The effect of voltage harmonic distortion to the repetition rate and apparent charge of partial discharge pulse
The insulation condition monitoring has the potential to pre-empt catastrophic failure by identifying trends of insulation degradation. One approach to identifying the insulation degradation is by monitoring the partial discharge (PD) behavior through the Partial-discharge phase-resolved images properties. These properties can be obtained using digital registration containing and reflecting both the real and statistical character of PD pulses generated in the insulating systems. In the high voltage diagnostic, the PD images are used for assessment of insulation systems. The level and harmonic content of the testing voltage are crucial for a proper interpretation of the PD images. Small variations in the harmonic content can change the measured partial discharge patterns. Hence, the presence of harmonics should be noticed and observed for all partial discharge measurements. This research is focused on observing the characteristics of partial discharge repetition rate and apparent charge of a Partial Discharge pulse when the voltage input contains harmonic distortions. The harmonics distortion will be adjusted in both order and level of harmonic distortion. The generated harmonics distortions are on the individual order of 3rd, 5th, and 7th and its combination (3rd and 5th, 3rd and 7th, 5th and 7th, 3rd and 5th and 7th). The total harmonic distortion level of every individual and combination harmonics will be set in five variations 2%, 3%, 5%, 7%, and 10%. All measurement schemes will be performed under two scenarios; the first is equalized peak voltage and the second is equalized root means square voltage. The partial discharge measurement is conducted using partial discharge detector connected to the oscilloscope. Needle – Plate electrode configuration is used to produce partial discharges. The gap distance of electrode configuration is 1,3 cm while the voltage source applied is 15 kV. The Partial Discharge data are collected only for the inception of Partial Discharge detected. The result shows that the voltage harmonic distortion can affect the pulse repetition rate and the apparent charge of Partial Discharge pulse. The distortion, for both individual and combination harmonics, may increase the pulse repetition rate of Partial Discharge produced. Furthermore, it may produce different apparent charge value between equalized peak voltage and equalized RMS voltage applied.
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