Single-magnet-ring dual-processing-circuit switching wide-range leakage current sensor and method

Abstract

The invention discloses a single-magnet-ring dual-processing-circuit switching wide-range leakage current sensor and method. A magnetic core works in a deep magnetic saturation state based on a magnetic modulation principle and is used for sensing a leakage current signal; the square wave self-oscillation circuit is used for sending a square wave signal to the coil by utilizing the inductance effect of the coil; each of the two signal processing circuits comprises a filter, a proportional amplifier and a lock-in amplifier, and only amplification factors of the proportional amplifiers are different, and the proportional amplifiers are used for processing induced leakage current signals; and the microprocessor is used for analyzing and processing the signal output by the signal processing circuit. The system can monitor the insulation state of the energy storage system in real time, effectively improves the safety and reliability of the system, and is suitable for photovoltaic power generation, wind power generation and other application scenes related to the energy storage system.

Description

Technical Field

[0001] The present invention belongs to the technical field of current sensors, and in particular relates to a large-range leakage current sensor and method for switching between a single magnetic ring and dual processing circuits. Background Art

[0002] With the rapid rise of renewable energy and the growing demand for electricity, energy storage systems are becoming increasingly important in modern power networks. These systems not only help balance supply and demand, but also improve the stability and reliability of the entire power grid. Diverse energy storage technologies such as lithium-ion batteries, lead-acid batteries and supercapacitors have been widely adopted and used in many key areas such as power peak regulation, load regulation, backup power supply and power quality control. In these applications, the safety and reliability of energy storage systems are crucial.

[0003] Since energy storage systems usually operate under high voltage and high current conditions, their insulation condition plays a decisive role in the safety of the system. Once the insulation material is damaged or aged, leakage current may occur, which will not only lead to energy waste, but also cause serious safety risks such as electric shock or fire. Therefore, continuous monitoring of the insulation condition of the energy storage system, especially the detection of leakage current, is crucial to ensure the safe operation of the system.

[0004] In the online evaluation of the insulation status of power cables, accurate measurement of weak DC current is particularly critical. Real-time detection of DC leakage current is an effective insulation monitoring method that can track the insulation condition of the cable. Since these leakage currents are very weak, usually below 20 microamperes, high-precision DC sensors are required to ensure safe and accurate measurement.

[0005] DC current measuring devices are divided into two categories: contact and non-contact. Among them, non-contact measurement is safer and more reliable due to its electrical isolation characteristics. Non-contact DC current measuring devices mainly include Hall current sensors, MR sensors and magnetic modulators (fluxgate sensors). Although Hall sensors can measure constant or changing magnetic fields, they have low sensitivity and are susceptible to temperature drift and accuracy issues. In contrast, magnetic modulators have been more widely used in non-contact DC current measurement due to their high sensitivity, low noise and stable working performance.

[0006] Defects and shortcomings of the existing technology: Insufficient sensitivity: Traditional leakage current sensors have limited detection capabilities for tiny leakage currents and can only detect leakage currents above the milliampere level. It is difficult to detect early insulation degradation problems, resulting in poor early warning effects.

[0007] Small measuring range: The measuring range of traditional leakage current sensors cannot cover both microampere-level leakage current and leakage current of several hundred milliamperes.

[0008] Poor anti-interference ability: The working environment of the energy storage system is complex, and traditional sensors are easily affected by factors such as electromagnetic interference and temperature changes, resulting in unstable measurement results or large errors.

[0009] Chinese patent CN202311764356.8 discloses a leakage electrical safety detection device for an energy storage system based on magnetic modulation technology, which includes: an energy storage battery; a high-voltage distribution box, which is electrically connected to the energy storage battery, and a DC leakage detection component is arranged inside the high-voltage distribution box. The DC leakage detection component includes a magnetic modulation current transformer and a controller. The positive and negative cables on the DC side pass through the center hole of the magnetic modulation current transformer at the same time. The magnetic modulation current transformer is connected to the controller, and the controller is used to send an excitation signal to the coil of the magnetic modulation current transformer; a converter, whose AC side is connected to the power grid and whose DC side is electrically connected to the high-voltage distribution box. However, its range is not clearly stated. It uses the average value of the sampling resistor voltage signal to reflect the leakage current size, which cannot avoid the interference of zero drift and has a large error. Summary of the invention

[0010] The object of the present invention is to provide a large-range leakage current sensor and method with single magnetic ring dual processing circuit switching to overcome the deficiencies in the prior art.

[0011] In order to achieve the above object, the present invention adopts the following technical solution: A large-range leakage current sensor with single magnetic ring and dual processing circuit switching, comprising: Single magnetic ring single coil sensor: Based on the magnetic modulation principle, the magnetic core works in a deep magnetic saturation state to sense the leakage current signal; the single coil is used as an excitation winding in the square wave self-excited oscillation circuit, and the voltage at both ends is a square wave, so that the core reaches oversaturation and generates a symmetrical alternating magnetic field. When the leakage current is not 0, the symmetry of the magnetic field is destroyed. The single coil is also used as a detection winding, and the duty cycle of the positive and negative half-waves in its output voltage signal changes, resulting in a change in the amplitude of its second harmonic. The magnitude of the leakage current can be obtained by measuring the amplitude of its second harmonic. Square wave self-excited oscillation circuit: uses the inductance effect of the coil to send a square wave signal to the coil; Signal processing circuit: including two sets of processing circuits, each including a filter, a proportional amplifier and a lock-in amplifier. The two proportional amplifiers have different amplification factors and are used to process the sensed leakage current signal; Microprocessor: used to analyze and process the signals output by the signal processing circuit.

[0012] A further improvement of the present invention is that it also includes: an alarm device: used to send out an alarm signal when it is detected that the leakage current exceeds a preset threshold.

[0013] A further improvement of the present invention is that the working method of the single magnetic ring single coil inductor is as follows: utilizing the BH curve characteristics of the magnetic ring, the square wave signal generated has caused the magnetic ring to enter a saturated state, so that the voltage signal at both ends of the sampling resistor has a steep rise and a steep drop region, and when there is no leakage current on the total power connection line of the energy storage system, no external magnetic field caused by the leakage current will be generated in the magnetic core, so that the voltage signal waveform at both ends of the sampling resistor is symmetrical in the positive and negative half cycles during the excitation cycle; and when there is a leakage current on the total power connection line of the energy storage system, the leakage current will generate an external magnetic field inside the magnetic core; when the external magnetic field is in the same direction as the internal magnetic field, the magnetic core is more likely to reach magnetic saturation; when the external magnetic field is in opposite directions to the internal magnetic field, the magnetic core reaches magnetic saturation more slowly, so that the voltage signal waveform at both ends of the sampling resistor is asymmetrical in the positive and negative half cycles during the excitation cycle, so that the voltage signal generates a second harmonic, and the amplitude of the second harmonic is linearly related to the magnitude of the detected leakage current.

[0014] A further improvement of the present invention is that the working method of switching the signal processing circuit is as follows: initially, a first signal processing circuit using a proportional amplifier with a low amplification factor is used to monitor a larger leakage current; when the detection value is lower than 500 microamperes, the microprocessor sends a signal to the switching circuit to directly switch to a second signal processing circuit using a proportional amplifier with a high amplification factor; if the detection value is higher than 500 microamperes, the microprocessor sends a signal to the switching circuit to switch to the first signal processing circuit; the voltage signal on the sampling resistor is filtered, amplified, zeroed and amplified, and then enters the phase-locked amplifier to suppress the fundamental wave size and amplify the second harmonic component. After ADC sampling, the data is processed in the microprocessor, and a fast Fourier transform FFT is performed to obtain the accurate size of the second harmonic component; the microprocessor gives the corresponding leakage current size according to the linear relationship.

[0015] A further improvement of the present invention is that the first signal processing circuit is used to measure a leakage current of 500 microamperes to 100 milliamperes.

[0016] A further improvement of the present invention is that the second signal processing circuit is used to measure a leakage current of 10 microamperes to 500 microamperes.

[0017] A method for using a large-range leakage current sensor with a single magnetic ring and dual processing circuit switching, comprising: The coil is wound around the magnetic ring and connected to a square wave self-excited oscillation circuit. When the voltage on the sampling resistor reaches the comparator threshold, it automatically flips to generate an alternating and symmetrical AC signal. The voltage signal on the sampling resistor is input into the signal processing circuit, and then the circuit is switched according to the microprocessor signal; The signal amplified by different proportional amplifiers is used to extract and amplify the second harmonic component through a lock-in amplifier and sampled into a microprocessor through an ADC; The microprocessor performs fast Fourier transform (FFT) on the sampled signal to obtain the second harmonic component, and calculates the leakage current size according to the size of the obtained second harmonic component.

[0018] A further improvement of the present invention is that two sets of signal processing circuits are provided, each of which includes a filter, a proportional amplifier and a lock-in amplifier.

[0019] A further improvement of the present invention is that the two proportional amplifiers have different amplification factors.

[0020] A further improvement of the present invention is that when it is detected that the leakage current exceeds a preset threshold value, an alarm signal is sent out through an alarm device.

[0021] Compared with the prior art, the present invention has at least the following beneficial technical effects: 1. The present invention creatively uses a single magnetic core and a single coil in conjunction with two sets of signal processing circuits to successfully expand the range of the leakage current sensor to 10 microamperes to 100 milliamperes. Because the present invention creatively uses a single magnetic core and a single coil in conjunction with two sets of signal processing circuits, it solves the problem of limited range caused by limited amplification speed of a single signal processing circuit, and successfully expands the range of the leakage current sensor to 10 microamperes to 100 milliamperes 2. The present invention uses a lock-in amplifier to extract the weak second harmonic signal of the output signal. Because the present invention creatively uses a lock-in amplifier to process the voltage signal of the sampling resistor, it solves the problem that the second harmonic is smaller in amplitude than the fundamental wave and is difficult to extract, and achieves the effect of amplifying and extracting the second harmonic.

[0022] 3. The present invention utilizes the second harmonic of the output signal to reflect the magnitude of the measured leakage current, thereby improving the accuracy.

[0023] In summary, the present invention provides a large-range leakage current sensor and method with a single magnetic ring and dual processing circuit switching. It adopts a single coil design, has a simple structure, low cost, and high detection accuracy. By switching two sets of processing circuits, it can achieve a leakage current measurement range of 10 microamperes to 100 milliamperes. It can monitor the insulation status of the energy storage system in real time, effectively improve the safety and reliability of the system, and is suitable for photovoltaic power generation, wind power generation and other application scenarios involving energy storage systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is a schematic diagram of a single winding of an induction coil of a large-range leakage current sensor with a single magnetic ring and dual processing circuit switching in an embodiment of the present invention.

[0026] Figure 2 It is an equivalent circuit diagram of a large-range leakage current sensor with single magnetic ring and dual processing circuit switching in an embodiment of the present invention.

[0027] Figure 3 The present invention is a signal processing flow chart of a large-range leakage current sensor with single magnetic ring and dual processing circuit switching.

[0028] Figure 4 The present invention is a schematic diagram of the overall circuit structure of a large-range leakage current sensor with a single magnetic ring and dual processing circuit switching.

[0029] Figure 5 Schematic diagram of the test results of the leakage current sensor in this embodiment. DETAILED DESCRIPTION

[0030] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0032] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0033] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0035] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0036] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0037] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0038] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0039] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0040] Example 1 Figure 1 1 is a schematic diagram of a single winding of an induction coil of a large-range leakage current sensor with a single magnetic ring and dual processing circuit switching in an embodiment of the present invention. Figure 1 The specific winding method of a single coil and the approximate positional relationship of a square wave self-excited oscillation circuit are explained. Figure 2 It is an equivalent circuit diagram of a large-range leakage current sensor with single magnetic ring and dual processing circuit switching in an embodiment of the present invention. Figure 2 It shows that the single coil plays the role of the excitation winding.

[0041] The present invention provides a single magnetic ring dual processing circuit switching large-range leakage current sensor, comprising: a single magnetic ring single coil inductor: used for sensing leakage current signals; Square wave self-excited oscillation circuit: uses the inductance effect of the coil to send a square wave signal to the coil; signal processing circuit: there are two sets, each of which includes a filter, a proportional amplifier and an analog-to-digital converter, but one set of proportional amplifiers has a lower magnification factor for processing large leakage currents, and one set of proportional amplifiers has a higher magnification factor for processing small leakage currents; microprocessor: used to analyze and process the signal output by the signal processing circuit; alarm device: when the leakage current exceeds the preset threshold, an alarm signal is issued. Among them, the principle of the single magnetic ring single coil sensor is: using the BH curve characteristics of the magnetic ring, the square wave signal generated has caused the magnetic ring to enter a saturated state, so that the voltage signal at both ends of the sampling resistor has a steep rise and fall area. When there is no leakage current on the total power connection line of the energy storage system, the external magnetic field caused by the leakage current will not be generated in the magnetic core, so that the voltage signal waveform at both ends of the sampling resistor is symmetrical in the positive and negative half cycles during the excitation cycle. When there is leakage current on the total power connection line of the energy storage system, the leakage current will generate an external magnetic field inside the magnetic core. When the external magnetic field is in the same direction as the internal magnetic field, the magnetic core is more likely to reach magnetic saturation; when the external magnetic field is in the opposite direction to the internal magnetic field, the magnetic core reaches magnetic saturation more slowly, so that the voltage signal waveform at both ends of the sampling resistor is asymmetric in the positive and negative half cycles during the excitation cycle, so that the voltage signal generates a second harmonic, and the amplitude of the second harmonic is linearly related to the magnitude of the detected leakage current. The principle of switching the signal processing circuit is: initially using a circuit with a low amplification factor proportional amplifier (signal processing circuit 1 is used to measure a leakage current of 500 microamperes to 100 milliamperes) to monitor a larger leakage current. When the detection value is lower than 500 microamperes, the microprocessor sends a signal to the switching circuit to directly switch to a circuit using a high amplification factor proportional amplifier (signal processing circuit 2 is used to measure a leakage current of 10 microamperes to 500 microamperes). If the detection value is higher than 500 microamperes, the microprocessor sends a signal to the switching circuit to switch to signal processing circuit 1. The voltage signal on the sampling resistor is filtered, amplified, zeroed and amplified before entering the phase-locked amplifier to suppress the fundamental wave and amplify the second harmonic component. After ADC sampling, the data is processed in the microprocessor and FFT (Fast Fourier Transform) is performed to obtain the accurate second harmonic component. The microprocessor gives the corresponding leakage current size based on the linear relationship.

[0042] Example 2 Figure 3 The working process of the entire DC leakage current sensor is explained in the form of a flow chart. Figure 4 The overall circuit structure and general process are explained.

[0043] The present invention provides a method for using a large-range leakage current sensor with a single magnetic ring and dual processing circuit switching, comprising: The coil is wound around the magnetic ring and connected to a square wave self-excited oscillation circuit. When the voltage on the sampling resistor reaches the comparator threshold, it automatically flips to generate an alternating and symmetrical AC signal. The voltage signal on the sampling resistor is input into the signal processing circuit, and then the circuit is switched according to the microprocessor signal; The signal amplified by different proportional amplifiers is used to extract and amplify the second harmonic component through a lock-in amplifier and sampled into a microprocessor through an ADC; The microprocessor performs fast Fourier transform (FFT) on the sampled signal to obtain the second harmonic component, and calculates the leakage current size according to the size of the obtained second harmonic component.

[0044] like Figure 5 The figure shows the test results of the leakage current sensor, which reflects that when the input DC leakage current is 0~100μA, the sensor has high accuracy and linearity. The accuracy can reach 10μA.

[0045] The invention points of the present invention are: 1. The present invention uses a single magnetic core and a single coil in conjunction with two sets of signal processing circuits to achieve a leakage current sensor range of 10 microamperes to 100 milliamperes through microprocessor control switching.

[0046] 2. The present invention uses an ADC sampling circuit to convert the analog signal output by the circuit into a digital signal and obtains the second harmonic size of the signal by using FFT (Fast Fourier Transform) through a microprocessor.

[0047] 3. The magnitude of the second harmonic of the output signal of the leakage current sensor is calculated to reflect the magnitude of the measured leakage current.

[0048] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0049] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A large-range leakage current sensor with single magnetic ring and dual processing circuit switching, characterized in that: include: Single magnetic ring single coil sensor: Based on the magnetic modulation principle, the magnetic core works in a deep magnetic saturation state to sense the leakage current signal; the single coil is used as an excitation winding in the square wave self-excited oscillation circuit, and the voltage at both ends is a square wave, so that the core reaches oversaturation and generates a symmetrical alternating magnetic field. When the leakage current is not 0, the symmetry of the magnetic field is destroyed. The single coil is also used as a detection winding, and the duty cycle of the positive and negative half-waves in its output voltage signal changes, resulting in a change in the amplitude of its second harmonic. The magnitude of the leakage current can be obtained by measuring the amplitude of its second harmonic. Square wave self-excited oscillation circuit: uses the inductance effect of the coil to send a square wave signal to the coil; Signal processing circuit: including two sets of processing circuits, each including a filter, a proportional amplifier and a lock-in amplifier. The two proportional amplifiers have different amplification factors and are used to process the sensed leakage current signal; Microprocessor: used to analyze and process the signals output by the signal processing circuit.

2. A single magnetic ring dual processing circuit switching large range leakage current sensor according to claim 1, characterized in that: Also includes: Alarm device: used to send out an alarm signal when it detects that the leakage current exceeds the preset threshold.

3. A single magnetic ring dual processing circuit switching large range leakage current sensor according to claim 1, characterized in that: The working method of the single magnetic ring single coil sensor is as follows: using the BH curve characteristics of the magnetic ring, the square wave signal generated has caused the magnetic ring to enter a saturated state, so that the voltage signal at both ends of the sampling resistor has a steep rise and a steep drop area. When there is no leakage current on the total power connection line of the energy storage system, no external magnetic field caused by the leakage current will be generated in the magnetic core, so that the voltage signal waveform at both ends of the sampling resistor is symmetrical in the positive and negative half cycles during the excitation cycle; when there is a leakage current on the total power connection line of the energy storage system, the leakage current will generate an external magnetic field inside the magnetic core; when the external magnetic field is in the same direction as the internal magnetic field, the magnetic core is more likely to reach magnetic saturation; when the external magnetic field is in the opposite direction to the internal magnetic field, the magnetic core reaches magnetic saturation more slowly, so that the voltage signal waveform at both ends of the sampling resistor is asymmetrical in the positive and negative half cycles during the excitation cycle, so that the voltage signal generates a second harmonic, and the amplitude of the second harmonic is linearly related to the magnitude of the detected leakage current.

4. A single magnetic ring dual processing circuit switching large range leakage current sensor according to claim 1, characterized in that: The working method of switching the signal processing circuit is as follows: initially, the first signal processing circuit of a proportional amplifier with a low amplification factor is used to monitor a larger leakage current. When the detection value is lower than 500 microamperes, the microprocessor sends a signal to the switching circuit to directly switch to the second signal processing circuit using a proportional amplifier with a high amplification factor. If the detection value is higher than 500 microamperes, the microprocessor sends a signal to the switching circuit to switch to the first signal processing circuit; the voltage signal on the sampling resistor is filtered, amplified, zeroed and amplified before entering the phase-locked amplifier to suppress the fundamental wave size and amplify the second harmonic component. After ADC sampling, the data is processed in the microprocessor and a fast Fourier transform FFT is performed to obtain the accurate size of the second harmonic component; the microprocessor gives the corresponding leakage current size based on the linear relationship.

5. A single magnetic ring dual processing circuit switching large range leakage current sensor according to claim 4, characterized in that: The first signal processing circuit is used to measure the leakage current of 500 microamperes to 100 milliamperes.

6. A single magnetic ring dual processing circuit switching large range leakage current sensor according to claim 4, characterized in that: The second signal processing circuit is used to measure the leakage current of 10 microamperes to 500 microamperes.

7. A method for using a large-range leakage current sensor with a single magnetic ring and dual processing circuit switching, characterized in that: include: The coil is wound around the magnetic ring and connected to a square wave self-excited oscillation circuit. When the voltage on the sampling resistor reaches the comparator threshold, it automatically flips to generate an alternating and symmetrical AC signal. The voltage signal on the sampling resistor is input into the signal processing circuit, and then the circuit is switched according to the microprocessor signal; The signal amplified by different proportional amplifiers is used to extract and amplify the second harmonic component through a lock-in amplifier and sampled into a microprocessor through an ADC; The microprocessor performs fast Fourier transform (FFT) on the sampled signal to obtain the second harmonic component, and calculates the leakage current size according to the size of the obtained second harmonic component.

8. The method for using a large-range leakage current sensor with a single magnetic ring and dual processing circuit switching according to claim 1, characterized in that: There are two sets of signal processing circuits, both of which include filters, proportional amplifiers and lock-in amplifiers.

9. The method for using a large-range leakage current sensor with a single magnetic ring and dual processing circuit switching according to claim 8, characterized in that: The two proportional amplifiers have different amplification factors.

10. The method for using a large-range leakage current sensor with single magnetic ring and dual processing circuit switching according to claim 8, characterized in that: When it is detected that the leakage current exceeds the preset threshold, an alarm signal is sent out through the alarm device.

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