A monitoring system and method for circuit breaker contact travel

Abstract

The present invention provides a monitoring system and method for the contact stroke of a circuit breaker, comprising: a metal target, a PCB coil, a measuring chip and a controller; the metal target is installed on the main shaft of the monitored circuit breaker or below the insulating pull rod; the PCB coil is installed parallel to the plane where the metal target is located, and the PCB coil and the metal target do not contact each other; the measuring chip is connected to the PCB coil, and the measuring chip is used to monitor the resonant signal of the PCB coil and obtain the inductance value based on the resonant signal when the movement of the main shaft of the circuit breaker or the insulating pull rod causes the relative position of the metal target and the PCB coil to move; the controller is connected to the measuring chip, and the controller is used to receive the inductance value sent by the measuring chip and determine the stroke of the circuit breaker contact. The present invention solves the problems of sensor installation and electromagnetic interference in the circuit breaker contact stroke monitoring system through non-contact measurement technology.

Description

Technical Field

[0001] The invention relates to an electric power monitoring system, and in particular to a monitoring system and a monitoring method for a circuit breaker contact stroke. Background Art

[0002] As a very important high-voltage switchgear, the circuit breaker is not only responsible for the normal connection and disconnection of the circuit in the power system, but also plays a role in the safety protection of the circuit and electrical appliances. Its good functional status is the key to the normal and safe operation of the substation and the circuit system. The travel-time characteristics of the moving contact during the opening and closing actions of the circuit breaker are the basis for calculating the opening and closing speeds, and are also important parameters for characterizing its mechanical characteristics and circuit breaking capabilities. Therefore, real-time online monitoring of the circuit breaker contact travel is crucial to improving the safety and reliability of the power system. However, the circuit breaker contacts are located in a fully enclosed vacuum bubble and cannot be directly monitored.

[0003] At present, the sensors used to monitor the travel-time characteristics of circuit breakers are mainly the following:

[0004] (1) Photoelectric sensors. Commonly used photoelectric sensors include incremental and absolute photoelectric encoders, linear grating scales, etc., and they achieve measurement by cooperating with measurement circuits. Photoelectric sensors have the advantages of small size, high precision, and strong reliability, but the matching measurement circuit is relatively complex, the overall cost of the solution is also high, the monitoring rate is low, and it cannot characterize the rapid change process of the contact stroke.

[0005] (2) Differential transformer displacement sensor. The differential transformer displacement sensor is a widely used inductive displacement sensor. Its primary side has a winding, and the secondary side consists of two windings connected in a differential manner to form an open transformer. The differential transformer displacement sensor has the advantages of good linearity, high measurement accuracy, and strong anti-interference ability, but its size is relatively large. For circuit breakers with a relatively compact internal space structure, this type of sensor will be difficult to install.

[0006] (3) Resistive displacement sensor. The basic measurement principle of the resistive displacement sensor is to determine the movement process of the circuit breaker moving contact by measuring the current flowing through the resistor or the change in the voltage across the resistor. There are two types of resistive sensors: linear displacement sensors and angular displacement sensors. Among them, linear displacement sensors are direct measurements, but their size is relatively large and sometimes limited by the installation space and installation position. Angular displacement sensors are small in size and are relatively easy to install and use. However, their measurement is indirect, requiring the measurement of the angular displacement curve of the main shaft, and then using the correspondence between the stroke of the moving contact and the rotation angle of the main shaft to indirectly obtain the linear displacement curve of the moving contact. Resistive displacement sensors have the advantages of high precision, long life and good linearity, but are easily affected by electromagnetic interference signals generated during switch action. Summary of the invention

[0007] In view of the problems existing in the existing circuit breaker contact travel monitoring system, such as high cost, inconvenient installation, low monitoring rate, susceptibility to electromagnetic interference, etc., the present invention provides a circuit breaker contact travel monitoring system, comprising:

[0008] Metal target, PCB coil, measurement chip and controller;

[0009] The metal target is installed on the main shaft of the monitored circuit breaker or below the insulating pull rod;

[0010] The PCB coil is installed parallel to the plane where the metal target is located, and the PCB coil and the metal target do not contact each other;

[0011] The measuring chip is connected to the PCB coil, and is used to monitor the resonance signal of the PCB coil and obtain the inductance value based on the resonance signal when the relative position of the metal target and the PCB coil moves due to the movement of the circuit breaker main shaft or the insulating pull rod;

[0012] The controller is connected to the measuring chip, and is used to receive the inductance value sent by the measuring chip and determine the stroke of the circuit breaker contact.

[0013] Preferably, the metal target comprises:

[0014] crescent hook shaped metal target;

[0015] One end of the crescent hook-shaped metal target is a crescent tip, and the other end is a cross section of a set width, and the curves at both ends of the cross section finally meet at the crescent tip;

[0016] The crescent hook-shaped metal target is installed on the main shaft of the circuit breaker.

[0017] Preferably, the metal target further comprises:

[0018] Arc-edged triangular metal target;

[0019] The two sides of the arc-edge triangle metal target are curved surfaces concave toward the centroid of the triangle, the third side is a straight line, and the arc-edge triangle is symmetrical along the perpendicular bisector;

[0020] The arc-edge triangular metal target is installed below the insulating pull rod of the circuit breaker.

[0021] Preferably, the material of the metal target includes: aluminum alloy material and stainless steel material.

[0022] Preferably, the PCB coil comprises: a multi-layer circuit board and a capacitor, each layer of the circuit board having a spiral coil;

[0023] Wherein, the number of layers of the circuit board is an even number.

[0024] Preferably, the spiral coils on adjacent circuit boards in the PCB coil have opposite rotation directions, and adjacent circuit boards with opposite rotation directions of the spiral coils are connected in series and then in parallel with the capacitor.

[0025] Preferably, the outer diameter of the spiral coil, the thickness of the copper wire, the number of coil turns, the line width and the line spacing, and the number of layers of the circuit board are determined by the parallel impedance of the measurement chip, the input signal resonant frequency and the capacitance value of the capacitor.

[0026] Preferably, the controller comprises:

[0027] Microcontroller and host computer;

[0028] The measuring chip is connected to the microcontroller, and the microcontroller is used to read the inductance value output by the measuring chip and send the relationship between the inductance value and time to the host computer;

[0029] The microcontroller is connected to the host computer, and the host computer is used to receive the relationship between the inductance value and time sent by the microcontroller, and convert the relationship between the inductance value and time into a circuit breaker contact stroke.

[0030] Preferably, the measurement chip comprises: an acquisition module, an analog-to-digital converter and a calculation module.

[0031] Preferably, the measurement chip is an inductance-to-digital converter.

[0032] Preferably, the inductance digital converter is connected to the PCB coil via a shielded cable.

[0033] Preferably, the distance between the PCB coil and the metal target is between 5 mm and 1 cm.

[0034] Based on the same inventive concept, the present invention also provides a method for monitoring the contact travel of a circuit breaker, comprising:

[0035] Based on the monitoring system, the monitored circuit breaker contact is monitored, the movement of the monitored circuit breaker contact drives the metal target to move, and when the relative position of the metal target and the PCB coil moves, the PCB coil generates a resonance signal;

[0036] The measuring chip monitors the resonance signal generated by the PCB coil, obtains an inductance value based on the resonance signal, and sends the inductance value to the controller;

[0037] The controller generates a travel of the monitored circuit breaker contact based on the received inductance value.

[0038] Preferably, before the monitored circuit breaker contacts are actuated, the following steps are included:

[0039] S01. Determine the size of the PCB coil and the distance between the PCB coil and the metal target according to the installation space of the monitored circuit breaker;

[0040] S02, setting the outer diameter, copper wire thickness, number of coil turns, line width, line spacing and number of circuit board layers of the spiral coil based on the size of the PCB coil, calculating the inductance value of the PCB coil through the outer diameter, copper wire thickness, number of coil turns, line width, line spacing and number of circuit board layers of the spiral coil; and calculating the series impedance of the PCB coil based on the resonant frequency value of the inductance digital converter input signal;

[0041] S03. Based on the current resonant frequency value, the inductance value of the PCB coil and the series impedance, the parallel impedance and capacitor capacitance value of the inductance digital converter are obtained, and it is determined whether the parallel impedance and capacitor capacitance value meet the parallel impedance range and capacitor capacitance value range of the inductance digital converter. If the parallel impedance and capacitor capacitance value meet the requirements, the PCB coil is set based on the outer diameter, copper wire thickness, coil turns, line width, line spacing and number of circuit board layers of the current spiral coil; otherwise, the outer diameter, copper wire thickness, coil turns, line width, line spacing, number of circuit board layers and resonant frequency value of the spiral coil are reselected, and step S02 is executed.

[0042] Preferably, the controller generates the travel of the monitored circuit breaker contact based on the received inductance value, comprising:

[0043] The microcontroller reads the inductance value output by the inductance digital converter and sends the inductance-time curve to the host computer;

[0044] The host computer converts the inductance-time curve into the travel-time curve of the monitored circuit breaker contact based on the inductance-contact travel data relationship correspondence table.

[0045] Preferably, before the monitoring system is operated, it includes:

[0046] The operating parameters of the inductance digital converter are set based on the relationship between the sampling rate of the monitoring system and the reference clock frequency and reference count register of the inductance digital converter.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The technical solution provided by the present invention comprises a metal target, a PCB coil, a measuring chip and a controller; the metal target is installed on the main shaft of a monitored circuit breaker or below an insulating pull rod; the PCB coil is installed parallel to the plane where the metal target is located, and the PCB coil and the metal target do not contact each other; the measuring chip is connected to the PCB coil, and the measuring chip is used to monitor the resonance signal of the PCB coil and obtain an inductance value based on the resonance signal when the movement of the main shaft of the circuit breaker or the insulating pull rod causes the relative position of the metal target and the PCB coil to move; the controller is connected to the measuring chip, and the controller is used to receive the inductance value sent by the measuring chip and determine the stroke of the circuit breaker contact. The non-contact measurement technology of the PCB coil and the metal target solves the problems of difficult sensor installation and susceptibility of the monitoring process to electromagnetic interference in the existing circuit breaker contact stroke monitoring system.

[0049] The technical solution provided by the present invention can improve the monitoring resolution and sampling rate by setting the reference clock frequency and the value of the reference count register of the measurement chip; it provides a low-cost, high-performance solution for monitoring the contact travel-time curve of the circuit breaker, which is conducive to the promotion and application of the online monitoring technology of the mechanical characteristics of the circuit breaker.

[0050] The technical solution provided by the present invention is a circuit breaker contact travel monitoring system based on an inductive sensor, which has low cost, a small sensor element and is easy to install, and can reduce the workload of debugging and operation and maintenance.

[0051] The technical solution provided by the present invention adopts non-contact measurement technology, and there is no physical connection between the electronic components in the sensor and the high-voltage equipment, which has a strong anti-electromagnetic interference performance.

[0052] The technical solution provided by the present invention has a high sampling rate of the monitoring system and a resolution up to sub-micron level, which fully meets the requirements of online monitoring of the mechanical state of the circuit breaker. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A framework diagram of a monitoring system for the contact travel of a circuit breaker in the present invention;

[0054] Figure 2 A detailed framework diagram of a monitoring system for the contact travel of a circuit breaker in an embodiment of the present invention;

[0055] Figure 3 A schematic diagram of the shape of a metal target installed on the main shaft of a circuit breaker according to the present invention;

[0056] Figure 4 It is a schematic diagram of the shape of the metal target installed below the insulating pull rod of the circuit breaker according to the present invention;

[0057] Figure 5 It is a schematic diagram of the connection of the spiral coil of the multilayer PCB of the present invention. DETAILED DESCRIPTION

[0058] In order to better understand the present invention, the content of the present invention is further described below in conjunction with the accompanying drawings and examples.

[0059] Figure 1 The present invention provides a circuit breaker contact travel monitoring system, comprising: a metal target, a PCB coil, a measurement chip and a controller;

[0060] The metal target is installed on the main shaft of the monitored circuit breaker or below the insulating pull rod;

[0061] The PCB coil is installed parallel to the plane where the metal target is located, and the PCB coil and the metal target do not contact each other;

[0062] The measuring chip is connected to the PCB coil, and is used to monitor the resonance signal of the PCB coil and obtain the inductance value based on the resonance signal when the relative position of the metal target and the PCB coil moves due to the movement of the circuit breaker main shaft or the insulating pull rod;

[0063] The controller is connected to the measuring chip, and is used to receive the inductance value sent by the measuring chip and determine the stroke of the circuit breaker contact.

[0064] The metal targets include: Figure 3 The crescent hook metal target shown and Figure 4 The arc-edged triangular metal target shown;

[0065] One end of the crescent hook-shaped metal target is a crescent tip, and the other end is a cross section of a set width, and the curves at both ends of the cross section finally meet at the crescent tip;

[0066] The crescent hook-shaped metal target is installed on the main shaft of the circuit breaker.

[0067] The two sides of the arc-edge triangle metal target are curved surfaces concave toward the centroid of the triangle, the third side is a straight line, and the arc-edge triangle is symmetrical along the perpendicular bisector;

[0068] The arc-edge triangular metal target is installed below the insulating pull rod of the circuit breaker.

[0069] The measurement chip may be an inductance-to-digital converter.

[0070] like Figure 2 As shown, the monitoring system provided in this embodiment includes: a metal target, a PCB coil, an inductance digital converter, a microcontroller and a host computer; the metal target is installed on the main shaft of the circuit breaker or below the insulating pull rod; the PCB coil is fixed near the metal target and parallel to the plane where the metal target is located; the inductance digital converter is connected to the PCB coil; the microcontroller is connected to the inductance digital converter through the SPI interface, and is connected to the interrupt output pin of the inductance digital converter through the GPIO; the host computer is connected to the microcontroller through the Ethernet interface.

[0071] Specifically, the metal target is made of aluminum alloy or stainless steel. Figure 3 or Figure 4 When the metal target is installed on the main shaft of the circuit breaker, Figure 3 When the metal target is installed under the insulating rod of the circuit breaker, Figure 4 The shapes shown above can make the output of the sensor and the stroke of the circuit breaker contact to be in a linear relationship.

[0072] The PCB coil is composed of a multi-layer printed circuit board and a capacitor; each layer of the circuit board has a spiral conductor, and the PCB coil does not contact the metal target.

[0073] The inductance digital converter and the microcontroller are installed in the low-voltage room of the switch cabinet; the inductance digital converter is connected to the PCB coil through a shielded cable.

[0074] The present invention provides a monitoring method based on a circuit breaker contact travel monitoring system, comprising the following steps:

[0075] (1) Design the working parameters of the PCB coil

[0076] 1) Determine the size of the PCB coil and the distance between the PCB coil and the metal target according to the installation space of the monitored circuit breaker;

[0077] 2) According to the PCB coil size and the resonant frequency f of the inductance digital converter input signal RES The range is determined by the outer diameter d of the spiral coil. out , copper wire thickness t, coil turns N, line width w, line spacing S, board layer number M to calculate PCB coil inductance L and series impedance R s ;

[0078] 3) According to the inductance digital converter parallel impedance R P and the range of capacitor capacitance C, check the PCB coil inductance L and series impedance Rs ; If C or R P If the range does not meet the requirements, reselect d out , t, N, w, S, M, and f RES value, proceed to steps 2) and 3);

[0079] 4) When the PCB coil is made of multi-layer boards, the spiral coils on adjacent layers rotate in opposite directions. Figure 5 As shown, assuming that the number of layers of the circuit board is M (M is an even number), the connection relationship between the spiral coils in different layers is as follows: the inner end points of the spiral coils of the 1st layer and the 2nd layer, the 3rd layer and the 4th layer, …, the M-1th layer and the Mth layer are connected through vias; the outer end points of the spiral coils of the 1st layer and the 3rd layer, the 2nd layer and the 4th layer, …, the M-2th layer and the Mth layer are connected through vias; the outer end points of the 1st layer and the Mth layer are respectively connected to the two pins of the capacitor.

[0080] (2) A metal target is installed on the main shaft of the circuit breaker or under the insulating pull rod, and a PCB coil is installed near the metal target, and the plane where the PCB coil is located is parallel to the metal target; the PCB coil and the metal target do not contact each other.

[0081] (3) According to the sampling rate F S The reference clock frequency f of the inductance digital converter is set according to the requirements. ref After the monitoring system is running, the microcontroller configures the reference count register (RCOUNT) and resolution of the inductance digital converter through the SPI interface and enables its interrupt output function. The spiral coil in the PCB coil acts as an inductor and resonates with the capacitor (the resonant frequency is f RES ); the resonant signal is transmitted to the signal input terminal of the inductance digital converter.

[0082] (4) When the circuit breaker is actuated, if the metal target is mounted on the main shaft, it will rotate with the main shaft; if the metal target is mounted under the insulating rod, it will move linearly with the insulating rod.

[0083] (5) After the relative position of the metal target and the PCB coil moves, the inductance of the PCB coil changes, which in turn causes the resonant frequency of the input signal of the inductance digital converter to change. After the inductance digital converter detects the change in resonant frequency, it sends an interrupt signal to the microcontroller; the microcontroller reads the inductance value output by the inductance digital converter through the SPI interface and sends the inductance-time curve value to the host computer through the Ethernet interface.

[0084] (6) The host computer uses the inductance-contact stroke data relationship table (the data relationship table is calibrated in the laboratory) to convert the inductance-time curve into the contact stroke-time curve.

[0085] Example 2

[0086] This embodiment is described with reference to various devices of specific models, including:

[0087] The metal target is made of aluminum alloy. Figure 3 The shape shown is installed on the main shaft of the circuit breaker; the outer diameter of the metal target is 4cm, the inner diameter is 2cm, and the thickness is 0.6mm.

[0088] The PCB coil is composed of a printed circuit board, a spiral conductor on the circuit board, and a surface-mount ceramic capacitor; the PCB coil does not contact the metal target.

[0089] The model of the inductance digital converter is LDC1101; the model of the microcontroller is STM32F207; and the host computer is an ordinary desktop computer or a laptop computer.

[0090] The inductance digital converter and the microcontroller are installed in the low-voltage room of the switch cabinet; the inductance digital converter is connected to the PCB coil through a shielded cable.

[0091] This embodiment monitors the contact travel of the circuit breaker based on the above monitoring system, and includes the following steps:

[0092] (1) Design the working parameters of the PCB coil

[0093] 1) Determine the size of the PCB coil and its distance from the metal target. Taking the KYN28-12 switch cabinet as an example, a PCB coil with a diameter of 2 cm can be installed near the main shaft of the circuit breaker, and the distance between the metal target and the PCB coil is 5 mm.

[0094] 2) According to the PCB coil size and the resonant frequency f of the inductance digital converter input signal RES The range is determined by the outer diameter d of the spiral coil. out , copper wire thickness t, coil turns N, line width w, line spacing S, board layer number M to calculate PCB coil inductance L and series impedance R s .

[0095] Take M = 2, d out =20mm, t=34.700μm, w=0.127mm, S=0.127mm, N=16, according to the principle of electromechanics, the inductance of PCB coil L≈19.154μH can be calculated.

[0096] For LDC1101, the input signal resonant frequency should satisfy 0.5MHz≤f RES ≤10MHz, take f RES =1.150MHz, R can be calculated s ≈8.169Ω.

[0097] 3) According to the inductance digital converter parallel impedance R P and the range of capacitor capacitance C, check the PCB coil inductance L and series impedance R s For LDC1101, the parallel impedance should satisfy 1kΩ≤R P ≤60kΩ, the capacitor capacitance value should satisfy 100pF≤C≤56000pF. RES , C, and L satisfy the following relationship:

[0098]

[0099] According to the above formula, C≈1000pF can be calculated. Parallel impedance R P With L, C, R s Satisfies the following relationship:

[0100]

[0101] According to the above formula, R P ≈2.345kΩ. If C or R P If the range does not meet the requirements, reselect d out , t, N, w, S, M, and f RES value, and proceed to steps 2) and 3).

[0102] 4) If the number of layers of the PCB coil circuit board is 2, the connection relationship between the spiral coils on the top layer and the bottom layer is as follows: the inner end points of the spiral coils on the top layer and the bottom layer are connected through vias; the outer end points of the top layer and the bottom layer are respectively connected to the two pins of the capacitor.

[0103] (2) A metal target is installed on the main shaft of the circuit breaker, and a PCB coil is installed near the metal target, and the plane where the PCB coil is located is parallel to the metal target; the PCB coil and the metal target do not contact each other.

[0104] (3) Assuming the system sampling rate F S Not less than 100kSPS, set the reference clock frequency f of the inductance digital converter LDC1101 ref (1MHz≤f ref After the monitoring system is running, the microcontroller configures the reference count register RCOUNT (3≤RCOUNT≤65535) of the inductance digital converter to 6 through the SPI interface, sets the resolution to 24 bits, and enables its interrupt output function. S ,RCOUNT,f ref The following relationship is satisfied:

[0105]

[0106] According to the above calculation, F S ≈105.960kSPS.

[0107] The spiral coil in the PCB coil acts as an inductor and resonates with the capacitor; the resonant signal is transmitted to the signal input terminal of the inductance digital converter.

[0108] (4) When the circuit breaker is activated, the metal target installed on the main shaft rotates with the main shaft.

[0109] (5) After the relative position of the metal target and the PCB coil moves, the inductance of the PCB coil changes, which in turn causes the resonant frequency of the input signal of the inductance digital converter to change. When the distance between the metal target and the PCB coil is 5 mm, the resonant frequency changes from 1.150 MHz to 1.208 MHz. After the inductance digital converter detects the change in resonant frequency, it sends an interrupt signal to the microcontroller; the microcontroller reads the inductance value output by the inductance digital converter through the SPI interface and sends the inductance-time curve value to the host computer through the Ethernet interface.

[0110] (6) The host computer uses the inductance-contact stroke data relationship table (the data relationship table is calibrated in the laboratory) to convert the inductance-time curve into the contact stroke-time curve.

[0111] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0112] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0113] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0114] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0115] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for monitoring the contact travel of a circuit breaker, characterized in that: include: Based on the monitoring system, the monitored circuit breaker contact is monitored, and the movement of the monitored circuit breaker contact drives the metal target to move. When the relative position of the metal target and the PCB coil moves, the PCB coil generates a resonance signal; The measuring chip monitors the resonance signal generated by the PCB coil, obtains an inductance value based on the resonance signal, and sends the inductance value to the controller; The controller generates the travel of the monitored circuit breaker contact based on the received inductance value; The measurement chip is an inductance digital converter; Before the monitored circuit breaker contacts are actuated, the method includes: S01. Determine the size of the PCB coil and the distance between the PCB coil and the metal target according to the installation space of the monitored circuit breaker; S02, setting the outer diameter, copper wire thickness, number of coil turns, line width, line spacing and number of circuit board layers of the spiral coil based on the size of the PCB coil, calculating the inductance value of the PCB coil through the outer diameter, copper wire thickness, number of coil turns, line width, line spacing and number of circuit board layers of the spiral coil; and calculating the series impedance of the PCB coil based on the resonant frequency value of the inductance digital converter input signal; S03, based on the current resonant frequency value, the inductance value of the PCB coil and the series impedance, the parallel impedance and the capacitor capacitance value of the inductance digital converter are obtained, and it is determined whether the parallel impedance and the capacitor capacitance value meet the parallel impedance range and the capacitor capacitance value range of the inductance digital converter. If the parallel impedance and the capacitor capacitance value meet the requirements, the PCB coil is set based on the outer diameter, copper wire thickness, coil turns, line width, line spacing and number of circuit board layers of the current spiral coil. Otherwise, the outer diameter, copper wire thickness, coil turns, line width, line spacing, number of circuit board layers and resonant frequency value of the spiral coil are reselected, and step S02 is executed; The controller generates the travel of the monitored circuit breaker contact based on the received inductance value, including: The microcontroller reads the inductance value output by the inductance digital converter and sends the inductance-time curve to the host computer; The host computer converts the inductance-time curve into the travel-time curve of the monitored circuit breaker contact based on the inductance-contact travel data relationship correspondence table; The monitoring system comprises: Metal target, PCB coil, measurement chip and controller; The metal target is installed on the main shaft of the monitored circuit breaker or below the insulating pull rod; The PCB coil is installed parallel to the plane where the metal target is located, and the PCB coil and the metal target do not contact each other; The measuring chip is connected to the PCB coil, and the movement of the circuit breaker main shaft or the insulating pull rod causes the relative position of the metal target and the PCB coil to move; The controller is connected to the measurement chip; The PCB coil comprises: a multi-layer circuit board and a capacitor, and each layer of the circuit board has a spiral coil; Wherein, the number of layers of the circuit board is an even number; The spiral coils on adjacent circuit boards in the PCB coil have opposite rotation directions; The adjacent circuit boards are connected in series and then connected in parallel with the capacitor.

2. The monitoring method according to claim 1, characterized in that: The metal target comprises: crescent hook shaped metal target; One end of the crescent hook-shaped metal target is a crescent tip, and the other end is a cross section of a set width, and the curves at both ends of the cross section finally meet at the crescent tip; The crescent hook-shaped metal target is installed on the main shaft of the circuit breaker.

3. The monitoring method according to claim 1, characterized in that: The metal target further comprises: Arc-edged triangular metal target; The two sides of the arc-edge triangle metal target are curved surfaces concave toward the centroid of the triangle, the third side is a straight line, and the arc-edge triangle is symmetrical along the perpendicular bisector; The arc-edge triangular metal target is installed below the insulating pull rod of the circuit breaker.

4. The monitoring method according to claim 1, characterized in that: The material of the metal target includes: aluminum alloy material or stainless steel material.

5. The monitoring method according to claim 1, characterized in that: The outer diameter of the spiral coil, the thickness of the copper wire, the number of coil turns, the line width and the line spacing and the number of layers of the circuit board are determined by the parallel impedance of the measurement chip and the resonant frequency value of the input signal and the capacitance value of the capacitor.

6. The monitoring method according to claim 1, characterized in that: The controller comprises: Microcontroller and host computer; The measuring chip is connected to the microcontroller, and the microcontroller is used to read the inductance value output by the measuring chip and send the relationship between the inductance value and time to the host computer; The microcontroller is connected to the host computer, and the host computer is used to receive the relationship between the inductance value and time sent by the microcontroller, and convert the relationship between the inductance value and time into a circuit breaker contact stroke.

7. The monitoring method according to any one of claims 2 to 6, characterized in that: The measuring chip comprises: an acquisition module, an analog-to-digital converter and a calculation module.

8. The monitoring method according to claim 1, characterized in that: The inductance digital converter is connected to the PCB coil via a shielded cable.

9. The monitoring method according to claim 1, characterized in that: The distance between the PCB coil and the metal target is between 5 mm and 1 cm.

10. The monitoring method according to claim 1 or 8, characterized in that: Before the monitoring system is put into operation, it includes: Obtaining the relationship between the reference clock frequency of the inductance digital converter and the reference count register; Based on the sampling rate of the monitoring system and the relationship, operating parameters of the inductance digital converter are set.

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