital signal processing, both based on classical PDM. The first solution uses the signal collection from two sources, one of them the usual PDM, the other a reference signal source to track the noise signals influencing the PDM. In the frequency domain as a first step a transfer function will be calculated between the two noise signals of PDM and of the reference. In the second step this transfer function is used to subtract the noise signal from the PDM signal. The second solution makes use of the different spectral characteristics of partial discharge (PDP) pulses and noise signals. Whereas the energy of PDP is spread over a wide frequency range most noise signals are concentrated on various frequencies, so removing high-energy spectral lines removes most of the noise.