Characterization and comprehension of corona partial discharge in air under power frequency to very low frequency voltage

Abstract

For the partial discharge test of electrical equipment with large capacitance, the use of lowfrequency voltage instead of power frequency voltage can effectively reduce the capacity requirements of test power supply. However, the validity of PD test under low frequency voltage needs to be evaluated. In order to investigate the influence of voltage frequency on corona discharge in the air, the discharge test of the tip-plate electrode under the frequency from 50 to 0.1 Hz is carried out based on the impulse current method. The results show that some of the main features of corona under low frequency do not change. The magnitude of discharge in a positive half cycle is obviously larger than that in a negative cycle. The magnitude of discharge and interval in positive cycle are random, while that in negative cycle are regular. With the decrease of frequency, the inception voltage increases. The variation trend of maximum and average magnitude and repetition rate of the discharge in positive and negative half cycle with the variation of voltage frequency and magnitude is demonstrated, with discussion and interpretation from the aspects of space charge transportation, effective discharge time and transition of discharge modes. There is an obvious difference in the phase resolved pattern of partial discharge and characteristic parameters of discharge patterns between power and low frequency. The experimental results can be the reference for mode identification of partial discharge under low frequency tests. The trend of the measured parameters with the variation of frequency provides more information about the insulation defect than traditional measurements under a single frequency (usually 50 Hz). Also it helps to understand the mechanism of corona discharge with an explanation of the characteristics under different frequencies.

Review of Partial Discharge Activity Considering Very-Low Frequency and Damped Applied Voltage

“…The increase trend was more obvious for the higher voltages. The average PD magnitude almost followed the same trend with the varying of frequency [35]. (c) Phase-resolved PD pattern.…”

“…(a) PDIV. Most of the results show that PDIV increases with the decrease of test frequency, for instance, corona discharge in air studied by Zhou et al [35], PD activity in discshaped cavities in polycarbonate insulation given in [32] and PD in XLPE cables with and without artificial internal defects in [72]. This slight increase can be explained by the influence of statistical time lag, as discussed in [32].…”

“…Surface discharge characteristics at low frequencies of 0.02 Hz, 0.1 Hz and power frequency test voltages have been compared in [34]. Zhou et al investigated the influence of test frequency on corona discharge in the air [35]. The effect of temperature on corona discharge and aging on cavity discharge was studied at very low frequency of 0.1 Hz by Nguyen et al [36][37][38].…”

“…However, Forssén and Edin concluded that PD pattern would significantly change with the test frequency without specifying the variation trend [6,30]. Zhou et al found that PD patterns distributed wider in positive corona discharge with the decrease of frequency [35]. PD tests involving surface discharges on polyethylene specimens were studied in [74].…”

Feature Extraction and Comprehension of Partial Discharge Characteristics in Transformer Oil from Rated AC Frequency to Very Low Frequency

“…The superscripts "+" and "−" correspond to a positive and negative half cycle, respectively. The detailed calculation methods of each characteristic parameter can be found in our previous research [33]. Table 1.…”