基于电磁辐射特性的直流电弧检测方法

Detection Method for DC Arc Based on Electromagnetic Radiation Characteristics

直流电源系统中的直流电弧由于难以熄灭,是导致系统故障的主要原因之一,对其检测方法展开研究具有重要意义。为此提出了一种基于电弧电磁辐射特性的直流电弧检测方法,通过搭建直流电弧产生装置模拟直流系统中松弛连接的情况,设计4阶Hilbert天线测量直流电弧电磁辐射信号。电弧的电磁辐射信号与电流突变信号变化一致,且突变脉冲的时间间隔满足Gamma分布。对不同的电流突变进行频谱分析发现,在该试验条件下,电磁辐射信号在频谱上存在明显的特征频率(12.9 MHz),并且不同回路电流下幅值最大的电磁辐射频率在12~14MHz范围内。与开关操作时的信号进行对比发现,直流电弧的最大幅值电磁辐射频率大于开关操作的最大频率,直流电弧脉冲的平均时间间隔(37μs)比开关操作时的时间间隔(7.4μs)长,开关操作时能够检测到多个持续时间较长的脉冲簇。电磁辐射信号的特征频率、脉冲时间间隔以及脉冲簇持续时间可作为直流电弧的检测参量判断电弧故障。

DC arc is the main cause of system faults since it is hard to extinguish DC arc in DC source systems. Therefore, it is of great significance to find an appropriate method to detect DC arc. A detection method for DC arc based on electromagnetic radiation characteristics is proposed. A DC arc generating device is built to simulate the relaxing connection in DC systems. A fourth-order Hilbert antenna is designed to detect electromagnetic radiation signals of DC arc. The electromagnetic signals of arc are in accordance with the abrupt change of current, and the interval of the abrupt current pulse meets Gamma distribution. The spectra of different abrupt change of current are analyzed. The results indicate that, under the present conditions, the electromagnetic signals have an obvious characteristic frequency（12.9 MHz）, and the maximum amplitude frequencies under different circuit current are in a range of 12~14 MHz. The maximum amplitude frequency of DC arc is higher than the frequency when operating switchgear. The interval of DC arc（37 μs） is longer than that of switch operations（7.4 μs）. Multiple long duration pulse clusters can be detected when operating switchgears. The results indicate that the characteristic frequency, pulse interval, and pulse clusters duration of electromagnetic radiation signals can be used as the detection parameters of DC arc to identify arc faults.