Zinc oxide arrester live detection method

Abstract

A zinc oxide arrester live detection method comprises the following steps: synchronously measuring a voltage signal and a current signal of a zinc oxide arrester by using a voltage monitoring device and a current detection device based on Beidou satellite time service; carrying out fundamental wave and harmonic wave combined analysis on the voltage and current signals by using a detection terminal based on fundamental waves and higher harmonic waves and adopting FFT (Fast Fourier Transform) conversion, and identifying and measuring the amplitude and phase angle of each harmonic wave of the voltage signals and the current signals to obtain resistive current for detecting the zinc oxide lightning arrester; wherein the remote synchronization data based on Beidou satellite time service synchronously triggers the current detection devices located at different positions; in the detection terminal, a crystal oscillator subjected to temperature compensation serves as a signal source of a DSP and serves as a sampling clock after frequency division and 1PPS synchronization, then the sampling clock is utilized to control data acquisition of a main CPU from the outside, and meanwhile, a microprocessor is adopted to extract absolute time corresponding to 1PPS from information provided by a Beidou satellite so as to set a time label for sampled data.

Description

Technical Field

[0001] The invention relates to the technical field of zinc oxide lightning arrester measurement, and in particular to a method for detecting a zinc oxide lightning arrester with electricity. Background Art

[0002] Zinc oxide arrester (MOA) is an important device for overvoltage protection in modern power systems. Due to the long-term exposure of zinc oxide arresters to system voltage, overvoltage, dirt and internal moisture, their insulation performance deteriorates and their nonlinear characteristics fail, causing MOA aging and even explosion. The consequences not only bring huge economic losses, but also seriously threaten the safe operation of the power grid. Therefore, testing the insulation performance of the arrester can detect and eliminate faults early and prevent accidents.

[0003] At present, the resistive current testers widely used in the market all adopt single-phase separate measurement, which cannot achieve accurate and simultaneous measurement of three phases. Carrying out on-site work has a certain labor intensity and labor cost. During the MOA test of the substation, on-site wiring must be carried out, and the on-site measurement loop should be reliably grounded at one point. The instability of the grounding point will affect the measurement results. It is often necessary to lay longer voltage leads and current leads. The on-site cable laying workload is large and the work intensity is high. Moreover, because the current measurement lead is too long and easy to entangle, the MOA lightning arrester leaks current test under operating conditions. There is phase interference when measuring 220kV and above lightning arresters on-site with power on. The measurement is easily affected by electric field interference, magnetic field interference, phase interference, system voltage fluctuations and high-order harmonic interference, resulting in large measurement errors. At the same time, due to too many current measurement leads, it is also easy to cause personal and equipment risks.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for detecting zinc oxide lightning arresters under power on condition that the method solves the problems of complex wiring, susceptibility to interference, large measurement errors and high risks to personal and equipment safety in on-site measurements of existing resistive current testers, and the method has accurate detection and is easy to use.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A zinc oxide lightning arrester live detection method of the present invention comprises:

[0008] The voltage signal and current signal of the zinc oxide lightning arrester are synchronously measured using a voltage monitoring device and a current detection device based on Beidou satellite timing;

[0009] The detection terminal uses the fundamental wave and higher harmonics and adopts FFT transformation to jointly analyze the fundamental wave and harmonics of the voltage and current signals. The harmonic analysis obtains the amplitudes and phase angles of the 3rd, 5th, 7th, and 9th harmonics of the voltage and resistive current, and calculates the fundamental wave resistive current, the resistive current under each harmonic, and the harmonic components of the voltage signal to judge the performance of the zinc oxide arrester;

[0010] Among them,

[0011] The current detection device includes multiple magnetic adsorption type wireless sensors arranged in three phases of corresponding multiple zinc oxide arresters, and in the way of multi-group interval synchronous measurement of current signals, the current signals are collected at the same time point for all zinc oxide arresters; among them, the current detection devices located at different positions are triggered by remote synchronous data synchronization based on Beidou satellite timing;

[0012] In the detection terminal, the crystal oscillator with temperature compensation is used as the signal source of the DSP, and after frequency division and 1PPS synchronization, it is used as the sampling clock. Then, the sampling clock is used to collect data from the external control main CPU. At the same time, the microprocessor extracts the absolute time corresponding to 1PPS from the information provided by the Beidou satellite to label the sampling data with time tags.

[0013] In the method described above, the current detection device is arranged in three phases of the zinc oxide arrester to synchronously measure the current signal in three phases.

[0014] In the method described above, the voltage monitoring device is fixedly installed on the secondary side of the voltage transformer for on-line monitoring of the voltage signal of the voltage transformer. Multiple current detection devices are distributed on the upright poles of the zinc oxide arrester to measure the current signal of the zinc oxide arrester. Among them, both the voltage monitoring device and the current detection device are communicatively connected to the Beidou satellite and communicatively connected to the detection terminal via a wireless communication module.

[0015] In the method described above, the current detection device magnetically adsorbs the upright pole of the zinc oxide arrester.

[0016] In the method described above, the rising edge of the Beidou satellite second pulse corresponds to a certain UTC moment, and the timing error is less than 20ns.

[0017] In the method described above, if the fundamental wave resistive current increases beyond a predetermined threshold, it is considered that the zinc oxide arrester is affected by moisture.

[0018] In the method described above, if the higher harmonic current increases beyond a predetermined value, it is considered that the zinc oxide arrester valve disc is aged.

[0019] In the method described above, the communication rate of the communication connection is at least 2MB / s.

[0020] Beneficial effects

[0021] Since the present invention realizes the live detection of the performance of zinc oxide arresters by means of a magnetic adsorption type wireless sensor to achieve wiring-free and multi-group synchronous measurement, and the technical means of multi-group interval synchronization can eliminate the inter-phase electromagnetic interference (such as comparing the harmonic characteristics of phase B / C when phase A is abnormal), therefore, the present invention solves the problems existing in the on-site measurement of existing resistive current testers, such as complex wiring, susceptibility to interference, large measurement errors, and high personal equipment safety risks. It can realize the synchronous measurement of the resistive current of zinc oxide arresters in the whole substation, and through the comparative analysis of the synchronous measurement data, it helps the operation and maintenance personnel quickly identify the zinc oxide arresters that need to be maintained or replaced, so as to ensure the safe and reliable operation of zinc oxide arresters, ensure the safety of electrical equipment, reduce the power outage time, and increase the safety and reliability of the system. The detection of the present invention is accurate and easy to use.

[0022] The above description is only an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and to the extent that those skilled in the art can implement it according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the following takes the specific implementation manner of the present invention as an example for illustration. Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings.

[0024] By reading the detailed description of the preferred specific implementation manners below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of showing the preferred implementation manners and are not considered as a limitation of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0025] In the drawings:

[0026] Figure 1 is a schematic diagram of the layout for live detection of a zinc oxide arrester provided by the present invention;

[0027] Figure 2 is a schematic diagram of a satellite synchronous clock for live detection of a zinc oxide arrester provided by the present invention;

[0028] Figure 3It is a schematic diagram for realizing the correlation modeling of moisture and aging by the multi - band harmonic joint analysis based on fundamental waves and higher - order harmonics provided by the present invention, and introducing machine learning for predicting the deterioration trend of zinc - oxide arresters.

[0029] The following further explains the present invention in conjunction with the accompanying drawings and embodiments. Specific Embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0031] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0032] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0033] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0034] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0035] In the present invention, unless otherwise clearly specified or limited, the terms "install", "connect", "couple", "fix", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral body; it may be a direct connection, or an indirect connection through an intermediate medium, and it may be the internal communication between two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In the present invention, unless otherwise clearly specified or limited, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0037] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0038] In one embodiment, as Figures 1 to 2 shown, the present invention provides a method for on-line detection of live zinc oxide arresters, which includes the following steps:

[0039] Fix and install a voltage monitoring device on the secondary side of the voltage transformer for on-line monitoring of the voltage signal of the voltage transformer. A plurality of current detection devices are distributed on the vertical pole of the zinc oxide arrester to measure the current signal of the zinc oxide arrester. Among them, both the voltage monitoring device and the current detection device are communicatively connected to the Beidou satellite and communicatively connected to the detection terminal via a wireless communication module;

[0040] Utilize the voltage monitoring device and the current detection device to synchronously measure the voltage signal and the current signal of the zinc oxide arrester based on the Beidou satellite time service;

[0041] The detection terminal is used to jointly analyze the fundamental wave and harmonics of the voltage and current signals based on the fundamental wave and higher harmonics and by using FFT transformation. In the harmonic analysis, the amplitudes and phase angles of the 3rd, 5th, 7th, and 9th harmonics of the voltage and resistive current are obtained, and the fundamental wave resistive current, the resistive current at each harmonic, and the harmonic components of the voltage signal are calculated to judge the performance of the zinc oxide lightning arrester. Further, in the harmonic analysis, data acquisition: the detection terminal receives the voltage and current signals sent by the voltage monitoring device and the current detection device through the wireless communication module. These signals are synchronously collected based on the synchronous time signal provided by the Beidou satellite timing module to ensure the accuracy and consistency of the data. FFT transformation: For example, the calculation and analysis unit in the detection terminal performs a fast Fourier transform (FFT) on the collected voltage and current signals. The FFT transformation converts the time-domain signal into a frequency-domain signal, so that the harmonic components in the signal can be analyzed. Harmonic identification and measurement: From the frequency-domain signal obtained by the FFT transformation, the harmonics of the voltage and current signals (including the fundamental wave and the 3rd, 5th, 7th, and 9th harmonics) are identified, and the amplitudes and phase angles of each harmonic are measured. The amplitude represents the magnitude of the harmonic, and the phase angle represents the phase difference between the harmonic and the fundamental wave. Further resistive current calculation: Using the amplitudes and phase angles of the identified harmonics and combining with the electrical characteristics of the zinc oxide lightning arrester, the resistive current is calculated. The resistive current is an important indicator for evaluating the performance of the zinc oxide lightning arrester and can reflect the aging degree and moisture condition of the arrester.

[0042] In one embodiment, at a certain moment, the voltage monitoring device and the current detection device synchronously collect the voltage and the three-phase current signals of A, B, and C. After the FFT transformation, the following frequency-domain signals are obtained: In the voltage signal, the fundamental wave amplitude is U1, and the phase angle is θ1; the 3rd harmonic amplitude is U3, and the phase angle is θ3;...; the nth harmonic amplitude is Un, and the phase angle is θn. In the current signal, the fundamental wave amplitude is I1, and the phase angle is φ1; the 3rd harmonic amplitude is I3, and the phase angle is φ3;...; the nth harmonic amplitude is In, and the phase angle is φn. Next, the calculation and analysis unit will use this harmonic information to calculate the resistive current. Taking the fundamental wave as an example, the resistive current component can be calculated by the following formula: I_R1 = I1 * cos(φ1 - θ1), where I_R1 represents the fundamental wave resistive current component, I1 represents the fundamental wave current amplitude, φ1 represents the fundamental wave current phase angle, and θ1 represents the fundamental wave voltage phase angle. Similarly, the resistive current components of other harmonics can be calculated and added together to obtain the total resistive current: I_R_total = I_R1 + I_R3 +... + I_Rn, where I_R_total represents the total resistive current, and I_R1, I_R3,..., I_Rn respectively represent the resistive current components of each harmonic.

[0043] Through the above steps and examples, harmonic analysis is performed on voltage and current signals using FFT transformation based on the method of each harmonic, and the amplitudes and phase angles of each harmonic are identified and measured to obtain the resistive current. This process provides important data support for the performance evaluation of zinc oxide arresters.

[0044] In a preferred embodiment of the described method, the current detection device is arranged on three phases of the zinc oxide arrester to synchronously measure the current signal in three phases.

[0045] In a preferred embodiment of the described method, the current detection device includes a plurality of magnetic adsorption type wireless sensors arranged on three phases of corresponding multiple zinc oxide arresters, and in a manner of synchronously measuring current signals at multiple intervals, the current signals are collected for all zinc oxide arresters at the same time point.

[0046] For this embodiment, since it realizes live detection of the performance of zinc oxide arresters through the magnetic adsorption type wireless sensors in a way of wiring-free + synchronous measurement in multiple groups, and the technical means of synchronous measurement at multiple intervals can eliminate electromagnetic interference between phases (such as comparing harmonic characteristics of phase B / C when phase A is abnormal), therefore, the present invention solves the problems existing in the on-site measurement of existing resistive current testers, such as complex wiring, susceptibility to interference, large measurement error, and high risks to personal and equipment safety. It can realize synchronous measurement of the resistive current of zinc oxide arresters in the whole substation, and through comparative analysis of the synchronous measurement data, help the operation and maintenance personnel quickly identify the zinc oxide arresters that need to be maintained or replaced, so as to ensure the safe and reliable operation of zinc oxide arresters, ensure the safety of electrical equipment, reduce the power outage time, increase the safety and reliability of the system. The detection of the present invention is accurate and easy to use.

[0047] In a preferred embodiment of the described method, each harmonic includes the fundamental wave and higher harmonics.

[0048] In a preferred embodiment of the described method, the current detection device magnetically adsorbs the vertical pole of the zinc oxide arrester.

[0049] In a preferred embodiment of the described method, based on the time synchronization of Beidou satellite, the current detection devices located at different positions are synchronously triggered for data synchronization. The rising edge of the Beidou satellite second pulse corresponds to a certain UTC time, and the timing error is less than 20 ns.

[0050] In a preferred embodiment of the described method, harmonic analysis obtains the amplitudes and phase angles of the 3rd, 5th, 7th, and 9th harmonics of the voltage and resistive current, and calculates the fundamental wave resistive current, the resistive current under each harmonic, and the harmonic components of the voltage signal to judge the performance of the zinc oxide arrester.

[0051] It should be noted that the fundamental wave is, for example, a 50 Hz fundamental wave; the 3rd, 5th, 7th, and 9th harmonics are high-order harmonics of 150 Hz, 250 Hz, 350 Hz, and 450 Hz respectively; through experiments, the 50 Hz fundamental wave can be used to characterize the overall moisture content of the zinc oxide lightning arrester, the 3rd harmonic can be used to characterize the non-linear deterioration of the grain boundaries of the zinc oxide lightning arrester, the 5th harmonic can be used to characterize partial discharge, and the 7th and 9th harmonics can be used to characterize the microstructural defects caused by aging. That is to say, the present invention innovatively utilizes the fundamental wave and high-order harmonics and conducts observations and experiments to characterize the performance changes such as moisture absorption and aging of the zinc oxide lightning arrester. These will be used as features in other embodiments described later. For details, please refer to the following text.

[0052] In a preferred embodiment of the method described above, if the resistive current of the fundamental wave increases by more than a predetermined threshold, it is considered that the zinc oxide lightning arrester is affected by moisture; if the high-order harmonic current increases by more than a predetermined value, it is considered that the varistor of the zinc oxide lightning arrester is aged.

[0053] In a preferred embodiment of the method described above, the communication rate of the communication connection is at least 2 MB / s.

[0054] In another embodiment, the voltage monitoring device is installed on the secondary side of the voltage transformer and is connected to the voltage signal of the voltage transformer through a lead wire to measure the voltage signal of the voltage transformer. The voltage signal is converted into a digital signal through an acquisition circuit and uploaded to the on-site monitoring terminal through a wireless communication module. The satellite time synchronization module communicates with the satellite through a built-in Beidou receiving chip, receives and processes the time signal sent by the satellite, and provides an accurate time reference for the acquisition of the voltage signal.

[0055] In another embodiment, the current detection device is installed on the pole of the zinc oxide lightning arrester and is fixed by magnetic adsorption to measure the current signal of the zinc oxide lightning arrester. The current signal is converted into a digital signal through an acquisition circuit and uploaded to the on-site monitoring terminal through a wireless communication module. The satellite time synchronization module communicates with the satellite through a built-in Beidou receiving chip, receives and processes the time signal sent by the satellite, and provides an accurate time reference for the acquisition of the current signal.

[0056] In another embodiment, the detection terminal is wirelessly connected to the voltage detection device and the current detection device via a wireless communication module. The detection terminal internally includes a satellite timing unit, a wireless communication module, and a calculation and analysis unit. The satellite timing unit communicates with the satellite through a built-in Beidou receiving chip, obtains a synchronous time signal based on Beidou satellite timing, and this signal is used to synchronously collect the voltage signal and current signal of the zinc oxide arrester to ensure the accuracy and consistency of the data. The calculation and analysis unit receives the current and voltage data uploaded by the voltage detection device and the current detection device through the wireless communication module, performs harmonic analysis on the voltage and current signals using FFT transformation based on the method of each harmonic, and calculates the amplitude and phase angle of each harmonic of the voltage signal and the current signal to obtain the resistive current for detecting the zinc oxide arrester. The wireless communication module exchanges data with the voltage detection device and the current detection device through the on-site wireless network.

[0057] In another embodiment, the live detection method of the zinc oxide arrester is implemented based on a wireless full-station zinc oxide arrester live testing device. It is based on the Beidou satellite synchronous MOA wireless resistive current live detection. The device is powered by a battery, uses wireless communication, and has a magnetic absorption installation. There is a separate detection device for each zinc oxide arrester, without the need to lay leads. Moreover, the wireless full-station zinc oxide arrester live testing device performs synchronous measurement through the Beidou satellite PPS pulse. Therefore, according to the on-site MOA detection requirements, it can perform three-phase synchronous measurement for a single interval, synchronous measurement for multiple groups of intervals, and full-station synchronous measurement, reducing measurement interference, eliminating potential safety hazards, and facilitating on-site detection. The Beidou satellite synchronous sampling technology is used to ensure that the measurement data of all arresters in the entire substation are collected at the same time point, thereby improving the consistency of the data and the accuracy of the measurement. There are a large number of electromagnetic interferences and induced voltage interferences in the measurement work carried out in the substation. These interferences will change with time and space and affect the measurement results of the resistive current of the MOA. The Beidou satellite synchronous technology helps to identify and eliminate this interference through precise time control because almost all the zinc oxide arrester live testing devices are simultaneously affected by the same external interference, and these interferences can be eliminated or reduced in data processing, thereby obtaining a more real resistive current value. Synchronous measurement can accurately evaluate the status of each zinc oxide arrester, timely detect potential problems, and accurately reflect the health status of the zinc oxide arrester. Using the Beidou satellite signal for synchronization, synchronous measurement of multiple (even all) arresters in the substation can be achieved. By eliminating the common-mode interference, the resistive current of each arrester can be measured more accurately, thereby more accurately evaluating its aging condition, which is helpful for the health monitoring of the entire system. Accurate measurement results can help the operation and maintenance personnel identify the zinc oxide arresters that need maintenance or replacement, thereby improving the efficiency and economy of the maintenance work.

[0058] In another embodiment, the arrangement of the live detection method of the zinc oxide arrester is as Figure 1As shown in the figure, the voltage monitoring device is fixedly installed on the secondary side of the voltage transformer, used for online monitoring of the voltage of the voltage transformer, and responding to the measurement request of the current detection device when there is a need to measure the resistive current in the system. Once the voltage monitoring device is installed, the wiring is fixed, and there is no need to repeat the wiring during subsequent measurement work. The current detection device is made in a distributed manner and can perform single-interval three-phase synchronous measurement, multi-group interval synchronous measurement, and full-station synchronous measurement according to the on-site MOA detection requirements. During measurement, the on-site detection terminal sends measurement commands to the voltage detection device and the current detection device through wireless communication. After receiving the measurement commands, the voltage detection device and the current detection device achieve synchronous measurement of voltage and current through the Beidou satellite module. Each detection device sends the measured data to the on-site detection terminal through wireless communication. The on-site detection terminal calculates the phase difference between the fundamental components of voltage and current through the harmonic algorithm based on Fourier series decomposition, and then obtains the resistive current of the MOA.

[0059] In another embodiment, for the synchronous acquisition of leakage current data of multiple zinc oxide arresters, the off-site synchronous data acquisition technology based on Beidou satellite time service is used to synchronously trigger the magnetic adsorption and wireless sensors located at different positions. Since the rising edge of the Beidou satellite second pulse precisely corresponds to a certain UTC time (with an error of 20 ns), the Beidou satellite time service synchronization has the characteristics of high precision, all-weather, and low cost, and can well meet the requirements of off-site synchronous data acquisition. The Beidou satellite system receiver can extract and output two time signals from the received information: one is the second pulse signal 1PPS, whose pulse front edge has a synchronization error with the international standard time of no more than 1 μs, and the other is the time information output through the serial port, which is given between 1PPS pulses and is used to indicate the UCT time (year, month, day, hour, minute, second), that is, the absolute time, corresponding to the 1PPS pulse. The synchronous acquisition here refers to controlling the data acquisition based on these two time signals, namely the second pulse signal 1PPS and the time information output through the serial port, to achieve synchronization. In contrast, the current sampling circuit generally performs sampling under the control of an internal timer timing interrupt. However, due to the low stability of the external crystal oscillator used by the single-chip microcomputer, the synchronous error of the synchronous sampling controlled by this scheme exceeds 1 s.

[0060] Therefore, the present invention selects a highly stable temperature-compensated crystal oscillator as the high-stability crystal oscillator and uses it as the signal source of the DSP. After frequency division and 1PPS synchronization, it is used as the sampling clock. Then, based on this sampling clock signal, the data acquisition of the external control main CPU is controlled. At the same time, the microprocessor extracts the absolute time corresponding to 1PPS from the information provided by the Beidou satellite to label the sampling data with time tags, thereby achieving synchronous sampling.

[0061] It should be emphasized that by adopting this satellite synchronous clock design, it is possible to receive Beidou satellite timing signals to tame the OCXO (high-stability thermostatic crystal oscillator, also known as ultra-high stability thermostatic crystal oscillator, hereinafter referred to as thermostatic crystal oscillator) inside the detection terminal, so as to provide a high-stability primary clock synchronization signal based on UTC standard time and self-improving monitoring. For this embodiment, it should be noted that the conventional GPS synchronous timekeeping error is usually at the microsecond level (such as 1 μs), and the drift will be even greater after the satellite loses lock. However, through this embodiment of the present invention, it is possible to achieve a drift < 1 μs within 72 hours after the satellite loses lock.

[0062] In another embodiment, a closed-loop control timekeeping technology is further adopted, and the sensor has a self-learning function to cope with characteristics such as the aging drift of the high-stability thermostatic crystal oscillator, thereby achieving temperature compensation. Even after the satellite signal is interrupted or a fault occurs (i.e., the satellite loses lock), it is still possible to output an accurate time synchronization signal before the satellite signal is restored (for example, in an extreme case, the satellite signal interruption or fault can be maintained for 72 hours), so as to achieve high-precision synchronous sampling.

[0063] Exemplarily, for the aging drift characteristics of the high-stability thermostatic crystal oscillator (OCXO), combined with the closed-loop control timekeeping technology and the sensor self-learning function, the following is a complete temperature compensation embodiment, which includes the following steps:

[0064] Record the crystal temperature T1 of the crystal oscillator, the case temperature T2 of the crystal oscillator, the instantaneous deviation Δf between the output frequency of the crystal oscillator and its nominal frequency, and the current control voltage VC of the crystal oscillator every few seconds (for example, 10 s);

[0065] When the instantaneous deviation Δf exceeds the threshold (for example, 0.1 μs), dynamically adjust the current control voltage VC of the crystal oscillator through the PID closed-loop control strategy and record the correction value of the control voltage, so that the instantaneous deviation Δf approaches 0;

[0066] Among them,

[0067] When the satellite loses lock, perform the following steps:

[0068] Calculate the temperature compensation drift according to the current crystal temperature T1 of the crystal oscillator, the case temperature T2 of the crystal oscillator and the following temperature compensation model :

[0069] ,

[0070] where T0 is the nominal constant temperature of the crystal oscillator, and the coefficients a, b, and c are obtained by fitting historical data;

[0071] Furthermore, predict the long-term aging drift caused by crystal oscillator aging according to the following aging model :

[0072] ,

[0073] Among them, t0 is the initial activation time or factory time of the crystal oscillator, t is the current time, and k and d are obtained by fitting historical data;

[0074] Furthermore, the sum of the temperature compensation drift and the long-term aging drift is used as the current instantaneous deviation Δf after the satellite loses lock. The current control voltage VC of the crystal oscillator is dynamically adjusted through a PID closed-loop control strategy, and the correction value of the control voltage is recorded to make the instantaneous deviation Δf approach 0.

[0075] Exemplarily, units with data processing capabilities such as microprocessors use the recursive least squares method (RLS) to dynamically update the above coefficients a, b, c, k, and d, and refit at equal intervals of every 1 hour or every 24 hours to adapt to performance changes caused by crystal aging and temperature drift characteristics.

[0076] Exemplarily, the correction value of the control voltage is recorded to generate a table, so as to skip the above temperature compensation model and / or aging model in the case of too large temperature mutation, find the correction value of VC through the table lookup method to make the instantaneous deviation Δf approach 0, and perform wireless alarm after table lookup to remind operation and maintenance.

[0077] In another embodiment, as Figure 2As shown in the figure, the specific process of the synchronous clock and data processing includes: The Beidou satellite system receiver receives the time signal sent by the Beidou satellite system, provides a high-precision time reference, and generates an accurate time mark (TOD) according to the time signal provided by the Beidou satellite system, and sends it to the micro-control unit. At the same time, it sends the second pulse signal to the field programmable gate array. The micro-control unit is responsible for the overall management of the system, including time synchronization, status monitoring, etc. It sends the received accurate time mark (TOD) to the field programmable gate array through the parallel bus. The field programmable gate array is used to process the received accurate time mark (TOD) and the second pulse signal, execute signal processing algorithms, extract time information, etc., and send the information to the time signal output unit, the crystal oscillator and the data acquisition module. The time signal output unit converts the time signal calculated by the field programmable gate array into a high-precision time mark (TOD), a second pulse signal and the International Electrotechnical Commission IRIG standard type B time code for time signal output. The crystal oscillator is used to generate a stable 10 MHz frequency signal as the clock source for each component inside the system. The data acquisition module samples the analog signal using the clock signal provided by the OCXO and converts it into a digital signal. The sampling process can be synchronized by the 10 MHz signal to ensure the accuracy and synchronization of data acquisition. The management unit sets parameters and controls communication with the micro-control unit through the serial port. The network time protocol management unit enables the micro-control unit to support the network time protocol through the Ethernet port.

[0078] The second pulse signal 1PPS (One Pulse Per Second) is a high-precision time synchronization signal. It utilizes the time service function of the Beidou satellite to ensure that the leading edge of each pulse corresponds precisely to the Coordinated Universal Time (UTC), with an error of no more than 1 microsecond. In the zinc oxide arrester live detection device disclosed in the present invention, the second pulse signal 1PPS is used to control the synchronous signal for collecting current and voltage. That is to say, when the device needs to collect the current and voltage data of the zinc oxide arrester, it will wait for the leading edge of the second pulse signal 1PPS to arrive, and then simultaneously start the collection process of current and voltage. In this way, since all collection operations start at the same time point, it can ensure that the collected current and voltage data are synchronous, providing an accurate basis for subsequent data analysis and processing.

[0079] The time information output via the serial port is another time signal extracted from the Beidou satellite system receiver, which contains detailed UTC time information (year, month, day, hour, minute, second). In the zinc oxide arrester live detection device disclosed in the present invention, the time information output via the serial port is used to timestamp the collected digital signals. That is to say, whenever the device collects a set of current and voltage data, it will immediately obtain the current UTC time information from the Beidou satellite system receiver and attach this time information as a timestamp to the collected data. In this way, each set of data is attached with an accurate time tag, and it can be clearly known at what time point these data are collected, which is very important for subsequent data analysis and processing. Its technical effect is to accurately know the time interval and sequence between each set of data. The combined use of these two fully realizes the synchronous analysis of current and voltage data.

[0080] In another embodiment, also to avoid the heavy on-site communication cable laying work for the synchronous collection of leakage current data of multiple zinc oxide arresters, a wireless communication method is adopted to directly transmit the collected data to the on-site detection terminal wirelessly. Its advantages are strong emergency response, suitable for data transmission of devices with large-scale distribution, and simple and convenient to use. To minimize the workload of on-site live detection operations, the detection terminal adopts an integrated design, integrating a data acquisition module, a lithium battery power supply, a wireless communication module, and a satellite synchronization module. During measurement, the device can be fixed on the vertical pole under the zinc oxide arrester by magnetic attraction for measurement.

[0081] In another embodiment, the harmonic method is based on the fundamental wave method and uses FFT transformation to perform harmonic analysis on the synchronously detected voltage and current signals, obtaining the amplitudes and phase angles of the 3rd, 5th, 7th, and 9th harmonics of the voltage and resistive current. Based on the resistive-capacitive network method, considering the power grid harmonics, and filtering out harmonic interference, the fundamental wave resistive current and the resistive current under each harmonic are accurately calculated. This effectively improves the accuracy of the resistive current calculation, can effectively and accurately calculate the resistive current of the lightning arrester, and makes up for the fact that the fundamental wave method completely ignores the influence of the high-order harmonics of the resistive current. It can not only detect the increase in the fundamental wave resistive current caused by the moisture absorption of the zinc oxide lightning arrester, but also detect the increase in the resistive high-order harmonic current caused by the aging of the varistor in the zinc oxide lightning arrester. And the harmonic method can obtain the harmonic components of the voltage signal, so as to consider the influence caused by the voltage harmonics and comprehensively judge to draw a correct conclusion, thereby making a judgment on the performance of the zinc oxide lightning arrester. The harmonic method described in the present invention analyzes the fundamental wave and high-order harmonics, not only provides a more comprehensive evaluation of the lightning arrester performance, can sensitively detect problems such as moisture absorption or varistor aging of the zinc oxide lightning arrester, which may be ignored in the fundamental wave method, but also considers the influence of the voltage harmonic components on the lightning arrester performance, making the performance judgment more accurate and scientific. Through the harmonic method, the state and performance of the zinc oxide lightning arrester can be more accurately evaluated, especially when considering the harmonic components of the current and voltage. This method provides an efficient and comprehensive technical means for the maintenance and fault diagnosis of lightning arresters in the power system.

[0082] In another embodiment, the detection terminal consists of a lithium battery power supply, a signal conditioning unit, a high-speed ADC acquisition unit, an FPGA processing unit, an SRAM high-speed cache, a Beidou timing unit, a wireless communication module, and a calculation and analysis unit. The timing accuracy of the Beidou module is less than 20 ns on average, and the communication distance of the wireless communication module can reach 500 m in an open area. The detection terminal is a fully automatic instrument that can synchronously measure voltage and current data with a single wiring, and has a harmonic analysis function; an anti-interference function to ensure accurate and reliable data; it can be used for both AC and DC, with a large-capacity lithium-ion battery built-in, and can continuously work for about 6 hours after a single charge; it adopts a wireless measurement method and wireless data transmission, eliminating the cumbersome long-distance wiring and reducing the labor intensity. The power supply module provides a stable 12 VDC power supply for the entire live detection device of the zinc oxide lightning arrester.

[0083] Exemplarily, the structure of the detection terminal includes:

[0084] The signal acquisition module is used to collect the leakage current signal and voltage signal of the zinc oxide arrester, and perform preliminary amplification and filtering on the collected analog signals for subsequent processing. The signal conditioning module further processes the collected signals, such as amplification, filtering, isolation, etc., to improve the quality and stability of the signals and make them meet the requirements of subsequent ADC acquisition. The high-speed analog-to-digital conversion unit converts the conditioned analog signals into digital signals and provides high-precision digital signal output. The FPGA processing module preprocesses the collected digital signals, performs real-time processing on the digital signals, and extracts the characteristic parameters of the zinc oxide arrester. The MCU processing module serves as the control center of the entire system, responsible for data reception, storage, processing, and transmission, receives the data output by the FPGA processing module, and stamps the time. The SRAM cache module provides high-speed data storage and reading services for the MCU, stores the data output by the MCU processing module for subsequent processing. The ZigBee module realizes wireless data transmission, and sends the data output by the data processing module to remote devices wirelessly. The satellite synchronous clock module obtains the time signal sent by the Beidou satellite system and provides a high-precision time synchronization signal. The data processing module realizes communication with the on-site monitoring terminal to ensure the accuracy and integrity of the data.

[0085] See Figure 3 , in another embodiment, the present invention realizes the correlation modeling of moisture absorption and aging based on the multi-band harmonic joint analysis of fundamental waves and higher harmonics, and introduces machine learning for predicting the degradation trend of zinc oxide arresters. Among them,

[0086] Realizing the correlation modeling of moisture absorption and aging based on the multi-band harmonic joint analysis of fundamental waves and higher harmonics includes the following steps:

[0087] Under the trigger of the 1PPS pulse, collect the leakage current waveform of the zinc oxide arrester (MOA) and the corresponding voltage waveform, continuously for at least 1 second, and cover the 50Hz fundamental wave and its 3rd, 5th, 7th, and 9th higher harmonics, and simultaneously collect the corresponding ambient temperature and humidity;

[0088] Use wavelet transform to filter out high-frequency interference;

[0089] Normalize the current amplitude and voltage amplitude according to the sensor range;

[0090] Perform FFT transform to extract the characteristics of the 50Hz fundamental wave and the 3rd, 5th, 7th, and 9th higher harmonics;

[0091] For n taking the 3rd, 5th, 7th, and 9th higher harmonics, calculate the following parameters for the nth harmonic: the amplitude An n 、the phase shift φn n 、the total harmonic distortion rate THD of the nth harmonic, and the high-frequency harmonic ratio HFR;

[0092] Under controlled laboratory conditions, simulate different aging stages (accelerated aging tests) and moisture levels (humidity control), collect harmonic data to construct a benchmark database;

[0093] Establish a joint probability model to quantify the coupling effect of aging and moisture; Exemplarily, the coupling effect is, for example, the following joint probability: 、 , to distinguish the performance changes dominated by aging (high-frequency harmonic anomalies) and moisture (fundamental wave phase anomalies).

[0094] Introduce machine learning for the degradation trend prediction of zinc oxide arresters, which includes the following steps:

[0095] Continuously collect the current waveform, the corresponding voltage waveform, and the corresponding ambient temperature and humidity. Using a 72-hour sliding window, calculate the dynamic time-series characteristics of each harmonic: harmonic parameters including the fundamental wave, 3rd, 5th, 7th, and 9th high-order harmonics, namely the mean, variance, and growth rate of harmonic amplitude, harmonic phase shift, total harmonic distortion rate, and high-frequency harmonic ratio, as well as the frequency-domain energy entropy; among them, the frequency-domain energy entropy is used to characterize the complexity of harmonic distribution;

[0096] For the degradation classification of zinc oxide arresters, construct a classification model based on gradient boosting trees. Among them, the input of the model is the real-time values of each harmonic and the real-time values of ambient temperature and humidity, and the output is the categories corresponding to different degradation levels (such as degradation levels 1, 2, and 3);

[0097] For the trend prediction of zinc oxide arresters, construct an attention mechanism model based on LSTM. Among them, the input of the model is the dynamic time-series characteristics of each harmonic, and the output is the predicted value of the high-frequency harmonic ratio HFR.

[0098] Regarding the training of the classification model, exemplarily, use 5-fold cross-validation to optimize the GBDT hyperparameters (such as tree depth, learning rate);

[0099] Regarding the training of the attention mechanism model, exemplarily, use the past 24 groups of harmonic data (such as 1 group per hour).

[0100] Furthermore, evaluate the degradation index DI based on the predicted value of the high-frequency harmonic ratio HFR:

[0101] 。

[0102] Exemplarily,

[0103] DI < 0.3: Normal;

[0104] 0.3 ≤ DI < 0.6: Early warning;

[0105] DI ≥ 0.6: Immediate maintenance.

[0106] If DI is continuously detected to be rising for multiple consecutive months, such as six consecutive months, a warning can be given as soon as possible to prompt operation and maintenance.

[0107] It can be seen that, compared with the prior art which can only judge the performance of zinc oxide arresters based on fundamental waves, the present invention realizes the precise management of the full life cycle of the state of zinc oxide arresters through the combination of joint multi-dimensional analysis of fundamental waves and high-order harmonics and machine learning time series prediction, upgrades from "passive threshold alarm" to "active health prediction", and significantly improves the reliability of the power grid.

[0108] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields. The above specific embodiments are merely illustrative and guiding, rather than restrictive. Those of ordinary skill in the art can also make many forms under the inspiration of this specification and without departing from the scope protected by the claims of the present invention, and these all belong to the scope of protection of the present invention.

Claims

1. A method for detecting the charged state of a zinc oxide lightning arrester, characterized in that: It includes the following steps: The voltage signal and current signal of the zinc oxide lightning arrester are synchronously measured using a voltage monitoring device and a current detection device based on Beidou satellite timing; The detection terminal is used to perform a fundamental wave and harmonic joint analysis on the voltage and current signals based on the fundamental wave and higher harmonics and adopts FFT transformation. The harmonic analysis obtains the amplitude and phase angle of the 3rd, 5th, 7th and 9th harmonics of the voltage and resistive current, and calculates the fundamental resistive current and the resistive current under each harmonic as well as the harmonic components of the voltage signal to judge the performance of the zinc oxide lightning arrester; in, The current detection device includes a plurality of magnetic wireless sensors arranged on the three phases of the corresponding plurality of zinc oxide lightning arresters, and collects current signals from all zinc oxide lightning arresters at the same time point in a manner of synchronously measuring current signals at multiple intervals; wherein the remote synchronous data based on Beidou satellite timing synchronously triggers the current detection devices located at different positions; In the detection terminal, the temperature-compensated crystal oscillator is used as the signal source of the DSP, and is used as the sampling clock after frequency division and 1PPS synchronization. The sampling clock is then used to externally control the data acquisition of the main CPU. At the same time, a microprocessor is used to extract the absolute time corresponding to 1PPS from the information provided by the Beidou satellite to give a time tag to the sampled data.

2. The method according to claim 1, characterized in that The current detection device is arranged on the three phases of the zinc oxide lightning arrester to synchronously measure the current signal of the three phases.

3. The method according to claim 1, characterized in that A voltage monitoring device is fixedly installed on the secondary side of the voltage transformer for online monitoring of the voltage signal of the voltage transformer. Multiple current detection devices are distributed on the vertical poles of the zinc oxide lightning arrester to measure the current signal of the zinc oxide lightning arrester. The voltage monitoring device and the current detection device are both communicatively connected to the Beidou satellite and the detection terminal via a wireless communication module.

4. The method according to claim 1, characterized in that The current detection device magnetically attracts the zinc oxide arrester pole.

5. The method according to claim 1, characterized in that The rising edge of the Beidou satellite second pulse corresponds to a certain UTC time, and the timing error is less than 20ns.

6. The method according to claim 1, characterized in that If the fundamental resistive current increases beyond a predetermined threshold, it is considered that the zinc oxide arrester is damp.

7. The method according to claim 1, characterized in that If the high-order harmonic current increases beyond the preset value, it is considered that the zinc oxide lightning arrester valve plate is aging.

8. The method according to claim 1, characterized in that The communication link must have a communication rate of at least 2MB / s.

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