Abstract This paper deals with a time-frequency analysis of the measured partial discharge (PD) currents in different insulation gases. These gas environments consist of a pure SF6 (sulphur-hexafluoride) and sulphur-hexafluoride and nitrogen (1 % SF6 + 99 % N2) mixture, under both positive and negative lightning impulse (LI) voltage stresses. In this study, the short time Fourier transform was used to extract the time-frequency information of PDs for different gases at different pressures, and these results were compared to each other. Thus, the relationship between the time, amplitude, and frequency of PD currents was studied. Moreover, some statistical formulas, such as mean, standard deviation, kurtosis, and skewness were applied to the time-dependent PD current data. As a result, a correlation between obtained statistical results and PD frequencies was examined. In most cases, the frequency of partial discharge decreased when the pressure increased. The amplitude of the partial discharges for negative polarity was more than that for positive polarity gas insulations. The partial discharge amplitudes of the pressure of 2 bar were mostly high compared to other pressures. This case demonstrated that SF6 had a maximum minimum character in terms of breakdown. The partial discharge frequency of a 1 % SF6 mixture was higher than that of pure SF6. It is thought that SF6 suppresses the discharge frequency, and statistical evaluations support the experimental results.

中文翻译：

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雷电冲击下不同气体环境下局部放电电流脉冲的时频分析

摘要 本文涉及在不同绝缘气体中测得的局部放电 (PD) 电流的时频分析。这些气体环境由纯 SF6（六氟化硫）、六氟化硫和氮气（1% SF6 + 99% N2）混合物组成，在正负雷电脉冲 (LI) 电压应力下。本研究采用短时傅里叶变换提取不同压力下不同气体的局部放电时频信息，并将这些结果相互比较。因此，研究了 PD 电流的时间、幅度和频率之间的关系。此外，一些统计公式，如均值、标准差、峰态和偏度被应用于时间相关的局部放电电流数据。因此，检查了获得的统计结果和 PD 频率之间的相关性。在大多数情况下，随着压力的增加，局部放电的频率会降低。负极性的局部放电幅度大于正极性气体绝缘的局部放电幅度。与其他压力相比，2 巴压力的局部放电幅度大多较高。该案例表明，SF6 在击穿方面具有最大最小特性。1% SF6 混合物的局部放电频率高于纯 SF6 混合物的局部放电频率。人们认为SF6 抑制了放电频率，统计评估支持了实验结果。负极性的局部放电幅度大于正极性气体绝缘的局部放电幅度。与其他压力相比，2 巴压力的局部放电幅度大多较高。该案例表明，SF6 在击穿方面具有最大最小特性。1% SF6 混合物的局部放电频率高于纯 SF6 混合物的局部放电频率。人们认为SF6 抑制了放电频率，统计评估支持了实验结果。负极性的局部放电幅度大于正极性气体绝缘的局部放电幅度。与其他压力相比，2 巴压力的局部放电幅度大多较高。该案例表明，SF6 在击穿方面具有最大最小特性。1% SF6 混合物的局部放电频率高于纯 SF6 混合物的局部放电频率。人们认为SF6 抑制了放电频率，统计评估支持了实验结果。