Duan Dapeng

Experimental study and feature extraction on UHF partial discharge detection for typical model in air

In this paper, in order to represent three kinds of typical partial discharge respectively happened in dielectric, out of dielectric and surface of dielectric, five kinds of typical partial discharge models, which included needle to plate, needle to needle, plate to plate, surface and air void, were designed and manufactured with aluminum. Based on the designed models, an experiment system of ultra high frequency partial discharge detection was comprised with non-partial discharge transformer, 2.5 GHz bandwidth oscilloscope, broad band amplifier and the developed double helical antenna. Afterwards, partial discharge experiments were carried out in air, and the method recommended in IEC60270 was referenced to measure the apparent quantity of partial discharge in pC. The experimental waveforms were given out. At last, the characteristics of the ultra high frequency signals excited by partial discharge were analyzed in time domain, frequency domain and wavelet coefficients. Using kernel principal component analysis, the feature extraction was realized. Then, several characteristics, which included deflection, protruding, frequency distributing, decay time, wavelet coefficients and so on, were proposed to describe the ultra high frequency signals. The conclusion educed in this paper is significant to research the feature extraction and pattern recognition of ultra high frequency partial discharge detection for high voltage apparatus.

A novel algorithm of dielectric loss measurement based on orthogonal decomposition

The physical meanings and definition of dielectric loss factor-tandelta was analyzed under the harmonic condition. Voltage and current were defined as vectors in normed linear space. By using the characteristic of orthogonal vector in inner product space, the current signal was decomposed to active and reactive currents. Subsequently, a novel digital algorithm of tandelta measurement, which was defined as ratio of norms of the active current and currents, was presented based on orthogonal decomposition. Lastly, the proposed algorithm was simulated under several conditions. The simulation results show that the proposed algorithm is correct and predominant compared with the harmonic analysis method, and that the algorithm has physical meanings, simple calculation, precise measurement result and strong anti-interference capability.