A fault arc sensor and detection method based on voltage measurement

Abstract

The present invention discloses a fault arc sensor and a detection method based on voltage measurement, characterized in that the fault arc sensor comprises a voltage detection unit, an analog-to-digital conversion unit, a processor unit and a communication unit, the input end of the voltage detection unit is installed between the detection section and the load on the detection line, the input end of the analog-to-digital conversion unit is electrically connected to the output end of the voltage detection unit, and its output end is electrically connected to the input end of the processor unit. Compared with the prior art, the advantages of the present invention are that the voltage detection unit collects the voltage signal on the detection line and converts it into a digital signal through the analog-to-digital conversion unit, and the processor unit analyzes and compares the number of real inflection points in the positive half cycle of the sine of the sampling point after receiving the digital signal, so as to judge whether there is a fault arc on the detection line, the measurement is accurate and fast, and has the characteristics of high fault arc recognition rate and low false alarm rate.

Description

Technical Field

[0001] The present invention relates to the technical field of arc detection, and in particular to a fault arc sensor and a detection method based on voltage measurement. Background Art

[0002] In daily life, due to the long-term overload operation of electrical lines and equipment in the power distribution system, poor electrical connections, etc., the insulation layer of the cable ages, greatly reducing the insulation effect of the cable, and with the formation of carbonization paths, it is very easy to cause fault arcs. Once this fault arc causes combustion, it is difficult to extinguish, eventually causing serious fires and endangering people's lives and property. Therefore, it is particularly important to detect the arc in time when it occurs. Summary of the invention

[0003] The present invention provides a fault arc sensor and a detection method based on voltage measurement, which solves the technical problem of being able to detect the arc in the circuit in time.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A fault arc sensor based on voltage measurement comprises a voltage detection unit, an analog-to-digital conversion unit, a processor unit and a communication unit. The input end of the voltage detection unit is installed between the detection section and the load on the detection line, the input end of the analog-to-digital conversion unit is electrically connected to the output end of the voltage detection unit, and its output end is electrically connected to the input end of the processor unit.

[0006] The voltage detection unit is a voltage sensor, which is manufactured on a flexible PCB board and has a ring structure. The detection circuit passes through the center of the voltage sensor, and the upper plate of the voltage sensor is coupled to the voltage of the detection circuit, and the lower plate is grounded. The voltage detection on the detection circuit is achieved through the voltage detection unit.

[0007] The analog-to-digital conversion unit includes a conditioning circuit and a digital-to-analog converter. The input end of the conditioning circuit is electrically connected to the output end of the voltage detection unit, the input end of the digital-to-analog converter is electrically connected to the output end of the conditioning circuit, and its output end is electrically connected to the input end of the processor unit. Through the cooperation of the conditioning circuit and the digital-to-analog converter, the voltage signal is converted into a digital signal that can be processed by the processor unit.

[0008] The input end of the communication unit is electrically connected to the output end of the processor unit, and the output end thereof is electrically connected to the alarm system. The communication unit sends the fault arc signal issued by the processor unit to the alarm system to issue an alarm message.

[0009] A fault arc detection method based on voltage measurement comprises the following steps:

[0010] a. Obtaining a voltage signal from a detection circuit through a voltage detection unit;

[0011] b. Processing the voltage signal and converting it into a digital signal through an analog-to-digital conversion unit;

[0012] c. Continuously sampling the digital signal through a processor unit to obtain continuous sampling points with sinusoidal distribution;

[0013] d. Determine whether the sampling point is in the positive half cycle of the sine wave through the processor unit. If the sampling point is in the positive half cycle of the sine wave, execute steps e to f. When the sampling point is in the positive half cycle of the sine wave, its amplitude is larger and easier to determine and process.

[0014] e. determining the number h of real inflection points in the positive half cycle of the sine wave by the processor unit;

[0015] f. Compare h with threshold value 3 through the processor unit. If h is greater than threshold value 3, issue an arc fault signal.

[0016] In step c, the time sequence number of the sampling point is n, the amplitude of the continuous sampling points in the sine is x(n) (n=0, 1, 2...N-1), and the amplitude of the sampling points within the range of M in the sine is mean filtered to obtain several mean values ​​y(n), where This reduces the interference value and makes the judgment of whether the sampling point is within the positive half cycle of the sine wave more accurate.

[0017] In the step d, a dynamic threshold a is set in the processor unit, and the mean y(n) is compared with the dynamic threshold a by the processor unit. If the mean y(n) is greater than the dynamic threshold a for 10 consecutive times, it is determined that the sampling point is within the positive half cycle of the sine wave.

[0018] In the step d, a threshold value 5 is set in the processor unit, and the time serial numbers i and j of adjacent inflection points are selected by the processor unit from the continuous sampling points, and the serial number difference c of adjacent inflection points is calculated according to the formula c=ji, and then the serial number difference c is compared with the threshold value 5. If the serial number difference c is greater than or equal to the threshold value 5, the sampling point j is counted, thereby obtaining the preliminary number of inflection points e.

[0019] In the step d, a threshold value 3 is set in the processor unit, and the processor unit compares the preliminary number of inflection points e with the threshold value 3. If the preliminary number of inflection points e is greater than the threshold value 3, the threshold value a is increased; if the preliminary number of inflection points e is less than the threshold value 3, the threshold value a is reduced; if the preliminary number of inflection points e is equal to the threshold value 3, the threshold value a is kept unchanged, thereby continuously adjusting the threshold value a to make the judgment of whether the sampling point is in the positive half cycle of the sine more accurate.

[0020] In the step e, a threshold of 3.7% is set in the processor unit, and the maximum amplitude MAX of the continuous sampling points and the amplitudes g(n) and g(n-1) of the adjacent inflection points are selected by the processor unit in the positive half cycle of the sine wave, and the maximum amplitude MAX of the continuous sampling points and the amplitudes g(n) and g(n-1) of the adjacent inflection points are selected according to the formula The ratio f is calculated and then compared with the threshold value 3.7%. If the ratio f is greater than or equal to the threshold value 3.7%, the sampling point n is counted, thereby obtaining the number of true inflection points h.

[0021] After adopting the above structure, the advantages of the present invention compared with the prior art are:

[0022] The voltage detection unit collects the voltage signal on the detection line and converts it into a digital signal through the analog-to-digital conversion unit. After receiving the digital signal, the processor unit analyzes and compares the number of real inflection points within the sinusoidal positive half cycle of the sampling point, thereby determining whether there is a fault arc on the detection line. The measurement is accurate and fast, and has the characteristics of high fault arc recognition rate and low false alarm rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a circuit diagram of a fault arc sensor based on voltage measurement in the present invention.

[0024] Figure 2 It is a schematic diagram of the installation of a fault arc sensor based on voltage measurement in the present invention.

[0025] As shown in the figure: 1. Voltage detection unit, 2. Processor unit, 3. Conditioning circuit, 4. Digital-to-analog converter, 5. Communication unit. DETAILED DESCRIPTION

[0026] The following description is only a preferred embodiment of the present invention, and does not limit the protection scope of the present invention. The present invention is further described below in conjunction with the drawings and embodiments.

[0027] For example, see Figure 1 to Figure 2 As shown:

[0028] The arc fault detection method based on voltage measurement utilizes an arc fault sensor based on voltage measurement to realize arc detection on a detection line, wherein the arc fault sensor includes a voltage detection unit 1, an analog-to-digital conversion unit, a processor unit 2 and a communication unit 5.

[0029] The arc fault detection method comprises the following steps:

[0030] a. A voltage signal is obtained from the detection circuit through a voltage detection unit 1. The input end of the voltage detection unit 1 is installed between the detection section and the load on the detection circuit. The voltage detection unit 1 is a voltage sensor. The voltage sensor is manufactured on a flexible PCB board and has a ring structure. The detection circuit passes through the center of the voltage sensor, and the upper plate of the voltage sensor is coupled with the voltage of the detection circuit, and the lower plate is grounded.

[0031] b. Process the voltage signal and convert it into a digital signal through an analog-to-digital conversion unit. The analog-to-digital conversion unit includes a conditioning circuit 3 and a digital-to-analog converter 4. The input end of the conditioning circuit 3 is electrically connected to the output end of the voltage detection unit 1, the input end of the digital-to-analog converter 4 is electrically connected to the output end of the conditioning circuit 3, and its output end is electrically connected to the input end of the processor unit 2.

[0032] c. Continuously sample the digital signal through the processor unit 2 to obtain continuous sampling points with sinusoidal distribution. The time sequence number of the sampling point is n. The amplitude of the continuous sampling point in the sine is x(n) (n=0,1,2...N-1), N is an arbitrary integer, and the amplitude of the sampling point in the sine within the range of M is averaged and filtered to obtain several mean values ​​y(n), where M is the window width, which is usually selected as an odd number. This mean filtering method can reduce a large number of interference signals and ensure the accuracy of the sampling points.

[0033] d. Determine whether the sampling point is in the positive half cycle of the sine wave through the processor unit 2, set a dynamic threshold a in the processor unit 2, and the dynamic threshold a is 2.4% of the maximum value under the current analog-to-digital conversion accuracy. Compare the mean y(n) with the dynamic threshold a through the processor unit 2. If the mean y(n) is greater than the dynamic threshold a for 10 consecutive times, it is determined that the sampling point is in the positive half cycle of the sine wave. If the mean y(n) is less than or equal to the dynamic threshold a for 10 consecutive times, it is determined that the sampling point leaves the positive half cycle of the sine wave.

[0034] Among them, the dynamic threshold a needs to be corrected after being set to ensure the judgment accuracy of the processor unit 2. The threshold 5 is set in the processor unit 2. The processor unit 2 selects the time serial numbers i and j of adjacent inflection points in continuous sampling points, and calculates the serial number difference c of adjacent inflection points according to the formula c=ji. Then, the serial number difference c is compared with the threshold 5. If the serial number difference c is greater than or equal to the threshold 5, the sampling point j is counted, thereby obtaining the preliminary number of inflection points e. This method can avoid the sampling points from being counted in small-amplitude ripple changes under normal circumstances.

[0035] Threshold 3 is set in processor unit 2, and the processor unit 2 compares the preliminary inflection point number e with threshold 3. If the preliminary inflection point number e is greater than threshold 3, threshold a is increased by 1%. If the preliminary inflection point number e is less than threshold 3, threshold a is reduced by 1%. If the preliminary inflection point number e is equal to threshold 3, threshold a is kept unchanged, and the maximum value of threshold a is 10% and the minimum value is 1%.

[0036] If the sampling point is within the positive half cycle of the sine wave, then steps e to f are executed.

[0037] e. Determine the number of real inflection points h in the positive half cycle of the sine wave through the processor unit 2, set a threshold of 3.7% in the processor unit 2, select the maximum amplitude MAX of the continuous sampling points and the amplitudes g(n) and g(n-1) of the adjacent inflection points in the positive half cycle of the sine wave through the processor unit 2, and calculate the value of the maximum amplitude MAX in the continuous sampling points and the amplitudes g(n) and g(n-1) of the adjacent inflection points according to the formula The ratio f is calculated and then compared with the threshold value 3.7%. If the ratio f is less than the threshold value 3.7%, the sampling point n is not counted. If the ratio f is greater than or equal to the threshold value 3.7%, the sampling point n is counted, thereby obtaining the number of true inflection points h.

[0038] f. Compare h with threshold 3 through processor unit 2. If h is less than or equal to threshold 3, it means there is no fault arc on the detection line, and processor unit 2 does not act. If h is greater than threshold 3, processor unit 2 sends out a fault arc signal.

[0039] Among them, under normal circumstances, the ripple on the voltage signal is small and the waveform is relatively smooth. In the positive half cycle of the voltage signal sine, the number of real inflection points will not exceed 3 times. When a fault arc occurs on the detection line, high-frequency voltage noise will be generated in the detection line. At this time, the overall ripple amplitude of the voltage signal will be larger than the ripple amplitude when no fault arc occurs, and the change is faster. In the positive half cycle of the voltage signal sine, the number of real inflection points will be greater than 3. Therefore, by judging the number of real inflection points in the positive half cycle of the voltage signal sine, it can be determined whether there is a fault arc on the detection line.

[0040] The input end of the communication unit 5 is electrically connected to the output end of the processor unit 2, and its output end is electrically connected to the alarm system. The fault arc signal emitted by the processor unit 2 is sent to the alarm system through the communication unit 5, and the alarm system immediately sends an alarm message to prompt the staff.

[0041] The present invention and its embodiments are described above, and such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A fault arc detection method based on voltage measurement, characterized in that: The steps include: a. obtaining a voltage signal from a detection circuit through a voltage detection unit (1); b. Processing the voltage signal and converting it into a digital signal through an analog-to-digital conversion unit; c. continuously sampling the digital signal through the processor unit (2) to obtain continuous sampling points with sinusoidal distribution; d. judging, by the processor unit (2), whether the sampling point is within the positive half cycle of the sine wave; if the sampling point is within the positive half cycle of the sine wave, executing steps e to f; e. determining, by the processor unit (2), the number h of real inflection points in the positive half cycle of the sine wave; f. Comparing h with a threshold value 3 by the processor unit (2), and if h is greater than the threshold value 3, issuing a fault arc signal; in the step c, the time sequence number of the sampling point is n, the amplitude of the continuous sampling points in the sine is x(n) (n=0, 1, 2...N-1), and the amplitude of the sampling points within the range of M in the sine is mean filtered to obtain a plurality of mean values ​​y(n), wherein M is the window width, which is an odd number.

2. A fault arc detection method based on voltage measurement according to claim 1, characterized in that: In the step d, a dynamic threshold a is set in the processor unit (2), and the mean value y(n) is compared with the dynamic threshold a by the processor unit (2). If the mean value y(n) is greater than the dynamic threshold a for 10 consecutive times, it is determined that the sampling point is within the positive half cycle of the sine wave.

3. A fault arc detection method based on voltage measurement according to claim 2, characterized in that: In the step d, a threshold value 5 is set in the processor unit (2), and the time serial numbers i and j of adjacent inflection points are selected from the continuous sampling points by the processor unit (2), and the serial number difference c of the adjacent inflection points is calculated according to the formula c=ji, and then the serial number difference c is compared with the threshold value 5. If the serial number difference c is greater than or equal to the threshold value 5, the sampling point j is counted, thereby obtaining a preliminary number of inflection points e.

4. A fault arc detection method based on voltage measurement according to claim 3, characterized in that: In the step d, a threshold value 3 is set in the processor unit (2), and the processor unit (2) compares the number of preliminary inflection points e with the threshold value 3. If the number of preliminary inflection points e is greater than the threshold value 3, the threshold value a is increased; if the number of preliminary inflection points e is less than the threshold value 3, the threshold value a is decreased; if the number of preliminary inflection points e is equal to the threshold value 3, the threshold value a is kept unchanged.

5. A fault arc detection method based on voltage measurement according to claim 4, characterized in that: In the step e, a threshold value of 3.7% is set in the processor unit (2), and the maximum amplitude MAX of the continuous sampling points and the amplitudes g(n) and g(n-1) of the adjacent inflection points are selected by the processor unit (2) within the positive half cycle of the sine wave, and the maximum amplitude MAX of the continuous sampling points and the amplitudes g(n) and g(n-1) of the adjacent inflection points are selected according to the formula The ratio f is calculated and then compared with the threshold value 3.7%. If the ratio f is greater than or equal to the threshold value 3.7%, the sampling point n is counted, thereby obtaining the number of true inflection points h.

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