Online detection method and protection device for direct current system arc faults

Abstract

The invention discloses an online detection method and protection device for direct current system arc faults. Characteristics of current alternating components of a power circuit in the power-on starting process, the normal work process and the overload fault process of the power circuit and characteristics of the current alternating components of the power circuit during arc generating are combined, selected arc current characteristic components include peak-to-peak values and standard deviations of a time domain and a frequency component power sum within the range from 1 kHz to 100 kHz after noise of specific frequency points of a load is filtered, mahalanobis distance values of the real-time characteristic components and the characteristic components in the power-on starting process, the normal work process and the overload fault process of the power circuit through a mahalanobis distance algorithm, and the mahalanobis distance values are compared with a threshold value set in the learning process to detect whether a single arc is generated or not. By means of the technical scheme, the online detection method and protection device have advantages of being high in university, high in detection rate and low in misjudgment rate, and can be widely applied to low-voltage and high-voltage electric power systems and photovoltaic cell systems of airplanes, electric vehicles and ships, and civil high-voltage direct current power distribution systems.

Description

technical field [0001] The invention relates to an on-line detection method and protection device for arc faults in a DC power system, belonging to the field of electrotechnical technology. Background technique [0002] DC arc faults often occur in aircraft, electric vehicles, photovoltaic power plants and other electrical systems that contain DC power. The arc fault is caused by the aging of the insulation performance of the wire and cable, insulation damage, air humidity, and loose connection terminals. There is no zero-crossing point in the DC arc, and it is not easy to extinguish the arc. If it is not protected in time, a long-term arc may occur; when it occurs, it is accompanied by sparks and bright light, which can generate high temperatures above 1000 ° C, resulting in further damage to the insulation of wires and cables. Even cause an electrical fire. [0003] The characteristics of DC arc faults are very different from those of AC arc faults: the AC arc current is...

AI Technical Summary

Problems solved by technology

[0011] (1) Since the frequency band of the arc fault frequency feature is also the frequency band of the switching frequency of many switching power supplies and power electronic loads, the difference in the nature of the load has a greater impact on the arc judgment results, which is likely to cause misjudgment;

[0012] (2) According to the different power supply voltage levels of the DC system, the frequency bands distributed by the frequency characteristics of the arc fault current are quite different; especially in the high-voltage DC system, it is easier to form a stable burning arc than the low-voltage system, and the frequency of the arc current The amplitude of the characteristic quantity is greatly reduced, and it is easy to misjudge the arc fault only from the frequency characteristic;

[0013] (3) The DC arc fault has strong randomness. The arc fault current is a random and non-stationary signal. Fast Fourier decomposition (FFT) is an analysis method for a stationary signal. Only the frequency component analysis results of FFT are used to judge the arc Faults can easily lead to inaccurate judgment results

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