Surface discharge analysis at trapezoidal testing voltage waveforms

Surface discharge (SD), as one important partial discharge (PD) source, were measured in the test cell representing the surface discharge, with polycarbonate plate as the insulating material covered completely on the bottom ground electrode. This study compares PD patterns stimulated by sinusoidal voltage and by several forms of trapezoid-wave voltage, including the limiting cases of triangular and approximately square-wave voltages. Trapezoid-based voltage waveforms are considered as a potential new off-line diagnostic method for PD sources. The results show that surface discharge produced in the asymmetric test cell shows strong asymmetric behavior during the constant-voltage period between two polarities under trapezoidal and square voltage waveforms. A faster rise time and increased duration of the constant peak-voltage part of the waveform caused more obvious asymmetry of the surface discharge.