Multi-frequency residual current detection device and detection method thereof

Abstract

The invention relates to the technical field of current detection, in particular to a multi-frequency residual current detection device and method, and the device comprises a wire, a first mutual inductor, a second mutual inductor, a power supply, and a sensor module. The sensor module comprises an electromagnetic A-type residual current detection unit, an electronic high-frequency residual current detection unit, an electronic B-type residual current detection unit, an excitation unit and a shell; when the sensor module is not powered, the electromagnetic A-type residual current detection unit analyzes the electromotive force detected by the first mutual inductor; when the sensor module supplies power, the excitation unit adjusts the magnetic flux of the second mutual inductor, the electronic B-type residual current detection unit analyzes the alternating induced electromotive force detected by the second mutual inductor, and the electronic high-frequency residual current detection unit analyzes the electromotive force of the first mutual inductor. A complete detection link from zero-sequence current generation to signal output is constructed according to a high-frequency threshold output signal, and the magnetic field-electromotive force change caused by the zero-sequence current is accurately captured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current detection, in particular to a multi-frequency residual current detection device and a detection method thereof. BACKGROUND

[0002] In modern power systems, the widespread application and diversification of electrical equipment have greatly improved the convenience of production and life, but at the same time, it has also brought increasingly complex residual current problems. As a key hidden danger for the safe operation of power systems, the accurate detection of residual current is crucial for preventing electrical accidents. Traditional residual current detection devices mainly focus on the detection of power frequency (50Hz or 60Hz) residual current. Through electromagnetic induction principle, zero sequence current transformer is used to sense the zero sequence current generated when three-phase current vector and is not zero, and then trigger the protection action. In the early stage of simple power environment dominated by power frequency electrical equipment, such detection devices can effectively play a role, to a certain extent, to ensure the safety of electrical systems.

[0003] However, with the rapid progress of science and technology, new types of electrical equipment are emerging, and the in-depth application of power electronics technology in various fields has significantly changed the operating characteristics of power systems. A large number of nonlinear loads, such as frequency converters, switching power supplies, rectifiers, etc., will generate rich harmonics during operation, resulting in multiple frequency components in the residual current. These harmonics not only have a wide frequency range, from tens of hertz to thousands of hertz or even higher, but also have complex and variable amplitude and phase relationships. For example, the high-frequency harmonic current generated by the frequency converter in the industrial automation production line will cause the residual current to present a complex waveform, and the traditional power frequency residual current detection device is difficult to effectively identify and detect this type of high-frequency harmonic residual current, which is prone to misjudgment or misjudgment, and cannot effectively ensure the safe operation of the electrical system.

[0004] At the same time, the continuous expansion of direct current electrical scenarios also brings new challenges to residual current detection. In the solar photovoltaic power generation system, if insulation damage occurs during the transmission and conversion of direct current generated by photovoltaic panels, direct current residual current will be generated. During the charging process of electric vehicle charging facilities, direct current residual current may also be generated due to equipment failure or line problems. The direct current power supply system of communication base stations also has similar risks; traditional detection devices have little detection capability for direct current residual current, and if direct current residual current cannot be detected and processed in time, it may cause equipment damage, fire and other serious accidents, which seriously threatens the safe and stable operation of the power system and the safety of personnel and property. In view of this, we propose a multi-frequency residual current detection device and a detection method thereof. SUMMARY

[0005] The purpose of this invention is to solve the problem that scientific and technological progress has greatly changed the operating characteristics of the power system, nonlinear loads generate multi-frequency harmonic residual currents, which are difficult to identify with traditional power frequency detection devices and are prone to missed judgments and misjudgments; the expansion of DC power usage scenarios has brought new challenges, and traditional devices are almost unable to detect DC residual currents. If they are not handled in time, they may cause serious accidents such as equipment damage and fire, threatening the safety of the power system and the safety of personnel and property.

[0006] To achieve the above object, the present invention provides a multi-frequency residual current detection device, comprising a conductor, a first mutual inductor, a second mutual inductor, a power supply, and a sensor module; The magnetic cores of the first mutual inductor and the second mutual inductor pass through the conductor; the power supply is used to power the sensor module; the sensor module includes an electromagnetic type A residual current detection unit, an electronic high-frequency residual current detection unit, an electronic type B residual current detection unit, an excitation unit, and a housing; When the sensor module is not powered, the electromagnetic type A residual current detection unit analyzes the electromotive force detected by the first transformer and outputs a reminder signal according to the threshold; when the sensor module is powered, the excitation unit adjusts the magnetic flux of the second transformer, and the electronic type B residual current detection unit analyzes the alternating induced electromotive force detected by the second transformer to obtain the residual current value.

[0007] As a further improvement of the present technical solution, after the current flows through the conductor to generate zero-sequence current, according to Ampere's loop theorem, the zero-sequence current generates a magnetic field around the first transformer. The first transformer is composed of a magnetic core and a coil. The magnetic core gathers the magnetic field generated by the zero-sequence current, causing the magnetic flux passing through the first transformer coil to change. At this time, an induced electromotive force is generated in the coil. The induced electromotive force is the number of turns of the coil of the first transformer multiplied by the proportional coefficient, and then multiplied by the rate of change of the magnetic flux.

[0008] As a further improvement of the present technical solution, the induced electromotive force is output to the electromagnetic type A residual current detection unit, and the electromagnetic type A residual current detection unit sets an electromotive force threshold. If the induced electromotive force is greater than the electromotive force threshold, a signal is output.

[0009] The beneficial effect of the above-mentioned further scheme is to build a complete detection chain from zero-sequence current generation to signal output, use the Ampere loop theorem and the principle of electromagnetic induction to accurately capture the magnetic field-electromotive force changes caused by zero-sequence current, and quickly respond to faults with the help of threshold judgment. When zero-sequence current abnormalities occur in the electrical system (such as insulation damage and other faults), signals can be sent in time to effectively prevent electrical fires, equipment damage and electric shock risks caused by zero-sequence current, improve the safety and reliability of electrical system operation, and ensure the stability of the power environment.

[0010] On the basis of the above technical scheme, the application can also be improved as follows: the induced electromotive force is output to the electronic high-frequency residual current detection unit, the electronic high-frequency residual current detection unit periodically samples the induced electromotive force, converts continuous analog signals into discrete digital signals, and then converts the time-domain signal originally changing with time into a frequency-domain signal with frequency as a variable through a Fourier transform algorithm to extract the signal frequency in the induced electromotive force; and a high-frequency threshold is set, if the signal frequency is greater than or equal to the high-frequency threshold, it is determined that the induced electromotive force is a high-frequency zero sequence current signal; and if the signal frequency is less than the high-frequency threshold, it is determined that the induced electromotive force is an alternating zero sequence current signal and is output to the excitation unit.

[0011] The beneficial effect of the above further scheme is that the frequency characteristics of the induced electromotive force are accurately identified, different frequency residual current signals are classified and processed, the problem of insufficient identification of high-frequency residual current in traditional detection is solved, the signal frequency characteristics are accurately extracted through digital sampling and Fourier transform, the signal type is intelligently determined according to the frequency threshold, the high-frequency signal is responded in time to protect high-frequency sensitive equipment, the alternating signal is reasonably output to ensure the cooperative work of the excitation unit, and the comprehensiveness and accuracy of multi-frequency residual current detection are improved, so that the identification and disposal of various residual current risks are more accurate and efficient in complex power consumption scenarios, and the safety protection capability of the electrical system is enhanced.

[0012] On the basis of the above technical scheme, the application can also be improved as follows: when the Fourier transform algorithm in the electronic high-frequency residual current detection unit converts continuous time-domain signals into frequency-domain signals, the signal amplitude of each frequency after conversion is analyzed respectively.

[0013] As a further improvement of the technical scheme, when the induced electromotive force is a high-frequency zero sequence current signal, the electronic high-frequency residual current detection unit integrates the induced electromotive force within the sampling time, divides the product of the number of turns of the first mutual inductor and the proportional coefficient, and finally adds an integral constant to obtain the current value corresponding to the induced electromotive force; and a current threshold is set, if the current value is greater than or equal to the current threshold, the output signal is output.

[0014] As a further improvement of the technical scheme, the excitation unit outputs an alternating zero sequence current signal, the multi-frequency alternating current output by the excitation unit flows into the coil of the second mutual inductor, changes the magnetic flux in the magnetic core, and then the second mutual inductor detects the alternating induced electromotive force.

[0015] As a further improvement of the technical scheme, the alternating induced electromotive force detected by the second mutual inductor is determined by the number of turns of the coil and the change rate of the magnetic flux in the magnetic core, the current on the wire changes the stable alternating magnetic field, and the direct current or alternating current induced electromotive force is separated by detecting the change of the high-frequency alternating magnetic field.

[0016] The beneficial effects of the above further scheme are that the alternating current-magnetic flux-induced electromotive force conversion link is constructed, the former uses integral operation and threshold determination to improve the accuracy of high-frequency zero sequence current detection and the timeliness of fault response, effectively capturing high-frequency leakage risk, and the latter expands the detection dimension of alternating zero sequence current with the cooperation of the excitation unit and the second transformer, enriches the coverage range of multi-frequency residual current detection, and the cooperation of the two makes the system more comprehensive and accurate in monitoring different characteristic zero sequence currents, enhances the residual current fault identification and disposal capability of the electrical system, and ensures the safety and stability of power consumption.

[0017] On the basis of the above technical scheme, the application can also be improved as follows: the residual current value in the excitation unit is equal to the product of the offset and the turns of the coil of the second transformer, the proportional coefficient and the sampling time interval; the offset is determined by the turns of the coil of the second transformer and the rate of change of the magnetic flux, and the rate of change of the magnetic flux is associated with the residual current, the proportional coefficient and the excitation frequency.

[0018] A multi-frequency residual current detection method, comprising the following steps: Step one: when the sensor module is not powered, the electromotive force detected by the first transformer; Step two: the electronic high-frequency residual current detection unit analyzes the electromotive force detected by the first transformer and outputs a warning signal according to the high-frequency threshold value; Step three: when the sensor module is powered, the excitation unit adjusts the magnetic flux of the second transformer; Step four: the electronic B-type residual current detection unit analyzes the alternating induced electromotive force detected by the second transformer, obtains the residual current value, and outputs a warning signal according to the current threshold value.

[0019] In addition to the purposes, features and advantages described above, the application has other purposes, features and advantages. The application will be further described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The overall module schematic diagram of the application.

[0021] The meanings of the various reference numbers in the drawings are as follows: 1, wire; 2, first transformer; 3, second transformer; 4, power supply; 5, sensor module; 501, electromagnetic A-type residual current detection unit; 502, electronic high-frequency residual current detection unit; 503, electronic B-type residual current detection unit; 504, excitation unit; 505, housing. DETAILED DESCRIPTION

[0022] Clearly, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present application.

[0023] A multi-frequency residual current detection device, in combination with the drawings in the present application Figure 1 , comprising a wire 1, a first mutual inductor 2, a second mutual inductor 3, a power supply 4, and a sensor module 5; The magnetic core of the first mutual inductor 2 and the second mutual inductor 3 passes through the wire 1; the power supply 4 is used to supply power to the sensor module 5; the sensor module 5 comprises an electromagnetic type A residual current detection unit 501, an electronic type high-frequency residual current detection unit 502, an electronic type B residual current detection unit 503, an excitation unit 504, and a housing 505; When the sensor module 5 is not powered, the electronic type high-frequency residual current detection unit 502 analyzes the electromotive force detected by the first mutual inductor 2 and outputs a warning signal according to a high-frequency threshold value; when the sensor module 5 is powered, the excitation unit 504 adjusts the magnetic flux of the second mutual inductor 3, and the electronic type B residual current detection unit 503 analyzes the alternating induced electromotive force detected by the second mutual inductor 3 to obtain a residual current value, and the specific working principle is as follows: The first mutual inductor 2 is used to detect the induced electromotive force in the wire 1 The specific working principle is that the first mutual inductor 2 detects a zero sequence current: Wherein, is the magnetic flux in the magnetic core of the first mutual inductor 2, is a proportional coefficient, which is related to the magnetic core permeability, coil turns, magnetic path length and other parameters of the first mutual inductor 2, is the zero sequence current; Then the first mutual inductor 2 converts the zero sequence current into an induced electromotive force and outputs to the electromagnetic type A residual current detection unit 501: ; wherein is the induced electromotive force, is the coil turns of the first mutual inductor 2, is the rate of change of the zero sequence current, which dynamically converts the change of the magnetic flux in the magnetic core of the first mutual inductor 2 into the induced electromotive force , so that the subsequent electromagnetic type A residual current detection unit 501 can directly process the voltage signal, adapt to the detection requirements of conventional electronic circuits, and the coil turns of the first mutual inductor 2 can be designed as needed, increasing the number of turns It can amplify the induced electromotive force and improve the detection capability of small zero-sequence current changes, so that the system can respond to the fault current in a timely manner.

[0024] When sensor module 5 is not powered: Output induced electromotive force Output to electromagnetic type A residual current detection unit 501, electromagnetic type A residual current detection unit 501 sets the electromotive force threshold , if the induced electromotive force >Electromotive force threshold , then the signal is output to realize residual current monitoring in the power-off state, expand the application scenarios (such as leakage investigation during circuit power outage maintenance, long-term monitoring in low-power scenarios), ensure uninterrupted detection of residual current under various power supply conditions (including power failure), and improve the safety and reliability of the electrical system.

[0025] When the sensor module 5 is powered: Induced electromotive force Output to the electronic high-frequency residual current detection unit 502, which analyzes the induced electromotive force Signal frequency :The electronic high-frequency residual current detection unit 502 periodically samples the induced electromotive force , convert the continuous analog signal into a discrete digital signal, and then convert the time domain signal into a frequency domain signal through fast Fourier transform (FFT) to extract the induced electromotive force The signal frequencies contained in: ,in , is the sampling frequency, is the sampling time interval, In order to increase the number of sampling points, the fast Fourier transform (FFT) is used to efficiently analyze the signal frequency components, accurately distinguish high-frequency and non-high-frequency zero-sequence currents, and provide a basis for subsequent classification processing. The digital processing is adapted to modern electronic circuits, which facilitates the integration of intelligent analysis functions (such as real-time spectrum display and frequency anomaly warning), thereby improving the accuracy and intelligence of detection.

[0026] Setting the high frequency threshold , if the signal frequency ≥ high frequency threshold When , the induced electromotive force is determined is the high-frequency zero-sequence current signal; Induced electromotive force When it is a high-frequency zero-sequence current signal, the electronic high-frequency residual current detection unit 502 analyzes the induced electromotive force Corresponding current value ,in is the current value, is the sampling time interval, is the sampling point number, C is the initial current value; and a current threshold is set , if the current value ≥ current threshold , then the output signal; if the signal frequency < high frequency threshold , it means that the current signal corresponding to the induced electromotive force does not meet the high frequency characteristics, and its frequency characteristics are consistent with the performance of direct current or low frequency zero sequence current, so it is determined that the induced electromotive force is an alternating zero sequence current signal (direct current or low frequency zero sequence current).

[0027] The excitation unit 504 receives the alternating zero sequence current signal, and the output alternating current flows into the coil of the second mutual inductor 3. According to the Ampere loop theorem, the magnetic field strength generated by the alternating current current satisfies: , wherein is the closed integral path of the magnetic circuit, is the number of turns of the coil of the second mutual inductor 3; the alternating current , wherein is the instantaneous value of the alternating current output by the excitation unit 504 to the second mutual inductor 3, reflecting the real-time size of the current change over time; is the excitation current amplitude; is the angular frequency; is the excitation frequency; and the alternating current magnetic field strength generated by the current will generate a magnetic field in the surrounding space, and the magnetic field generated by the alternating current will also change periodically over time. Since the second mutual inductor 3 has a magnetic core, the alternating magnetic field will cause the magnetic flux in the magnetic core to change alternately; , wherein is the magnetic induction intensity, and S is the area through which the magnetic field passes.

[0028] The second mutual inductor 3 detects the alternating induced electromotive force: , wherein is the number of turns of the coil of the second mutual inductor 3, is the rate of change of magnetic flux; and outputs the alternating induced electromotive force to the electronic type B residual current detection unit 503, and the electronic type B residual current detection unit 503 analyzes the alternating induced electromotive force to obtain the residual current value: , wherein is the sampling time interval, is the offset (the difference in amplitude of the positive and negative half cycles), is the change in magnetic flux, is the magnetic flux is the proportional coefficient of the current value; the current threshold is set , if the residual current value ≥ current threshold , then the output signal; The above-mentioned alternating current is output by the excitation unit 504 , so that the second mutual inductor 3 magnetic flux changes alternately, based on the principle of electromagnetic induction, so that the second mutual inductor 3 can detect and output alternating induced electromotive force containing direct current or low-frequency zero sequence current information , to provide an analyzable signal for the electronic type B residual current detection unit 503, so that the residual current value which is difficult to detect directly is converted into an easily identifiable alternating induced electromotive force signal through "coupling" with the alternating current, and with the help of mature alternating current signal detection technology, the residual current value is accurately captured and analyzed, making up for the insufficient response of the high-frequency detection unit to such currents, perfecting the full-band coverage of residual current detection, improving the comprehensiveness and accuracy of the identification of abnormal conditions such as electrical system leakage and grounding faults, and ensuring electrical safety.

[0029] For the present application, are there any other alternatives that can also achieve the purpose of the present application: 1. The power supply 4 can also be used; 2. The wire 1 can be a single-phase power supply system, or a three-phase, three-phase plus N or direct current, etc. Common power supply system main line.

[0030] 3. The first mutual inductor 2 and the second mutual inductor 3 can be installed in the same shell or use the same magnetic core, etc. Merging scheme; 4. The sensor module 5 can be any combination of electromagnetic type A residual current detection unit 501, electronic type high-frequency residual current detection unit 502, electronic type B residual current detection unit 503, excitation unit 504 and any part of the shell 505.

[0031] 5. The output signal can be digital, analog, communication signal, or all three signals; 6. The first mutual inductor 2, the second mutual inductor 3 and the sensor module 5 can be installed in the same shell.

[0032] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A multi-frequency residual current detection device, characterized in that: It comprises a conductor (1), a first mutual inductor (2), a second mutual inductor (3), a power supply (4), and a sensor module (5); The magnetic cores of the first mutual inductor (2) and the second mutual inductor (3) pass through the conductor (1); the power supply (4) is used to supply power to the sensor module (5); the sensor module (5) comprises an electromagnetic type A residual current detection unit (501), an electronic high-frequency residual current detection unit (502), an electronic type B residual current detection unit (503), an excitation unit (504), and a housing (505); When the sensor module (5) is not powered, the electromagnetic type A residual current detection unit (501) analyzes the electromotive force detected by the first mutual inductor (2) and outputs a reminder signal according to a threshold value; when the sensor module (5) is powered, the excitation unit (504) adjusts the magnetic flux of the second mutual inductor (3), and the electronic type B residual current detection unit (503) analyzes the alternating induced electromotive force detected by the second mutual inductor (3) to obtain a residual current value.

2. The multi-frequency residual current detection device according to claim 1, characterized in that: After a current flows through the conductor (1) to generate a zero-sequence current, the zero-sequence current generates a magnetic field around the first mutual inductor (2) according to the Ampere loop theorem. The first mutual inductor (2) is composed of a magnetic core and a coil. The magnetic core gathers the magnetic field generated by the zero-sequence current, causing the magnetic flux passing through the coil of the first mutual inductor (2) to change. At this time, an induced electromotive force is generated in the coil. The induced electromotive force is the number of turns of the coil of the first mutual inductor (2) multiplied by a proportional coefficient, and then multiplied by the rate of change of the magnetic flux.

3. The multi-frequency residual current detection device according to claim 2, characterized in that: The induced electromotive force is output to the electromagnetic type A residual current detection unit (501), and the electromagnetic type A residual current detection unit (501) sets an electromotive force threshold, and outputs a signal if the induced electromotive force is greater than the electromotive force threshold.

4. The multi-frequency residual current detection device according to claim 2, characterized in that: The induced electromotive force is output to the electronic high-frequency residual current detection unit (502), which periodically samples the induced electromotive force, converts the continuous analog signal into a discrete digital signal, and then converts the time domain signal that originally changes with time into a frequency domain signal with frequency as a variable through a Fourier transform algorithm, extracting the signal frequency in the induced electromotive force; and setting a high-frequency threshold. If the signal frequency is greater than or equal to the high-frequency threshold, the induced electromotive force is determined to be a high-frequency zero-sequence current signal; if the signal frequency is less than the high-frequency threshold, the induced electromotive force is determined to be an alternating zero-sequence current signal.

5. The multi-frequency residual current detection device according to claim 4, characterized in that: When the Fourier transform algorithm in the electronic high-frequency residual current detection unit (502) converts a continuous time domain signal into a frequency domain signal, the amplitude of each converted frequency signal is analyzed respectively.

6. The multi-frequency residual current detection device according to claim 4, characterized in that: When the induced electromotive force is a high-frequency zero-sequence current signal, the electronic high-frequency residual current detection unit (502) integrates the induced electromotive force within a sampling time, divides the integrated value by the product of the number of turns of the coil of the first mutual inductor (2) and the proportional coefficient, and finally adds an integral constant to obtain a current value corresponding to the induced electromotive force; and simultaneously sets a current threshold, and outputs a signal if the current value is ≥ the current threshold.

7. The multi-frequency residual current detection device according to claim 4, characterized in that: The excitation unit (504) outputs an alternating zero-sequence current signal. The multi-frequency alternating current output by the excitation unit (504) flows into the coil of the second mutual inductor (3), changing the magnetic flux in the magnetic core, and then the second mutual inductor (3) detects the alternating induced electromotive force.

8. The multi-frequency residual current detection device according to claim 7, characterized in that: The alternating induced electromotive force detected by the second mutual inductor (3) is determined by the number of turns of its coil and the rate of change of the magnetic flux in the magnetic core. The current on the conductor (1) changes the stable alternating magnetic field, and the DC or AC induced electromotive force is separated by detecting the change of the high-frequency alternating magnetic field.

9. The multi-frequency residual current detection device according to claim 8, characterized in that: The offset is determined by the number of coil turns flowing into the second mutual inductor (3) and the rate of change of the magnetic flux, and the rate of change of the magnetic flux is associated with the residual current, the proportional coefficient and the excitation frequency.

10. A multi-frequency residual current detection method, applied to the multi-frequency residual current detection device according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: When the sensor module (5) is not powered, the electromotive force detected by the first mutual inductor (2); Step 2: The electronic high-frequency residual current detection unit (502) analyzes the electromotive force detected by the first mutual inductor (2) and outputs a warning signal according to a high-frequency threshold; Step three: when the sensor module (5) is powered, the excitation unit (504) adjusts the magnetic flux of the second mutual inductor (3); Step 4: The electronic type B residual current detection unit (503) analyzes the alternating induced electromotive force detected by the second mutual inductor (3), obtains the residual current value, and outputs a warning signal according to the current threshold.

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