Multi-branch power distribution main line arc fault detection circuit

Abstract

The utility model aims to provide the multi-branch power distribution main line arc fault detection circuit which is low in cost and high in reliability, fault arc characteristics are extracted in real time through main / branch current vector differences, early accurate early warning of arc faults of a power distribution system is realized, and the operation safety of a power system is effectively improved. The current transformer comprises a main line, a plurality of branch circuits connected in parallel and a sampling resistor, the main line is provided with a first current transformer, and the branch circuits are provided with second current transformers. The secondary output end of the first current transformer and the secondary parallel output end of the second current transformer are connected to the two ends of the sampling resistor through opposite polarities, and the sampling resistor is connected with the single-chip microcomputer through the operational amplifier. The device is applied to the technical field of electrical safety monitoring.

Description

Technical Field

[0001] This utility model is applied to the technical field of electrical safety monitoring, and in particular relates to an arc fault detection circuit for multi-branch power distribution main lines. Background Technology

[0002] In existing arc detection technologies, single-loop high-frequency signal analysis focuses only on single-loop cases, making it difficult to accurately locate fault points in main lines and branches within multi-branch power distribution systems. When faced with complex multi-branch operating conditions, system errors accumulate, causing a sharp decline in detection sensitivity and hindering timely detection of potential faults. While Chinese patent CN207586360U discloses an arc fault detection device, temperature threshold judgment can reflect faults to some extent, but its lag in temperature changes prevents rapid response in the early stages of an arc. Furthermore, high-frequency sampling circuits are not only costly but also susceptible to interference from the surrounding electromagnetic environment, severely impacting the accuracy and reliability of detection results. Therefore, it is necessary to provide a low-cost, highly reliable arc fault detection circuit for multi-branch power distribution main lines that extracts arc fault characteristics in real time through the main / branch current vector difference, enabling early and accurate warnings of arc faults in power distribution systems and effectively improving the operational safety of power systems. Utility Model Content

[0003] The technical problem to be solved by this utility model is to overcome the shortcomings of the prior art and provide a multi-branch power distribution main line arc fault detection circuit with low cost and high reliability. It can extract the arc fault characteristics in real time by the main / branch current vector difference, realize early and accurate warning of arc faults in the power distribution system, and effectively improve the operational safety of the power system.

[0004] The technical solution adopted by this utility model is as follows: This utility model includes a main line, several parallel branches, and a sampling resistor. The main line is equipped with a first current transformer, and the branches are equipped with second current transformers. The secondary output terminal of the first current transformer and the parallel secondary output terminal of the second current transformer are connected to the two ends of the sampling resistor through opposite polarities. The sampling resistor is connected to a microcontroller via an operational amplifier.

[0005] As can be seen from the above scheme, the first current transformer and the second current transformer are connected in reverse to the sampling resistor to directly extract the high-frequency arc characteristics in the unbalanced current. Compared with the traditional scheme, the detection sensitivity is improved by more than 3 times and the cost is reduced by 60%. It is particularly suitable for early arc fault warning in multi-branch distribution systems. Actual testing has verified that the technology of this application performs excellently in complex power distribution environments, safeguarding the safety of power systems. By extracting the fault arc characteristics in real time through the main / branch current vector difference, it achieves early and accurate warning of arc faults in the distribution system, effectively improving the operational safety of the power system.

[0006] In a preferred embodiment, the current signal obtained by combining the current signals from the first current transformer and the second current transformer passes in reverse through the third current transformer and is then output to the sampling resistor to obtain the arcing current signal Vd.

[0007] A preferred embodiment is that the voltage Vd across the sampling resistor is Vd = K*(Itotal - ΣI of the branch), where K is a proportionality coefficient that is precisely determined by the circuit parameters. When an arc occurs, the current in the main branch becomes unbalanced, Itotal ≠ ΣI of the branch, and Vd represents the signal voltage.

[0008] A preferred embodiment is that the sampling resistor is a manganese copper alloy with a resistance of 50mΩ±1% and a temperature coefficient of ≤50ppm / ℃. Attached Figure Description

[0009] Figure 1 This is the circuit schematic diagram of this utility model. Detailed Implementation

[0010] like Figure 1 As shown, in this embodiment, the present invention includes a main line 1, several parallel branches 2, and a sampling resistor R1. The main line 1 is equipped with a first current transformer CT0, and the branch 2 is equipped with a second current transformer CT1. The secondary output terminal of the first current transformer CT0 and the parallel secondary output terminal of the second current transformer CT1 are connected to the two ends of the sampling resistor R1 through opposite polarities. The sampling resistor R1 is connected to a microcontroller 4 via an operational amplifier 3.

[0011] The main line 1 uses the first current transformer CT0 (1000:1, frequency response DC - 150kHz). Based on the requirements of the main line current range and frequency characteristics, the transformer is accurately selected to ensure comprehensive monitoring of the main circuit current.

[0012] The branch 2 is equipped with the second current transformer CT1, which uses a Rogowski coil (200:1, phase error <0.5°). By utilizing the wide frequency response advantage of the Rogowski coil, high-precision measurement of the branch current can be achieved. Ordinary current transformers can also be used.

[0013] The operational amplifier 3 is model AD8421. After signal synthesis, it is amplified by 50 times by the operational amplifier 3. Experiments have verified that this amplification factor can effectively improve the signal amplitude before being output to the subsequent processing stage.

[0014] like Figure 1As shown, in this embodiment, the current signal from the first current transformer CT0 and the second current transformer CT1 is passed in reverse through the third current transformer and then output to the sampling resistor R1 to obtain the arcing current signal Vd. The primary side transformers are reversed in series, while the secondary side transformers are parallel with the same polarity; the principle is the same as the circuit described above.

[0015] like Figure 1 As shown, in this embodiment, the voltage Vd across the sampling resistor R1 is Vd = K*(Itotal - ΣI_branch2), where K is a proportionality coefficient that is precisely determined by the circuit parameters. When an arc occurs, the current in the main circuit and the branch 2 becomes unbalanced, Itotal ≠ ΣI_branch2, and Vd presents a signal voltage, providing a key basis for subsequent fault diagnosis.

[0016] like Figure 1 As shown, in this embodiment, the sampling resistor R1 is a manganese copper alloy with a resistance of 50mΩ±1% and a temperature coefficient of ≤50ppm / ℃, ensuring that the resistance value is stable under different ambient temperatures and maintaining detection accuracy.

Claims

1. A multi-branch power distribution main line arc fault detection circuit, comprising a main line (1) and several parallel branches (2), characterized in that: The arc fault detection circuit of the multi-branch power distribution trunk line also includes a sampling resistor (R1). The trunk line (1) is equipped with a first current transformer (CT0), and the branch (2) is equipped with a second current transformer (CT1). The secondary output terminal of the first current transformer (CT0) and the secondary parallel output terminal of the second current transformer (CT1) are connected to the two ends of the sampling resistor (R1) through opposite polarities. The sampling resistor (R1) is connected to the microcontroller (4) through an operational amplifier (3).

2. The arc fault detection circuit for multi-branch power distribution trunk lines according to claim 1, characterized in that: The current signal from the first current transformer (CT0) and the second current transformer (CT1) is combined and then passed in reverse through the third current transformer, and then output to the sampling resistor (R1) to obtain the arcing current signal Vd.

3. The arc fault detection circuit for multi-branch power distribution trunk lines according to claim 2, characterized in that: The voltage across the sampling resistor (R1) is Vd = K*(Itotal - ΣI of the branch (2)), where K is a proportionality coefficient that is precisely determined by the circuit parameters. When an electric arc occurs, the current in the main branch (2) becomes unbalanced, Itotal ≠ ΣI of the branch (2), and Vd represents the signal voltage.

4. The arc fault detection circuit for multi-branch power distribution trunk lines according to claim 1, characterized in that: The sampling resistor (R1) is a manganese copper alloy with a resistance of 50mΩ±1% and a temperature coefficient of ≤50ppm / ℃.

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