CN108333457A - Lightning arrestor on-line monitoring methods based on Internet of Things Network Communication and device - Google Patents

Abstract

A lightning arrester online monitoring method and device based on Internet of Things communication. The online detection device takes a CPU module as the core, and the CPU module is respectively connected to a sampling module, an ambient temperature detection module, a power supply module, a liquid crystal display module, and a communication module. The online monitoring method includes: Measure the total leakage current of the arrester; collect the bus voltage; discretely digitize, Fourier transform and calculate the collected total leakage current and bus voltage of the arrester to obtain the total resistive current, the fundamental wave value of the resistive current and each value of the real-time total leakage current. The sub-harmonic value is vertically compared with the previous value to judge the fault, pollution, damp or aging of the arrester. The invention can detect and troubleshoot lightning arresters early, avoid explosion accidents, and can carry out data remote transmission on the leakage current of the lightning arrester, the resistive current component and the number of actions of the reaction lightning arrester, avoiding the complicated manual recording and meter reading, and greatly improving the operation and maintenance staff productivity.

Description

Online monitoring method and device for lightning arrester based on Internet of Things communication

technical field

The invention relates to an intelligent substation in a power system, in particular to an online monitoring method and device for an arrester based on Internet of Things communication.

Background technique

The Internet of Things technology is an important part of the smart grid's perception of external information, and it has broad application prospects in the power system. As the technical core and equipment extension of the smart grid, the smart substation enables the specific application of various key technologies of the Internet of Things.

Metal oxide surge arresters are commonly used equipment in smart power stations to ensure the normal operation of the power system without causing damage. The main principle of this surge arrester (also known as MOA) is to conduct nonlinear regulation through the atmospheric overvoltage or internal overvoltage applied to the equipment, so as to ensure that the voltage applied to the protected equipment is within the normal range. However, in actual work, this kind of arrester may be damaged due to overvoltage, causing relatively large current leakage. After the leakage occurs, it will also cause additional loss of power, causing serious damage to the MOA, and even serious accidents may occur, endangering personal and property safety. Therefore, in the power industry, we must pay great attention to the regular maintenance of the arrester and detect the leakage of the arrester. Only in this way can the normal operation of the MOA be guaranteed and the safe operation of the power system be guaranteed.

Surge arresters are important electrical equipment to protect power equipment from overvoltage hazards in the power grid, and the reliability of their operation will directly affect the safety of the power system. Metal oxide arresters are widely used in substations due to their advantages of no gap, no freewheeling and large flow capacity. However, under the action of the operating voltage, the surge arrester will have a leakage current flow, and the heat generated will increase the temperature of the resistor sheet. In this case, long-term work will cause the resistor sheet of the arrester to age. Due to the influence of environmental conditions, the resistors of the arrester will be affected by moisture and deteriorate, which will increase the leakage current during normal operation. Once an overvoltage occurs in the system, the arrester may thermally collapse or even explode, and the arrester will lose its function. Therefore, continuous online monitoring of the operating status of the arrester is required to ensure the safe operation of the arrester.

There are two traditional lightning arrester monitoring methods. One is to conduct regular power failure test inspections. This method requires power failure, the added experimental voltage is too low, and the test cycle is long. The equipment needs to be manually moved to the site for inspection. The operation is cumbersome and cannot be real-time. Reflect the insulation condition of the arrester; the second is the continuous power detection method, which records data such as leakage current by connecting the measuring instrument to the ground terminal of the arrester. This method does not consider eliminating factors such as phase-to-phase interference, nor can it accurately select the reference phase And voltage, there are still shortcomings such as the test cycle is too long, and faults cannot be found in time. Therefore, the traditional monitoring method is not only complicated but also consumes manpower and material resources. It cannot timely and accurately reflect the status of the arrester, and cannot meet the current development needs of smart substations.

Contents of the invention

The technical problem to be solved by the present invention is: to solve the problems existing in the above-mentioned prior art, and to provide an online monitoring method and device for lightning arresters based on Internet of Things communication, on the one hand, it can ensure the safe operation warning of lightning arresters in substations, early detection and troubleshooting The arrester can avoid the explosion accident of the arrester. On the other hand, the data of the leakage current of the arrester and the resistive current component of the reaction arrester and the number of actions can be transmitted remotely, eliminating the complexity of manual recording and meter reading, and greatly improving the work efficiency of operation and maintenance personnel.

The technical scheme adopted in the present invention is:

A lightning arrester online monitoring device based on Internet of Things communication, with a CPU module as the core, the input end of the CPU module is connected with a sampling module, an ambient temperature detection module and a power supply module, and the adopting module is connected to the current transformer of the lightning arrester and the voltage Transformer, the ambient temperature detection module is connected to the temperature sensor of the lightning arrester, the power supply module is connected to the mains power supply; the output end of the CPU module is connected to the liquid crystal display module, and the liquid crystal display module is connected to the liquid crystal display; the CPU module also A communication module is connected and communicates with the communication module, and the communication module communicates wirelessly with the system master station of the intelligent substation.

In the above technical solution, the sampling module includes a current transformer and a voltage transformer of the lightning arrester, an active second-order filter circuit, and an ADC converter, and the ADC converter is a converter that converts analog quantities into digital quantities, so The above ADC converter uses hardware phase-locked loop technology for follow-up frequency acquisition, and each power frequency cycle is designed to analyze and measure 128 sampling points of the third harmonic component of leakage current.

A method for online monitoring of lightning arresters based on Internet of Things communication, comprising:

The first step is to measure the total leakage current from the middle point of the lower end of the three-phase arrester to the ground: connect the upper ends of the three-phase arrester to the three-phase grid bus, and connect the lower ends of the three-phase arrester together to form the middle point of the connection, and connect the middle From point to ground, the total leakage current from the connection midpoint to ground is collected through the current transformer. When the insulation performance of the three-phase arrester is normal, the sum of the third harmonics of the three-phase leakage current is very small. When a certain phase arrester fails When , the phase amplitude of the fundamental component of the leakage current of each phase will change, resulting in the inability of each component to cancel each other, so that the total leakage current value is greatly increased, and the total leakage current increase value is used as the characteristic quantity of the arrester fault diagnosis;

In the second step, the resistive current fundamental wave component of the total leakage current is used as the characteristic quantity reflecting the deterioration process of the arrester: during the operation of the arrester, when the internal valve plate is aging, damp and the surface is dirty, the total leakage current does not change much, but accounts for The resistive current of 10-20% of the total leakage current is greatly increased, so the resistive current can sensitively reflect the deterioration process of the arrester; because the resistance of the zinc oxide valve plate of the arrester has nonlinear volt-ampere characteristics, the flowing resistive current contains basic Wave, third, fifth and higher harmonics, in which the fundamental wave component of the resistive current is not disturbed by the higher harmonics of the power grid, and can reflect the deterioration process of the arrester; because the arrester is in the small current area for a long time, the flow through The high-frequency component of the valve plate is extremely small, and the arrester valve plate can be approximately regarded as a parallel circuit of a nonlinear resistor and a capacitor. The total leakage current flowing through the valve plate is mainly resistive current and capacitive current components;

The third step is to collect the bus voltage through the voltage transformer;

The fourth step is to discretely digitize the collected arrester total leakage current and bus voltage, and obtain the fundamental value of the total leakage current and bus voltage in the frequency domain and the phase and amplitude of each harmonic through Fourier transform. And separate the real-time total resistive current value, resistive current fundamental wave value and resistive current harmonic value from the real-time total leakage current;

The fifth step is to compare the total resistive current value, resistive current fundamental wave value and resistive current harmonic value separated from the real-time total leakage current with the previous total resistive current value and resistive current fundamental wave value of the arrester Compared vertically with each harmonic value of the resistive current, if the percentage of the resistive current to the total leakage current increases significantly, the fundamental wave has a larger increase than the first measured value, while the harmonic does not increase significantly compared to the first measured value, It can be determined that the arrester is polluted or the interior is damp; if the percentage of resistive current in the total leakage current increases significantly, among them, the harmonic wave has a larger increase than the first measurement value, and the fundamental wave does not increase significantly compared with the first measurement value, it can be determined as The arrester is aging.

In the above technical solution, the discrete digitization of the collected arrester total leakage current and bus voltage refers to digitizing the discrete signals of the arrester total leakage current and bus voltage, so that the function values of the discrete signals only take finite values.

In the above technical solution, the total leakage current of the lightning arrester and the bus voltage collected are discretely digitized, and the fundamental wave value and each harmonic of the total leakage current and the bus voltage are obtained in the frequency domain through Fourier transform and operation. The phase and magnitude of , specifically:

The grid voltage and the total leakage current all satisfy the Dirichli condition, and the Fourier expansion of the bus voltage is:

In the formula, U ₀ is the DC voltage value, U _km is the kth harmonic amplitude, m is the maximum value, α _k is the kth harmonic phase angle of the bus voltage, ω is the angular frequency, t is the initial time, and k is each Sub-harmonic components, k=1, 2, 3....

The Fourier expansion of the total leakage current is:

In the formula, I ₀ is the DC component of the total leakage current, I _km is the k-order harmonic amplitude of the total leakage current, and β _k is the k-order harmonic phase angle of the total leakage current.

In the small current region, the capacitance is almost constant, and the capacitive component of the total leakage current can be obtained from (5-1):

In the above formula, the kth harmonic amplitude of the capacitive component of the total leakage current is: I _ckm =kωCU _km .

Because the bus voltage and the resistive component of the leakage current are in the same phase, their harmonics are also in the same phase. If I _rk is the resistive current amplitude of the kth harmonic, the resistive current is:

And because i _x =i _r + _ic , substituting (5-2), (5-3), and (5-4) into it has:

Multiply both sides of the formula (5-5) by sin(nωt+α _n ) at the same time, and take the definite integral within a certain period, there is:

According to the orthogonality property of the product of trigonometric functions in one cycle:

For formula (5-6), only when k=n, the definite integral of the corresponding item is not equal to 0, which can be simplified as:

Using the integral and difference formulas of trigonometric functions to simplify (5-9):

Using the orthogonal properties of trigonometric functions, we can get:

have to:

have to:

F:

I _rk =I _km cos(β _k -α _k )=I _km [cos α _k cos β _k +sin α _k sin β _k ] (5-13)

Similarly, multiply both sides of (5-5) by cos(nωt+α _n ) at the same time, and take the definite integral in the same period. According to the orthogonality characteristic of trigonometric functions, the definite integral is not zero only when k=n item. After simplification, the harmonics of the capacitive current can be obtained as:

I _ck ＝I _km sin(β _k -α _k )＝I _km [cos α _k cos β _k -sin α _k sin β _k ] (5-14)

This method is used to separate the total resistive current value, resistive current fundamental wave value and resistive current harmonic values from the total leakage current.

The above total leakage current is divided into two parts: capacitive current value and resistive current value, so it is separated from the total leakage current value; the purpose of collecting the bus voltage is to calculate the capacitive component of the total leakage current, from the formula (5-1) The formula (5-3) can be obtained by transformation, and the final result formula (5-14) reflects that α _k is the kth harmonic phase angle of the bus voltage.

In the above technical solution, when pollution and internal damp faults are alarmed, the setting values of resistive current proportion, fundamental wave growth amplitude and harmonic growth amplitude are 0-99 online; , The setting value of fundamental wave growth amplitude and harmonic growth amplitude can be set online from 0 to 99.

The lightning arrester online monitoring method and device based on the Internet of Things communication of the present invention remotely transmits the collected data to the main station through the Internet of Things communication. If the lightning arrester fails, the host machine will send a fault alarm signal, and the monitoring personnel will notify the maintenance personnel to go to the site for inspection Repair or replace the arrester. It greatly reduces the complexity of manual inspection work and the loss caused by power failure tests. It can automatically collect data and transmit the data to the monitoring room remotely, which is convenient for monitoring personnel to find faults and defects of arresters in time and replace arresters under necessary conditions. The lightning arrester in the system implements intelligent, real-time and reliable monitoring, eliminates hidden troubles and improves power supply reliability.

Advantage effect

(1) Accurate measurement, adopts high-precision active zero-flux feedthrough transformer, and automatically selects the magnification according to the magnitude of the measured ground current to achieve high-precision measurement.

(2) The data is reliable. The measurement unit has a complete fault detection mechanism, which can timely and accurately reflect the working status of the arrester, ensuring the authenticity and accuracy of the data source.

(3) The degree of automation is high. By sampling and analyzing the leakage current of the arrester and the bus voltage, the unmanned online monitoring of the arrester equipment in the substation is realized, and the operating status of the arrester can be judged more accurately and effectively.

(4) The system is flexible, reliable, and low in investment cost. GSM/GPRS is used for communication between the detection device and the system master station. The above communication configuration enhances the reliability, flexibility and applicability of the system, and saves a lot of construction costs for network communication infrastructure.

(5) The maintenance is simple, the device adopts a modular design, meets the standardization requirements, has a high degree of versatility and interchangeability, and can repair or replace all components including sensors without affecting the operation of the equipment.

Description of drawings:

Fig. 1 is the structural schematic diagram of the device complete machine of the present invention;

Fig. 2 is a working principle diagram of the sampling module of the present invention;

Fig. 3 is the detection principle diagram of lightning arrester of the present invention;

Fig. 4 is a simulation diagram of the equivalent circuit of the arrester valve plate of the present invention.

Detailed ways:

Referring to Figure 1, the lightning arrester online monitoring device based on Internet of Things communication includes a sampling module, a CPU module, a liquid crystal display module, a wireless communication module, an ambient temperature detection module, and a power supply module.

(1) Sampling module module

The sampling module includes a voltage transformer, a current transformer, a second-order filter circuit, and an ADC conversion circuit. After the sampling signal is filtered by an active second-order filter circuit, the third harmonic component of the leakage current is obtained. The third harmonic component of the leakage current and the grid voltage are obtained through 16-bit ADC analog-to-digital conversion with high sampling accuracy. The ADC converter uses hardware phase-locked loop technology for follow-up frequency acquisition, and each power frequency cycle is designed to sample 128 points for analysis and calculation of the third harmonic component of leakage current.

(2) CPU module

Adopt high-performance 32-bit DSP chip provided by Texas Instruments, powerful data processing function, support at least 16 channels of analog quantity acquisition and 32 channels of programmable digital quantity, support two channels of SPI serial ports, 4 channels of general-purpose serial ports, which is the core part of the entire system operation , Data acquisition, fault judgment, and remote communication of the control device.

(3) Liquid crystal display module

Centralized display of device information and human-computer interaction interface for parameter modification.

(4) Wireless communication module

The main function is short-distance wireless communication GSM/GPRS (to the main station of the system), which transmits the operation information and fault alarm signals of the arrester device in a wireless form, and conducts two-way communication with the main station.

(5) Ambient temperature monitoring module

Obtain the internal ambient temperature of the device through the temperature sensor

(6) Power module

The power module adopts AC/DC220V to DC5V, 12V, 24V switching power supply to provide a stable DC5V power supply for the device, and reserves one DC12V and DC24V power output.

The main functions and characteristics of the lightning arrester online monitoring device based on Internet of Things communication of the present invention are as follows:

(1) Collect the leakage current and reference voltage of the arrester device, calculate the fundamental wave and the third harmonic of the lightning arrester current, count the number of lightning strikes and the lightning strike time, etc.;

(2) Collect the bus voltage and reference voltage of the PT unit, and calculate the fundamental wave and the third harmonic component of the bus voltage;

(3) Support system time synchronization;

(4) Wireless upload of measurement data and alarm information;

(5) Safe and reliable, the voltage channel adopts isolated V/I conversion, so as to avoid short circuit of PT secondary side and reduce signal distortion;

(6) High-precision temperature and humidity sensors are used to collect the internal temperature and humidity of the device in real time;

(7) Equipment self-inspection;

(8) Remote parameter modification and program upgrade;

The main technical parameters

(1) Measurement range of AC reference voltage: ≦500kV;

(2) Leakage current measurement: 100μA～100mA accuracy 1%;

(3) Capacitive current measurement: 100μA～100mA accuracy 5%;

(4) The third harmonic current: 100μA～100mA, the accuracy is 5%;

(5) Resistive current measurement: 100μA～100mA accuracy 5%;

(6) Current sampling method: The current channel is a sampling method of built-in core-through small current sensor, and the information distortion is small;

(7) Voltage sampling method: wired mode (the voltage signal of the voltage transformer (or the instrument winding of the experimental transformer) is connected to the voltage channel through the supporting V/I conversion active sensor as a reference voltage signal);

(8) Power supply mode: AC220V or internal battery;

(9) Communication method: GSM/GPRS (to the system master station).

The lightning arrester online monitoring method based on Internet of Things communication of the present invention is as follows:

During the operation of the zinc oxide arrester, when the internal valve plate of the arrester is aging, damp and the surface is dirty, the total leakage current does not change much, but the resistive current accounting for 10%-20% of the total leakage current increases greatly, so the resistive current In order to sensitively reflect the deterioration process of the zinc oxide arrester. Due to the non-linear volt-ampere characteristics of the resistance of the zinc oxide valve, the resistive current flowing contains fundamental, third, fifth and higher harmonics, and the magnitude of the fundamental component of the resistive current is not affected by the higher order of the power grid. Harmonic interference, and can reliably reflect the deterioration of the arrester.

Since the arrester is in the small current region for a long time, the high-frequency component flowing through the valve plate is extremely small, so the valve plate of the arrester can be approximately regarded as a parallel circuit of a nonlinear resistor and a capacitor. The total leakage current flowing through the valve plate is mainly resistive and capacitive current components, and its equivalent circuit is shown in the simulation diagram shown in Figure 4:

I _x =I _r +I _c , where I _x is the leakage current, I _r is the resistive current, and I _c is the capacitive current.

The total leakage current of the arrester and the bus voltage collected by the device of the present invention are discretely digitized, and the fundamental wave values of the current and voltage as well as each

Subharmonic phase and amplitude.

The grid voltage and the total leakage current all satisfy the Dirichli condition, and the Fourier expansion of the bus voltage is:

In the formula, U ₀ is the DC voltage value, U _km is the kth harmonic amplitude, m is the maximum value, α _k is the kth harmonic phase angle of the bus voltage, ω is the angular frequency, t is the initial time, and k is each Sub-harmonic components, k=1, 2, 3....

The Fourier expansion of the total leakage current is:

In the formula, I ₀ is the DC component of the total leakage current, I _km is the k-order harmonic amplitude of the total leakage current, and β _k is the k-order harmonic phase angle of the total leakage current.

In the small current region, the capacitance is almost constant, and the capacitive component of the total leakage current can be obtained from (5-1):

In the above formula, the kth harmonic amplitude of the capacitive component of the total leakage current is: I _ckm =kωCU _km ;

Because the bus voltage and the resistive component of the leakage current are in the same phase, their harmonics are also in the same phase. If I _rk is the resistive current amplitude of the kth harmonic, the resistive current is:

And because i _x =i _r + _ic , substituting (5-2), (5-3), and (5-4) into it has:

Multiply both sides of the formula (5-5) by sin(nωt+α _n ) at the same time, and take the definite integral within a certain period, there is:

According to the orthogonality property of the product of trigonometric functions in one cycle:

For formula (5-6), only when k=n, the definite integral of the corresponding item is not equal to 0, which can be simplified as:

Using the integral and difference formulas of trigonometric functions to simplify (5-9):

Using the orthogonal properties of trigonometric functions, we can get:

have to:

have to:

F:

I _rk =I _km cos(β _k -α _k )=I _km [cos α _k cos β _k +sin α _k sin β _k ] (5-13)

Similarly, multiply both sides of (5-5) by cos(nωt+α _n ) at the same time, and take the definite integral in the same period. According to the orthogonality characteristic of trigonometric functions, the definite integral is not zero only when k=n item. After simplification, the harmonics of the capacitive current can be obtained as:

I _ck ＝I _km sin(β _k -α _k )＝I _km [cos α _k cos β _k -sin α _k sin β _k ] (5-14)

The total leakage current is divided into two parts: capacitive current value and resistive current value, so it is expressed as separated from the total leakage current value; collecting the bus voltage is also to calculate the capacitive component of the total leakage current, from the formula (5-1 ) can be transformed into formula (5-3), and the final result formula (5-14) can also reflect that α _k is the kth harmonic phase angle of the bus voltage.

Using this method to separate the total resistive current value, resistive current fundamental wave value and resistive current harmonic value from the total leakage current, and through longitudinal comparison with the previous measured values, the operation of the arrester can be comprehensively analyzed working conditions.

If the percentage of the resistive current in the total leakage current increases significantly, and the fundamental wave has a larger increase than the first measured value, but the harmonic does not increase significantly compared with the first measured value, it can be determined that the arrester is polluted or the interior is damp; if the resistive The percentage of the current to the total leakage current has increased significantly. Among them, the harmonic has a larger increase than the first measured value, and the fundamental wave has not increased significantly compared with the first measured value. It can be determined that the arrester is aging.

Fault judgment:

Pollution, internal damp fault alarm: resistive current proportion, fundamental wave growth amplitude, harmonic growth amplitude, setting value 0-99 can be set online.

Arrester aging alarm: resistive current proportion, fundamental wave growth amplitude, harmonic growth amplitude, setting value 0-99 can be set online.

Claims (6)

1. A lightning arrester online monitoring device based on Internet of Things communication, is characterized in that: take CPU module as core, the input end of described CPU module is connected with sampling module, ambient temperature detection module and power supply module, described adoption module connects lightning arrester A current transformer and a voltage transformer, the ambient temperature detection module is connected to the temperature sensor of the lightning arrester, the power supply module is connected to the mains power supply; the output end of the CPU module is connected to a liquid crystal display module, and the liquid crystal display module is connected to a liquid crystal display ; The CPU module is also connected with a communication module and communicates with the communication module, and the communication module communicates wirelessly with the system master station of the intelligent substation. 2. The lightning arrester online monitoring device based on Internet of Things communication according to claim 1, characterized in that: the sampling module includes a current transformer and a voltage transformer of the lightning arrester, an active second-order filter circuit, and an ADC converter, The ADC converter is a converter that converts analog quantities into digital quantities. The ADC converter uses hardware phase-locked loop technology for follow-up acquisition, and each power frequency cycle is designed to analyze the third harmonic component of the metering leakage current. 128 sampling points. 3. A lightning arrester online monitoring method based on Internet of Things communication, characterized in that: comprising: The first step is to measure the total leakage current from the middle point of the lower end of the three-phase arrester to the ground: connect the upper ends of the three-phase arrester to the three-phase grid bus, and connect the lower ends of the three-phase arrester together to form the middle point of the connection, and connect the three-phase arrester to the middle point. From the midpoint to the ground, collect the total leakage current from the midpoint to the ground through the current transformer. When the insulation performance of the three-phase arrester is normal, the sum of the third harmonics of the three-phase leakage current is very small. When a certain phase arrester appears When a fault occurs, the phase amplitude of the fundamental component of the leakage current of each phase will change, resulting in the inability of each component to cancel each other out, resulting in a substantial increase in the total leakage current value, and this increase in the total leakage current is used as the characteristic quantity of the arrester fault diagnosis; In the second step, the resistive current fundamental wave component of the total leakage current is used as the characteristic quantity reflecting the deterioration process of the arrester: during the operation of the arrester, when the internal valve plate is aging, damp and the surface is dirty, the total leakage current does not change much, but accounts for The resistive current of 10-20% of the total leakage current is greatly increased, so the resistive current can sensitively reflect the deterioration process of the arrester; because the resistance of the zinc oxide valve plate of the arrester has nonlinear volt-ampere characteristics, the flowing resistive current contains basic Wave, third, fifth and higher harmonics, in which the fundamental wave component of the resistive current is not disturbed by the higher harmonics of the power grid, and can reflect the deterioration process of the arrester; because the arrester is in the small current area for a long time, the flow through The high-frequency component of the valve plate is extremely small, and the arrester valve plate can be approximately regarded as a parallel circuit of a nonlinear resistor and a capacitor. The total leakage current flowing through the valve plate is mainly resistive current and capacitive current components; The third step is to collect the bus voltage through the voltage transformer; The fourth step is to discretely digitize the collected arrester total leakage current and bus voltage, and obtain the fundamental value of the total leakage current and bus voltage in the frequency domain and the phase and amplitude of each harmonic through Fourier transform. And separate the real-time total resistive current value, resistive current fundamental wave value and resistive current harmonic value from the real-time total leakage current; The fifth step is to compare the total resistive current value, resistive current fundamental wave value and resistive current harmonic value separated from the real-time total leakage current with the previous total resistive current value and resistive current fundamental wave value of the arrester Compared vertically with each harmonic value of the resistive current, if the percentage of the resistive current to the total leakage current increases significantly, the fundamental wave has a larger increase than the first measured value, while the harmonic does not increase significantly compared to the first measured value, It can be determined that the arrester is polluted or the interior is damp; if the percentage of resistive current in the total leakage current increases significantly, among them, the harmonic wave has a larger increase than the first measurement value, and the fundamental wave does not increase significantly compared with the first measurement value, it can be determined as The arrester is aging. 4. The lightning arrester online monitoring method based on Internet of Things communication according to claim 3, characterized in that: said carrying out discrete digitization of the lightning arrester total leakage current and bus voltage collected refers to the arrester total leakage current, bus voltage The discrete signal is digitized so that the function value of the discrete signal only takes a finite value. 5. The lightning arrester online monitoring method based on Internet of Things communication according to claim 3, characterized in that: said total leakage current of the lightning arrester and the bus voltage of the collection are carried out to discrete digitization, through Fourier transform and calculation, in the frequency domain Calculate the fundamental value of the total leakage current and the bus voltage and the phase and amplitude of each harmonic, specifically: The grid voltage and the total leakage current all satisfy the Dirichli condition, and the Fourier expansion of the bus voltage is: In the formula, U ₀ is the DC voltage value, U _km is the kth harmonic amplitude, m is the maximum value, α _k is the kth harmonic phase angle of the bus voltage, ω is the angular frequency, t is the initial time, and k is each Sub-harmonic components, k=1, 2, 3.... The Fourier expansion of the total leakage current is: In the formula, I ₀ is the DC component of the total leakage current, I _km is the k-order harmonic amplitude of the total leakage current, and β _k is the k-order harmonic phase angle of the total leakage current. In the small current region, the capacitance is almost constant, and the capacitive component of the total leakage current can be obtained from (5-1): In the above formula, the kth harmonic amplitude of the capacitive component of the total leakage current is: I _ckm =kωCU _km ; Because the bus voltage and the resistive component of the leakage current are in the same phase, their harmonics are also in the same phase. If I _rk is the resistive current amplitude of the kth harmonic, the resistive current is: And because i _x =i _r + _ic , substituting (5-2), (5-3), and (5-4) into it has: Multiply both sides of the formula (5-5) by sin(nωt+α _n ) at the same time, and take the definite integral within a certain period, there is: According to the orthogonality property of the product of trigonometric functions in one cycle: For formula (5-6), only when k=n, the definite integral of the corresponding item is not equal to 0, which can be simplified as: Using the integral and difference formulas of trigonometric functions to simplify (5-9): Using the orthogonal properties of trigonometric functions, we can get: have to: have to: F: I _rk =I _km cos(β _k -α _k )=I _km [cos α _k cos β _k +sin α _k sin β _k ] (5-13) Similarly, multiply both sides of (5-5) by cos(nωt+α _n ) at the same time, and take the definite integral in the same period. According to the orthogonality characteristic of trigonometric functions, the definite integral is not zero only when k=n item. After simplification, the harmonics of the capacitive current can be obtained as: I _ck ＝I _km sin(β _k -α _k )＝I _km [cos α _k cos β _k -sin α _k sin β _k ] (5-14) Use this method to separate the total resistive current value, resistive current fundamental wave value and resistive current harmonic values from the total leakage current; The total leakage current is divided into two parts: capacitive current value and resistive current value, so it is separated from the total leakage current value; the bus voltage is collected to calculate the capacitive component of the total leakage current, which is transformed from formula (5-1) The formula (5-3) can be obtained, and the final result formula (5-14) reflects that α _k is the kth harmonic phase angle of the bus voltage. 6. The lightning arrester online monitoring method based on Internet of Things communication according to claim 3, characterized in that: when pollution and internal damp faults are alarmed, the resistive current proportion, fundamental wave growth amplitude and harmonic growth amplitude are set The value 0-99 can be set online; when the arrester is aging and alarming, the setting values of resistive current proportion, fundamental wave growth amplitude and harmonic growth amplitude 0-99 can be set online.