Method and system for detecting vacuum degree of vacuum arc-extinguishing chamber based on high-frequency electron multiplication method

Abstract

The invention relates to a method and system for detecting the vacuum degree of a vacuum arc-extinguishing chamber based on a high-frequency electron multiplication method, and the method comprises the following steps: constructing a vacuum arc-extinguishing chamber model, and determining the voltage and frequency of an external high-frequency power supply through the motion law of charged particles, the high-frequency pre-breakdown characteristics of the vacuum arc-extinguishing chamber and a secondary electron multiplication theory; a high-frequency power supply meeting the parameters is added to the two ends of the vacuum arc-extinguishing chamber, and after discharging occurs in the vacuum arc-extinguishing chamber, the magnitude of ion current generated by positive ion directional movement is obtained through detection; adjusting the vacuum pressure in the vacuum arc-extinguishing chamber, and constructing a relation curve between the ion current and the vacuum degree of the vacuum arc-extinguishing chamber; a high-frequency power supply is applied to the two ends of the vacuum arc-extinguishing chamber to be measured, when discharge is generated in the vacuum arc-extinguishing chamber, the ion current is detected, and the vacuum degree is obtained by comparing the calibration curve. Compared with the prior art, the method has the advantages of simplicity and convenience in operation, less interference, high reliability and the like.

Description

Technical Field

[0001] This invention relates to the field of power system planning technology, and in particular to a method and system for detecting the vacuum level of a vacuum interrupter based on the high-frequency electron multiplication method. Background Technology

[0002] Vacuum circuit breakers, as core switching equipment in medium-voltage power systems, bear the dual mission of control and protection: reliably switching load current under normal operation and rapidly interrupting fatal short-circuit currents during faults, serving as the first line of defense for ensuring the safe and stable operation of the power grid. Their core technology—the vacuum interrupter—achieves oil-free and pollution-free safe interruption thanks to the extremely strong arc-extinguishing capability and insulation strength provided by the high-vacuum medium, while also possessing outstanding advantages such as compact structure, long lifespan, and maintenance-free operation. This not only makes them widely used in various critical scenarios from substations to new energy power plants but also serves as the cornerstone for building smart distribution networks, achieving fault self-healing, and efficient power supply. Their reliability directly determines the modernization level and power supply quality of the entire power system. Among these factors, the vacuum level of the vacuum interrupter is crucial for ensuring its safe operation.

[0003] The critical pressure for normal operation of a vacuum interrupter is... When the vacuum level in the arc-extinguishing chamber falls below this critical value, the insulation and arc-extinguishing performance of the vacuum arc-extinguishing chamber will be affected. The main reasons for the decrease in arc-extinguishing chamber vacuum include: aging or damage to the chamber seals leading to chronic leakage; the release of trace amounts of gas from internal metal materials under the high temperature of the electric arc; or minor manufacturing defects. The serious consequences are that increased gas pressure inside the arc-extinguishing chamber significantly reduces insulation strength, making it unable to effectively extinguish the arc when the current crosses zero. This not only causes breaking failures and equipment malfunctions but may also lead to operational overvoltages due to arc reignition, and even catastrophic accidents such as circuit breaker explosions, seriously threatening the safe and stable operation of the power system.

[0004] Currently, the only method capable of indirect quantitative measurement is magnetron discharge. Magnetron discharge involves separating the moving and stationary contacts of a vacuum interrupter by a certain distance, placing the vacuum interrupter inside an electromagnetic coil, and simultaneously applying a high-voltage pulsed electric field to the moving and stationary contacts. This generates a pulsed magnetic field within the vacuum interrupter, synchronized with the high voltage, causing the cathode to emit electrons. These electrons undergo a helical motion under the influence of the pulsed magnetic field, significantly increasing their path and the probability of collisions with residual gas molecules. The ionization produced by these collisions forms an ion current under the influence of the electric field. The ion current and the gas pressure within the vacuum interrupter are approximately linearly related; therefore, the vacuum level inside the interrupter can be obtained based on the magnitude of the ion current. However, magnetron discharge has significant drawbacks in practical field applications, including cumbersome operation, susceptibility to interference, and large data dispersion.

[0005] Existing technologies have also proposed some online monitoring methods. For example, patent application CN119517684A discloses an online monitoring method for the vacuum degree of the vacuum interrupter chamber of a high-voltage switchgear. This method involves using an overcurrent transformer to measure the main circuit current value of the high-voltage switchgear at the moment of opening and closing; performing a fast Fourier transform to analyze the spectrum of the main circuit current at the moment of opening and closing to obtain the arc spectrum value; calculating the remaining electrical life of the contacts based on the current value at this breaking moment; and calculating the vacuum degree of the vacuum interrupter chamber of the high-voltage switchgear based on the main circuit current value at the moment of opening and closing, the arc spectrum value at the moment of opening and closing, and the current contact life. However, existing methods also suffer from insufficient reliability and are difficult to meet actual engineering needs. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a vacuum degree detection method and system for vacuum interrupters based on the high-frequency electron multiplication method that is easy to operate, less susceptible to interference, and highly reliable.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for detecting the vacuum level of a vacuum interrupter based on the high-frequency electron multiplication method includes the following steps: Step S1: Construct a vacuum interrupter model and determine the voltage and frequency of the applied high-frequency power supply by studying the laws of charged particle motion, the high-frequency pre-breakdown characteristics of the vacuum interrupter, and the secondary electron multiplication theory. Step S2: Based on the voltage and frequency of the external high-frequency power supply calculated in step S1, apply the high-frequency power supply that meets the parameters to both ends of the vacuum interrupter. After the discharge occurs inside the vacuum interrupter, detect the ion current generated by the directional movement of positive ions. Step S3: With the high-frequency power supply operating frequency and output voltage amplitude fixed, adjust the vacuum pressure inside the vacuum interrupter multiple times, repeat step S2, and construct the relationship curve between the collected ion current and the vacuum degree of the vacuum interrupter. Use this relationship curve as the calibration curve. Step S4: Apply a high-frequency power supply to both ends of the vacuum interrupter to be measured. After a discharge occurs inside the vacuum interrupter, detect the extracted ion current and determine the vacuum level of the vacuum interrupter by comparing it with the calibration curve.

[0008] Furthermore, in step S1, the vacuum interrupter model is simplified and constructed using parallel plate electrodes under vacuum.

[0009] In step S1, determining the voltage and frequency of the applied high-frequency power supply specifically includes: Step S11: Analyze the pre-breakdown characteristics in the vacuum interrupter, and determine the voltage amplitude of the applied high-frequency power supply by the relationship between the breakdown electric field strength, spacing and pressure during the discharge of the vacuum interrupter; Step S12: Using the secondary electron multiplication theory, the number of electrons and ions generated during arc-extinguishing chamber discharge is increased by utilizing the electron multiplication effect; Step S13: Analyze the electron motion law in the vacuum interrupter to obtain the frequency of the applied electric field that conforms to the secondary electron multiplication theory, thereby determining the frequency of the applied high-frequency power supply.

[0010] Furthermore, step S11 specifically includes: Based on parallel plate electrodes, the relationship between the breakdown electric field strength, spacing, and pressure between the moving and stationary contacts is established: in, For effective field strength, For spacing, For pressure, The electron temperature corresponds to the effective field strength and air pressure. This is the first ionization coefficient of Thomson. Boltzmann's constant; Based on the above relationship, the applied electric field strength is determined, thereby determining the voltage amplitude of the applied high-frequency power supply.

[0011] Furthermore, the high-frequency voltage that conforms to the aforementioned secondary electron multiplication theory satisfies the following conditions: ① The intensity of the high-frequency voltage can make the electron energy large enough to cause the latter to generate when bombarding the contact electrode. Secondary launch, This represents the secondary emission coefficient; ②The half-cycle of the high-frequency voltage is exactly equal to the transit time of the electron between the electrodes.

[0012] Furthermore, in step S13, the relationship for determining the frequency of the applied high-frequency power supply is as follows: in, The charge-to-mass ratio of electrons. The frequency of the high-frequency electric field, Let be the phase angle of the electric field when an electron leaves the electrode surface. The ratio of the velocity of the bombarding electron to that of the primary secondary electron. =1,2,3…….

[0013] Furthermore, in step S2, a purely resistive resistor is connected in series when the high-frequency power supply that meets the parameters is applied across the vacuum interrupter.

[0014] Furthermore, in step S2, the presence or absence of light in the vacuum chamber is used to determine whether a discharge has occurred inside the vacuum interrupter.

[0015] Furthermore, in steps S2 and S4, the ion current is detected by a detection system capable of detecting weak current signals and resistant to interference.

[0016] This invention also provides a vacuum degree detection system for a vacuum interrupter based on the high-frequency electron multiplication method, comprising: The high-frequency power supply determination module is used to construct a vacuum interrupter model. It determines the voltage and frequency of the applied high-frequency power supply by using the laws of charged particle motion, the high-frequency pre-breakdown characteristics of the vacuum interrupter, and the secondary electron multiplication theory. An ion current acquisition module is used to detect the ion current generated by the directional movement of positive ions after a high-frequency power supply is applied outside the vacuum arc interrupter and a discharge occurs inside. The high-frequency power supply meets the voltage and frequency determined by the high-frequency power supply determination module. The calibration curve construction module is used to obtain the ion current corresponding to different vacuum pressures inside the vacuum interrupter when the frequency and voltage of the high-frequency power supply are fixed, and to construct the relationship curve between the collected ion current and the vacuum degree of the vacuum interrupter, and use this relationship curve as the calibration curve. The actual detection module is used to acquire the ion current collected by the ion current acquisition module when a high-frequency power supply is applied to the vacuum interrupter to be measured. By comparing the calibration curve of the ion current, the vacuum degree of the vacuum interrupter to be measured is obtained.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The high-frequency electron multiplication method excitation source used in this invention only requires a high-frequency power supply. Compared with traditional methods, it requires less equipment, is easier to operate, is less susceptible to interference, has high reliability, and has good application prospects.

[0018] 2. The present invention uses a high-frequency power supply to excite the arc-extinguishing chamber to discharge, which causes less damage to the vacuum arc-extinguishing chamber. Therefore, the vacuum level of the circuit breaker can be detected without affecting its future operating status.

[0019] 3. The vacuum degree detection method proposed in this invention can detect the vacuum degree of vacuum switches in actual operation, and has great practical value.

[0020] 4. This invention abandons the magnetic field of the traditional magnetic discharge method and instead uses a high-frequency power supply to excite the arc-extinguishing chamber. It has the advantages of strong anti-interference, simple operation, flexible and portable equipment, and low cost, and meets the current requirements of power system operation and maintenance for testing the vacuum degree of the arc-extinguishing chamber. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the vacuum degree detection process of the vacuum interrupter chamber of the present invention; Figure 2 This is a schematic diagram of the discharge mechanism process; Figure 3 This is a schematic diagram comparing the mechanisms of high-frequency electron multiplication and magnetron discharge. Figure 4 This is a schematic diagram of the experimental circuit principle; Figure 5 This is a schematic diagram of the detection system principle; Figure 6 This is a schematic diagram of an IV converter circuit; Figure 7 This is a schematic diagram of the experimental operation equipment for a vacuum interrupter; Figure 8 This is a schematic diagram showing the peak ion current changing with the internal gas pressure of the arc-extinguishing chamber. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0023] Example 1 This embodiment provides a method for detecting the vacuum level of a vacuum interrupter based on high-frequency electron multiplication. Specifically, a high-frequency power supply with a specific frequency and voltage amplitude excites the vacuum interrupter, inducing a secondary electron multiplication effect. The positive ions generated after this secondary electron multiplication effect have a negative correlation with the vacuum level of the vacuum interrupter. Therefore, the magnitude of the ion current at each vacuum level can be recorded, and a calibration curve between the ion current and the vacuum level can be created. Using this calibration curve, the vacuum level of the vacuum interrupter can be determined in actual operation using the ion current generated by the high-frequency power supply excitation. For detailed procedures, refer to [reference needed]. Figure 1 As shown, it includes the following steps: Step S1: Construct a vacuum interrupter model and determine the voltage and frequency of the applied high-frequency power supply by studying the laws of charged particle motion, the high-frequency pre-breakdown characteristics of the vacuum interrupter, and the secondary electron multiplication theory. Step S2: Based on the voltage and frequency of the external high-frequency power supply calculated in step S1, apply the high-frequency power supply that meets the parameters to both ends of the vacuum interrupter. After the discharge occurs inside the vacuum interrupter, detect the ion current generated by the directional movement of positive ions. Step S3: With the high-frequency power supply operating frequency and output voltage amplitude fixed, adjust the vacuum pressure inside the vacuum interrupter multiple times, repeat step S2, and construct the relationship curve between the collected ion current and the vacuum degree of the vacuum interrupter. Use this relationship curve as the calibration curve. Step S4: Apply a high-frequency power supply to both ends of the vacuum interrupter to be measured. After a discharge occurs inside the vacuum interrupter, detect the extracted ion current and determine the vacuum level of the vacuum interrupter by comparing it with the calibration curve.

[0024] In this embodiment, only high-frequency power supplies with specific parameters can meet the requirements. Therefore, before using a high-frequency power supply to excite the vacuum interrupter, it is necessary to analyze the pre-breakdown characteristics and the movement process of charged particles in the vacuum interrupter, and determine the frequency and amplitude of the high-frequency power supply in conjunction with the secondary electron multiplication theory. The specific steps are as follows: (1) Analyzing the pre-breakdown characteristics in a vacuum interrupter, when the frequency of the applied electric field is high enough, the motion of the charged particles cannot keep up with the change of the electric field, and the charged particles can be considered to be stationary. The prerequisite for discharge in a vacuum interrupter is that the electron formation rate is greater than the loss rate caused by diffusion. Therefore, the motion of electrons in a high-frequency electric field determines the discharge process in the interrupter. Currently, in the quantitative analysis of the breakdown electric field of a vacuum interrupter, the moving and stationary contacts in the interrupter can be regarded as the two ends of a parallel plate electrode. The electric field between the two ends of the moving and stationary contacts is the factor that determines the ionization of gas molecules in the interrupter. For the discharge in the interrupter, the distance between the moving and stationary contacts also affects the loss of electrons due to diffusion, thereby affecting the process of ionization of molecules caused by the electric field between the moving and stationary contacts. For the discharge process in a vacuum interrupter, the breakdown electric field strength, distance and pressure between the moving and stationary contacts have the following relationship: (1) in, The effective electric field strength between the moving and stationary contacts. The distance between the moving and stationary contacts. The pressure inside the vacuum interrupter. The electron temperature corresponds to the effective field strength and air pressure. This is the first ionization coefficient of Thomson. is Boltzmann's constant. The applied electric field strength can be determined by the relationship between the breakdown electric field strength, the distance between the moving and stationary contacts, and the gas pressure, thus determining the voltage amplitude of the applied high-frequency power supply.

[0025] According to the diffusion theory of gas breakdown, when the mean free path and amplitude of electrons are less than the breakdown gap, and the gap is much smaller than the wavelength, the electron attachment and recombination losses can be ignored. The breakdown condition can be determined using the electron continuity equation. (2) in Electron concentration; It is the net proliferation rate of each electron per unit time; that is, the difference between the ionization rate and the attachment rate. The electron flux density that diffuses through a unit area per unit time is: (3) Where D is the electron diffusion coefficient, which should be a variable because the temperature varies at different locations in space (related to the field strength).

[0026] It increases with increasing field strength, until... Until it is no longer negative. Therefore, This is the breakdown condition; therefore, when the electron concentration at the boundary is 0, the electron concentration inside the tube is... The constant condition (breakdown condition) can be expressed as: (4) here: (5) in, The diffusion length of the breakdown interval is The eigenvalues ​​obtained by solving the equation without changing the spatial coordinates; This refers to the electrode spacing.

[0027] As ordered , (High-frequency volume ionization coefficient), then the equation can be rewritten as: (6) When the pressure decreases, two processes occur simultaneously: ① Increased electron free path length enhances ionization ability; ② Enhanced diffusion increases electron consumption. After a certain critical value, the second process becomes dominant. Therefore, as the vacuum level increases, the ionization ability of electrons weakens, and fewer positive ions are produced. When the pressure is initially reduced, the former process dominates, and the electron concentration increases; subsequently, the latter process dominates, and the electron concentration decreases. A schematic diagram of the discharge mechanism is shown below. Figure 2 As shown.

[0028] (2) Apply a DC high voltage of several kilovolts to the electrodes in a vacuum. When the pressure is less than At Pa, the galvanometer in the circuit generally shows no reading. This is because, under these conditions, the electron flow drawn by various emissions from the cathode (such as field emission, photoelectric emission, etc.) is far from reaching the level that the galvanometer can indicate. Similarly, since the number of primary electrons n per second is very small, and the average flight path d of each electron is also short (d equal to the electrode spacing), the total electron flight path per second is: (7) The electron's flight path is also short, making it very unlikely that gas molecules in space will ionize, thus the current rise cannot indicate the ion current value.

[0029] However, if a suitable magnetic field is applied according to different electrode structures, electrons will fly from the cathode to the anode in a circuitous manner, thus greatly increasing the electron's flight path. Therefore, the total electron flight path per second reaches [a certain value]. (8) Here The average increase in flight range for each electron. The ion current can be as large as 10⁶ or higher, which greatly increases the possibility of electron ionization of gas molecules, reaching a level that a galvanometer can indicate. Since this ion current is related to the mean free path of electrons in the gas, it can be used as an indicator of pressure. This is the working principle of a magnetic discharge vacuum tester.

[0030] To make d grow to d. It is quite difficult to achieve this without using a magnetic field. Therefore, it is necessary to achieve this under conditions where there is no magnetic field. To achieve the value shown in equation (8), it is necessary to use (9) The method, namely increasing the number of electrons, is... Times. Of course, equations (8) and (9) are merely methods of representation to illustrate the problem; here, the two... The values ​​are not required to be equal, and neither method considers the effect of electron recombination. A schematic diagram comparing the mechanisms of the high-frequency electron multiplication method and the magnetron discharge method is shown below. Figure 3 As shown.

[0031] The physical mechanism by which high-frequency electron multiplication increases the number of electrons is based on the theory of secondary electron multiplication, which is described as follows: Let the distance between the moving and stationary contacts be d. When the moving contact emits an electron, if the potential of the stationary contact is higher than that of the moving contact, the electron will fly towards the stationary contact. When the electron energy is high enough, it can bombard the surface of the stationary contact and produce more than one electron, i.e., the secondary emission coefficient. If the electric field immediately reverses when electrons are emitted from the stationary contact, these electrons will bombard the moving contact, producing... There are 10 electrons. After m collisions, the number of electrons will increase. One, and it is possible to achieve: (10) Therefore, in order to satisfy the secondary electron multiplication effect and achieve the purpose of ionizing gas molecules, a high-frequency voltage needs to be applied to the moving and stationary contacts, and the following conditions must be met: ① The intensity of the high-frequency voltage can make the electron energy large enough to cause the latter to generate when bombarding the contact electrode. Secondary launch; ② Its half-period is exactly equal to the transit time of an electron between the electrodes.

[0032] If the secondary electron multiplication effect occurs in the vacuum interrupter, then after each high-frequency half-cycle, the total number of spatial electrons increases, and the total number of positive ions also increases.

[0033] (3) Of course, even if the frequency of the high-frequency field is very high, the number of electrons will not increase indefinitely with the value of m, but generally speaking, it is possible to maintain a stable discharge between the electrodes. The number of ions in this discharge space should be related to the concentration of gas molecules in that space region, that is, it can indicate the gas pressure. Since the secondary electrons emitted on the electrodes have an initial velocity, the phase relationship between the emitted electrons and the high-frequency field should also be considered. The relationship between the parameters of the secondary electrons in the high-frequency electric field is as follows: (11) Here The charge-to-mass ratio of electrons. The frequency of the high-frequency electric field, Let be the phase angle of the electric field when an electron leaves the electrode surface. The ratio of the velocity of the bombarding electron to that of the primary secondary electron, and =1,2,3…….

[0034] This allows us to obtain the required frequency of the external power supply.

[0035] Since the formula is derived under certain conditions, when using the high-frequency electron multiplication theory to detect vacuum level, it is necessary to ensure stable discharge in the vacuum interrupter.

[0036] In step S2, based on the calculated voltage and frequency of the external power supply, a power supply meeting the parameters is applied across the vacuum interrupter. A high-frequency power supply meeting the parameters is used to induce a discharge within the vacuum interrupter. After observing the discharge inside the vacuum interrupter, a high DC voltage is applied to the shield to obtain the ion current generated by the directional movement of positive ions. The magnitude of the ion current is detected using a current detection system. See the detailed experimental circuit diagram below. Figure 4 As shown. When conducting vacuum interrupter discharge experiments, since the excitation of the vacuum interrupter is performed using a high-frequency power supply, and the inductive impedance increases significantly at high frequencies compared to power frequencies, it is necessary to select transmission lines with low inductive impedance and use purely resistive resistors in the circuit. This can reduce the influence of inductive impedance on the ion current.

[0037] The ion current collected from the shield is quite weak, and existing current detection systems cannot accurately detect the experimental current. Therefore, a specialized detection system for weak current signals is needed. Since weak current signals are easily interfered with by other signals, the primary consideration is to improve the anti-interference capability of the current detection system. The specific schematic diagram of the detection system can be found in [reference needed]. Figure 5 As shown.

[0038] Weak signal detection is a technique specifically designed to suppress noise. During signal transmission, not only is the desired weak signal present, but also noise interference. Only by suppressing noise interference during the amplification of the desired weak signal can the useful signal be extracted. Therefore, the minimum signal that a detection system can detect depends on the noise of the preamplifier. Considering the noise immunity of an amplifier used for detecting weak currents requires taking into account the components required at the input stage.

[0039] Specifically, this embodiment detects ion current using a detection system capable of detecting weak current signals and resistant to interference, such as... Figure 5 As shown, the detection system includes an isolation circuit, an IV conversion circuit, an amplifier circuit, a voltage output circuit, a calibration circuit, a power supply system, a signal acquisition circuit, and a CPU. The isolation circuit, IV conversion circuit, amplifier circuit, voltage output circuit, signal acquisition circuit, and CPU are connected sequentially. The isolation circuit, IV conversion circuit, amplifier circuit, and voltage output circuit form a first unit structure, which is externally shielded. The power supply system supplies power to the isolation circuit, IV conversion circuit, amplifier circuit, and voltage output circuit. The calibration circuit is connected to the IV conversion circuit. The isolation circuit, IV conversion circuit, amplifier circuit, voltage output circuit, calibration circuit, and power supply system form a second unit structure, which is externally shielded. In this embodiment, the detection system uses existing structures, achieving weak current detection through the amplifier circuit and achieving anti-interference through the double-layer shielding structure.

[0040] This embodiment selects an operational amplifier using a junction field-effect transistor (JFET) with high input resistance and low gate-source capacitance. Low-noise components such as low-noise capacitors are chosen, the low-noise operating point of the circuit is determined, noise matching is performed, and the required feedback and compensation are determined based on the amplifier's specifications. Simultaneously, when considering interference immunity, external interference is suppressed through circuit board wiring, dust and moisture protection, and other measures.

[0041] The current signal generated by high-frequency power supply excitation is typically only tens of microamperes. However, directly transmitting this current using conventional shielded wires is easily interfered with, thus affecting the input current signal. To address this interference, a driven shield is needed in the design of the detection system to achieve anti-interference. After the positive ion current on the vacuum interrupter's shield is extracted, the current input lead undergoes double-layer shielding. A driven shield is used in the inner layer to ensure that both the inner shield and the current lead are grounded, thereby reducing electrostatic shielding during current transmission.

[0042] To meet detection requirements, the weak input current signal needs to be converted into a voltage signal using an IV converter circuit. A schematic diagram of the IV converter circuit is shown below. Figure 6 As shown. To make the result after IV conversion easier to measure, Rf must be very large; otherwise, it is difficult to measure weak currents. It is usually taken to the MG level. Meanwhile, the circuit's response speed is crucial. In micro-current measurement circuits, the response time of a large circuit with zero-resistance current discharge is usually limited by the time constant formed by the resistor Rf and the input parasitic capacitance in the circuit. If the resistor Rf is too large, it will increase the amplifier's response time, affecting the measurement of rapidly changing current signals. The purpose of detecting ion current signals is achieved by detecting voltage signals.

[0043] Parasitic capacitance and noise in a circuit can affect the accuracy and stability of measurements, and may even cause self-oscillation. Careful wiring and component placement can reduce the impact of parasitic capacitance and noise. Specific operations mainly include: (1) A decoupling capacitor must be added between the power supply and ground of each integrated circuit.

[0044] (2) The distance between the power line and the ground line is close. A decoupling capacitor is added between the power line and the ground line. At the same time, both the power line and the ground line are made of thick wire.

[0045] (3) Place the high-power devices at the edge of the circuit and ground them separately to reduce mutual interference between devices.

[0046] (4) Keep interference signal sources such as motors away from sensitive devices such as microcontrollers.

[0047] (5) At low frequencies, a single-point grounding can be used to reduce noise interference caused by impedance coupling.

[0048] The voltage signal converted from a weak current is amplified and sampled at a certain frequency. The sampled digital signal is then transmitted to the CPU, thereby enabling visualization of the current signal.

[0049] With the high-frequency power supply operating at a fixed frequency, the vacuum pressure inside the vacuum interrupter is adjusted using a turbomolecular pump in the laboratory. The equipment diagram in the laboratory is shown below. Figure 7 As shown, the discharge state of the vacuum interrupter was observed by checking whether the vacuum chamber emitted light in the laboratory. The ion current during the discharge of the vacuum interrupter under different vacuum levels was recorded. The relationship between the ion current collected by the shield and the vacuum level of the interrupter was analyzed. Through multiple experiments, the relationship curve between the magnitude of the ion current and the vacuum level was plotted.

[0050] The mechanism of high-frequency power supply excitation of arc-extinguishing chamber discharge is that discharge is easier over shorter distances. For the convenience of on-site testing, when testing the vacuum level of the arc-extinguishing chamber of a vacuum circuit breaker in the actual field, the vacuum arc-extinguishing chamber needs to be disassembled, the contacts closed and then slowly separated. This allows for a shorter contact distance, making it easier to test the ion current generated by the high-frequency power supply discharge.

[0051] The relationship curve between vacuum ion current and the vacuum degree of the arc-extinguishing chamber was obtained in the laboratory, such as... Figure 8 As shown, this relationship curve and a high-frequency power supply can be used to detect the vacuum level of the vacuum interrupter in a vacuum circuit breaker. The specific operating procedure involves applying a high-frequency power supply to both the moving and stationary contacts of the vacuum interrupter to be measured. After discharge occurs inside the interrupter, an ion current detection system is used to detect the ion current drawn from the shield. The detected ion current is then compared with the calibration curve to determine the vacuum level of the vacuum interrupter.

[0052] If the above methods are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0053] Example 2 This embodiment provides a vacuum level detection system for a vacuum interrupter based on the high-frequency electron multiplication method, comprising a high-frequency power supply determination module, an ion current acquisition module, a calibration curve construction module, and an actual detection module, wherein: The high-frequency power supply determination module is used to construct a vacuum interrupter model. It determines the voltage and frequency of the applied high-frequency power supply by using the laws of charged particle motion, the high-frequency pre-breakdown characteristics of the vacuum interrupter, and the secondary electron multiplication theory. An ion current acquisition module is used to detect the ion current generated by the directional movement of positive ions after a high-frequency power supply is applied outside the vacuum arc interrupter and a discharge occurs inside. The high-frequency power supply meets the voltage and frequency determined by the high-frequency power supply determination module. The calibration curve construction module is used to obtain the ion current corresponding to different vacuum pressures inside the vacuum interrupter when the frequency and voltage of the high-frequency power supply are fixed, and to construct the relationship curve between the collected ion current and the vacuum degree of the vacuum interrupter, and use this relationship curve as the calibration curve. The actual detection module is used to acquire the ion current collected by the ion current acquisition module when a high-frequency power supply is applied to the vacuum interrupter to be measured. By comparing the calibration curve of the ion current, the vacuum degree of the vacuum interrupter to be measured is obtained.

[0054] The rest is the same as in Example 1.

[0055] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for detecting the vacuum level of a vacuum interrupter based on the high-frequency electron multiplication method, characterized in that, Includes the following steps: Step S1: Construct a vacuum interrupter model and determine the voltage and frequency of the applied high-frequency power supply by studying the laws of charged particle motion, the high-frequency pre-breakdown characteristics of the vacuum interrupter, and the secondary electron multiplication theory. Step S2: Based on the voltage and frequency of the external high-frequency power supply calculated in step S1, apply the high-frequency power supply that meets the parameters to both ends of the vacuum interrupter. After the discharge occurs inside the vacuum interrupter, detect the ion current generated by the directional movement of positive ions. Step S3: With the high-frequency power supply operating frequency and output voltage amplitude fixed, adjust the vacuum pressure inside the vacuum interrupter multiple times, repeat step S2, and construct the relationship curve between the collected ion current and the vacuum degree of the vacuum interrupter. Use this relationship curve as the calibration curve. Step S4: Apply a high-frequency power supply to both ends of the vacuum interrupter to be measured. After a discharge occurs inside the vacuum interrupter, detect the extracted ion current and determine the vacuum level of the vacuum interrupter by comparing it with the calibration curve.

2. The vacuum degree detection method for a vacuum interrupter based on the high-frequency electron multiplication method according to claim 1, characterized in that, In step S1, the vacuum interrupter model is simplified and constructed using parallel plate electrodes under vacuum.

3. The vacuum degree detection method for a vacuum interrupter based on the high-frequency electron multiplication method according to claim 2, characterized in that, In step S1, determining the voltage and frequency of the applied high-frequency power supply specifically includes: Step S11: Analyze the pre-breakdown characteristics in the vacuum interrupter, and determine the voltage amplitude of the applied high-frequency power supply by the relationship between the breakdown electric field strength, spacing and pressure during the discharge of the vacuum interrupter; Step S12: Using the secondary electron multiplication theory, the number of electrons and ions generated during arc-extinguishing chamber discharge is increased by utilizing the electron multiplication effect; Step S13: Analyze the electron motion law in the vacuum interrupter to obtain the frequency of the applied electric field that conforms to the secondary electron multiplication theory, thereby determining the frequency of the applied high-frequency power supply.

4. The vacuum degree detection method for a vacuum interrupter based on the high-frequency electron multiplication method according to claim 3, characterized in that, Step S11 is as follows: Based on parallel plate electrodes, the relationship between the breakdown electric field strength, spacing, and pressure between the moving and stationary contacts is established: in, For effective field strength, For spacing, For pressure, The electron temperature corresponds to the effective field strength and air pressure. This is the first ionization coefficient of Thomson. Boltzmann's constant; Based on the above relationship, the applied electric field strength is determined, thereby determining the voltage amplitude of the applied high-frequency power supply.

5. The vacuum degree detection method for a vacuum interrupter based on the high-frequency electron multiplication method according to claim 3, characterized in that, High-frequency voltages conforming to the secondary electron multiplication theory satisfy the following conditions: ① The intensity of the high-frequency voltage can make the electron energy large enough to cause the latter to generate when bombarding the contact electrode. Secondary launch, This represents the secondary emission coefficient; ②The half-cycle of the high-frequency voltage is exactly equal to the transit time of the electron between the electrodes.

6. The vacuum degree detection method for a vacuum interrupter based on the high-frequency electron multiplication method according to claim 3, characterized in that, In step S13, the relationship for determining the frequency of the applied high-frequency power supply is as follows: in, The charge-to-mass ratio of electrons. The frequency of the high-frequency electric field, Let be the phase angle of the electric field when an electron leaves the electrode surface. The ratio of the velocity of the bombarding electron to that of the primary secondary electron. =1,2,3…….

7. The vacuum degree detection method for a vacuum interrupter based on the high-frequency electron multiplication method according to claim 1, characterized in that, In step S2, a purely resistive resistor is connected in series when a high-frequency power supply that meets the parameters is applied across the vacuum interrupter.

8. The vacuum degree detection method for a vacuum interrupter based on the high-frequency electron multiplication method according to claim 1, characterized in that, In step S2, the presence or absence of light in the vacuum chamber is used to determine whether a discharge has occurred inside the vacuum interrupter.

9. The vacuum degree detection method for a vacuum interrupter based on the high-frequency electron multiplication method according to claim 1, characterized in that, In steps S2 and S4, the ion current is detected by a detection system that can detect weak current signals and is resistant to interference.

10. A vacuum degree detection system for a vacuum interrupter based on the high-frequency electron multiplication method, characterized in that, include: The high-frequency power supply determination module is used to construct a vacuum interrupter model. It determines the voltage and frequency of the applied high-frequency power supply by using the laws of charged particle motion, the high-frequency pre-breakdown characteristics of the vacuum interrupter, and the secondary electron multiplication theory. An ion current acquisition module is used to detect the ion current generated by the directional movement of positive ions after a high-frequency power supply is applied outside the vacuum arc interrupter and a discharge occurs inside. The high-frequency power supply meets the voltage and frequency determined by the high-frequency power supply determination module. The calibration curve construction module is used to obtain the ion current corresponding to different vacuum pressures inside the vacuum interrupter when the frequency and voltage of the high-frequency power supply are fixed, and to construct the relationship curve between the collected ion current and the vacuum degree of the vacuum interrupter, and use this relationship curve as the calibration curve. The actual detection module is used to acquire the ion current collected by the ion current acquisition module when a high-frequency power supply is applied to the vacuum interrupter to be measured. By comparing the calibration curve of the ion current, the vacuum degree of the vacuum interrupter to be measured is obtained.

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