Evaluation Study on Wavelet Denoising of Antenna-based PD Measurements in Strong Interference Environments considering a New Reliability Score of Pulse Detection

Abstract

Partial discharge (PD) interference suppression represents an important aspect in diagnosis and maintenance of equipment in the power transmission network and thus contributes to ensuring transmission reliability. PD diagnosis includes the detection of PD using suitable measurement methods like non-contact electromagnetic methods such as antennas. An important step of measuring PD with antennas is the interference suppression of the measurement signals for further processing. Especially in the case of contactless detection of PD using antenna structures, other signals are coupled in additional to the actual PD signal. This requires interference suppression processes for pulse extraction of the PD pulses from the disturbed signal as well as evaluation criteria that measure the interference suppression and the reliability of the PD pulse detection of these processes. In the context of this work, a suitability study is carried out to select the mother wavelets and estimation methods within the framework of wavelet denoising. This is done by a preliminary study with synthetic signals in which a real noise environment is added, which is several times stronger than the synthetic PD signal. The best combinations are then applied to real PD signals measured in a strong interference environment. In addition to the conventional evaluation criteria for noise reduction and signal distortion, a new evaluation criterion, the reliability score of impulse detection, is introduced. The methodical approach also reliably determines whether generated PD are isolated, as a transmission line-bound reflection-free decoupling of the PD signal takes place simultaneously.