Simplified arc detection circuit and detection method

Abstract

The invention discloses a simple electric arc detection circuit and a detection method. The simple electric arc detection circuit comprises a detection circuit and an MCU microprocessor connected with the output of the detection circuit. The detection circuit comprises a current loop, a rectifier bridge, a resistor RL1, a transient voltage suppressor (TVS), an electrolytic capacitor C1 and a comparator. The output end of the current loop is connected to the input end of the rectifier bridge, the output end of the rectifier bridge is connected to the two ends of the resistor RL1, the transient voltage suppressor TVS and the electrolytic capacitor C1 are both connected with the resistor RL1 in parallel, the negative electrode of the electrolytic capacitor C1 is grounded, the positive electrode of the electrolytic capacitor C1 is further connected with the in-phase input end of the comparator, and the in-phase input end of the comparator is connected with the output end of the rectifier bridge. The inverted input end of the comparator is connected with the VREF, and the output end of the comparator serves as an output port GPIO interface of the detection circuit. By simplifying the design of the arc detection circuit, the dependence on a complex algorithm and a large number of components is reduced, so that the whole circuit is simpler and more convenient, the cost is lower, and the detection efficiency and accuracy are improved.

Description

Technical Field

[0001] The present invention relates to the field of arc fault detection, and in particular to a simplified arc detection circuit and a detection method. Background Art

[0002] Electricity is one of the main energy sources in today's society. Both the daily life of residents and the development of various industries cannot be separated from the support of electrical equipment. With the increasing types and number of electrical equipment, the complexity of circuits is also increasing, which leads to an increasing number of electrical fires. Fault arc is a serious type of fault in electrical equipment and power systems. It usually causes equipment damage and even electrical fires, resulting in serious property losses and casualties. There are many reasons for the occurrence of fault arcs. Some electrical equipment may be mechanically damaged during installation or operation. For example, when the wire is in a humid environment, moisture will reduce the resistance of the insulating material, making it easier for the current to break through the insulation layer and form an arc. When the electrical equipment runs beyond its rated load, it may cause overheating, further weakening the insulation performance, thereby causing a fault arc. At the same time, low-voltage fault arcs are also hidden and uncertain, which increases the difficulty of detection. Therefore, the research on fault arc detection methods is of great significance to improving the safety and reliability of equipment and ensuring the stable operation of the power system.

[0003] Most of the existing AC fault arc detection technologies use a combination of one or several parameters and set a fixed judgment threshold based on the parameter characteristics. The calculated parameter value is compared with the judgment threshold to determine whether a fault arc occurs. However, in actual use, it is not so easy to obtain the circuit environment load parameters. Therefore, it is necessary to propose a simplified low-voltage fault arc detection method. Summary of the invention

[0004] The technical problem to be solved by the present invention is to reduce the computing power requirement and improve the accuracy of fault arc identification. In order to solve the above problems, a simplified arc detection circuit and detection method are provided.

[0005] The object of the present invention is achieved in the following manner:

[0006] A simplified arc detection circuit comprises a detection circuit and an MCU microprocessor connected to the output of the detection circuit; the detection circuit comprises a current loop, a rectifier bridge, a resistor RL1, a transient suppression diode TVS, an electrolytic capacitor C1 and a comparator; the output of the current loop is connected to the input end of the rectifier bridge, the output end of the rectifier bridge is connected to the two ends of the resistor RL1, the transient suppression diode TVS and the electrolytic capacitor C1 are both connected in parallel with the resistor RL1, the negative electrode of the electrolytic capacitor C1 is grounded, the positive electrode of the electrolytic capacitor C1 is also connected to the non-inverting input end of the comparator, and the inverting input end of the comparator is connected to VREF The output end of the comparator serves as the output port GPIO interface of the detection circuit.

[0007] The rectifier bridge includes a diode D1, a diode D2, a diode D3 and a diode D4, the cathode of the diode D1 is connected to the anode of the diode D2, the cathode of the diode D2 is connected to the cathode of the diode D4, the anode of the diode D4 is connected to the cathode of the diode D3, the anode of the diode D3 is connected to the anode of the diode D1, one end of the output of the current loop is connected to the cathode of the diode D1 and the anode of the diode D2, and the other end of the output of the current loop is connected to the cathode of the diode D3 and the anode of the diode D4; one end of the resistor RL1 is connected to the cathode of the diode D2 and the cathode of the diode D4, and the other end of the resistor RL1 is connected to the anode of the diode D1 and the anode of the diode D3;

[0008] A detection method using the simplified arc detection circuit, the detection method comprising the following steps:

[0009] S1: The output port GPIO of the detection circuit is connected to the GPIO port of the MCU microprocessor. When the GPIO level has a rising or falling edge, the MCU triggers the timing t1, and the timing ends when the rising edge is restored;

[0010] S2: When the GPIO level rises or falls again, the MCU triggers timing t2, and the timing ends when the GPIO level falls or rises;

[0011] S3: Compare the absolute value of the two timing differences to see if it is greater than the set value a, where a = 1 / 4f × (1-C1 × 2f × V REF / I), f is the frequency of the induced current in Hz, C1 is the capacitance of the electrolytic capacitor in the circuit in F, I is the driving current of the comparator input terminal selected by the circuit, generally a fixed value in A, V REF The circuit reference unit is V;

[0012] S4: If the absolute value of the difference is greater than or equal to a, the value of k is incremented by 1, and the initial value of k is 0;

[0013] S5: When the number of times a occurs continuously for three times or more, that is, k ≥ 3, it is judged that the state is arcing, otherwise it is judged to be a normal state and S2 is executed;

[0014] S6: If the absolute value of the difference is not greater than or equal to a, the value of k is set to 0, and it is judged to be in a normal state, and S2 is executed.

[0015] The output end of the MCU microprocessor is connected to a status indication circuit for displaying the status after determination. The status indication circuit includes an indicator light, a buzzer or a display screen.

[0016] Beneficial effects of the present invention: The present invention simplifies the design of the arc detection circuit, reduces the reliance on complex algorithms and a large number of components, and makes the entire circuit simpler and more cost-effective. At the same time, the circuit only needs to output high and low level signals, and can use a low-performance MCU to achieve accurate detection of arc faults, thereby improving detection efficiency and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a circuit diagram of the detection circuit of the present invention.

[0018] Figure 2 It is a principle block diagram of the arc detection circuit of the present invention.

[0019] Figure 3 It is a flow chart of the detection method of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0021] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same technical meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0022] like Figure 1 and Figure 2 As shown, a simplified arc detection circuit includes a detection circuit and an MCU microprocessor connected to the output of the detection circuit; the detection circuit includes a current loop, a rectifier bridge, a resistor RL1, a transient suppression diode TVS, an electrolytic capacitor C1 and a comparator; the output of the current loop is connected to the input end of the rectifier bridge, the output end of the rectifier bridge is connected to the two ends of the resistor RL1, the transient suppression diode TVS and the electrolytic capacitor C1 are both connected in parallel with the resistor RL1, the negative electrode of the electrolytic capacitor C1 is grounded, the positive electrode of the electrolytic capacitor C1 is also connected to the non-inverting input end of the comparator, and the inverting input end of the comparator is connected to V REF The output end of the comparator serves as the output port GPIO interface of the detection circuit.

[0023] The rectifier bridge includes a diode D1, a diode D2, a diode D3 and a diode D4, the cathode of the diode D1 is connected to the anode of the diode D2, the cathode of the diode D2 is connected to the cathode of the diode D4, the anode of the diode D4 is connected to the cathode of the diode D3, the anode of the diode D3 is connected to the anode of the diode D1, one end of the output of the current loop is connected to the cathode of the diode D1 and the anode of the diode D2, and the other end of the output of the current loop is connected to the cathode of the diode D3 and the anode of the diode D4; one end of the resistor RL1 is connected to the cathode of the diode D2 and the cathode of the diode D4, and the negative electrode of the resistor RL1 is connected to the anode of the diode D1 and the anode of the diode D3;

[0024] Figure 2 The detection circuit is composed of a current loop, four low voltage dropout diodes, a sampling resistor RL1, a transient suppression diode TVS, an electrolytic capacitor C1 and a comparator. The comparator compares the voltage at the A terminal of the detection circuit with V REF The voltage size, where the live wire current forms an induced current on the current loop, which acts on the sampling resistor RL1 after passing through the rectifier bridge to form a voltage signal. The transient suppression diode TVS mainly suppresses the interference and circuit damage caused by the current mutation. The electrolytic capacitor C1 mainly stores energy for filtering. Under normal current, the voltage waveform at point A is a straight line or regular jumps; under arc current, due to the zero-break phenomenon of the arc, the induced current is small or almost non-existent; the electric energy that can be formed on the sampling resistor RL1 after passing through the rectifier bridge is low, and the electrolytic capacitor C1 does not store enough energy, forming irregular voltage jumps. The comparator compares its voltage change with the preset reference V REF Size, using this phenomenon to design detection circuits, comparators mainly simplify the output signal to the sampling or processing equipment for counting or measurement.

[0025] The working principle of the detection circuit is as follows: the induced current formed by the current loop of the detection circuit on the live wire acts on the sampling resistor RL1 after passing through the rectifier bridge to form a voltage signal. The transient suppression diode TVS mainly suppresses the interference and circuit damage caused by the current mutation. The electrolytic capacitor C1 mainly stores energy and filters. The positive terminal of the electrolytic capacitor C1 is point A. Under normal current, the voltage waveform at point A is a straight line or regularly jumps. Under arc current, due to the zero-break phenomenon of the arc, the induced current is small or almost non-existent. After passing through the rectifier bridge, the electric energy that can be formed on the sampling resistor RL1 is low, and the electrolytic capacitor C1 does not store enough energy, forming irregular voltage jumps. The comparator compares its voltage change with the preset reference V REF Size, voltage jump to V REF When it is used as a comparison benchmark, the comparator outputs a signal with an inverted original level to the MCU microprocessor for timing and counting.

[0026] like Figure 3As shown, a detection method using the simplified arc detection circuit is provided, and the detection method comprises the following steps:

[0027] S1: The output port GPIO of the detection circuit is connected to the GPIO port of the MCU microprocessor. When the GPIO level has a rising or falling edge, the MCU triggers the timing t1, and the timing ends when the GPIO level has a falling or rising edge;

[0028] S2: When the GPIO level rises or falls again, the MCU triggers timing t2, and the timing ends when the GPIO level falls or rises;

[0029] S3: Compare the absolute value of the two timing differences to see if it is greater than the set value a.

[0030] Where a = 1 / 4f × (1-C1 × 2f × V REF / I), f is the frequency of the induced current in Hz, C1 is the capacitance of the electrolytic capacitor in the circuit in F, I is the driving current of the comparator input terminal selected by the circuit, generally a fixed value in A, V REF The circuit reference unit is V);

[0031] S4: If the absolute value of the difference is greater than or equal to a, the value of k is incremented by 1, and the initial value of k is 0;

[0032] S5: When the number of times a occurs continuously for three times or more, that is, k ≥ 3, it is judged that the state is arcing, otherwise it is judged to be normal and S2 is executed;

[0033] S6: If the absolute value of the difference is not greater than or equal to a, the value of k is set to 0, and it is judged to be in a normal state, and S2 is executed.

[0034] The output end of the MCU microprocessor is connected to a status indication circuit for displaying the status after determination. The status indication circuit includes an indicator light, a buzzer or a display screen.

[0035] The detection circuit in the present invention detects arc faults through current sensing, rectification and comparison of voltage jumps, and outputs simple high and low level signals for judging the arc state. Compared with other solutions that require complex algorithm logic, it saves a lot of components. The MCU microprocessor only needs an 8-bit or lower performance single-chip microcomputer to realize the fault arc judgment state. After the judgment, the state output can be an indicator light / buzzer or a status indication device such as a display screen. Accurate detection can be achieved through a low-performance MCU, which effectively improves the detection efficiency and accuracy of the fault arc and is suitable for electrical fire prevention and equipment safety assurance.

[0036] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several changes and improvements can be made without departing from the overall concept of the present invention, which should also be regarded as the scope of protection of the present invention.

Claims

1. A simplified arc detection circuit, characterized in that: The invention comprises a detection circuit and an MCU microprocessor connected to the output of the detection circuit; the detection circuit comprises a current loop, a rectifier bridge, a resistor RL1, a transient suppression diode TVS, an electrolytic capacitor C1 and a comparator; the output of the current loop is connected to the input end of the rectifier bridge, the output end of the rectifier bridge is connected to the two ends of the resistor RL1, the transient suppression diode TVS and the electrolytic capacitor C1 are both connected in parallel with the resistor RL1, the negative electrode of the electrolytic capacitor C1 is grounded, the positive electrode of the electrolytic capacitor C1 is also connected to the non-inverting input end of the comparator, and the inverting input end of the comparator is connected to V REF The output end of the comparator serves as the output port GPIO interface of the detection circuit.

2. The simplified arc detection circuit according to claim 1, characterized in that: The rectifier bridge includes a diode D1, a diode D2, a diode D3 and a diode D4, the cathode of the diode D1 is connected to the anode of the diode D2, the cathode of the diode D2 is connected to the cathode of the diode D4, the anode of the diode D4 is connected to the cathode of the diode D3, the anode of the diode D3 is connected to the anode of the diode D1, one end of the output of the current loop is connected to the cathode of the diode D1 and the anode of the diode D2, and the other end of the output of the current loop is connected to the cathode of the diode D3 and the anode of the diode D4; one end of the resistor RL1 is connected to the cathode of the diode D2 and the cathode of the diode D4, and the other end of the resistor RL1 is connected to the anode of the diode D1 and the anode of the diode D3.

3. A detection method using the simplified arc detection circuit according to any one of claims 1 or 2, characterized in that: The detection method comprises the following steps: S1: The output port GPIO of the detection circuit is connected to the GPIO port of the MCU microprocessor. When the GPIO level has a rising or falling edge, the MCU triggers the timing t1, and the timing ends when the rising edge is restored; S2: When the GPIO level rises or falls again, the MCU triggers timing t2, and the timing ends when the GPIO level falls or rises; S3: Compare the absolute value of the two timing differences to see if it is greater than the set value a, where a = 1 / 4f × (1-C1 × 2 × V REF / I), f is the frequency of the induced current in Hz, C1 is the capacitance of the electrolytic capacitor in the circuit in F, I is the driving current of the comparator input terminal selected by the circuit, generally a fixed value in A, V REF The circuit reference unit is V; S4: If the absolute value of the difference is greater than or equal to a, the value of k is incremented by 1, and the initial value of k is 0; S5: When the number of times a occurs continuously for three times or more, that is, k ≥ 3, it is judged that the state is arcing, otherwise it is judged to be a normal state and S2 is executed; S6: If the absolute value of the difference is not greater than or equal to a, the value of k is set to 0, and it is judged to be in a normal state, and S2 is executed.

4. The detection method according to claim 3, characterized in that: The output end of the MCU microprocessor is connected to a status indication circuit for displaying the status after determination. The status indication circuit includes an indicator light, a buzzer or a display screen.

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