Self-powered MOA multi-parameter monitoring intelligent counter

Abstract

The invention relates to the technical field of lightning arrester test, and discloses a line lightning arrester resistive current self-energized monitoring system, which comprises an energy taking unit and a measuring unit, and is characterized in that the energy taking unit is connected with the measuring unit; the measuring unit comprises a single-chip microcomputer acquisition unit, a display unit, a storage unit and a communication unit. The energy taking unit comprises a transient large-current energy taking circuit and a steady-state weak-current energy taking circuit, and the transient large-current energy taking circuit and the steady-state weak-current energy taking circuit are used together to supply power to the measuring unit; according to the self-energized MOA multi-parameter monitoring intelligent counter, transient large current and steady-state weak current are fused to obtain energy, the stability and reliability of environment energy obtaining and energy supply of the counter are improved, accurate monitoring of the operation state of a lightning arrester is facilitated, the counter is suitable for the complex electromagnetic working condition of the lightning arrester, long-term maintenance is not needed, practicability is achieved, and the counter is suitable for popularization and application. The equipment power supply cost is reduced, the safety and reliability of power grid operation are further guaranteed, the power supply quality is improved, and the economic loss is reduced; by measuring multiple parameters of action current times, amplitude, polarity and time, the problem of single action current parameter of a conventional counter is solved, and richer MOA action current characteristic parameter measurement is provided.

Description

Technical Field

[0001] The invention relates to the technical field of multi-parameter monitoring counters, and in particular to a self-powered MOA multi-parameter monitoring intelligent counter. Background Art

[0002] Yunnan is located in a low-latitude plateau area and is one of the areas with a high incidence of thunderstorms in the country. Severe thunderstorms occur frequently. Metal oxide lightning arresters have become the key to lightning and other forms of overvoltage protection for infrastructure and power equipment such as transmission lines, substations, and converter stations due to their good nonlinear characteristics, large current capacity, and low residual voltage.

[0003] Accurately recording and preserving the operation of lightning arresters can effectively reflect the lightning strike area and the intensity of lightning activity, and take measures to deal with lightning strike disasters in the power transmission system in the corresponding area, improve the stability of power grid operation, and improve the reliability of MOA overvoltage protection and the safety of power grid operation.

[0004] Existing arrester counters (such as JCQ-3 arrester monitor) can only record the number of MOA actions and display the full current amplitude. On the one hand, it lacks the embodiment of the action current amplitude, polarity and action time, and cannot effectively distinguish the type of overvoltage that causes the arrester to act, and cannot provide a time reference for overvoltage failures in power equipment. Residual voltage is an important basis for insulation coordination between the arrester and other protected equipment, but the residual voltage of MOA is closely related to the action current amplitude. At the same time, insulation breakdown is also related to the overvoltage polarity. Therefore, the size and polarity of the MOA action current are also important bases for overvoltage analysis. Existing MOA counters have no action current time information and cannot effectively correspond to overvoltage events.

[0005] At present, the intelligent grid of power transmission and transformation equipment is being built to improve the intelligent detection and monitoring level of power transmission and transformation equipment. The digitization and intelligence of MOA counters is one of the development goals of intelligent monitoring devices. However, due to the high power and power consumption of intelligent sensors, the power supply problem of distributed sensors at some nodes has become increasingly prominent. Summary of the invention

[0006] Based on the above situation, the present invention provides a method to improve the stability and reliability of the counter's environmental energy supply, reduce the equipment power supply cost, solve the problem of the single action current parameter of the conventional counter, and realize a truly self-powered MOA multi-parameter monitoring intelligent counter with uninterrupted and continuous energy supply.

[0007] The technical solution adopted by the present invention is:

[0008] A self-powered MOA multi-parameter monitoring intelligent counter comprises an energy taking unit and a measuring unit, wherein the energy taking unit is connected to the measuring unit;

[0009] The measuring unit includes a single-chip computer acquisition unit, a display unit, a storage unit and a communication unit; the single-chip computer acquisition unit measures the action current frequency, amplitude, polarity and time parameters, displays the parameters through the display unit, stores the measured parameters through the storage unit, and transmits signals to the outside world through the communication unit;

[0010] The energy acquisition unit includes a transient large current energy acquisition circuit and / or a steady-state weak current energy acquisition circuit. The transient large current energy acquisition circuit and the steady-state weak current energy acquisition circuit are used in combination to power the measurement unit.

[0011] Furthermore, the transient high current energy harvesting circuit includes an energy harvesting coil, a front-end overvoltage protection module, a rectifier and filter module, an overvoltage protection module, a charging capacitor module and a step-down module;

[0012] The energy collection coil is installed on the grounding wire of the lightning arrester; the rectifier filter module is a rectifier bridge connected to the energy collection coil; the buck module is a DC / DC buck module connected to the measuring unit and the rectifier filter module; the front-end overvoltage protection module and the overvoltage protection module are unidirectional transient voltage suppression diodes arranged on the connection line between the rectifier filter module and the energy collection coil, and the connection line between the rectifier filter module and the buck module; the charging capacitor module is a capacitor arranged on the connection line between the rectifier filter module and the buck module, and between the buck module and the measuring unit;

[0013] The energy harvesting coil absorbs energy from the transient high current channel through electromagnetic induction, and then outputs the energy to the microcontroller acquisition unit after overvoltage protection, rectification, charging, and voltage stabilization processing of each unit module.

[0014] Furthermore, the energy extraction coil includes a coil shielding shell, a circuit shielding shell, a magnetic core, a coil winding, a ZnO resistor and a copper busbar; the coil shielding shell is connected to the circuit shielding shell, the coil shielding shell has a gap both horizontally and vertically, the magnetic core is placed in the coil shielding shell, and an air gap structure is adopted, the air gap width is 1mm, and the material is silicon steel; the coil winding is wound on the outer wall of the magnetic core; the upper and lower terminals of the ZnO resistor are connected to the arrester grounding wire busbar, and at the same time, the terminals of the ZnO resistor lead out the copper busbar and are connected to the entrance end of the current energy extraction circuit.

[0015] Furthermore, the design process of the energy taking coil includes the following steps:

[0016] Step 1 Equivalent circuit model of the coil:

[0017] The equivalent circuit of the energy harvesting coil includes the coil self-inductance L0, internal resistance R0, stray capacitance C0 and coil mutual inductance M. The coil equivalent circuit satisfies:

[0018]

[0019] Where M is the mutual inductance coefficient, which indicates the degree of coupling between two circuits or coils; i1 and i2 are the ground current and induced current respectively; t is the time variable; L0 is the self-inductance coefficient; u c0 is a voltage signal, indicating the voltage applied to the coil;

[0020] Step 2: Calculation formula for each parameter:

[0021]

[0022] Where L0 is the self-inductance coefficient; μ0, μ e are the relative magnetic permeability of the core and the magnetic permeability of vacuum respectively; N is the number of turns of the winding; a, b, h are the inner diameter, outer diameter and thickness of the core respectively; R0 is the internal resistance; ρ is the resistivity of the copper wire; d is the diameter of the copper wire; C0 is the stray capacitance; ε r , ε0 are the relative dielectric constant of insulation and the dielectric constant of vacuum respectively; M is the mutual inductance coefficient;

[0023] Step 3 Saturation analysis:

[0024] Under high-amplitude lightning current conditions, the magnetic core will be saturated with a certain probability; according to the basic theorem of magnetic circuit, the linear relationship between the signal coil B and the magnetic field strength H is expressed as:

[0025]

[0026] Where B is the magnetic induction intensity; H is the magnetic field intensity; μ0, μ e are the relative magnetic permeability of the core and the magnetic permeability of vacuum respectively; N0 is the number of turns of the primary coil; i1 is the primary current value; l is the length of the magnetic circuit;

[0027] Step 4: Calculation of core parameters:

[0028] Using an unclosed silicon steel core, the air gap length is l g , then the equivalent relative magnetic permeability μ of the magnetic core e It is expressed as:

[0029]

[0030] In the formula, μ e is the equivalent relative magnetic permeability of the core; l g is the air gap length; μ r is the relative magnetic permeability of the material;

[0031] Step 5 Initial conditions and equivalent model:

[0032] When i1 is the lightning current, the change rates of i1 and i2 are both large, then:

[0033]

[0034] Where i1 is the primary current; i2 is the induced current; L0 is the self-inductance coefficient; t is the time variable; R0 is the internal resistance; u c0 is a voltage signal, indicating the voltage applied to the coil;

[0035] So it can be simplified to:

[0036]

[0037] The initial condition of the coil is set to zero, and the transfer function of the equivalent model expressed by the Laplace operator s is:

[0038]

[0039] Wherein, H(s) represents the transfer function; I1(s) is the primary current in the Laplace transform domain; I2(s) is the induced current in the Laplace transform domain; M is the mutual inductance coefficient; L0 is the self-inductance coefficient; N is the inverse of the ratio of self-inductance to mutual inductance;

[0040] Step 6: Parameter substitution and calculation:

[0041] Substitute the inner diameter a, outer diameter b, thickness h, number of turns N, and equivalent relative permeability μe of the magnetic core of the energy extraction coil into the parameter calculation formula in step 2 to obtain the parameters of the designed energy extraction coil.

[0042] Furthermore, based on the design of the energy harvesting coil, the design process of the transient high current energy harvesting circuit includes the following steps:

[0043] Step I: Transient high current energy harvesting circuit:

[0044] The energy-taking coil is responsible for providing convertible voltage for subsequent circuits. The secondary-side current passes through the rectifier circuit of the rectifier filter module, converts the AC voltage into DC voltage, and charges the charging capacitor module. Then, the charging capacitor module slowly discharges to power the buck chip of the DC / DC buck module. The transient voltage suppression tube of the overvoltage protection module is used in the circuit to suppress the voltage that exceeds the designed voltage range.

[0045] Step II Charging and Energy Conservation:

[0046] Capacitor C3 on the line connecting the current filter module and the step-down module: During the charging process, the charging process of capacitor C3 can be analyzed by charge conservation. The specific formula is:

[0047]

[0048] Where, T is the lightning current period; i1 is the grounding current; N2 is the number of turns of the energy extraction winding; U cmax is the maximum voltage of capacitor C3;

[0049] Step III Power Requirement Analysis:

[0050] After charging, the C3 energy storage should meet the energy demand of the online monitoring device during the working process. The average power consumption p of the online monitoring device during the working process is taken as 50mW, and the output duration ton of the energy-taking circuit is not less than 0.5s. According to the law of energy conservation:

[0051]

[0052] Where U ce is the voltage of capacitor C3 after working for ton time, η is the conversion efficiency of DC / DC buck module; p is the average power consumption of the online monitoring device during working process, ton is the output duration of energy extraction circuit;

[0053] Step IV Component Selection and Calculation:

[0054] Choose the step-down chip MK9016 with a wide input voltage range. Its input voltage range is 5V-100V, it provides a maximum output current capability of 0.6A, ultra-low standby power consumption, and a standby current of ≤100μA;

[0055] Take the corresponding value of capacitor C3 and substitute it into the maximum calculation of ground current i1 to obtain the corresponding maximum voltage U of capacitor C3 cmax ; According to the capacitor C3 voltage U after working for ton time ce The value is related to the minimum input voltage U of the DC / DC chip c0 Compare and determine whether the requirement of 50mW power supply is met for more than 0.5s;

[0056] Step V Lightning current amplitude calculation:

[0057] When the maximum input voltage is 100V, the lightning current amplitude is obtained by calculation, and the excess lightning current energy is discharged through the transient voltage suppression diode of the overvoltage protection module;

[0058] Step VI Transient Voltage Suppression Components:

[0059] The unidirectional transient voltage suppression diode installed on the connection line between the rectifier filter module and the step-down module adopts a single-phase 5KP100A with a clamping voltage of 100V; the unidirectional transient voltage suppression diode installed on the connection line between the rectifier filter module and the energy extraction coil needs to suppress the AC voltage in both directions, and adopts 5KP150CA;

[0060] The rectifier bridge of the rectifier and filter module is constructed using the ultra-fast recovery diode SF54.

[0061] Furthermore, the steady-state weak current energy extraction circuit includes a lightning arrester valve plate, a ZnO varistor, a rectifier module, a voltage-stabilizing capacitor module, and a DC / DC step-down conversion circuit module;

[0062] The arrester valve plate and ZnO varistor are installed on the grounding wire of the arrester and are located between the energy extraction coil and the arrester; the rectifier module is a rectifier bridge connected in parallel with the ZnO varistor; the DC / DC step-down conversion circuit module is a DC / DC module connected to the rectifier module, and the voltage stabilizing capacitor module is a unidirectional transient voltage suppression diode and capacitor connected between the rectifier module and the DC / DC step-down conversion circuit module, and the rectifier module is connected to the unidirectional transient voltage suppression diode through an inductor.

[0063] Furthermore, the steady-state weak current energy-taking circuit connects the high-resistance grounding energy-taking loop to the grounding down conductor of the lightning arrester, and the AC leakage current flowing through the lightning arrester charges the charging capacitor after rectification, and then outputs DC energy to the measuring unit through DC / DC step-down conversion; the output end uses an energy storage capacitor for energy storage; the front end of the rectifier circuit is provided with overvoltage protection through a ZnO varistor and a lightning arrester valve plate;

[0064] After the steady-state weak current energy-harvesting circuit is connected in parallel with the ZnO varistor, it is connected in series to the arrester grounding line. Under the power frequency voltage, the arrester grounding wire passes the power frequency AC leakage current with an amplitude of mA level. Under the mA level current, the resistance of the ZnO varistor is extremely large and is approximately open circuit, so the leakage current flows to the energy-harvesting circuit.

[0065] Furthermore, after the leakage current of the arrester enters the energy-taking circuit, the leakage current is rectified by the rectifier bridge of the rectifier module, and the rectifier bridge adopts a withstand-voltage Schottky diode with a small conduction voltage drop; the rectified pulsating DC passes through the inductor and the capacitor of the voltage-stabilizing capacitor module, and then is converted into electric energy by the DC / DC module of the DC / DC step-down conversion circuit module;

[0066] The inductor plays the role of smoothing waves and limiting current mutations; the capacitor of the voltage stabilizing capacitor module is connected in parallel with the unidirectional transient voltage suppression diode to limit the voltage difference across the capacitor of the voltage stabilizing capacitor module so that it does not exceed the DC / DC module input voltage upper limit of the DC / DC step-down conversion circuit module. The DC / DC module adopts a wide input voltage range chip; multiple MY31-10kA-100V ZnO varistors are connected in parallel.

[0067] Furthermore, the voltage stabilizing capacitor module and the DC / DC buck conversion circuit of the steady-state weak current energy-harvesting circuit share a group with the charging capacitor module and the buck module of the transient large current energy-harvesting circuit;

[0068] The steady-state current energy-harvesting circuit is connected in parallel with the ZnO varistor to the ground loop, and the transient current energy-harvesting circuit obtains energy from the ground wire through a through-type coil. The front ends of the two energy-harvesting circuits are similar, but they share a charging capacitor and a DC / DC buck conversion module. The output end of the DC / DC buck conversion module is connected to a supercapacitor for energy storage.

[0069] The leakage current is rectified by the rectifier bridge of the steady-state weak current energy-taking circuit. The rectifier bridge adopts a withstand-voltage Schottky diode with a small conduction voltage drop. The voltage direction across the diode in the rectifier bridge is opposite to the conduction direction.

[0070] The output of the energy harvesting coil is connected to a bidirectional transient voltage suppression diode to limit the input voltage and discharge excess energy. The secondary current of the energy harvesting coil is rectified by the rectifier bridge of the transient large current energy harvesting circuit to charge the charging capacitor. The rectifier bridge of the transient large current energy harvesting circuit uses a high-power ultra-fast recovery diode SF54 to construct a full-bridge rectification; the diode on the rectifier bridge of the transient large current energy harvesting circuit isolates the ZnO varistor, the rectifier bridge of the steady-state weak current energy harvesting circuit from the transient current energy harvesting circuit, the charging capacitor has a capacitance of 33μF, and the DC / DC module output is connected to the supercapacitor and the load.

[0071] The beneficial effects of the present invention are:

[0072] The self-powered MOA multi-parameter monitoring intelligent counter improves the stability and reliability of the counter's environmental energy supply by utilizing the fusion of transient large current and steady-state weak current to obtain energy, which is conducive to accurately monitoring the operating status of the lightning arrester. It is suitable for complex electromagnetic working conditions of the lightning arrester, does not require long-term maintenance, is practical, and reduces the power supply cost of the equipment, thereby further ensuring the safety and reliability of the power grid operation, improving the power supply quality, and reducing economic losses; by measuring the number of action currents, amplitude, polarity and time, the problem of the single action current parameter of conventional counters is solved, and more abundant MOA action current characteristic parameter measurements are provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a structural diagram of the connection between the single-chip microcomputer acquisition unit and the storage unit;

[0074] Figure 2 It is a schematic diagram of the principle frame structure of the energy acquisition unit;

[0075] Figure 3 It is a schematic diagram of the structure of the energy taking coil;

[0076] Figure 4 It is a schematic diagram of the principle structure of a steady-state weak current energy extraction circuit;

[0077] Figure 5 It is a schematic diagram of the coil equivalent circuit structure;

[0078] Figure 6 It is a schematic diagram of energy harvesting coil parameters;

[0079] Figure 7 It is a schematic diagram of the principle structure of the transient large current energy extraction circuit;

[0080] Figure 8This is a schematic diagram of the steady-state weak current energy extraction circuit principle;

[0081] Fig. 9 It is a schematic diagram of the fusion energy-harvesting power supply circuit;

[0082] Fig.10 This is a schematic diagram of a typical circuit structure of a DC / DC module;

[0083] In the figure, 101 is a coil shielding shell; 102 is a circuit shielding shell; 103 is a magnetic core; 104 is a coil winding; 105 is a ZnO resistor; and 106 is a copper busbar. DETAILED DESCRIPTION

[0084] The following will be combined with the drawings of the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0085] Example 1

[0086] This embodiment provides a self-powered MOA multi-parameter monitoring intelligent counter, including an energy acquisition unit and a measurement unit, wherein the energy acquisition unit is connected to the measurement unit. Figure 1 As shown, the measuring unit includes a single-chip acquisition unit, a display unit, a storage unit and a communication unit; the single-chip acquisition unit is used to measure the number of action currents, amplitude, polarity and time parameters, display the parameters through the display unit, store the measured parameters through the storage unit, and transmit signals to the outside world through the communication unit. The energy acquisition unit includes a transient large current energy acquisition circuit and a steady-state weak current energy acquisition circuit, and the transient large current energy acquisition circuit and the steady-state weak current energy acquisition circuit are used in combination to power the measuring unit.

[0087] like Figure 2 As shown, the transient large current energy harvesting circuit includes an energy harvesting coil, a front-end overvoltage protection module, a rectifier and filter module, an overvoltage protection module, a charging capacitor module and a step-down module; the energy harvesting coil is installed on the grounding wire of the lightning arrester, and it absorbs energy from the transient large current channel through electromagnetic induction, and then outputs the energy to the single-chip microcomputer acquisition unit after overvoltage protection, rectification, charging and voltage stabilization processing of each unit module.

[0088] like Figure 3As shown, the energy-taking coil includes a coil shielding shell 101, a circuit shielding shell 102, a magnetic core 103, a coil winding 104, a ZnO resistor 105 and a copper bus 106. The coil shielding shell 101 is connected to the circuit shielding shell 102. The coil shielding shell 101 has a gap in the horizontal and vertical directions. The magnetic core 103 is placed in the coil shielding shell, and adopts an air gap structure with an air gap width of 1 mm. The material is silicon steel. The coil winding 104 is wound on the outer wall of the magnetic core 103. The upper and lower terminals of the ZnO resistor 105 are connected to the arrester grounding wire bar. At the same time, the terminals of the ZnO resistor 105 lead to the copper bus 106 and are connected to the entrance end of the current energy-taking circuit.

[0089] like Figure 4 As shown, the steady-state weak current energy-harvesting circuit includes a lightning arrester valve plate, a ZnO varistor, a rectifier module, a voltage-stabilizing capacitor module and a DC / DC step-down conversion circuit module; the lightning arrester valve plate and the ZnO varistor are installed on the grounding wire of the lightning arrester and are located between the energy-harvesting coil and the lightning arrester; the rectifier module is connected in parallel with the ZnO varistor; the voltage-stabilizing capacitor module and the DC / DC step-down conversion circuit respectively adopt the charging capacitor module and the step-down module of the transient large current energy-harvesting circuit.

[0090] In this embodiment, by utilizing the fusion of transient large current and steady-state weak current to obtain energy, the stability and reliability of the counter's environmental energy supply are improved, which is conducive to accurately monitoring the operating status of the lightning arrester. It is suitable for complex electromagnetic working conditions of the lightning arrester, does not require long-term maintenance, has practicality, and reduces the power supply cost of the equipment, thereby further ensuring the safety and reliability of the power grid operation, improving the power supply quality, and reducing economic losses. By measuring multiple parameters such as the number of action currents, amplitude, polarity, and time, the problem of the single action current parameter of conventional counters is solved, and richer MOA action current characteristic parameter measurements are provided.

[0091] Example 2

[0092] Based on Example 1, this example provides a specific design process of the energy extraction coil, including the following steps:

[0093] Step 1 Equivalent circuit model of the coil:

[0094] The equivalent circuit of the energy extraction coil is as follows: Figure 5 As shown; the equivalent circuit of the energy harvesting coil includes the coil self-inductance L0, internal resistance R0, stray capacitance C0 and coil mutual inductance M. The coil equivalent circuit satisfies:

[0095]

[0096] Where M is the mutual inductance coefficient, which indicates the degree of coupling between two circuits or coils; i1 and i2 are the ground current and induced current respectively; t is the time variable; L0 is the self-inductance coefficient; u c0It is a voltage signal, which indicates the voltage applied to the coil.

[0097] Step 2: Calculation formula for each parameter:

[0098]

[0099] Where L0 is the self-inductance coefficient; μ0, μ e are the relative magnetic permeability of the core and the magnetic permeability of vacuum respectively; N is the number of turns of the winding; a, b, h are the inner diameter, outer diameter and thickness of the core respectively; R0 is the internal resistance; ρ is the resistivity of the copper wire; d is the diameter of the copper wire; C0 is the stray capacitance; ε r , ε0 are the relative dielectric constant of insulation and the dielectric constant of vacuum respectively; M is the mutual inductance coefficient.

[0100] Step 3 Saturation analysis:

[0101] Under high-amplitude lightning current conditions, the magnetic core will be saturated with a certain probability; according to the basic theorem of magnetic circuit, the linear relationship between the signal coil B and the magnetic field strength H is expressed as:

[0102]

[0103] Where B is the magnetic induction intensity; H is the magnetic field intensity; μ0, μ e are the relative magnetic permeability of the core and the magnetic permeability of vacuum respectively; N0 is the number of turns of the primary coil; i1 is the primary current value; l is the length of the magnetic circuit;

[0104] Considering the coil application scenario as a flat steel grounding wire for lightning arrester grounding, with a cross-sectional size of 40*5mm and considering the thickness margin of the shielding shell, the inner diameter of the coil is a=0.05m and the outer diameter is b=0.06m, then the magnetic path length l is calculated to be 0.35m.

[0105] Step 4: Calculation of core parameters:

[0106] If a closed silicon steel core is used, μe=8000, and the designed lightning current measurement range is 5kA-100kA, the maximum magnetic induction intensity is calculated by formula (3) as 2.01×core (103)T, which is higher than the saturation magnetic induction intensity of 1.7T.

[0107] Therefore, an unclosed silicon steel core is used, and the air gap length is l g , then the equivalent relative magnetic permeability μ of the magnetic core e It is expressed as:

[0108]

[0109] In the formula, μ e is the equivalent relative magnetic permeability of the core; l g is the air gap length; μ r is the relative magnetic permeability of the material.

[0110] Step 5 Initial conditions and equivalent model:

[0111] According to formula (4), take l g =10mm, μe=35.8, and then according to formula (3), the magnetic core is not saturated under lightning current conditions;

[0112] When i1 is the lightning current, the change rates of i1 and i2 are both large, then:

[0113]

[0114] Where i1 is the primary current; i2 is the induced current; L0 is the self-inductance coefficient; t is the time variable; R0 is the internal resistance; u c0 is a voltage signal, indicating the voltage applied to the coil;

[0115] Then formula (1) can be approximately expressed as:

[0116]

[0117] The initial condition of the coil is zero, and the transfer function of the equivalent model expressed by the Laplace operator s is:

[0118]

[0119] Where H(s) represents the transfer function; I1(s) is the primary current in the Laplace transform domain; I2(s) is the induced current in the Laplace transform domain; M is the mutual inductance coefficient; L0 is the self-inductance coefficient; and N is the inverse of the ratio of self-inductance to mutual inductance.

[0120] Step 6: Parameter substitution and calculation:

[0121] According to the parameters and dimensions of the energy extraction coil mentioned above, i.e., the inner diameter of the coil a = 0.05m, the outer diameter b = 0.06m, and the height h = 0.03m, the length of the magnetic core is taken into consideration, the number of coil turns N = N2 = 50, and the equivalent relative magnetic permeability of the magnetic core μe = 35.8, and then substituted into formula (2), the parameters of the designed energy extraction coil are calculated as follows: Figure 6 shown.

[0122] Based on the design of the energy harvesting coil above, this embodiment provides a specific structure of a transient large current energy harvesting circuit, such as Figure 7 As shown, the buck module is a DC / DC buck module connected to the measuring unit and the rectifier and filter module; the front-end overvoltage protection module and the overvoltage protection module are unidirectional transient voltage suppression diodes arranged on the connection line between the rectifier and filter module and the energy extraction coil, and on the connection line between the rectifier and filter module and the buck module; the charging capacitor module is a capacitor arranged on the connection line between the rectifier and filter module and the buck module, and between the buck module and the measuring unit.

[0123] The design process of the transient high current energy harvesting circuit is as follows:

[0124] Step I: Overview of transient high current energy harvesting circuit functions:

[0125] The energy harvesting coil provides a voltage that can be converted into electrical energy for the subsequent energy harvesting circuit. The secondary side current passes through the rectifier circuit to convert the AC voltage into a DC voltage, which charges the charging capacitor module. Its voltage value is within the input voltage range of the buck chip of the DC / DC buck module. The charging capacitor module then slowly discharges the DC / DC buck chip and provides DC power to the outside through the DC / DC buck chip. The transient voltage suppression tubes at the front and back ends of the circuit suppress and discharge the voltage that exceeds the designed voltage range.

[0126] Step II Charging and Energy Conservation:

[0127] The output of the through-type energy-collecting coil is equivalent to the large energy storage capacitor C3 directly connected in parallel. The coil stray capacitance C0 can be ignored. The trace charge released by C3 to the DC / DC buck chip during the short-term charging process is ignored. From the perspective of charge conservation, the charging process of C3 is analyzed as follows:

[0128]

[0129] Where, T is the lightning current period; i1 is the grounding current; N2 is the number of turns of the energy-taking winding. Considering the core length, N2=50, U cmax is the maximum voltage of C3; considering the 8 / 20μs lightning wave with a short period of 40μs, and approximating it with a triangular wave, we have:

[0130]

[0131] Step III Power Requirement Analysis:

[0132] After charging, the C3 energy storage should meet the energy demand of the online monitoring device during the working process. The average power consumption p of the online monitoring device during the working process is taken as 50mW, including analog-to-digital conversion (ADC), CPU processing and data storage operations, taking into account the initialization of the acquisition unit and storage circuit, and multiple signal acquisition processing and storage time. The output duration of the energy-taking circuit is t on Not less than 0.5s, take t on =0.5s, according to the law of conservation of energy:

[0133]

[0134] Where U ce is the voltage of capacitor C3 after working for ton time. According to the above analysis, U ce Should be greater than the minimum input voltage U of the DC / DC chipc0 ; η is the conversion efficiency of the DC / DC module, and η=90% is taken in the analysis; p is the average power consumption of the online monitoring device during operation; t on It is the output duration of the energy-taking circuit.

[0135] Step IV Component Selection and Calculation:

[0136] In order to improve the application scope of the energy-taking circuit to convert electrical energy, this design selects the buck chip MK9016 with a wide input voltage range, with an input voltage range of 5V to 100V, a maximum output current capability of 0.6A, ultra-low standby power consumption, and a standby current of ≤100μA;

[0137] According to equations (9) and (10), take C3 = 68 μF and substitute it into I 1max =5kA calculation, get U cmax =29.4V, at this time, the voltage of C3 after working for ton time is U ce =7.1V, greater than the minimum input voltage U of the DC / DC chip c0 , meeting the requirement of supplying energy at 50mW for more than 0.5s;

[0138] Further, the maximum input voltage is 100V, and according to formula (9), U is calculated to be cmax =100V, the corresponding lightning current amplitude is 17.0kA, that is, the excess lightning current energy exceeding 17.0kA is discharged through the transient voltage suppression diode. The project adopts transient voltage suppression diode (TVS). Under the impact of instantaneous high power, TVS can change its own impedance at a very high speed, absorb a very large current, and clamp the voltage at both ends to a predetermined value;

[0139] In order to discharge excess lightning current energy, the unidirectional transient voltage suppression diode TVS2 installed on the connection line between the rectifier and filter module and the step-down module adopts a single-phase 5KP100A with a clamping voltage of 100V; the unidirectional transient voltage suppression diode TVS1 installed on the connection line between the rectifier and filter module and the energy extraction coil needs to suppress the AC voltage in both directions and adopts 5KP150CA; the rectifier bridge B1 of the rectifier and filter module is constructed with an ultra-fast recovery diode SF54.

[0140] Example 3

[0141] Based on Example 1, this example provides a specific structure of a steady-state weak current energy extraction circuit, such as Figure 8As shown, the arrester valve plate and the ZnO varistor are installed on the grounding wire of the arrester and are located between the energy extraction coil and the arrester; the rectifier module is a rectifier bridge connected in parallel with the ZnO varistor; the DC / DC step-down conversion circuit module is a DC / DC module connected to the rectifier module, and the voltage stabilizing capacitor module is a unidirectional transient voltage suppression diode and capacitor connected between the rectifier module and the DC / DC step-down conversion circuit module, and the rectifier module is connected to the unidirectional transient voltage suppression diode through an inductor.

[0142] The steady-state weak current energy-taking circuit connects the high-resistance grounding energy-taking loop to the arrester grounding lead. The AC leakage current flowing through the arrester is rectified to the charging capacitor, and then DC / DC step-down conversion is performed to output DC energy to the measurement system. The output end uses energy storage capacitors for energy storage. To prevent excessive voltage from invading and damaging the steady-state weak current energy-taking circuit, an overvoltage protection is set at the front end of the rectifier circuit through a ZnO varistor and an arrester valve.

[0143] When the arrester operates at industrial frequency voltage, the ZnO varistor is equivalent to the insulation resistance, and the leakage current ranges from tens of microamperes to several milliamperes; but as the working time of the zinc oxide arrester increases, the arrester valve plate will age and become damp, the insulation performance will decrease, the leakage current will increase, the valve plate volt-ampere characteristic curve will decrease, and the leakage current will reach tens of milliamperes.

[0144] The energy harvesting circuit formed by the steady-state weak current energy harvesting circuit is connected in parallel with the ZnO varistor and then connected in series to the arrester grounding line. Under the power frequency voltage, the arrester grounding wire passes the power frequency AC leakage current with an amplitude of mA level. Under the mA level current, the resistance of the ZnO varistor is extremely large and is approximately open circuit, so the leakage current flows to the steady-state weak current energy harvesting circuit.

[0145] After the leakage current enters the steady-state weak current energy-taking circuit, it is rectified by the rectifier bridge B2; the rectifier bridge B2 uses a withstand-voltage Schottky diode with a small conduction voltage drop. The rectified pulsating DC passes through the inductor L and capacitor C5, and then the DC / DC module performs power conversion. The inductor L plays a role in smoothing and limiting current mutations. The capacitor C5 is connected in parallel with the unidirectional transient voltage suppression diode TVS3 to limit the voltage difference between the two ends of the capacitor C5 so that it does not exceed the upper limit of the DC / DC module input voltage; the DC / DC module uses a wide input voltage range chip.

[0146] The design principle of the steady-state weak current energy-harvesting circuit is as follows:

[0147] For DC voltage, capacitor C5 has large capacitive reactance. The impedance at the end of the circuit is mainly determined by the DC / DC module and the load. The ground leakage current is equivalent to a DC source, and it is assumed that after capacitor C5 is charged, the current flows through the DC / DC module. According to the energy conservation theorem:

[0148] I2 g R e η=p1 (11)

[0149] In the formula, I g is the effective value of the ground leakage current; R e is the equivalent resistance of the DC / DC module and the load; η is the conversion efficiency of the DC / DC step-down module, and η=90% is taken in the analysis; p1 is the average power consumption of the subsequent detection device during operation, calculated by formula (11), and Re is determined by the load power.

[0150] At the same time, the product of ground leakage current and equivalent resistance should be greater than the starting voltage of the DC / DC module:

[0151] I g R e ≥U co (12)

[0152] Where U C0 This is the minimum input voltage of the DC / DC chip.

[0153] First, the same DC / DC module uses the MK9016 step-down chip, and takes p1 = 50mW, I g =10mA, by formula (11), the equivalent resistance R e =556Ω, then the DC / DC module input voltage = I g R e =5.56V, satisfying formula (12).

[0154] Overvoltage protection uses ZnO varistors. The basic characteristic of ZnO varistors is the nonlinear relationship between current and voltage. When the voltage applied across it is lower than a certain threshold voltage (varistor voltage), the resistance value drops sharply with the increase of voltage, and can be as small as the ohm level or milliohm level; when the voltage decreases, the varistor returns to its original state. ZnO varistors have excellent nonlinear characteristics and large surge tolerance. They are suitable for absorbing lightning, electrical system operation, and impact overvoltages generated by electrostatic pulses to protect various electrical and electronic products.

[0155] Compared with other types of surge suppressors, ZnO zinc oxide varistors have many important features as follows:

[0156] 1. The varistor has a wide voltage range, ranging from a few volts to several thousand volts for a single chip; 2. The impulse current withstand voltage and impulse capacity are large; 3. The limiting voltage (residual voltage) is low; 4. The response speed is fast (ns level); 5. The volt-ampere characteristics are symmetrical on the front and back surfaces; 6. No follow-up current; 7. Long service life.

[0157] In this embodiment, a plurality of MY31-10kA-100V ZnO varistors are connected in parallel.

[0158] Example 4

[0159] On the basis of Embodiment 2 and Embodiment 3, the present embodiment provides a mode in which the energy acquisition unit adopts a transient large current energy acquisition circuit and a steady weak current energy acquisition circuit; Fig. 9 As shown, the voltage stabilizing capacitor module and the DC / DC buck conversion circuit of the steady-state weak current energy-harvesting circuit share a group with the charging capacitor module and the buck module of the transient large current energy-harvesting circuit.

[0160] The steady-state current energy harvesting circuit is connected in parallel with the ZnO varistor R2 to the arrester grounding loop, and the transient current energy harvesting circuit obtains energy from the grounding wire through a through-type coil. The front ends of the two energy harvesting circuits are similar to the aforementioned energy harvesting circuits in Examples 2 and 3, but share a charging capacitor (voltage-stabilizing capacitor) C6 and a DC / DC step-down conversion module. The output end of the DC / DC step-down conversion module is connected to a supercapacitor C7 for energy storage.

[0161] Working principle of the energy taking unit:

[0162] Under normal working voltage, the leakage current of the arrester grounding wire is approximately steady-state, with an amplitude of mA level; at this time, the ZnO varistor connected in parallel with the steady-state weak current energy-harvesting circuit mode has good nonlinear characteristics, that is, the resistance of the ZnO varistor is extremely large under small current conditions; therefore, for the steady-state current energy-harvesting circuit, it is approximately open circuit, and the leakage current flows to the steady-state current energy-harvesting circuit.

[0163] At the same time, for the leakage current of steady-state AC, the secondary side current induced by the energy harvesting coil of the transient large current energy harvesting circuit through electromagnetic induction is extremely small, close to 0. At this time, the voltage at point a of the steady-state energy harvesting circuit is higher than the voltage at point b of the transient current energy harvesting circuit. The diode of the rectifier bridge B4 of the transient large current energy harvesting circuit isolates the transient current energy harvesting circuit from the steady-state current energy harvesting circuit, so the transient current energy harvesting circuit will not affect the steady-state current energy harvesting circuit.

[0164] Obviously, under normal operating voltage, energy is obtained by the steady-state current energy-taking circuit, which includes the ZnO varistor R2, the rectifier bridge B3, the inductor L1, the unidirectional transient voltage suppression diode TVS4 (shared), the capacitor C6 (shared), and the DC / DC module (shared).

[0165] The leakage current is rectified by the rectifier bridge B3. The rectifier bridge B3 uses a withstand-voltage Schottky diode with a small conduction voltage drop. The voltage direction across the diode in the rectifier bridge B3 is opposite to the conduction direction; therefore, the energy-taking coil and the unidirectional transient voltage suppression diode TVS4 of the transient current energy-taking circuit are isolated. The rectified pulsating DC passes through the inductor L1 and the voltage-stabilizing capacitor C6, and then the DC / DC buck module performs electrical energy conversion. The inductor L plays the role of smoothing the wave and limiting the current mutation. The capacitor C6 is connected in parallel with the unidirectional transient voltage suppression diode TVS4. Similarly, the voltage difference across the capacitor C6 needs to be limited so that it does not exceed the upper limit of the DC / DC module input voltage. The DC / DC module uses the wide input voltage range chip MK9016 buck chip, and the output voltage is set to 3V. The typical DC / DC module application circuit is as follows Fig.10 shown.

[0166] Under overvoltage conditions, transient current passes through the arrester grounding wire. The transient current is considered to be 5kA ~ 100kA. According to the nonlinear characteristics of the ZnO varistor, when a large current passes through it, its resistance value is close to 0. The transient current flows into the earth through the varistor. The ZnO resistor uses multiple MY31-10kA-100V in parallel or customized to ensure a sufficiently large current capacity.

[0167] like Figure 6 As shown, at this time, the potentials of points c and d of the rectifier bridge B3 of the steady-state current energy-harvesting circuit are 0, and the entrance of the steady-state current energy-harvesting circuit is short-circuited. The energy-harvesting coil of the transient current energy-harvesting circuit obtains energy from the transient large current through electromagnetic induction. At this time, energy passes through the transient current energy-harvesting circuit, and the voltage at point a is greater than 0. Therefore, the voltage direction is opposite to the forward direction of the diode of the rectifier bridge B3. The diode of the rectifier bridge B3 isolates the ZnO varistor R2 at the front end of the steady-state current energy-harvesting circuit, the rectifier bridge B3 and the transient current energy-harvesting circuit, and the steady-state energy-harvesting circuit is not affected by the transient current.

[0168] Obviously, under overvoltage conditions, energy is obtained by the transient current energy extraction circuit, which includes an energy extraction coil, a bidirectional transient voltage suppression diode TVS5, a rectifier bridge B4, a unidirectional transient voltage suppression diode TVS4 (shared), a capacitor C6 (shared), and a DC / DC step-down module (shared).

[0169] The output of the energy harvesting coil is connected to a bidirectional transient voltage suppression diode TVS5 to limit the input voltage and discharge excess energy. The secondary current of the energy harvesting coil is rectified by the rectifier bridge B4 to charge the charging capacitor C6. The rectifier bridge B4 uses a high-power ultra-fast recovery diode SF54 to construct a full-bridge rectifier. The diode meets the requirements of large rectification current (maximum pulse peak current 150A), small conduction voltage drop, large reverse withstand voltage value, and fast response time. At this time, the rectifier bridge B4 diode isolates the ZnO varistor R2, the rectifier bridge B3 and the transient current energy harvesting circuit. The capacitance of capacitor C6 is 33μF as above, and the DC / DC module output is connected to the supercapacitor C7 and the load.

[0170] In this embodiment, if Figure 3 As shown, the transverse gap of the coil shielding shell 101 allows the main magnetic field of the current to enter the energy-taking coil, and the longitudinal gap is used to prevent the formation of bypass magnetic flux on the coil shielding shell 101, so that the magnetic field is concentrated on the coil shielding shell 101, and cannot enter the interior to induce the coil winding 104. The coil winding 104 is wound in an intermittent manner to reduce the influence of the skin effect on the internal resistance when the frequency is high. The enameled copper wire with a cross-sectional diameter of 1mm is evenly wound with 50 turns, and connected to the energy-taking circuit through the connection hole to achieve transient large current energy taking. The transient current and steady-state current fusion energy-taking power supply, under normal working voltage, because the arrester grounding leakage current is approximately uninterrupted, the steady-state current energy-taking circuit takes energy. Under overvoltage, when the transient current passes, the steady-state current energy-taking circuit is short-circuited, and the transient current energy-taking circuit works and obtains energy, thereby achieving truly uninterrupted and continuous energy supply.

[0171] In summary, in combination with Example 1, Example 2, Example 3 and Example 4, the self-powered MOA multi-parameter monitoring intelligent counter, when working, the energy taking coil absorbs energy from the transient large current channel through electromagnetic induction, and then outputs the energy to the single-chip microcomputer acquisition unit after overvoltage protection, rectification, charging and voltage stabilization processing of each unit module.

[0172] The main functions achieved are: during normal operation, the leakage current energy-harvesting circuit is connected in parallel with the ZnO resistor which is nearly open-circuited, and the current flowing through the circuit is the leakage current. Therefore, a coreless coil is installed at the entrance to realize the full current measurement of the arrester leakage current without adding a new detection circuit; the transient current coil and the energy-harvesting coil are placed together in a shielding shell with the signal coil wound with a magnetic core to simplify the structure and reduce the volume, thereby realizing the arrester action counting and transient current characteristic parameter monitoring.

[0173] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A self-powered MOA multi-parameter monitoring intelligent counter, characterized in that: It includes an energy taking unit and a measuring unit, wherein the energy taking unit is connected with the measuring unit; The measuring unit includes a single-chip computer acquisition unit, a display unit, a storage unit and a communication unit; the single-chip computer acquisition unit measures the action current frequency, amplitude, polarity and time parameters, displays the parameters through the display unit, stores the measured parameters through the storage unit, and transmits signals to the outside world through the communication unit; The energy acquisition unit includes a transient large current energy acquisition circuit and / or a steady-state weak current energy acquisition circuit. The transient large current energy acquisition circuit and the steady-state weak current energy acquisition circuit are used in combination to power the measurement unit.

2. The self-powered MOA multi-parameter monitoring intelligent counter according to claim 1 is characterized in that: The transient high current energy extraction circuit includes an energy extraction coil, a front-end overvoltage protection module, a rectifier and filter module, an overvoltage protection module, a charging capacitor module and a step-down module; The energy collection coil is installed on the grounding wire of the lightning arrester; the rectifier filter module is a rectifier bridge connected to the energy collection coil; the buck module is a DC / DC buck module connected to the measuring unit and the rectifier filter module; the front-end overvoltage protection module and the overvoltage protection module are unidirectional transient voltage suppression diodes arranged on the connection line between the rectifier filter module and the energy collection coil, and the connection line between the rectifier filter module and the buck module; the charging capacitor module is a capacitor arranged on the connection line between the rectifier filter module and the buck module, and between the buck module and the measuring unit; The energy harvesting coil absorbs energy from the transient high current channel through electromagnetic induction, and then outputs the energy to the microcontroller acquisition unit after overvoltage protection, rectification, charging, and voltage stabilization processing of each unit module.

3. The self-powered MOA multi-parameter monitoring intelligent counter according to claim 1 is characterized in that: The energy-taking coil comprises a coil shielding shell, a circuit shielding shell, a magnetic core, a coil winding, a ZnO resistor and a copper busbar; the coil shielding shell is connected to the circuit shielding shell, the coil shielding shell has a gap both in the transverse and longitudinal directions, the magnetic core is placed in the coil shielding shell, and adopts an open air gap structure with an air gap width of 1 mm, and the material is silicon steel; the coil winding is wound on the outer wall of the magnetic core; the upper and lower terminals of the ZnO resistor are connected to the arrester grounding wire busbar, and at the same time, the terminals of the ZnO resistor lead out the copper busbar and are connected to the entrance end of the current energy-taking circuit.

4. The self-powered MOA multi-parameter monitoring intelligent counter according to claim 2, characterized in that: The design process of the energy taking coil includes the following steps: Step 1 Equivalent circuit model of the coil: The equivalent circuit of the energy harvesting coil includes the coil self-inductance L0, internal resistance R0, stray capacitance C0 and coil mutual inductance M. The coil equivalent circuit satisfies: Where, M is the mutual inductance coefficient, which indicates the degree of coupling between two circuits or coils; i1 and i2 are the ground current and induced current respectively; t is the time variable; L0 is the self-inductance coefficient; u c0 is a voltage signal, indicating the voltage applied to the coil; Step 2: Calculation formula for each parameter: Where L0 is the self-inductance coefficient; μ0, μ e are the relative magnetic permeability of the core and the magnetic permeability of vacuum respectively; N is the number of turns of the winding; a, b, h are the inner diameter, outer diameter and thickness of the core respectively; R0 is the internal resistance; ρ is the resistivity of the copper wire; d is the diameter of the copper wire; C0 is the stray capacitance; ε r , ε0 are the relative dielectric constant of insulation and the dielectric constant of vacuum respectively; M is the mutual inductance coefficient; Step 3 Saturation analysis: Under high-amplitude lightning current conditions, the magnetic core will be saturated with a certain probability; according to the basic theorem of magnetic circuit, the linear relationship between the signal coil B and the magnetic field strength H is expressed as: Where B is the magnetic induction intensity; H is the magnetic field intensity; μ0, μ e are the relative magnetic permeability of the core and the magnetic permeability of vacuum respectively; N0 is the number of turns of the primary coil; i1 is the primary current value; l is the length of the magnetic circuit; Step 4: Calculation of core parameters: Using an unclosed silicon steel core, the air gap length is l g , then the equivalent relative magnetic permeability μ of the magnetic core e It is expressed as: In the formula, μ e is the equivalent relative magnetic permeability of the core; l g is the air gap length; μ r is the relative magnetic permeability of the material; Step 5 Initial conditions and equivalent model: When i1 is the lightning current, the change rates of i1 and i2 are both large, then: Where i1 is the primary current; i2 is the induced current; L0 is the self-inductance coefficient; t is the time variable; R0 is the internal resistance; u c0 is a voltage signal, indicating the voltage applied to the coil; So it can be simplified to: The initial condition of the coil is set to zero, and the transfer function of the equivalent model expressed by the Laplace operator s is: Wherein, H(s) represents the transfer function; I1(s) is the primary current in the Laplace transform domain; I2(s) is the induced current in the Laplace transform domain; M is the mutual inductance coefficient; L0 is the self-inductance coefficient; N is the inverse of the ratio of self-inductance to mutual inductance; Step 6: Parameter substitution and calculation: Substitute the inner diameter a, outer diameter b, thickness h, number of turns N, and equivalent relative permeability μe of the magnetic core of the energy extraction coil into the parameter calculation formula in step 2 to obtain the parameters of the designed energy extraction coil.

5. The self-powered MOA multi-parameter monitoring intelligent counter according to claim 4 is characterized in that: Based on the design of the energy harvesting coil, the design process of the transient high current energy harvesting circuit includes the following steps: Step I: Transient high current energy harvesting circuit: The energy-taking coil is responsible for providing convertible voltage for subsequent circuits. The secondary-side current passes through the rectifier circuit of the rectifier filter module, converts the AC voltage into DC voltage, and charges the charging capacitor module. Then, the charging capacitor module slowly discharges to power the buck chip of the DC / DC buck module. The transient voltage suppression tube of the overvoltage protection module is used in the circuit to suppress the voltage that exceeds the designed voltage range. Step II Charging and Energy Conservation: Capacitor C3 on the line connecting the current filter module and the step-down module: During the charging process, the charging process of capacitor C3 can be analyzed by charge conservation. The specific formula is: Where, T is the lightning current period; i1 is the grounding current; N2 is the number of turns of the energy extraction winding; U cmax is the maximum voltage of capacitor C3; Step III Power Requirement Analysis: After charging, the C3 energy storage should meet the energy demand of the online monitoring device during the working process. The average power consumption p of the online monitoring device during the working process is taken as 50mW, and the output duration of the energy-taking circuit is t on Not less than 0.5s; According to the law of conservation of energy: Where U ce For work on The voltage of capacitor C3 after time; η is the conversion efficiency of DC / DC buck module; p is the average power consumption of the online monitoring device during operation; t on The output duration of the energy-taking circuit; Step IV Component Selection and Calculation: Choose the step-down chip MK9016 with a wide input voltage range. Its input voltage range is 5V-100V, it provides a maximum output current capability of 0.6A, ultra-low standby power consumption, and a standby current of ≤100μA; Take the corresponding value of capacitor C3 and substitute it into the maximum calculation of ground current i1 to obtain the corresponding maximum voltage U of capacitor C3 cmax ; According to the capacitor C3 voltage U after working for ton time ce The value is related to the minimum input voltage U of the DC / DC chip c0 Compare and determine whether the requirement of 50mW power supply is met for more than 0.5s; Step V Lightning current amplitude calculation: When the maximum input voltage is 100V, the lightning current amplitude is obtained by calculation, and the excess lightning current energy is discharged through the transient voltage suppression diode of the overvoltage protection module; Step VI Transient Voltage Suppression Components: The unidirectional transient voltage suppression diode installed on the connection line between the rectifier filter module and the step-down module adopts a single-phase 5KP100A with a clamping voltage of 100V; the unidirectional transient voltage suppression diode installed on the connection line between the rectifier filter module and the energy extraction coil needs to suppress the AC voltage in both directions, and adopts 5KP150CA; The rectifier bridge of the rectifier and filter module is constructed using the ultra-fast recovery diode SF54.

6. The self-powered MOA multi-parameter monitoring intelligent counter according to claim 2 is characterized in that: The steady-state weak current energy extraction circuit includes a lightning arrester valve plate, a ZnO varistor, a rectifier module, a voltage-stabilizing capacitor module and a DC / DC step-down conversion circuit module; The arrester valve plate and ZnO varistor are installed on the grounding wire of the arrester and are located between the energy extraction coil and the arrester; the rectifier module is a rectifier bridge connected in parallel with the ZnO varistor; the DC / DC step-down conversion circuit module is a DC / DC module connected to the rectifier module, and the voltage stabilizing capacitor module is a unidirectional transient voltage suppression diode and capacitor connected between the rectifier module and the DC / DC step-down conversion circuit module, and the rectifier module is connected to the unidirectional transient voltage suppression diode through an inductor.

7. The self-powered MOA multi-parameter monitoring intelligent counter according to claim 6 is characterized in that: The steady-state weak current energy-taking circuit connects the high-resistance grounding energy-taking loop to the arrester grounding lead, and the AC leakage current flowing through the arrester charges the charging capacitor after rectification, and then outputs DC energy to the measuring unit through DC / DC step-down conversion; the output end uses an energy storage capacitor for energy storage; the front end of the rectifier circuit is provided with overvoltage protection through a ZnO varistor and a valve plate of the arrester; After the steady-state weak current energy-harvesting circuit is connected in parallel with the ZnO varistor, it is connected in series to the arrester grounding line. Under the power frequency voltage, the arrester grounding wire passes the power frequency AC leakage current with an amplitude of mA level. Under the mA level current, the resistance of the ZnO varistor is extremely large and is approximately open circuit, so the leakage current flows to the energy-harvesting circuit.

8. The self-powered MOA multi-parameter monitoring intelligent counter according to claim 5 is characterized in that: After the leakage current of the arrester enters the energy-taking circuit, the leakage current is rectified by the rectifier bridge of the rectifier module. The rectifier bridge adopts a withstand-voltage Schottky diode with a small conduction voltage drop. The rectified pulsating DC passes through the inductor and the capacitor of the voltage-stabilizing capacitor module, and then is converted into electric energy by the DC / DC module of the DC / DC step-down conversion circuit module. The inductor plays the role of smoothing waves and limiting current mutations; the capacitor of the voltage stabilizing capacitor module is connected in parallel with the unidirectional transient voltage suppression diode to limit the voltage difference across the capacitor of the voltage stabilizing capacitor module so that it does not exceed the DC / DC module input voltage upper limit of the DC / DC step-down conversion circuit module. The DC / DC module adopts a wide input voltage range chip; multiple MY31-10kA-100V ZnO varistors are connected in parallel.

9. The self-powered MOA multi-parameter monitoring intelligent counter according to claim 1 is characterized in that: The voltage stabilizing capacitor module and DC / DC buck conversion circuit of the steady-state weak current energy extraction circuit share a group with the charging capacitor module and buck module of the transient large current energy extraction circuit; The steady-state current energy-harvesting circuit is connected in parallel with the ZnO varistor to the ground loop, and the transient current energy-harvesting circuit obtains energy from the ground wire through a through-type coil. The front ends of the two energy-harvesting circuits are similar, but they share a charging capacitor and a DC / DC buck conversion module. The output end of the DC / DC buck conversion module is connected to a supercapacitor for energy storage. The leakage current is rectified by the rectifier bridge of the steady-state weak current energy-taking circuit. The rectifier bridge adopts a withstand-voltage Schottky diode with a small conduction voltage drop. The voltage direction across the diode in the rectifier bridge is opposite to the conduction direction. The output of the energy harvesting coil is connected to a bidirectional transient voltage suppression diode to limit the input voltage and discharge excess energy. The secondary current of the energy harvesting coil is rectified by the rectifier bridge of the transient large current energy harvesting circuit to charge the charging capacitor. The rectifier bridge of the transient large current energy harvesting circuit uses a high-power ultra-fast recovery diode SF54 to construct a full-bridge rectification; the diode on the rectifier bridge of the transient large current energy harvesting circuit isolates the ZnO varistor, the rectifier bridge of the steady-state weak current energy harvesting circuit from the transient current energy harvesting circuit, the charging capacitor has a capacitance of 33μF, and the DC / DC module output is connected to the supercapacitor and the load.

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