Electric arc detection circuit and detection method

Abstract

The invention discloses an arc detection circuit and method, the circuit comprises a low-frequency sampling circuit and a high-frequency sampling circuit, and the input end of the circuit is connected with a low-frequency current loop and a high-frequency current loop sleeving a detected cable; the input end of the ADC acquisition circuit is respectively connected with the output ends of the low-frequency sampling circuit and the high-frequency sampling circuit, and analog signals output by the low-frequency sampling circuit and the high-frequency sampling circuit are converted into digital signals; and the MCU is connected with the output end of the ADC acquisition circuit. Through the synergistic effect of the low-frequency acquisition circuit and the high-frequency acquisition circuit, the accuracy and reliability of arc detection are improved, the dynamic adjustment capability of the system is effectively supported, and timely early warning and processing of potential faults are ensured. Through acquisition of a small amount of data and use of a simple fault arc feature extraction method, the operand is effectively reduced, and the requirement for hardware cost is also reduced; the multi-logic cycle judgment enables the fault arc and the switch arc characteristics to be effectively distinguished, and the recognition accuracy is improved.

Description

Technical Field

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

[0002] With the continuous development of social economy, the number of fire accidents is also increasing. The main cause of electrical fires is that the insulation layer of the lines inside the house has aged or been damaged due to long-term load operation. Such line conditions are prone to cause series-parallel arc faults between lines or line-to-ground short circuit faults. Compared with the characteristic of increased short-circuit current in short-circuit faults, the current amplitude in the line is small when a low-voltage fault arc occurs and is easily affected by grid noise. Traditional circuit detection devices cannot effectively detect line fault arcs, so the protection fails. The conductive path formed after the insulation material is broken down causes the arc to continue to burn. The local high temperature generated during the burning can easily ignite the surrounding combustibles and cause a fire, which seriously threatens the safety of life and property.

[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 characteristics of the parameters. The calculated parameter value is compared with the judgment threshold. If the parameter value is within the judgment interval, it is determined that an arc has occurred, otherwise no arc has occurred. However, in actual use, the acquisition and calculation of parameters require a certain amount of computing power, which increases the cost of the detection equipment. Therefore, a simple parameter acquisition and feature calculation method is needed to reduce the equipment cost for use. Summary of the invention

[0004] The technical problem to be solved by the present invention is to design a simple parameter acquisition and feature calculation method, and combine it with multiple logical judgments to effectively improve the recognition accuracy and reduce the investment cost of the detection equipment. In order to solve the above problems, an arc detection circuit and detection method are provided.

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

[0006] An arc detection circuit, the circuit comprising a low-frequency sampling circuit and a high-frequency sampling circuit, the input end of which is connected to a low-frequency current loop and a high-frequency current loop on a cable under test;

[0007] An ADC acquisition circuit, whose input end is connected to the output end of the low-frequency sampling circuit and the high-frequency sampling circuit respectively, converts the analog signals output by the low-frequency sampling circuit and the high-frequency sampling circuit into digital signals;

[0008] The MCU is connected to the output end of the ADC acquisition circuit.

[0009] The low-frequency sampling circuit includes a rectifier bridge composed of four diodes and a sampling resistor RL1. 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, and the anode of the diode D3 is connected to the anode of the diode D1. One end of the output of the low-frequency 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 low-frequency current loop is connected to the cathode of the diode D3 and the anode of the diode D4. One end of the sampling resistor RL1 is connected to the cathode of the diode D2 and the cathode of the diode D4, and this end is used as the ADC1 acquisition end; the other end of the sampling resistor RL1 is connected to the anode of the diode D1 and the anode of the diode D3, and this end is also connected to the reference voltage V REF connect.

[0010] The high-frequency sampling circuit includes a resistor RL2, and both ends of the output end of the high-frequency current loop are respectively connected to both ends of the resistor RL2, one end of the resistor RL2 is also connected to one end of the resistor R1, and the other end of the resistor RL2 is also connected to one end of the resistor R2, the other end of the resistor R1 is respectively connected to one end of the resistor R3 and the inverting input end of the operational amplifier, the other end of the resistor R3 is respectively connected to the output end of the operational amplifier and one end of the resistor R4, the other end of the resistor R2 is connected to the non-inverting input end of the operational amplifier, the other end of the resistor R4 is connected to one end of the capacitor C1 to form a specific frequency band filtering circuit, and this end serves as the ADC2 acquisition end, and the other end of the capacitor C1 is grounded.

[0011] The low frequency refers to a frequency of 0 to 10 KHz, and the high frequency refers to a frequency of 10 to 50 KHz.

[0012] A detection method using the arc detection circuit, the method comprising the following steps:

[0013] S1: The waveform characteristics are collected through the low-frequency acquisition circuit and the high-frequency acquisition circuit. After passing through the ADC, the analog signal is converted into a digital signal and handed over to the MCU for data processing;

[0014] S2: MCU processes the data collected by ADC, which includes ADC1 data of low-frequency sampling circuit and ADC2 data of high-frequency sampling circuit;

[0015] S3: Process the data collected by the low-frequency sampling circuit and convert the ADC1 data into voltage data. REF As a reference, when the converted voltage data is at V REF The timing is triggered when the data is within the range of ±a. If the subsequent data is not within this range, the timing ends. a is the set threshold difference. The specific value of this value can be set when using it, which is determined by the interference degree of the specific use environment. The greater the interference degree, the greater the value of a.

[0016] S4: Record three times in data V REF The timing data of interval t0, t1, t2 are sorted in ms;

[0017] S5: Determine whether the population variance of t0, t1, and t2 is less than or equal to 1. If it is less than or equal to 1, it is determined to be in a normal state, otherwise, execute step S6;

[0018] S6: Assign t2 to t0, clear the values ​​of t1 and t2, collect the next t1 and t2, and execute steps S4-S6;

[0019] S7: If the overall variance of t0, t1, and t2 is greater than 1, the high-frequency sampling circuit data is normalized, and the ADC2 data array of the three corresponding time periods of t0, t1, and t2 is normalized, and the i-th data point of the ADC2 data in a single time period is defined as S i , the normalized formula is K i =Sign(S i -S A ), where S A V is the reference stable point for sampling REF The corresponding digital value, K i For data S i The normalized value;

[0020] S8: After the data is normalized in step S7, calculate the K of t0, t1, and t2 three times i The number of differences in the number of neighbors is given by X n =|K2—K1|+…+|K i —K i-1 |; As above, three trigger timings t0, X0, t1, and X2 of t2 are calculated;

[0021] S9: Determine whether the overall variance of the three X0, X1, and X2 is less than or equal to 1. If it is less than or equal to 1, it is determined to be in a normal state; if it is not less than or equal to 1, it is determined to be in an arc state.

[0022] The MCU is connected to a screen or a human-computer interaction device and is used to output a display status, which includes a normal state and an arc state.

[0023] Beneficial effects of the present invention: Through the synergy of low-frequency and high-frequency acquisition circuits, the present invention not only improves the accuracy and reliability of arc detection, but also effectively supports the dynamic adjustment capability of the system, ensuring timely warning and processing of potential faults. The acquisition of a small amount of data and the use of a simple fault arc feature extraction method effectively reduce the amount of calculation, and the demand for hardware costs is also reduced; it is suitable for independent device operation of edge devices. Multi-logic loop judgment enables the fault arc and switch arc features to be effectively distinguished, increasing the accuracy of recognition. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a circuit diagram of a low-frequency acquisition circuit and a high-frequency acquisition circuit in the present invention.

[0025] Figure 2 It is a principle block diagram of the arc detection circuit of the present invention.

[0026] Figure 3 It is a flow chart of the detection method of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0028] 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.

[0029] An arc detection circuit, the circuit comprising a low-frequency sampling circuit and a high-frequency sampling circuit, the input end of which is connected to a low-frequency current loop and a high-frequency current loop on a cable under test;

[0030] An ADC acquisition circuit, whose input end is connected to the output end of the low-frequency sampling circuit and the high-frequency sampling circuit respectively, converts the analog signals output by the low-frequency sampling circuit and the high-frequency sampling circuit into digital signals;

[0031] The MCU is connected to the output end of the ADC acquisition circuit.

[0032] like Figure 1As shown, the low-frequency sampling circuit includes a rectifier bridge composed of four diodes and a sampling resistor RL1. 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, and the anode of the diode D3 is connected to the anode of the diode D1. One end of the output of the low-frequency 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 low-frequency current loop is connected to the cathode of the diode D3 and the anode of the diode D4. One end of the sampling resistor RL1 is connected to the cathode of the diode D2 and the cathode of the diode D4, and this end is used as the ADC1 acquisition end; the other end of the sampling resistor RL1 is connected to the anode of the diode D1 and the anode of the diode D3, and this end is also connected to the reference voltage V REF connect.

[0033] The low-frequency sampling circuit converts the alternating current signal through a rectifier bridge composed of four diodes and then folds the alternating current signal to V REF Then the ADC acquisition circuit samples it;

[0034] The high-frequency sampling circuit includes a resistor RL2, two ends of the output end of the high-frequency current loop are respectively connected to the two ends of the resistor RL2, one end of the resistor RL2 is also connected to one end of the resistor R1, and the other end of the resistor RL2 is also connected to one end of the resistor R2, the other end of the resistor R1 is respectively connected to one end of the resistor R3 and the inverting input end of the operational amplifier, the other end of the resistor R3 is respectively connected to the output end of the operational amplifier and one end of the resistor R4, the other end of the resistor R2 is connected to the non-inverting input end of the operational amplifier, the other end of the resistor R4 is connected to one end of the capacitor C1 to form a specific frequency band filtering circuit, and this end serves as the ADC2 acquisition end, and the other end of the capacitor C1 is grounded.

[0035] The high-frequency electrical sampling circuit converts the alternating current signal into a voltage signal after passing through the resistor RL2, and then amplifies it through the operation input device to become a voltage signal at V REF The alternating signal with the reference zero point is sampled by the ADC acquisition circuit; the high-frequency current loop and the low-frequency current loop are both put on the live wire to form a detection circuit.

[0036] The low frequency refers to a frequency of 0 to 10 KHz, and the high frequency refers to a frequency of 10 to 50 KHz.

[0037] A detection method using the arc detection circuit, the method comprising the following steps:

[0038] S1: The waveform characteristics are collected through the low-frequency acquisition circuit and the high-frequency acquisition circuit. After passing through the ADC, the analog signal is converted into a digital signal and handed over to the MCU for data processing;

[0039] S2: MCU processes the data collected by ADC, which includes ADC1 data of low-frequency sampling circuit and ADC2 data of high-frequency sampling circuit;

[0040] S3: Process the data collected by the low-frequency sampling circuit and convert the ADC1 data into voltage data. REF As a reference, when the converted voltage data is at V REF When the interval is ±a, the timing is triggered. If the subsequent data is not in this interval, the timing ends. a is the set threshold difference. The specific value of this value can be set when using it, which is determined by the interference degree of the specific use environment. The greater the interference degree, the greater the value of a.

[0041] S4: Record three times in data V REF The timing data of interval t0, t1, t2 are sorted in ms;

[0042] S5: Determine whether the population variance of t0, t1, and t2 is less than or equal to 1. If it is less than or equal to 1, it is determined to be in a normal state, otherwise, execute step S6;

[0043] S6: Assign t2 to t0, clear the values ​​of t1 and t2, collect the next t1 and t2, and execute steps S4-S6;

[0044] S7: If the overall variance of t0, t1, and t2 is greater than 1, the high-frequency sampling circuit data is normalized, and the ADC2 data array of the three corresponding time periods of t0, t1, and t2 is normalized, and the i-th data point of the ADC2 data in a single time period is defined as S i , the normalized formula is K i =Sign(S i -S A ), where S A V is the reference stable point for sampling REF The corresponding digital value, K i For data S i The normalized value;

[0045] S8: After the data is normalized in step S7, calculate the K of t0, t1, and t2 three times i The number of differences in the number of neighbors is given by X n =|K2—K1|+…+|K i —K i-1 |; As above, three trigger timings t0, X0, t1, and X2 of t2 are calculated;

[0046] S9: Determine whether the overall variance of the three X0, X1, and X2 is less than or equal to 1. If it is less than or equal to 1, it is determined to be in a normal state; if it is not less than or equal to 1, it is determined to be in an arc state.

[0047] The MCU is connected to a screen or a human-computer interaction device and is used to output a display status, which includes a normal state and an arc state.

[0048] In this detection method, the low-frequency acquisition circuit is mainly responsible for capturing the slow-changing trends and background noise in the signal. These data provide basic information for subsequent numerical simplification judgments. When the collected data falls into the set reference range, the circuit can trigger timing to monitor potential arc events. On the other hand, the high-frequency acquisition circuit focuses on the rapidly changing signal characteristics. When the data processing results of the low-frequency acquisition circuit indicate that there may be an arc in the circuit, the high-frequency acquisition circuit will capture the transient waveform generated during the arc discharge process in real time. After normalization, this part of the data can reveal the slight fluctuations of the signal, which can further help the system make more accurate judgments and responses.

[0049] The present invention effectively reduces the amount of calculation by acquiring a small amount of data and using a simple fault arc feature extraction method, and the demand for hardware cost is also reduced; it is suitable for independent device operation of edge devices. Multi-logic loop judgment enables the fault arc and switch arc features to be effectively distinguished, increasing the accuracy of recognition.

[0050] 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. An arc detection circuit, characterized in that: The circuit comprises a low-frequency sampling circuit and a high-frequency sampling circuit, and its input end is connected to the low-frequency current loop and the high-frequency current loop on the cable under test; An ADC acquisition circuit, whose input end is connected to the output end of the low-frequency sampling circuit and the high-frequency sampling circuit respectively, converts the analog signals output by the low-frequency sampling circuit and the high-frequency sampling circuit into digital signals; The MCU is connected to the output end of the ADC acquisition circuit.

2. The arc detection circuit according to claim 1, characterized in that: The low-frequency sampling circuit includes a rectifier bridge composed of four diodes and a sampling resistor RL1. 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, and the anode of the diode D3 is connected to the anode of the diode D1. One end of the output of the low-frequency 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 low-frequency current loop is connected to the cathode of the diode D3 and the anode of the diode D4. One end of the sampling resistor RL1 is connected to the cathode of the diode D2 and the cathode of the diode D4, and this end is used as the ADC1 acquisition end; the other end of the sampling resistor RL1 is connected to the anode of the diode D1 and the anode of the diode D3, and this end is also connected to the reference voltage V REF connect.

3. The arc detection circuit according to claim 1, characterized in that: The high-frequency sampling circuit includes a resistor RL2, and both ends of the output end of the high-frequency current loop are respectively connected to both ends of the resistor RL2, one end of the resistor RL2 is also connected to one end of the resistor R1, and the other end of the resistor RL2 is also connected to one end of the resistor R2, the other end of the resistor R1 is respectively connected to one end of the resistor R3 and the inverting input end of the operational amplifier, the other end of the resistor R3 is respectively connected to the output end of the operational amplifier and one end of the resistor R4, the other end of the resistor R2 is connected to the non-inverting input end of the operational amplifier, the other end of the resistor R4 is connected to one end of the capacitor C1 to form a specific frequency band filtering circuit, and this end serves as the ADC2 acquisition end, and the other end of the capacitor C1 is grounded.

4. The arc detection circuit according to claim 1, characterized in that: The low frequency refers to a frequency of 0 to 10 KHz, and the high frequency refers to a frequency of 10 to 50 KHz.

5. A detection method using the arc detection circuit according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1: The waveform characteristics are collected through the low-frequency acquisition circuit and the high-frequency acquisition circuit. After passing through the ADC, the analog signal is converted into a digital signal and handed over to the MCU for data processing; S2: MCU processes the data collected by ADC, which includes ADC1 data of low-frequency sampling circuit and ADC2 data of high-frequency sampling circuit; S3: Process the data collected by the low-frequency sampling circuit and convert the ADC1 data into voltage data. REF As a reference, when the converted voltage data is at V REF The timing is triggered when the data is within the range of ±a. If the subsequent data is not within this range, the timing ends. a is the set threshold difference. The specific value of this value can be set when using it, which is determined by the interference degree of the specific use environment. The greater the interference degree, the greater the value of a. S4: Record three times in data V REF The timing data of interval t0, t1, t2 are sorted in ms; S5: Determine whether the population variance of t0, t1, and t2 is less than or equal to 1. If it is less than or equal to 1, it is determined to be in a normal state, otherwise, execute step S6; S6: Assign t2 to t0, clear the values ​​of t1 and t2, collect the next t1 and t2, and execute steps S4-S6; S7: If the overall variance of t0, t1, and t2 is greater than 1, the high-frequency sampling circuit data is normalized, and the ADC2 data array of the three corresponding time periods of t0, t1, and t2 is normalized, and the i-th data point of the ADC2 data in a single time period is defined as S i , the normalized formula is K i =Sign(S i -S A ), where S A V is the reference stable point for sampling REF The corresponding digital value, K i For data S i The normalized value; S8: After the data is normalized in step S7, calculate the K of t0, t1, and t2 three times i The number of differences in the number of neighbors is given by X n =|K2—K1|+…+|K i —K i-1 |; As above, three trigger timings t0, X0, t1, and X2 of t2 are calculated; S9: Determine whether the overall variance of the three X0, X1, and X2 is less than or equal to 1. If it is less than or equal to 1, it is determined to be in a normal state; if it is not less than or equal to 1, it is determined to be in an arc state.

6. The detection method according to claim 5, characterized in that: The MCU is connected to a screen or a human-computer interaction device and is used to output a display status, which includes a normal state and an arc state.

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