Online monitoring device for lightning arrester of 10kV switch cabinet

Abstract

The invention discloses a 10kV switch cabinet lightning arrester on-line monitoring device and a 10kV switch cabinet lightning arrester on-line monitoring method. The device comprises a detection unit, a signal processing unit, a micro-control unit and a communication unit. The detection unit collects lightning arrester leakage current and lightning current signals through a specially-made micro-current transformer. The signal processing unit filters, amplifies and identifies the weak signal; the micro-control unit calculates a leakage current value in real time, performs lightning current counting, evaluates the health state of the lightning arrester by adopting a multi-parameter model fusing the leakage current value, the change rate of the leakage current value and the number of lightning strokes, and generates graded early warning information; and the communication unit uploads all data and evaluation results to a remote monitoring center in real time. According to the invention, the problem that the lightning arrester in the switch cabinet cannot be effectively monitored on line in the prior art is effectively solved, the transformation from regular maintenance to state maintenance is realized, and the power supply reliability is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of power operation and maintenance technology, and in particular to an online monitoring device for 10kV switchgear surge arresters. Background Technology

[0002] Zinc oxide surge arresters are critical devices in power systems that protect primary equipment in power generation, transmission, transformation, and distribution systems from damage caused by lightning overvoltages and switching overvoltages. Their core component is the zinc oxide resistance element, which possesses excellent nonlinear volt-ampere characteristics. Under normal operating voltage, a small power frequency leakage current flows through the arrester. The magnitude of this current is an important indicator of the arrester's insulation condition and aging degree. If the arrester deteriorates due to prolonged exposure to operating voltage, transient overvoltages, or environmental influences, its insulation performance will decrease, leading to a significant increase in leakage current. This may ultimately trigger thermal breakdown, causing the arrester to break down and lose its protective function, thus endangering the safe operation of the protected equipment.

[0003] Currently, monitoring the condition of surge arresters mainly relies on two methods: one is periodic manual inspection, which uses visual checks to detect external defects such as damage and discharge traces, but cannot detect internal performance degradation; the other is periodic power outages for preventative tests, such as measuring DC reference voltage and leakage current. These methods have significant time lags, cannot reflect the true condition of the surge arrester under real-time operating conditions, and require power outages, affecting power supply reliability.

[0004] With the development of smart grids and condition-based maintenance, online monitoring of primary equipment has become a trend. Currently, other major equipment in 10kV switchgear (such as circuit breakers and instrument transformers) has been gradually equipped with online monitoring sensors. However, for zinc oxide surge arresters inside the cabinet, due to their extremely weak leakage current signal (typically in the tens to hundreds of microamperes), and the confined space and severe electromagnetic interference inside the switchgear, accurately and reliably monitoring their total current (including resistive and capacitive components) online faces significant technical challenges. Existing technologies struggle to stably extract such weak power frequency current signals under strong electromagnetic interference environments, making it even more difficult to accurately count instantaneous lightning currents.

[0005] Therefore, developing an online monitoring device that is suitable for the internal environment of 10kV switchgear and can accurately monitor the leakage current of surge arresters and capture lightning current is of great significance for realizing early warning of surge arrester status and ensuring the safe operation of the power grid.

[0006] The information disclosed in this background section is included only to enhance the understanding of the context of this disclosure, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] One objective of this invention is to provide an online monitoring device for 10kV switchgear surge arresters, which can accurately monitor the leakage current of surge arresters and capture lightning current within 10kV switchgear, thereby enabling early warning of surge arrester status and ensuring the safe operation of the power grid.

[0008] To achieve the above objectives, the present invention provides an online monitoring device for 10kV switchgear surge arresters, comprising:

[0009] The detection unit is coupled to the grounding lead of the surge arrester to collect the leakage current signal and lightning current signal flowing through the surge arrester;

[0010] A signal processing unit, connected to the detection unit, is used to filter and amplify the acquired leakage current signal and identify the lightning current signal.

[0011] The microcontroller unit is connected to the signal processing unit and is used to calculate the leakage current value of the surge arrester in real time based on the processed signal and count the lightning current, and to evaluate the health status of the surge arrester in real time based on these data.

[0012] A communication unit is connected to the microcontroller unit;

[0013] The microcontroller unit is configured to upload the assessment results representing the health status, leakage current value, and lightning current count data to the remote monitoring system in real time through the communication unit, thereby realizing online real-time monitoring and early warning of the arrester's operating status.

[0014] Optionally, the detection unit includes a specially designed micro-current transformer. This micro-current transformer uses an open-core magnetic core structure made of high-permeability nanocrystalline alloy material and is mounted on the grounding lead of the surge arrester. The secondary winding of the micro-current transformer is wound with multi-layer shielded wire and placed inside an electromagnetic shielding cover. The micro-current transformer is specifically configured such that the turns ratio of its primary side to its secondary side is greater than 1000:1, enabling the micro-current transformer to convert a primary leakage current with a frequency of 50Hz and an amplitude of 10μA to 500μA into a secondary current signal with an amplitude of 10nA to 500nA, and simultaneously convert a lightning current signal with an amplitude greater than 0.5A into a secondary current signal of the same proportion.

[0015] Optionally, the signal processing unit includes:

[0016] A current-to-voltage conversion circuit is connected to the secondary side of the micro current transformer to convert the secondary side current signal into a voltage signal.

[0017] A high-order active filter amplifier circuit is connected to the current-to-voltage conversion circuit, and its center frequency is set to 50Hz. It is used to perform power frequency narrowband filtering and amplification on the voltage signal to suppress high-frequency electromagnetic interference.

[0018] An analog-to-digital converter is used to convert the filtered and amplified analog signal into a digital signal and provide it to the microcontroller unit.

[0019] Optionally, the signal processing unit further includes a lightning current triggering circuit, which includes a high-speed comparator configured to compare the voltage signal output by the current-to-voltage conversion circuit with a preset reference voltage, and when the voltage signal exceeds the reference voltage, immediately send a hardware interrupt signal to the microcontroller unit to trigger a lightning current count.

[0020] Optionally, the microcontroller is configured to calculate the real-time leakage current value by performing a fast Fourier transform on the filtered and amplified digital signal, extracting the power frequency fundamental component, and calculating the actual effective value of the leakage current based on the transformation ratio coefficient of the micro current transformer.

[0021] Optionally, the microcontroller unit is configured to assess the health status of the surge arrester in real time by:

[0022] A multi-parameter evaluation model is established, which uses the real-time leakage current value I, the rate of change of the leakage current value relative to the initial value dI / dt, and the number of lightning current accumulations N as input parameters.

[0023] The microcontroller unit has a pre-stored risk assessment function Risk=f(I,dI / dt,N) trained based on historical fault data. This function is used to calculate a comprehensive risk score.

[0024] The microcontroller compares the comprehensive risk score with multiple preset risk thresholds, thereby outputting graded status information including "normal", "attention", "warning", and "alarm", and uploading it in real time through the communication unit.

[0025] Optionally, the microcontroller unit is also configured to: when generating state information of "attention" level or above, synchronously record and store key data segments that trigger the state, including leakage current waveforms and timestamps of the event over a period of time before and after, and retrieve the data through the communication unit.

[0026] Optionally, a status indicator unit is also included, connected to the microcontroller unit, wherein the status indicator unit is configured to drive indicator lights or liquid crystal displays of different colors to display the local status based on the status information generated by the microcontroller unit.

[0027] Optionally, the communication unit is an RS-485 bus interface or a wireless communication module.

[0028] Optionally, the device is powered by the operating power supply of the switch cabinet and includes a power management circuit configured to convert the AC / DC 220V or DC 110V operating power supply of the switch cabinet into the operating voltage required by the chips inside the device.

[0029] The beneficial effects of this invention are as follows: It provides an online monitoring device for 10kV switchgear surge arresters, which continuously collects signals through the detection unit, and the signal processing unit and microcontroller unit complete real-time calculation and intelligent analysis locally. Finally, it actively and in real-time uploads key data such as evaluation results, leakage current values ​​and lightning current counts to a remote monitoring system (such as a substation integrated automation system or cloud platform) through an indispensable communication unit.

[0030] This design allows maintenance personnel to monitor the health status of each surge arrester in real time from a remote center, realizing the transformation from "periodic maintenance" to "condition-based maintenance," truly reflecting the value of "online real-time monitoring," and enabling timely early warnings before faults occur, greatly improving power supply reliability. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A schematic diagram of the structure of the 10kV switchgear surge arrester online monitoring device provided in the embodiment.

[0033] In the picture:

[0034] 1. Detection unit; 2. Signal processing unit; 3. Microcontroller unit; 4. Communication unit. Detailed Implementation

[0035] In this invention, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of the invention. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this invention, as long as there is no technical contradiction or conflict, the technical features mentioned in each embodiment can be combined in any way to form a corresponding implementable technical solution.

[0036] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit the invention.

[0037] In the description of this invention, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " generally indicates that the preceding and following objects have an "or" logical relationship.

[0038] In this invention, terms such as “first” and “second” are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy, or order between these entities or operations.

[0039] Without further limitations, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this invention is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0040] Similar to the understanding in the Examination Guidelines, in this invention, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments of this invention, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0041] In the description of the embodiments of the present invention, the spatial related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of the present invention or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0042] Unless otherwise explicitly stated or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this invention, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral arrangement; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this invention according to the specific circumstances.

[0043] See Figure 1 This embodiment provides an online monitoring device for 10kV switchgear surge arresters, comprising:

[0044] The detection unit 1 is used to be coupled to the grounding lead of the surge arrester to collect the leakage current signal and lightning current signal flowing through the surge arrester;

[0045] Signal processing unit 2, which is connected to the detection unit, is used to filter and amplify the collected leakage current signal and identify the lightning current signal.

[0046] The microcontroller unit 3 is connected to the signal processing unit and is used to calculate the leakage current value of the surge arrester in real time based on the processed signal and count the lightning current, and to evaluate the health status of the surge arrester in real time based on these data.

[0047] Communication unit 4 is connected to the microcontroller unit;

[0048] The microcontroller unit is configured to upload the assessment results representing the health status, leakage current value, and lightning current count data to the remote monitoring system in real time through the communication unit, thereby realizing online real-time monitoring and early warning of the arrester's operating status.

[0049] The core innovation of this device lies in constructing a complete, real-time closed-loop monitoring chain from signal sensing to remote status updates. Fundamentally different from existing technologies that rely on manual periodic inspections or offline testing, this device continuously collects signals through its detection unit, while the signal processing unit and microcontroller unit perform real-time calculations and intelligent analysis locally. Finally, through an indispensable communication unit, it proactively and in real-time uploads key data such as assessment results, leakage current values, and lightning current counts to a remote monitoring system (such as a substation integrated automation system or cloud platform). This design allows maintenance personnel to monitor the health status of each surge arrester in real-time from a remote center, realizing a shift from "periodic maintenance" to "condition-based maintenance," truly demonstrating the value of "online real-time monitoring," and enabling timely early warnings before faults occur, greatly improving power supply reliability.

[0050] In this embodiment, the detection unit includes a specially designed micro-current transformer. The micro-current transformer adopts an open magnetic core structure made of high-permeability nanocrystalline alloy material and is fitted onto the grounding lead of the surge arrester. The secondary winding of the micro-current transformer is wound with multi-layer shielded wire and placed inside an electromagnetic shielding cover. The micro-current transformer is specifically configured such that the turns ratio of its primary side to its secondary side is greater than 1000:1, so that the micro-current transformer can convert a primary leakage current with a frequency of 50Hz and an amplitude of 10μA to 500μA into a secondary current signal with an amplitude of 10nA to 500nA, and at the same time convert a lightning current signal with an amplitude greater than 0.5A into a secondary current signal of the same proportion.

[0051] In this embodiment, the current transformer is not a standard component, but a special design to solve the problem of measuring nA-level signals. The high-permeability nanocrystalline alloy core ensures extremely high sensitivity under power frequency conditions, effectively capturing microampere-level primary currents. The open core structure facilitates field installation without disconnecting the grounding lead. The secondary winding uses multi-layer shielded wire and is equipped with an electromagnetic shielding cover to resist strong electromagnetic interference within the switchgear, a key measure to ensure the signal-to-noise ratio. By explicitly limiting the turns ratio to greater than 1000:1 and specifying the current conversion range (10μA to 500μA to 10nA to 500nA), the operating range of the current transformer is defined, enabling it to accurately measure minute leakage currents while transmitting large lightning current signals without distortion. This wide dynamic range design is the hardware foundation of this invention.

[0052] Furthermore, the signal processing unit includes:

[0053] A current-to-voltage conversion circuit is connected to the secondary side of the micro current transformer to convert the secondary side current signal into a voltage signal.

[0054] A high-order active filter amplifier circuit is connected to the current-to-voltage conversion circuit, and its center frequency is set to 50Hz. It is used to perform power frequency narrowband filtering and amplification on the voltage signal to suppress high-frequency electromagnetic interference.

[0055] An analog-to-digital converter is used to convert the filtered and amplified analog signal into a digital signal and provide it to the microcontroller unit.

[0056] The current-to-voltage conversion circuit typically consists of an operational amplifier with high input impedance, converting nanoamp-level current into a easily processed voltage signal. The high-order active filter amplifier circuit is the core of this unit; the higher the order, the better the filtering effect. This implementation preferably uses a fourth-order or higher Butterworth or Chebyshev filter, with the center frequency strictly set at 50Hz and an extremely narrow bandwidth, thus effectively filtering out high-frequency switching noise and harmonic interference, amplifying only the power frequency signal. The analog-to-digital converter uses a high-resolution ADC chip to ensure accurate digitization of the amplified signal. These three circuit stages are interconnected, working together to extract and purify the easily obscured weak but useful signals.

[0057] Optionally, the signal processing unit further includes a lightning current triggering circuit, which includes a high-speed comparator configured to compare the voltage signal output by the current-to-voltage conversion circuit with a preset reference voltage, and when the voltage signal exceeds the reference voltage, immediately send a hardware interrupt signal to the microcontroller unit to trigger a lightning current count.

[0058] Lightning currents are extremely short-lived (on the order of microseconds), making them highly susceptible to being missed if detected using software polling methods. This implementation employs a high-speed comparator (with a response time on the order of nanoseconds) to construct a hardware triggering loop. This circuit runs parallel to the main signal conditioning path, directly monitoring the raw signal voltage after current-to-voltage conversion. A preset reference voltage is precisely calculated and set at a level far exceeding the maximum possible power frequency leakage signal amplitude but below the typical lightning current induced voltage. When a lightning current arrives, the signal voltage instantaneously exceeds this threshold, and the high-speed comparator immediately responds and outputs a clear digital pulse (hardware interrupt signal) to the microcontroller. This hardware comparison-based interrupt mechanism ensures the accuracy and reliability of lightning current counting and is an indispensable part of achieving "full current" monitoring.

[0059] In this embodiment, the microcontroller is configured to calculate the real-time leakage current value by performing a fast Fourier transform on the filtered and amplified digital signal, extracting the power frequency fundamental component, and calculating the actual effective value of the leakage current based on the transformation ratio coefficient of the micro current transformer.

[0060] In complex electromagnetic environments, directly measuring the peak or RMS value of a signal can result in significant errors due to the presence of numerous harmonics and noise interference. In this embodiment, the microcontroller is configured to execute a Fast Fourier Transform (FFT) algorithm. This algorithm converts a segment of the time-domain signal sampled by the ADC into a frequency-domain signal, allowing for precise separation of the 50Hz fundamental component, harmonic components, and noise. By extracting the amplitude of the 50Hz fundamental component for calculation, the influence of other frequency interferences can be completely eliminated. Combined with the micro-current transformer ratio coefficient pre-stored in the microcontroller, the true and clean RMS value of the power frequency leakage current can be calculated. This spectrum analysis-based measurement method significantly improves the accuracy and reliability of monitoring data, providing a high-quality data foundation for subsequent condition assessments.

[0061] In this embodiment, the microcontroller unit is configured to evaluate the health status of the surge arrester in real time by means of the following:

[0062] A multi-parameter evaluation model is established, which uses the real-time leakage current value I, the rate of change of the leakage current value relative to the initial value dI / dt, and the number of lightning current accumulations N as input parameters.

[0063] The microcontroller unit has a pre-stored risk assessment function Risk=f(I,dI / dt,N) trained based on historical fault data. This function is used to calculate a comprehensive risk score.

[0064] The microcontroller compares the comprehensive risk score with multiple preset risk thresholds, thereby outputting graded status information including "normal", "attention", "warning", and "alarm", and uploading it in real time through the communication unit.

[0065] Unlike simple single-threshold comparisons, this implementation establishes a multi-parameter evaluation model. This model comprehensively considers the real-time leakage current value (I), reflecting the current insulation level of the surge arrester; the leakage current change rate (dI / dt), which better predicts early deterioration trends; and the cumulative number of lightning currents (N), reflecting the cumulative stress it has endured. The risk assessment function Risk=f(I,dI / dt,N), pre-stored within the microcontroller, is obtained through machine learning training on a large amount of historical normal operation data and fault case data. It can more scientifically characterize the nonlinear relationship between the three parameters and the health status of the surge arrester. By comparing the calculated comprehensive risk score with multi-level thresholds, graded status information such as "normal," "caution," "warning," and "alarm" can be output. This data-driven and multi-parameter fusion-based evaluation method significantly improves the accuracy of diagnosis and early warning capabilities compared to traditional methods, while reducing false alarms and missed alarms.

[0066] Furthermore, the microcontroller unit is also configured to: when generating state information of "attention" level or above, synchronously record and store key data segments that trigger the state, including leakage current waveforms and timestamps of the event over a period of time before and after, and retrieve the data through the communication unit.

[0067] This embodiment adds a crucial data traceability function to the intelligent assessment. When the microcontroller determines that the surge arrester's status is abnormal ("Attention" or above), it not only generates an alarm message but also automatically triggers a data logging process. This process saves raw data (such as leakage current waveform data) and key markers (such as precise timestamps) for a period of time before and after the triggering event. This data forms a "black box" record, which can be remotely read through the communication unit. This function provides maintenance personnel with valuable post-event analysis data, allowing them to replay the changes in electrical quantities before and after the fault, accurately pinpoint the cause of the problem, and greatly facilitate fault diagnosis and subsequent equipment quality improvement.

[0068] Optionally, the 10kV switchgear surge arrester online monitoring device further includes a status indication unit, which is connected to the microcontroller unit. The status indication unit is configured to drive indicator lights or liquid crystal displays of different colors to display the local status based on the status information generated by the microcontroller unit.

[0069] The status indicator unit serves as the interface for direct communication between the device and on-site inspection personnel. It can consist of a set of multi-color LEDs (e.g., solid green for normal operation, solid yellow for alert, flashing yellow for warning, and solid red for alarm) and / or a small LCD screen. The microcontroller drives the corresponding display components based on the evaluation results, allowing inspection personnel to quickly and intuitively understand the current basic status of the surge arrester simply by observing the device panel on the cabinet door, without the need for any specialized tools, thus achieving the most convenient local monitoring.

[0070] In this embodiment, the communication unit is an RS-485 bus interface or a wireless communication module. The RS-485 bus interface is a widely used, mature, and interference-resistant wired communication method in industrial monitoring, particularly suitable for reliable data transmission in complex electromagnetic environments such as substations. Wireless communication modules (such as 4G, NB-IoT, or LoRa) provide flexible networking solutions without the need for additional wiring, especially suitable for scenarios where laying communication cables is difficult, such as power distribution automation and distributed switchgear. These two communication methods cover the main application scenarios of this device, ensuring that evaluation results and monitoring data can be flexibly and reliably accessed by various types of remote monitoring systems.

[0071] Optionally, the device is powered by the operating power supply of the switch cabinet and includes a power management circuit configured to convert the AC / DC 220V or DC 110V operating power supply of the switch cabinet into the operating voltage required by the chips inside the device.

[0072] To maximize the device's versatility and ease of installation, its power supply is designed to draw power directly from the existing operating power supply within the switch cabinet. This operating power supply is typically AC / DC 220V or DC 110V. The internal power management circuitry is a critical component, requiring a wide input voltage range, high isolation withstand voltage, and efficient voltage regulation and filtering performance. It must be able to convert the fluctuating field operating power supply into the stable, clean low-voltage DC power (e.g., ±12V, 5V, 3.3V) required by the chip. This design ensures stable and reliable operation of the device in harsh power environments, providing a fundamental guarantee for achieving "online" monitoring.

[0073] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. An online monitoring device for 10kV switchgear surge arresters, characterized in that, include: The detection unit is coupled to the grounding lead of the surge arrester to collect the leakage current signal and lightning current signal flowing through the surge arrester; A signal processing unit, connected to the detection unit, is used to filter and amplify the acquired leakage current signal and identify the lightning current signal. The microcontroller unit is connected to the signal processing unit and is used to calculate the leakage current value of the surge arrester in real time based on the processed signal and count the lightning current, and to evaluate the health status of the surge arrester in real time based on these data. A communication unit is connected to the microcontroller unit; The microcontroller unit is configured to upload the assessment results representing the health status, leakage current value, and lightning current count data to the remote monitoring system in real time through the communication unit, thereby realizing online real-time monitoring and early warning of the arrester's operating status.

2. The 10kV switchgear surge arrester online monitoring device according to claim 1, characterized in that, The detection unit includes a specially designed micro-current transformer. This micro-current transformer uses an open-core magnetic core structure made of high-permeability nanocrystalline alloy material and is mounted on the grounding lead of the surge arrester. The secondary winding of the micro-current transformer is wound with multi-layer shielded wire and placed inside an electromagnetic shielding cover. The micro-current transformer is specifically configured such that the turns ratio of its primary side to its secondary side is greater than 1000:1, enabling the micro-current transformer to convert a primary leakage current with a frequency of 50Hz and an amplitude of 10μA to 500μA into a secondary current signal with an amplitude of 10nA to 500nA, and simultaneously convert a lightning current signal with an amplitude greater than 0.5A into a secondary current signal of the same proportion.

3. The 10kV switchgear surge arrester online monitoring device according to claim 2, characterized in that, The signal processing unit includes: A current-to-voltage conversion circuit is connected to the secondary side of the micro current transformer to convert the secondary side current signal into a voltage signal. A high-order active filter amplifier circuit is connected to the current-to-voltage conversion circuit, and its center frequency is set to 50Hz. It is used to perform power frequency narrowband filtering and amplification on the voltage signal to suppress high-frequency electromagnetic interference. An analog-to-digital converter is used to convert the filtered and amplified analog signal into a digital signal and provide it to the microcontroller unit.

4. The 10kV switchgear surge arrester online monitoring device according to claim 3, characterized in that, The signal processing unit further includes a lightning current triggering circuit, which contains a high-speed comparator configured to compare the voltage signal output by the current-to-voltage conversion circuit with a preset reference voltage, and when the voltage signal exceeds the reference voltage, immediately send a hardware interrupt signal to the microcontroller unit to trigger a lightning current count.

5. The 10kV switchgear surge arrester online monitoring device according to claim 1, characterized in that, The microcontroller unit is configured to calculate the real-time leakage current value by performing a fast Fourier transform on the filtered and amplified digital signal, extracting the power frequency fundamental component, and calculating the actual effective value of the leakage current based on the transformation ratio coefficient of the micro current transformer.

6. The 10kV switchgear surge arrester online monitoring device according to claim 1, characterized in that, The microcontroller unit is configured to assess the health status of the surge arrester in real time by: A multi-parameter evaluation model is established, which uses the real-time leakage current value I, the rate of change of the leakage current value relative to the initial value dI / dt, and the number of lightning current accumulations N as input parameters. The microcontroller unit has a pre-stored risk assessment function Risk=f(I,dI / dt,N) trained based on historical fault data. This function is used to calculate a comprehensive risk score. The microcontroller unit compares the comprehensive risk score with multiple preset risk thresholds, thereby outputting graded status information including "normal", "attention", "warning" and "alarm", and uploading it in real time through the communication unit.

7. The 10kV switchgear surge arrester online monitoring device according to claim 6, characterized in that, The microcontroller unit is also configured to: when generating "attention" or higher level status information, synchronously record and store key data segments that trigger the status, including leakage current waveforms and timestamps of the event over a period of time before and after, and retrieve the data through the communication unit.

8. The 10kV switchgear surge arrester online monitoring device according to claim 1, characterized in that, It also includes a status indicator unit connected to the microcontroller unit, which is configured to drive indicator lights or liquid crystal displays of different colors to display the local status based on the status information generated by the microcontroller unit.

9. The 10kV switchgear surge arrester online monitoring device according to claim 1, characterized in that, The communication unit is an RS-485 bus interface or a wireless communication module.

10. The 10kV switchgear surge arrester online monitoring device according to claim 1, characterized in that, The device is powered by the operating power supply of the switch cabinet and includes a power management circuit configured to convert the AC / DC 220V or DC 110V operating power supply of the switch cabinet into the operating voltage required by the chips inside the device.

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