Zinc oxide arrester aging fault monitoring method and system based on fifth harmonic

Abstract

The invention discloses a zinc oxide arrester aging fault monitoring method and system based on fifth harmonics, and belongs to the technical field of high-voltage electrical equipment protection. The method comprises the following steps: acquiring the total leakage current of the zinc oxide arrester under different applied voltages; the different applied voltages comprise pure sine wave voltages and voltages with harmonic components; according to the total leakage current, obtaining leakage resistance current and third harmonic and fifth harmonic thereof; comparing the total leakage current, the leakage resistance current, the third harmonic and the fifth harmonic to obtain a monitoring index of the aging fault of the zinc oxide arrester; and obtaining a monitoring result of the aging fault of the zinc oxide arrester according to the monitoring index of the aging fault of the zinc oxide arrester and the applied voltage. According to the invention, the harmonic component is added into the applied voltage to simulate the harmonic interference of the power grid voltage, and the leakage current of the lightning arrester is analyzed to monitor whether the aging fault of the zinc oxide lightning arrester occurs.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage electrical equipment protection, and in particular to a method and system for monitoring the aging fault of zinc oxide lightning arresters based on fifth harmonics. Background Art

[0002] Zinc oxide lightning arresters are used to protect against transient overvoltages caused by severe lightning strikes and power grid switching operations. They have advantages such as good protection characteristics, fast response characteristics, and large current-carrying capacity, and are widely used in power systems. Any damaged or faulty lightning arrester will interfere with the normal operation of other electrical equipment in the power grid. Generally, after the valve disc of the lightning arrester fails, its conductivity will increase, and when the inner wall of the porcelain jacket is affected by moisture, surface creepage will occur, resulting in local heating. In severe cases, the lightning arrester may explode due to internal flashover breakdown, seriously affecting the normal operation of the zinc oxide lightning arrester. Therefore, it is necessary to monitor the faults and abnormalities of zinc oxide lightning arresters online to facilitate the replacement of the tripped lightning arresters.

[0003] Existing research has proposed various methods for monitoring the fault status of zinc oxide lightning arresters, such as the residual voltage method, power loss measurement method, leakage current measurement method, capacitive current compensation method, harmonic analysis method, etc. Among them, the leakage current measurement method is convenient for detection and has high result accuracy, and is one of the most widely used state evaluation technologies for lightning arresters.

[0004] After a zinc oxide lightning arrester fails, the total leakage current will increase significantly, and the waveform will also be significantly distorted. The total leakage current is the vector sum of the leakage resistance component and the leakage capacitance component As shown in Figure 1 , where the leakage resistance current is affected by the voltage applied to the lightning arrester, fault characteristics, and ambient temperature, and shows higher sensitivity to the faults and deterioration of the lightning arrester. Moreover, the change in the third harmonic of the resistance current is more significant than that of the fundamental wave. By analyzing the content of the third harmonic of the resistance current, the diagnosis of the fault status of the lightning arrester can be achieved. However, in addition to the influence of lightning arrester faults, the third harmonic of the resistance current is also affected by the harmonics in the grid voltage, especially the third harmonic of the voltage has a significant influence on the third harmonic of the resistance current, making it unable to accurately reflect the fault condition of the lightning arrester.

[0005] However, current research relies on the measurement of grid voltage harmonics, which increases the detection amount and calculation amount, and is not conducive to the rapidity and accuracy of online monitoring and positioning of lightning arrester faults. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies in the prior art and provide a method for monitoring the aging fault of zinc oxide arresters based on the fifth harmonic. Harmonic components are added to the applied voltage to simulate the harmonic interference of the grid voltage, and the leakage current of the arrester is analyzed to monitor whether the zinc oxide arrester has an aging fault.

[0007] To achieve the above object, the present invention is implemented by the following technical solutions:

[0008] On the one hand, the present invention provides a method for monitoring the aging fault of zinc oxide arresters based on the fifth harmonic, including:

[0009] Obtain the total leakage current of the zinc oxide arrester under different applied voltages; the different applied voltages include pure sine wave voltage and voltage with harmonic components;

[0010] According to the total leakage current, obtain the leakage resistance current and its third harmonic and fifth harmonic;

[0011] Compare the total leakage current, the leakage resistance current and its third harmonic and fifth harmonic to obtain the monitoring index of the aging fault of the zinc oxide arrester;

[0012] According to the monitoring index of the aging fault of the zinc oxide arrester and the applied voltage, obtain the monitoring result of the aging fault of the zinc oxide arrester.

[0013] Optionally, the voltage with harmonic components includes voltage third harmonic, voltage fifth harmonic, voltage seventh harmonic, voltage ninth harmonic and voltage eleventh harmonic.

[0014] Optionally, the shift current method is adopted. According to the total leakage current, obtain the leakage resistance current and its third harmonic and fifth harmonic, including:

[0015] Delay the original waveform of the total leakage current by one-quarter of its period to obtain a delayed waveform, and superimpose the original waveform of the total leakage current and the delayed waveform to obtain a superimposed waveform;

[0016] Use a peak time detector to obtain the peak time of the superimposed waveform, and delay the peak time of the superimposed waveform by one-quarter of its period to obtain the peak time of the capacitive current component;

[0017] Use a frequency detector to determine the frequency of the total leakage current to obtain the frequency of the capacitive current component;

[0018] Generate a capacitive current component waveform according to the frequency of the capacitive current component, the peak time of the capacitive current component and the peak amplitude of the capacitive current component, wherein the peak amplitude of the capacitive current component is the same as the peak amplitude of the total leakage current;

[0019] Subtract the total leakage current from the capacitive current component to obtain the leakage resistance current;

[0020] Perform a fast Fourier transform on the leakage resistance current to obtain the third harmonic and fifth harmonic of the leakage resistance current.

[0021] Optionally, compare the total leakage current, leakage resistance current, its third harmonic, and fifth harmonic of the zinc oxide arrester to obtain the monitoring indicators for the aging failure of the zinc oxide arrester, including:

[0022] Compare the peak changes of the total leakage current and leakage resistance current under voltage harmonics, and use the leakage resistance current as the preliminary monitoring indicator for the aging failure of the zinc oxide arrester;

[0023] Compare the peak changes of the third harmonic and fifth harmonic of the leakage resistance current under voltage harmonics, as well as the harmonic sensitivity of the third harmonic and fifth harmonic of the leakage resistance current, and use the fifth harmonic of the leakage resistance current as the final monitoring indicator for the aging failure of the zinc oxide arrester.

[0024] Optionally, the calculation formula for the harmonic sensitivity is:

[0025] ;

[0026] Where, represents the harmonic sensitivity; represents the total number of voltage experiments; 、 respectively represent the leakage current characteristic values under the i-th and i+1-th voltage experiments; 、 respectively represent the harmonic contents of the voltages applied across the zinc oxide arrester under the i-th and i+1-th voltage experiments.

[0027] Optionally, according to the monitoring indicators for the aging failure of the zinc oxide arrester and the applied voltage, obtain the monitoring results for the aging failure of the zinc oxide arrester, including:

[0028] In response to the applied voltage being within the first voltage range and the fifth harmonic of the leakage resistance current being greater than the first current threshold, the zinc oxide arrester has an aging failure; in response to the applied voltage not being within the first voltage range or the fifth harmonic of the leakage resistance current not being greater than the first current threshold, the zinc oxide arrester does not have an aging failure;

[0029] In response to the applied voltage being within the second voltage range and the fifth harmonic of the leakage resistance current being greater than the second current threshold, the zinc oxide arrester has an aging failure; in response to the applied voltage not being within the second voltage range or the fifth harmonic of the leakage resistance current not being greater than the second current threshold, the zinc oxide arrester does not have an aging failure;

[0030] When the applied voltage is within the third voltage range and the fifth harmonic of the leakage resistance current is greater than the third current threshold, the zinc oxide lightning arrester experiences an aging failure; when the applied voltage is not within the third voltage range or the fifth harmonic of the leakage resistance current is not greater than the third current threshold, the zinc oxide lightning arrester does not experience an aging failure; wherein, the fifth harmonic of the leakage resistance current is a monitoring index for the aging failure of the zinc oxide lightning arrester.

[0031] In a second aspect, the present invention provides a monitoring system for aging failure of zinc oxide lightning arresters based on the fifth harmonic, including:

[0032] A total leakage current acquisition module that acquires the total leakage current of the zinc oxide lightning arrester under different applied voltages; the different applied voltages include a pure sine wave voltage and a voltage with harmonic components;

[0033] A leakage resistance current calculation module that obtains the leakage resistance current and its third harmonic and fifth harmonic based on the total leakage current;

[0034] A monitoring index calculation module that compares the total leakage current, the leakage resistance current and its third harmonic and fifth harmonic to obtain a monitoring index for the aging failure of the zinc oxide lightning arrester;

[0035] A monitoring result calculation module that obtains a monitoring result for the aging failure of the zinc oxide lightning arrester based on the monitoring index for the aging failure of the zinc oxide lightning arrester and the applied voltage.

[0036] In a third aspect, the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the steps in the method for monitoring aging failure of zinc oxide lightning arresters based on the fifth harmonic as described in the first aspect.

[0037] In a fourth aspect, the present invention provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, it implements the steps in the method for monitoring aging failure of zinc oxide lightning arresters based on the fifth harmonic as described in the first aspect.

[0038] Compared with the prior art, the beneficial effects achieved by the present invention:

[0039] The present invention adds harmonic components to the applied voltage to simulate the harmonic interference of the grid voltage, analyzes the leakage current of the lightning arrester, and explores the changes in characteristic quantities under voltage harmonic interference, so as to reliably monitor whether the zinc oxide lightning arrester has an aging failure. This method has stronger anti-harmonic interference ability and is more suitable for the monitoring and positioning of aging failures of zinc oxide lightning arresters than the existing third harmonic analysis method. Description of the Drawings

[0040] Figure 1The following is a schematic structural diagram of the equivalent circuit model of the zinc oxide lightning arrester of the present invention in an embodiment;

[0041] Figure 2 The following is a schematic flow diagram of the method for monitoring the aging fault of the zinc oxide lightning arrester based on the fifth harmonic of the present invention in an embodiment;

[0042] Figure 3 The following is a schematic flow diagram of the harmonic extraction of the leakage resistance current of the present invention in an embodiment;

[0043] Figure 4 The following is a schematic experimental principle diagram of the present invention in an embodiment;

[0044] Figure 5 The following is a diagram of the voltage harmonic content of the present invention in an embodiment;

[0045] Figure 6 The following is a model of the shift current method of the present invention in an embodiment;

[0046] Figure 7 The following is a diagram of the percentage change of IT and IR of the present invention in an embodiment;

[0047] Figure 8 The following are the IR3rd and IR5th peak diagrams of the lightning arrester in the normal state of the present invention in an embodiment;

[0048] Figure 9 The following are the IR3rd and IR5th peak diagrams of the lightning arrester in the aging fault state of the present invention in an embodiment;

[0049] Figure 10 The following is a comparison diagram of the IR3rd and IR5th peaks between the normal state and the aging fault state of the present invention in an embodiment;

[0050] Figure 11 The following is a comparison diagram of the percentage change of IR3rd and IR5th between the normal state and the aging fault state under harmonic interference of the present invention in an embodiment;

[0051] Figure 12 The following is a schematic diagram of the principle of the method for monitoring and positioning the zinc oxide lightning arrester of the present invention in an embodiment. Specific embodiments

[0052] The technical solution of the present invention will be described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. Without conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0053] The term "and / or" is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, the character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0054] Embodiment 1

[0055] As Figure 2 shown, this embodiment introduces a method for monitoring the aging fault of zinc oxide arresters based on the fifth harmonic. Aiming at the existing technology that relies on the measurement of power grid voltage harmonics, which increases the detection amount and calculation amount and is not conducive to the rapidity and accuracy of on-line monitoring and positioning of arrester faults, this embodiment uses the fifth harmonic of the leakage resistance current as a new index for monitoring and positioning the faults of zinc oxide arresters. Harmonic components are added to the applied voltage to simulate the power grid voltage harmonic interference. According to Figure 1 the mathematical model of the arrester shown, the leakage current of the arrester is analyzed, the leakage resistance current is extracted by the shift current method, the fast Fourier transform (FFT) algorithm is executed to determine the harmonic components of the resistance current, and the change of characteristic quantities under voltage harmonic interference is explored. The method includes the following steps:

[0056] Step 1: Obtain the total leakage current of the zinc oxide arrester under different applied voltages, specifically:

[0057] As Figure 3 shown, first, build an experimental circuit. The schematic diagram of the experimental circuit is as Figure 4 shown, including an adjustable low-voltage power supply, a voltage regulator, an inductor, a step-up transformer, a capacitive voltage divider, a resistor, a zinc oxide arrester, and a high-precision current sensor; apply a voltage of 70 - 120 kV to the arrester through the adjustable low-voltage power supply, the inductor, and the step-up transformer, use the capacitive voltage divider to detect the applied voltage and obtain the harmonic components of the applied voltage based on the FFT algorithm, use the high-precision current sensor to extract the total leakage current, and use the resistor to protect the circuit.

[0058] Secondly, determine the applied voltage. The applied voltage includes Scheme 1 and Scheme 2. Scheme 1 is a pure sine wave voltage, and Scheme 2 is a voltage with harmonic components;

[0059] The voltage with harmonic components is a voltage with a total harmonic distortion of 5% to simulate the harmonic influence in the power grid, including the voltage third harmonic, the voltage fifth harmonic, the voltage seventh harmonic, the voltage ninth harmonic, and the voltage eleventh harmonic. In this embodiment, the contents of the voltage third harmonic V3rd, the voltage fifth harmonic V5th, the voltage seventh harmonic V7th, the voltage ninth harmonic V9th, and the voltage eleventh harmonic V11th are 3.6%, 1.8%, 1.21%, 0.95%, and 0.5% respectively, asFigure 5 as shown

[0060] Then, based on the established experimental circuit and the determined applied voltage, the total leakage current of the zinc oxide lightning arrester is obtained. In this embodiment, the parameters of the lightning arrester in the normal state are shown in Table 1.

[0061] Table 1 Parameters of Zinc Oxide Lightning Arrester in Normal State

[0062]

[0063] Adjust the low-voltage voltage source, apply a voltage of 70 - 120 kV to the zinc oxide lightning arrester through the step-up transformer, and measure the total leakage current IT.

[0064] Step 2: Adopt the shifted current method. According to the total leakage current, obtain the leakage resistance current, its third harmonic, and fifth harmonic. Specifically:

[0065] As Figure 6 shown is the Simulink model of the shifted current method. Input the total leakage current into the zero-crossing detector to determine the original waveform of the total leakage current.

[0066] Use the frequency detector to determine the frequency of the total leakage current and obtain the frequency of the capacitive current component; the frequency of the total leakage current is equal to the frequency of the capacitive current component.

[0067] Introduce the waveform of the total leakage current into a delay of one-quarter of its period to obtain a delayed waveform, and superimpose the original waveform of the total leakage battery and the delayed waveform to obtain a superimposed waveform.

[0068] Use the peak time detector to determine the peak time of the superimposed waveform, and delay the peak time of the superimposed waveform by one-quarter of its period to obtain the peak time of the capacitive current component.

[0069] Use the frequency of the capacitive current component, the peak time of the capacitive current component, and the peak amplitude of the capacitive current component to generate the waveform of the capacitive current component, where the peak amplitude of the capacitive current component is the same as the peak amplitude of the total leakage current.

[0070] By subtracting the capacitive current component IC from the total leakage current, finally extract the leakage resistance current IR.

[0071] After that, use the FFT algorithm for the leakage resistance current IR to determine the third harmonic IR3rd of the leakage resistance current IR and the fifth harmonic IR5th of the leakage resistance current IR. Conduct experiments on the zinc oxide lightning arrester respectively under the conditions of pure sine wave voltage and voltage with harmonic components, and measure and record the total leakage current IT, the leakage resistance current IR, its third harmonic IR3rd, and fifth harmonic IR5th.

[0072] The principle of the traditional capacitive current compensation method is that the capacitive current leads the system voltage by 90 degrees. In the displacement current method of this embodiment, compared with the traditional capacitive current compensation method, the system voltage is shifted forward by 90 degrees and inverted to compensate the capacitive current, so that the resistive current can be measured. There is no need to introduce voltage measurement using a voltage divider, and modules such as a frequency detector and a delay device are added to generate a quarter-cycle delay waveform, and then a leakage current waveform is generated.

[0073] Step 3: Compare the total leakage current, leakage resistance current, its third harmonic, and fifth harmonic to obtain the monitoring indicators for the aging failure of the zinc oxide arrester, specifically:

[0074] Under the conditions of pure sine wave voltage and voltage with harmonic components, a voltage of 70 - 120 kV was applied to the zinc oxide arrester respectively, and the peak value of the total leakage current IT was measured, as shown in Table 2.

[0075] Table 2 Total leakage current IT of two schemes

[0076]

[0077] The leakage resistance current IR was extracted from the total leakage current IT using the displacement current method, and its peak value was read, as shown in Table 3.

[0078] Table 3 Leakage resistance current IR of two schemes

[0079]

[0080] It can be seen from Table 2 and Table 3 that due to the addition of voltage harmonic components in the voltage with harmonic components, the total leakage current IT increased by 9.3 µA under the rated voltage, and the leakage resistance current IR increased by 11.5 µA. Calculate the percentage changes of the total leakage current IT and the leakage resistance current IR under the condition of voltage with harmonic components, as Figure 7 shown. The percentage increase of IT under the rated voltage is 0.63%, and the percentage increase of IR is 1.32%. It can be judged that the increase in the peak value of IR caused by voltage harmonics is more obvious than that of IT, because IR is more sensitive to the change of voltage harmonics. Therefore, the leakage resistance current IR is used as the preliminary monitoring indicator for the aging failure of the zinc oxide arrester;

[0081] Using the FFT algorithm for the leakage resistance current IR, the peak amplitudes of IR3rd and IR5th were calculated, as shown in Table 4.

[0082] Table 4 Peak amplitudes of IR3rd and IR5th

[0083]

[0084] In Solution 1, the amplitude and nonlinearity of the leakage resistance current IR change with the applied voltage, and there are harmonic components in the leakage resistance current IR. In Solution 2, voltage harmonic components are added, and the peaks of IR3rd and IR5th both increase, increasing by 12.7 µA and 2.9 µA respectively under the rated voltage. It can be seen that when the percentage weight of the voltage third harmonic V3rd is almost twice that of the voltage fifth harmonic V5th, the increase in the peak of IR3rd is 4.3 times that of the peak of IR5th, indicating that the increase in IR3rd caused by V3rd is more significant than the increase in IR5th caused by V5th. In the leakage resistance current IR, IR3rd is more susceptible to voltage harmonic components. Therefore, the fifth harmonic of the leakage resistance current is used as the final monitoring index for the aging fault of the zinc oxide arrester.

[0085] The peaks of IR3rd and IR5th extracted in Solution 1 are independent of the voltage harmonics. Therefore, by changing the magnitude of the applied voltage and comparing and analyzing the peak changes of IR3rd and IR5th, it is verified that IR5th can be used as the evaluation criterion for the aging fault of the zinc oxide arrester.

[0086] The peaks of IR3rd and IR5th extracted in Solution 2 are affected by voltage harmonics. To evaluate the anti-harmonic interference of the new characteristic quantity IR5th, the peak changes of IR3rd and IR5th under the influence of V3rd and V5th are analyzed, and the harmonic sensitivity is introduced to calculate the response sensitivity of the voltage harmonic content change of IR3rd and IR5th. The harmonic sensitivity The calculation formula is:

[0087] ;

[0088] Among them, represents the total number of voltage experiments; , respectively represent the leakage current characteristic quantity values under the i-th and (i + 1)-th voltage experiments; , respectively represent the harmonic contents of the voltages applied across the zinc oxide arrester under the i-th and (i + 1)-th voltage experiments.

[0089] The results show that the influence of the voltage fifth harmonic on the resistance current fifth harmonic is less than the influence of the voltage third harmonic on the resistance current third harmonic. This embodiment has a unique advantage in anti-voltage harmonic interference and can be used as an alternative index for the fault monitoring and location of the zinc oxide arrester.

[0090] Step 4: According to the monitoring index of the aging fault of the zinc oxide arrester and the applied voltage, obtain the monitoring result of the aging fault of the zinc oxide arrester, specifically:

[0091] Based on the relationship between the fifth harmonic of the leakage resistance current and the applied voltage, the basis for identifying the aging fault state of the zinc oxide arrester is formulated, that is:

[0092] In response to the applied voltage being in the first voltage range and the fifth harmonic of the leakage resistance current being greater than the first current threshold, the zinc oxide arrester has an aging fault; in response to the applied voltage not being in the first voltage range or the fifth harmonic of the leakage resistance current not being greater than the first current threshold, the zinc oxide arrester does not have an aging fault;

[0093] In response to the applied voltage being in the second voltage range and the fifth harmonic of the leakage resistance current being greater than the second current threshold, the zinc oxide arrester has an aging fault; in response to the applied voltage not being in the second voltage range or the fifth harmonic of the leakage resistance current not being greater than the second current threshold, the zinc oxide arrester does not have an aging fault;

[0094] In response to the applied voltage being in the third voltage range and the fifth harmonic of the leakage resistance current being greater than the third current threshold, the zinc oxide arrester has an aging fault; in response to the applied voltage not being in the third voltage range or the fifth harmonic of the leakage resistance current not being greater than the third current threshold, the zinc oxide arrester does not have an aging fault.

[0095] As Figure 12 shown, in this embodiment, IR5th is used as a new index in the fault judgment of the arrester. The leakage current of the zinc oxide arrester is detected by a high-precision current sensor, and through signal processing and data transmission, online monitoring can be realized. When the monitored value of IR5th is higher than the threshold, a reminder will be sent in time; combined with the GPS positioning system to accurately obtain the location of the faulty arrester.

[0096] Embodiment 2

[0097] On the basis of Embodiment 1, this embodiment introduces a test example of a method for monitoring the aging fault of a zinc oxide arrester based on the fifth harmonic:

[0098] Under Scheme 1 and Scheme 2, change the magnitude of the applied voltage, measure and calculate IR3rd and IR5th of the zinc oxide arrester. As Figures 8 - 9 shown, Figure 8 in (a) is the peak value of IR3rd of the zinc oxide arrester in the normal state, Figure 8 in (b) is the peak value of IR5th of the zinc oxide arrester in the normal state; Figure 9 in (a) is the peak value of IR3rd of the zinc oxide arrester in the aging fault state, Figure 9 in (b) is the peak value of IR5th of the zinc oxide arrester in the aging fault state;

[0099] It can be seen that under voltage harmonic interference, both current harmonics increase, but the change in IR3rd is larger and the change in IR5th is basically flat.

[0100] Comparing the data obtained from the first comparison scheme, as Figure 10 shown, Figure 10 in (a), it is the IR3rd peak value in the normal state and the IR3rd peak value in the aging fault state, Figure 10 in (b), it is the IR5th peak value in the normal state and the IR5th peak value in the aging fault state;

[0101] It can be seen that both the IR3rd and IR5th of the zinc oxide arrester in the aging fault state increase compared with the normal situation, indicating that both IR3rd and IR5th can indicate the aging fault state of the zinc oxide arrester.

[0102] Calculate the percentage changes of the IR3rd and IR5th peak values of the two arresters under harmonic interference respectively, as Figure 11 and Table 5 shown, Figure 11 in (a), it is the percentage change of the IR3rd in the normal state and the percentage change of the IR3rd in the aging fault state under harmonic interference, Figure 11 in (b), it is the percentage change of the IR5th in the normal state and the percentage change of the IR5th in the aging fault state under harmonic interference.

[0103] Table 5 Data analysis of the normal state and the aging fault state under harmonic interference

[0104]

[0105] It can be seen that harmonic interference causes a greater percentage change in IR3rd. And although in the second scheme, the percentage weight of V3rd is almost twice that of V5th, the peak value increase ratios of IR3rd of the two arresters in the normal state and the aging fault state under rated voltage are 2.55 times and 2.65 times higher than that of IR5th respectively, indicating that the influence of V3rd on the IR3rd peak value is greater than that of V5th on the IR5th peak value. This is because the nonlinearity of the zinc oxide arrester makes IR3rd increase more. It can also be seen that the percentage growth of the arrester in the aging fault state is higher than that in the normal state, verifying the monitoring effectiveness of the IR5th characteristic quantity, which can replace IR3rd as a new monitoring index.

[0106] Calculate the harmonic sensitivities S of IT, IR3rd and IR5th, and the results are shown in Table 6:

[0107] Table 6 Harmonic sensitivity analysis

[0108]

[0109] It can be seen that the IR5th harmonic sensitivity is less than other characteristic quantities, indicating that under the action of voltage containing harmonics, IR5th has a stronger ability to resist voltage harmonic interference for both the normal state and the aging fault state of the arrester.

[0110] In this embodiment, based on the relationship between the fifth harmonic of the resistive current and the applied voltage, the basis for identifying the aging fault state of the zinc oxide arrester is formulated, as shown in Table 7.

[0111] Table 7 Basis for Identifying the Aging Fault State of Zinc Oxide Arresters

[0112]

[0113] Specifically:

[0114] When 90 < U ≤ 98 and IR5th > 75, the zinc oxide arrester has an aging fault;

[0115] When 98 < U ≤ 100 and IR5th > 110, the zinc oxide arrester has an aging fault;

[0116] When U > 110 and IR5th > 300, the zinc oxide arrester has an aging fault;

[0117] Except for the above three cases, the zinc oxide arrester does not have an aging fault. Among them, U represents the applied voltage value.

[0118] Embodiment 3

[0119] Based on Embodiment 1 or 2, this embodiment introduces a monitoring system for the aging fault of zinc oxide arresters based on the fifth harmonic, including:

[0120] A total leakage current acquisition module that acquires the total leakage current of the zinc oxide arrester under different applied voltages; the different applied voltages include pure sine wave voltage and voltage with harmonic components;

[0121] A leakage resistance current calculation module that obtains the leakage resistance current and its third harmonic and fifth harmonic according to the total leakage current;

[0122] A monitoring index calculation module that compares the total leakage current, the leakage resistance current and its third harmonic and fifth harmonic to obtain the monitoring index of the aging fault of the zinc oxide arrester;

[0123] A monitoring result calculation module that obtains the monitoring result of the aging fault of the zinc oxide arrester according to the monitoring index of the aging fault of the zinc oxide arrester and the applied voltage.

[0124] For the specific function implementation of the above modules, refer to the relevant content in the methods of Embodiment 1 or 2, which will not be elaborated here.

[0125] Example 4

[0126] This example introduces a computer-readable storage medium with a computer program stored thereon. When the program is executed by a processor, it implements the steps in the method for monitoring the aging faults of zinc oxide arresters based on fifth harmonics as described in Example 1 or 2.

[0127] Example 5

[0128] This example introduces a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the steps in the method for monitoring the aging faults of zinc oxide arresters based on fifth harmonics as described in Example 1 or 2.

[0129] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0130] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one or more of the processes Figure 1 or multiple processes and / or blocks

[0131] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the specified functions in Figure 1 one or more of the processes Figure 1 or multiple processes and / or blocks

[0132] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operation steps are executed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions for implementing the steps specified in one process or a plurality of processes and / or blocks Figure 1 in one block or a plurality of blocks Figure 1 in the functions specified.

[0133] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit of the present invention and the scope protected by the claims. All of these are within the protection scope of the present invention.

Claims

1. A method for monitoring aging faults of zinc oxide lightning arresters based on fifth harmonic, characterized in that: include: Obtaining the total leakage current of the zinc oxide arrester under different applied voltages; the different applied voltages include pure sinusoidal voltages and voltages with harmonic components; According to the total leakage current, a leakage resistance current and its third harmonic and fifth harmonic are obtained; By comparing the total leakage current, leakage resistance current and its third harmonic and fifth harmonic, the monitoring index of zinc oxide arrester aging fault is obtained; According to the monitoring index of the zinc oxide lightning arrester aging fault and the applied voltage, the monitoring result of the zinc oxide lightning arrester aging fault is obtained.

2. The method for monitoring aging fault of zinc oxide lightning arrester based on fifth harmonic according to claim 1 is characterized in that: The voltage with harmonic components includes the third harmonic voltage, the fifth harmonic voltage, the seventh harmonic voltage, the ninth harmonic voltage and the eleventh harmonic voltage.

3. The method for monitoring aging fault of zinc oxide lightning arrester based on fifth harmonic according to claim 1 is characterized in that: The shift current method is used to obtain the leakage resistance current and its third harmonic and fifth harmonic according to the total leakage current, including: Delaying the original waveform of the total leakage current by a quarter of its period to obtain a delayed waveform, and superimposing the original waveform of the total leakage current and the delayed waveform to obtain a superimposed waveform; The peak time of the superimposed waveform is obtained by using a peak time detector, and the peak time of the superimposed waveform is delayed by one quarter of its cycle to obtain the peak time of the capacitive current component; The frequency of the total leakage current is determined by using a frequency detector to obtain the frequency of the capacitive current component; Generate a capacitance current component waveform according to the frequency of the capacitance current component, the peak time of the capacitance current component and the peak amplitude of the capacitance current component; wherein the peak amplitude of the capacitance current component is the same as the peak amplitude of the total leakage current; Subtract the total leakage current from the capacitive current component to obtain the leakage resistance current; Performing a fast Fourier transform on the leakage resistor current to obtain the third harmonic of the leakage resistor current and the fifth harmonic of the leakage resistor current.

4. The method for monitoring aging fault of zinc oxide lightning arrester based on fifth harmonic according to claim 1 is characterized in that: By comparing the total leakage current, leakage resistance current and its third harmonic and fifth harmonic of the zinc oxide arrester, the monitoring indicators of zinc oxide arrester aging failure are obtained, including: Compare the peak changes of total leakage current and leakage resistance current under voltage harmonics, and use leakage resistance current as a preliminary monitoring indicator for aging failure of zinc oxide lightning arresters; By comparing the peak changes of the third harmonic and the fifth harmonic of the leakage resistor current under voltage harmonics, as well as the harmonic sensitivity of the third harmonic and the fifth harmonic of the leakage resistor current, the fifth harmonic of the leakage resistor current is used as the final monitoring indicator of the aging failure of the zinc oxide lightning arrester.

5. The method for monitoring aging fault of zinc oxide lightning arrester based on fifth harmonic according to claim 4 is characterized in that: The calculation formula of the harmonic sensitivity is: ； in, Indicates harmonic sensitivity; represents the total number of voltage experiments; , Respectively represent the characteristic values ​​of leakage current under the i-th and i+1-th voltage tests; , They represent the harmonic content of the voltage applied across the zinc oxide arrester in the i-th and i+1-th voltage tests respectively.

6. The method for monitoring aging fault of zinc oxide lightning arrester based on fifth harmonic according to claim 1, characterized in that: According to the monitoring index of the zinc oxide lightning arrester aging fault and the applied voltage, the monitoring result of the zinc oxide lightning arrester aging fault is obtained, including: In response to the applied voltage being within the first voltage range and the fifth harmonic of the leakage resistance current being greater than the first current threshold, an aging fault occurs in the zinc oxide lightning arrester; in response to the applied voltage not being within the first voltage range or the fifth harmonic of the leakage resistance current being less than the first current threshold, no aging fault occurs in the zinc oxide lightning arrester; In response to the applied voltage being within the second voltage range and the fifth harmonic of the leakage resistance current being greater than the second current threshold, an aging fault occurs in the zinc oxide lightning arrester; in response to the applied voltage not being within the second voltage range or the fifth harmonic of the leakage resistance current being less than the second current threshold, no aging fault occurs in the zinc oxide lightning arrester; In response to the applied voltage being within the third voltage range and the fifth harmonic of the leakage resistance current being greater than the third current threshold, an aging fault occurs in the zinc oxide arrester; in response to the applied voltage not being within the third voltage range or the fifth harmonic of the leakage resistance current being less than the third current threshold, no aging fault occurs in the zinc oxide arrester; wherein the fifth harmonic of the leakage resistance current is a monitoring indicator for an aging fault of the zinc oxide arrester.

7. A zinc oxide arrester aging fault monitoring system based on fifth harmonic, characterized in that: include: A total leakage current acquisition module is used to acquire the total leakage current of the zinc oxide arrester under different applied voltages; the different applied voltages include pure sinusoidal voltages and voltages with harmonic components; A leakage resistance current calculation module, which obtains the leakage resistance current and its third harmonic and fifth harmonic according to the total leakage current; The monitoring index calculation module compares the total leakage current, leakage resistance current and its third harmonic and fifth harmonic to obtain the monitoring index of zinc oxide arrester aging fault; The monitoring result calculation module obtains the monitoring result of the aging failure of the zinc oxide lightning arrester according to the monitoring index of the aging failure of the zinc oxide lightning arrester and the applied voltage.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps in the fifth harmonic-based zinc oxide lightning arrester aging fault monitoring method as described in any one of claims 1 to 6 are implemented.

9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps in the method for monitoring aging faults of zinc oxide lightning arresters based on fifth harmonics as described in any one of claims 1 to 6 are implemented.

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