Differential high-frequency current sensor for series arc fault signal acquisition

Abstract

The invention relates to a differential high-frequency current sensor for series arc fault signal acquisition. The sensor comprises a shell (6). A magnetic ring (1) and a secondary winding (2) wound on the magnetic ring (1) are arranged in the shell (6), a primary conductor through hole (4) penetrating through the middle of the magnetic ring (1) is formed in the shell (6) to allow a differential primary current-carrying conductor to penetrate through, and an output terminal outgoing line groove (3) is formed in the shell (6) to allow an output terminal (5) of the secondary winding (2) to penetrate out. The sensor is beneficial to improving the accuracy, reliability and safety of series arc fault signal acquisition.

Description

technical field [0001] The invention relates to the field of electronic sensor devices, in particular to a differential high-frequency current sensor for collecting series arc fault signals. Background technique [0002] In low-voltage power distribution lines, the steady-state current in the normal state can reach several amps or even dozens of amps, and the frequency is 50Hz at the power frequency. It is found through experiments that when a series arc fault occurs, the current amplitude basically does not change, but the arc current Contains abundant noise, and its frequency can reach tens of kHz or even MHz. It can be seen from this that the high-frequency signal of the arc current when the fault occurs can be used as the basis for the occurrence of the arc fault. In the series fault arc detection of low-voltage distribution network, in order to detect the high-frequency noise of the current when the arc occurs, it is necessary to select a current sensor that can collec...

AI Technical Summary

Problems solved by technology

The traditional current transformer made of silicon steel is suitable for the collection of current signals in the industrial frequency range, but it cannot be used for the collection of high-frequency current signals

High-frequency current sensors can collect low-power, low-current, and high-frequency signals, but for low-voltage distribution lines with large currents, the magnetic core of the high-frequency current sensor is prone to saturation, resulting in distortion of the output signal and deterioration of the propagation characteristics.

In order to avoid saturation, methods such as increasing the inner and outer diameter of the magnetic core, increasing the volume, and opening the air gap of the magnetic core are usually used to reduce the magnetic flux inside the magnetic core, which limits the application range of high-frequency current sensors.

[0003] The existing methods for collecting current signals of series fault arcs have the following disadvantages and deficiencies: (1) The shunt needs to be connected in series to the line under test, and the collected signal is a current signal within the entire frequency range, which requires additional signal conditioning The circuit filters the signal to obtain a high-frequency fault arc signal. This method increases the hardware cost, and because the shunt is not electrically isolated from the tested line, there may be safety problems, which will endanger the safety of operators and measuring instruments.

(2) The electromagnetic current transformer is essentially a transformer, the primary side needs to be connected in series in the circuit under test, and the secondary side cannot be open circuited, and the transformer and the circuit under test are not electrically isolated, which still cannot ensure personal and instrument safety issues

Although the magnetic core Rogowski coil has a much larger response than the hollow Rogowski coil, the application of this sensor is limited due to the core saturation problem of the magnetic core Rogowski coil.

The saturation magnetic induction of the high-frequency magnetic core is generally low. If the measured current is too large and the working point of the magnetic core enters the saturation region of the magnetization curve, the magnetic permeability of the magnetic core will drop sharply and the sensing effect will be lost.

(6) The arc fault current transformer needs to be installed on the main road. When the low-power load branch is connected in parallel with the high-power load, if an arc fault occurs in the low-power load branch, the small current containing high-frequency noise will be absorbed by the high-power load. The current is shielded, and the commonly used current transformer is difficult to solve this problem

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