Low-voltage lightning surge comprehensive protection device and method based on nano-composite valve plate

Abstract

The application relates to a low-voltage lightning surge comprehensive protection device and method based on a nano composite valve sheet in the technical field of low-voltage power distribution system lightning protection, which comprises an input module, an overvoltage protection module, a signal acquisition module and a digital monitoring and processing module. The overvoltage protection module adopts a phase-phase and phase-ground multi-branch parallel lightning protection topology structure. Each branch is provided with a composite nonlinear protection unit composed of an electrically parallel nano modified SiC valve sheet group and a ZnO zinc oxide valve sheet group. The two kinds of valve sheet nonlinear characteristics are cooperatively matched to realize comprehensive lightning surge protection of a low-voltage power distribution system. The application can improve the lightning protection reliability of the low-voltage power distribution system, realize online monitoring and intelligent operation and maintenance of the lightning protection device, and has the characteristics of fast response speed, low residual voltage, high reliability and the like.

Description

Technical Field

[0001] This invention relates to the field of lightning protection technology for low-voltage power distribution systems, specifically to a low-voltage lightning surge integrated protection device based on nanocomposite valve plates and a lightning surge integrated protection method applied to the low-voltage lightning surge integrated protection device. Background Technology

[0002] With the widespread application of low-voltage power distribution systems in industrial production, commercial buildings, and infrastructure, the requirements for power supply reliability and operational safety of electrical equipment are constantly increasing. Lightning surges, characterized by high amplitude, short duration, and steep rise time, can easily couple into low-voltage power distribution systems through power lines, causing impact damage to sensitive electronic equipment, control systems, and electrical terminals. Therefore, configuring lightning protection devices in low-voltage power distribution systems is of great significance for reducing the hazards of lightning overvoltages and ensuring the safe operation of equipment.

[0003] Existing low-voltage lightning protection devices typically use zinc oxide (ZnO) varistor materials as the main nonlinear protection element, utilizing their nonlinear volt-ampere characteristics to achieve overvoltage limitation and surge energy discharge. However, single zinc oxide varistor materials still have certain limitations in practical applications: on the one hand, there is an insufficient match between its response characteristics and the rapid rise edge of lightning surges, making it difficult to maintain rapid clamping capability under extremely high-speed transient impacts; on the other hand, after long-term exposure to multiple lightning strikes or abnormal overvoltages, the performance of the varistor element will gradually degrade, and existing devices usually lack effective means of sensing the valve plate's operating status, leakage current changes, and aging degree, making it difficult to detect the degradation of protection performance in a timely manner.

[0004] Furthermore, overvoltage types in low-voltage power distribution systems are diverse. In addition to lightning surges, they may also be affected by transient processes such as operational impulses, resonant overvoltages, and single-phase intermittent arcing grounding. Traditional single protection components cannot simultaneously meet the requirements of rapid response, high energy tolerance, and long-term condition monitoring, and cannot adapt to the ever-increasing demands of intelligent power distribution systems for the reliability and operation and maintenance management capabilities of lightning protection devices.

[0005] Therefore, it is necessary to propose a low-voltage lightning surge integrated protection device with a novel nonlinear protection structure that can take into account both rapid response to lightning surges and high energy discharge capability, and has online monitoring and intelligent analysis functions for operation status, so as to improve the lightning protection level of low-voltage power distribution systems and the reliability of equipment operation. Summary of the Invention

[0006] The purpose of this invention is to provide a low-voltage lightning surge integrated protection device and method based on nanocomposite valve plates, so as to solve the problems that in existing low-voltage lightning protection devices, a single nonlinear protection element is difficult to simultaneously take into account the rapid response capability and high energy discharge capability of lightning surges, as well as the difficulty in monitoring the long-term operating status of the protection element and the inability to provide timely warning of performance degradation.

[0007] To address the aforementioned issues, this invention provides a low-voltage lightning surge integrated protection device based on nanocomposite valve plates, comprising an input module, an overvoltage protection module, a signal acquisition module, and a digital monitoring and processing module. The input module includes three phase lines L1, L2, L3, neutral line N, and protective grounding line PE, which are used to connect to the low-voltage power distribution system, complete the line connection and lightning protection grounding adaptation, so as to realize the acquisition of the operating status of the protected line by the protection device. The overvoltage protection module is electrically connected to the input module and is provided with multiple sets of independent parallel lightning surge discharge branches. Each lightning surge discharge branch is equipped with a composite nonlinear protection unit. The composite nonlinear protection unit is composed of a parallel connection of nano-modified SiC valve plate group and a ZnO zinc oxide valve plate group, forming a composite lightning protection structure with complementary characteristics. The nano-modified SiC valve plate group has ultra-fast response characteristics, which is used to quickly clamp the leading edge of lightning surges and suppress voltage changes. The ZnO zinc oxide valve plate group has high current carrying capacity and high energy tolerance characteristics, which is used to discharge the impact energy of high-energy lightning surges. Through the hierarchical synergy of the two, multi-level comprehensive lightning surge protection of low-voltage power distribution systems can be achieved, solving the defects of traditional single zinc oxide surge protection devices that cannot simultaneously take into account fast surge response and high energy discharge.

[0008] The signal acquisition module is weakly connected to and electrically isolated from the overvoltage protection module, and is used to acquire branch leakage current and line surge voltage signals under lightning protection conditions. The digital monitoring and processing module is electrically connected to the signal acquisition module, and is used to receive and analyze the acquired signals, determine the aging status of the valve plate lightning protection and the abnormal working condition of the line lightning, and realize the monitoring and alarm output of the device lightning protection status.

[0009] To achieve classified protection, the lightning surge discharge branch includes a phase-to-phase overvoltage protection branch and a phase-to-ground overvoltage protection branch; The phase-to-phase protection branch is connected between any two phase lines to suppress phase-to-phase lightning induced overvoltage; the phase-to-ground lightning protection branch is connected between the phase line and the protective grounding wire to discharge line-to-ground direct lightning strikes and induced lightning surges. Each protective branch is independently and connected in parallel to form an independent overvoltage energy discharge channel, achieving full coverage protection for all points and types of lightning impulse overvoltages in the low-voltage power distribution system.

[0010] The nano-modified SiC valve plate assembly possesses ultrafast response nonlinear characteristics, making it suitable for scenarios involving rapid suppression of lightning surge fronts; the ZnO zinc oxide valve plate assembly possesses high current-carrying capacity and high energy tolerance characteristics, making it suitable for scenarios involving the discharge of high-energy lightning surges; the differentiated current-voltage characteristics of the two components work together to simultaneously meet the dual lightning protection requirements of suppressing lightning transient spikes and discharging large-capacity lightning energy.

[0011] The nano-modified SiC valve plate adopts a nano-composite ceramic material structure, including nano-scale silicon carbide (SiC) functional powder, zinc oxide (ZnO) ceramic matrix material, and nano-modifying additive Bi2O3. The nano-scale silicon carbide (SiC) functional powder is uniformly distributed in the zinc oxide (ZnO) ceramic matrix. Through the composite of nano-components and the regulation of grain boundary structure during sintering, a stable nonlinear resistance characteristic is formed inside the composite material, thereby improving the valve plate's response capability to transient overvoltage and its impact resistance capability.

[0012] The ZnO zinc oxide valve plate assembly is made of zinc oxide varistor material and is used to absorb and release energy under high amplitude overvoltage conditions.

[0013] By combining nano-modified SiC composite valve plate groups with ZnO zinc oxide valve plate groups in parallel, two protection elements with different nonlinear current-voltage characteristics are combined to form a complementary structure, achieving comprehensive overvoltage protection that combines low-amplitude fast response with high-energy impulse discharge.

[0014] Furthermore, the signal acquisition module includes a leakage current detection unit, a voltage acquisition unit, an action count detection unit, and a time recording unit; The leakage current detection unit is used to collect real-time leakage current signals of the lightning surge discharge branch; the voltage acquisition unit adopts a capacitor voltage divider structure to collect lightning surge voltage signals and normal operating voltage signals of the power distribution line; the action count detection unit is used to identify and count the number of protection actions caused by lightning impact; the time recording unit is used to record the time information of the corresponding protection actions.

[0015] The signal acquisition module adopts a low-voltage acquisition circuit layout, which is electrically isolated from the main lightning protection circuit, effectively avoiding strong lightning impact interference and ensuring stable and reliable acquisition signals.

[0016] Furthermore, the digital monitoring and processing module has a built-in software timestamp generation function, which is used to match the precise action time information for each lightning protection action. The digital monitoring and processing module includes a digital processing unit MCU, a data storage module, and a power supply module. The power module provides a stable power supply for the digital processing unit (MCU), the data storage module, and various low-voltage functional units; the digital processing unit (MCU) is used to receive and parse surge voltage, leakage current, and lightning action data; the data storage module is used to store the device's lightning protection operation parameters, lightning action history records, valve status data, and alarm information.

[0017] Furthermore, the digital processing unit (MCU) includes a signal filtering module and a resistive current analysis module; The signal filtering module uses the internally generated power frequency reference signal as a benchmark and employs the Least Mean Square Error (LMS) adaptive algorithm to iteratively update the filter weight coefficients in real time. The formula for updating the weight coefficients is as follows: In the formula, These are the filter weight coefficients; For adaptive step size; This is an error signal; This is the reference input signal.

[0018] The above algorithm can effectively reduce the impact of power frequency harmonics and high-frequency interference on the detection signal, and obtain a more accurate fundamental voltage signal and fundamental current signal.

[0019] The resistive current analysis module receives the filtered fundamental voltage signal and fundamental current signal, and extracts the phase difference between them. To achieve the calculation of resistive current components, The formula for calculating the resistive current component is as follows: in: Represents the resistive current component; This represents the effective value of the total leakage current; This represents the phase difference between the fundamental voltage wave and the fundamental leakage current wave.

[0020] The resistive current component obtained by separation It can reflect the internal performance changes of nano-modified SiC composite valve plate groups and ZnO valve plate groups.

[0021] The MCU (Microcontroller Unit) calculates the resistive current component. Recorded values ​​of the initial state of the protection device Comparisons were made to determine the performance changes of the composite nonlinear protection unit; Specifically, when the following is detected: At that time, the valve plate was determined to be in normal condition; When detected: When the valve plate shows signs of aging, a warning message is output. When detected: When the valve plate reaches the end of its service life, a maintenance and replacement prompt will be output.

[0022] The aforementioned state evaluation method based on resistive current changes can identify the performance degradation trend of internal nonlinear protection components in advance before a significant fault occurs in the protection device, thereby improving the operational reliability of the protection device.

[0023] Furthermore, the digital monitoring and processing module also includes a status indication unit, a local alarm unit, a 4G wireless communication module, and an RS485 wired communication interface; The status indicator unit is used to display the lightning protection operation status of the device; the local alarm unit is used to output a local alarm when there is an abnormal lightning impact or the lightning protection performance of the valve plate exceeds the standard; the 4G wireless communication module and RS485 wired communication interface are used to upload lightning action data, valve plate lightning protection status, and alarm information to an external monitoring terminal; the RS485 wired communication interface is compatible with local debugging and field networking.

[0024] Furthermore, the low-voltage lightning surge integrated protection device also includes a remote monitoring terminal, which communicates bidirectionally with the digital monitoring and processing module; The remote monitoring terminal includes a data management platform and a mobile communication terminal, which are used to receive lightning protection operation data uploaded by the device, and realize online monitoring of lightning action in low-voltage systems, lightning protection status assessment, abnormal alarms, and valve plate life prediction and maintenance management.

[0025] This invention also provides a comprehensive lightning surge protection method for low-voltage power distribution systems, applied to the aforementioned low-voltage lightning surge protection device based on nanocomposite valve plates, comprising the following steps: S1. Collect terminal voltage signals, leakage current signals, number of protection actions, and action time information during the operation of the protection device through the signal acquisition module; S2. The collected data is processed and analyzed by the MCU (Microcontroller Unit). S3. When an abnormal operating state is detected, the corresponding level of status alarm information is sent to the remote monitoring terminal through the communication module. S4. The remote monitoring terminal evaluates the operating status of the protection device based on the operating data, action records, and status analysis results uploaded by the protection device, and outputs the status monitoring results and maintenance prompts.

[0026] Furthermore, step S2 specifically includes the following steps: S2-1. Perform digital filtering on the acquired voltage and leakage current signals to obtain voltage and current characteristic signals for state analysis. S2-2. Perform phase analysis based on the voltage characteristic signal and current characteristic signal to extract the resistive current component in the leakage current; S2-3. Compare the resistive current component with the preset aging criterion, and determine the operating status of the nanocomposite valve plate based on the comparison result. S2-4. Compare the acquired terminal voltage signal with the preset overvoltage criterion to determine the overvoltage type and the operating status of the composite nonlinear protection unit.

[0027] In summary, compared with the prior art, the present invention has the following technical advantages and beneficial effects: (1) This invention adopts a hierarchical protection topology with zinc oxide valves connected in series in the main circuit and a zinc oxide-nano-modified SiC parallel composite unit set at the rear end. The difference in the volt-ampere characteristics of the two types of valves is used to achieve synergistic operation. When the surge front arrives, the nano-modified SiC valves preferentially and quickly conduct and clamp the voltage to suppress the instantaneous overvoltage spike. Under high-energy lightning strike conditions, the front-end series zinc oxide valves and the rear-end parallel composite unit jointly divert and discharge energy, which not only improves the surge response speed but also improves the overall current carrying capacity, effectively reduces the impact residual voltage, and reduces the insulation stress of the downstream electrical equipment.

[0028] (2) The present invention sets up multiple independent protection branches for phase-to-phase and phase-to-ground to realize full-point overvoltage protection of low-voltage power distribution system, eliminate the protection blind zone of phase-to-phase and neutral line coupling surge, and can simultaneously cope with various transient interferences such as lightning induced surge and power grid operation overvoltage, and the protection coverage is more comprehensive.

[0029] (3) Each protection branch is equipped with independent leakage current sampling. With the strong and weak current isolation acquisition architecture, the resistive and capacitive components of leakage current can be separated, and the detection error caused by power frequency harmonics and strong electromagnetic interference on site can be suppressed. Combined with the built-in filtering and aging diagnosis algorithm of MCU, the degradation status of series valve plates and parallel composite units can be monitored respectively, and the aging trend of valve plates can be predicted. This changes the traditional mode of relying on manual inspection and facilitates intelligent operation and maintenance in unattended scenarios.

[0030] (4) Under the hierarchical topology, the series zinc oxide valve plate shares most of the continuous power frequency voltage, and the voltage stress of the parallel composite unit at the back end is reduced, which slows down the aging rate of nano-modified SiC and zinc oxide valve plate, extends the overall service life of the device, and improves the long-term operational reliability of the lightning protection device. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the low-voltage lightning surge integrated protection device based on nanocomposite valve plates of the present invention; Figure 2 This is a circuit diagram of the overvoltage protection module of the present invention; Figure 3 This is a schematic diagram of the structure of the composite nonlinear protection unit of the present invention; Figure 4 This is a schematic diagram comparing the volt-ampere characteristics of the nano-modified SiC composite valve plate group and the ZnO zinc oxide valve plate group of the present invention; Figure 5 This is a schematic diagram of the operation status monitoring and early warning process of the low-voltage lightning surge integrated protection device of the present invention. Detailed Implementation

[0032] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0033] like Figure 1 The low-voltage lightning surge protection device shown is based on a nanocomposite valve plate and is mainly used for the protection of various lightning surge overvoltages such as direct lightning strikes and induced lightning in low-voltage power distribution systems. It can also be used to assist in the suppression of switching overvoltages, resonant overvoltages and single-phase intermittent arc grounding transient overvoltages. The low-voltage lightning surge protection device includes an input module, an overvoltage protection module, a signal acquisition module and a digital monitoring and processing module.

[0034] Specifically, the input module is used to realize the electrical connection between the protection device and the low-voltage power distribution system, including the three-phase phase lines L1, L2, L3, neutral line N, and protective grounding line PE; In practical applications, the input module is connected to the power supply line of the low-voltage power distribution system. By collecting the operating voltage status on the power supply line, the protection device can protect against abnormal voltages such as lightning-induced overvoltage, switching overvoltage, resonant overvoltage, and single-phase intermittent arc grounding transient overvoltage generated during the operation of the low-voltage system.

[0035] Specifically, the overvoltage protection module is electrically connected to the input module and is used to quickly suppress and dissipate energy from various transient overvoltages caused by lightning strikes. Combined with... Figure 2 As shown, the overvoltage protection module includes a lightning surge discharge branch with multiple branches in parallel topology, and each of the lightning surge discharge branches is equipped with a composite nonlinear protection unit. Among them, the lightning surge discharge branch of the multi-branch parallel topology includes phase-to-phase overvoltage protection branch and phase-to-ground overvoltage protection branch; The phase-to-phase overvoltage protection branch is connected between any two phase lines, such as between L1 and L2, L2 and L3, and L3 and L1. It is mainly used to suppress lightning induced overvoltage between two phases in a low-voltage power distribution system. The phase-to-ground overvoltage protection branch is connected between each phase line and the protective grounding wire (PE) to provide a dedicated fast discharge path for direct lightning strikes to ground and induced lightning surges.

[0036] By using the above-mentioned multi-branch parallel topology, dedicated discharge channels are set up for different locations and different types of lightning surge overvoltages, enabling different types of abnormal overvoltages to respond quickly through the corresponding protection branches, greatly improving the adaptability and reliability of the device's lightning surge protection.

[0037] like Figure 3 As shown, the composite nonlinear protection unit includes a nano-modified SiC valve plate group and a ZnO zinc oxide valve plate group that are electrically connected in parallel. The two have complementary current-voltage characteristics and work together to solve the technical shortcomings of traditional single zinc oxide lightning protection devices that cannot simultaneously take into account fast response to lightning surge front and high-energy lightning discharge. Among them, the nano-modified SiC valve plate is made of a nonlinear resistive composite material with zinc oxide ceramic as the matrix and composite nano-silicon carbide powder, while the ZnO zinc oxide valve plate assembly is made of conventional high voltage sensitive zinc oxide resistor material.

[0038] In this embodiment, the nano-modified SiC valve plate is prepared using a nanocomposite ceramic material, comprising nanoscale silicon carbide (SiC) functional powder, zinc oxide (ZnO) ceramic matrix material, and nano-modifying additive Bi₂O₃. By combining the nano-SiC powder with the ZnO ceramic material and using the nano-modifying additive Bi₂O₃ to regulate the grain boundary structure, the composite valve plate forms a conductive network structure with nonlinear resistive characteristics, thereby improving its response to transient overvoltages and its impact energy withstand capability.

[0039] Depend on Figure 4 As shown in the voltage-current characteristic curves, the nano-modified SiC composite valve plate, due to the combination of nano-scale silicon carbide functional powder and zinc oxide (ZnO) ceramic matrix, and the regulation of the material's grain boundary structure by the nano-modifying additive Bi₂O₃, forms a composite ceramic structure with nonlinear resistance characteristics. Under low to medium amplitude overvoltages, this composite valve plate can enter the nonlinear response region earlier, causing its resistance characteristics to change with the increase of the applied voltage. This allows for rapid response in the initial stage of overvoltage and limits the voltage rise, reducing the transient overvoltage impact on the protected equipment.

[0040] Furthermore, the ZnO zinc oxide valve plate has a high nonlinear coefficient, maintains a high impedance state within the normal operating voltage range, and quickly enters a low-resistance conduction state under high-amplitude overvoltage, which can withstand a large inrush current and realize the absorption and discharge of overvoltage energy.

[0041] Therefore, in this embodiment, the nano-modified SiC valve plate group and the ZnO zinc oxide valve plate group are connected in parallel to form a composite nonlinear protection structure.

[0042] When low-amplitude lightning spikes and surge initiation overvoltages occur, the nano-modified SiC valve plate group responds preferentially and quickly limits voltage mutations; When the overvoltage amplitude rises sharply and is accompanied by a large amount of lightning energy input, the ZnO zinc oxide valve plate group takes the lead in conducting and discharging, completing the high-energy lightning surge protection. The two work together to achieve multi-level, all-condition comprehensive lightning surge protection.

[0043] To further verify the lightning protection performance of the composite nonlinear protection unit of the present invention in low-voltage power distribution systems of different voltage levels, this embodiment conducts lightning impulse tests on the key electrical parameters of the composite valve plate structure under the nominal voltage conditions of 400V, 660V, 750V, and 1000V systems. The test results are shown in Table 1 and... Figure 4 As shown.

[0044] Table 1 Key electrical parameters of composite nonlinear protection unit under different system nominal voltages As shown in the test data in Table 1, by matching and adjusting the ratio of nano-SiC and ZnO valve plate parameters, this invention can be adapted to low-voltage power distribution systems of various levels: the residual voltage value of 8 / 20μs, 5kA standard lightning impulse can be controlled within the range of 514V to 1126V at each voltage level, the peak surge suppression value can be stably controlled within 1.45pu, and the 2ms square wave current capacity can reach 600A, which fully meets the discharge requirements of high-energy lightning surges in low-voltage systems.

[0045] Specific parameter analysis shows that the residual voltage ratio of this device is approximately 1.65 under 400V system conditions and approximately 1.53 under 1000V system conditions. The overall residual voltage ratio is low, indicating excellent voltage limiting characteristics. Although the residual voltage ratio of this device is in the same range as most similar surge protection products on the market, the residual voltage values ​​for DC 1mA reference voltage, 8 / 20μs, and 5kA lightning impulse are generally higher in existing similar products. This results in higher clamping voltages when overvoltage occurs, subjecting downstream power distribution equipment to higher overvoltage stress. This device can effectively reduce the DC 1mA reference voltage and the residual voltage of 8 / 20μs and 5kA lightning impulses. When subjected to lightning overvoltage or switching overvoltage, it can limit the overvoltage amplitude to a lower level, reducing the overvoltage stress on downstream equipment and providing more reliable overvoltage protection for downstream power distribution equipment.

[0046] Specifically, the signal acquisition module is weakly connected to the overvoltage protection module and electrically isolated from the lightning protection main circuit, and is used to accurately acquire key operating status parameters of the device under lightning protection conditions; The signal acquisition module specifically includes a leakage current detection unit, a voltage acquisition unit, an action count detection unit, and a time recording unit. It eliminates the hardware timing structure and completely avoids timing errors caused by strong electromagnetic interference from lightning. Among them, the leakage current detection unit is used to collect the changes in leakage current of the valve plate of the composite nonlinear protection unit in real time, providing data support for the assessment of the aging state of the valve plate due to lightning strikes; the voltage acquisition unit adopts a capacitor voltage divider structure to accurately collect the normal operating voltage of the system and the abnormal voltage signal of lightning surge; the action count detection unit is used to identify and count the cumulative number of protection actions triggered by lightning surges.

[0047] The signal acquisition module is electrically isolated from the main protection circuit through a low-voltage detection circuit, which improves detection safety and operational reliability.

[0048] Specifically, the digital monitoring and processing module is electrically connected to the signal acquisition module and is used to filter and reduce noise, analyze signals, assess status, store data and output alarms on the acquired lightning condition data, so as to realize intelligent online monitoring of lightning protection devices. Specifically, it includes a digital processing unit MCU, a data storage module and a power supply module. The power module provides a stable and clean operating power supply for the MCU, data storage module, and all low-voltage acquisition and communication units. The MCU (Microcontroller Unit) is the core control unit responsible for receiving, parsing, and processing voltage, leakage current, and lightning protection action data. The data storage module is used to store system operating parameters, lightning protection action history, valve plate aging status data, and abnormal alarm records.

[0049] like Figure 5 As shown, in order to solve the detection error problem caused by power frequency harmonics, high frequency noise and strong electromagnetic interference from lightning strikes in low-voltage power distribution systems, and to improve the accuracy of valve plate aging assessment, the digital processing unit MCU in this embodiment has built-in adaptive digital filtering algorithm module and resistive current separation algorithm module.

[0050] Specifically, the adaptive digital filtering algorithm module uses the internally generated power frequency reference signal as a benchmark and employs the Least Mean Square Error (LMS) adaptive algorithm to iteratively update the filter weight coefficients in real time. The formula for updating the weight coefficients is as follows: In the formula, These are the filter weight coefficients; For adaptive step size; This is an error signal; This is the reference input signal.

[0051] The above algorithm can effectively reduce the impact of power frequency harmonics and high-frequency interference on the detection signal, and obtain a more accurate fundamental voltage signal and fundamental current signal.

[0052] The resistive current separation algorithm module receives the filtered fundamental voltage signal and fundamental current signal, and extracts the phase difference between them. This enables the calculation of resistive current components.

[0053] The formula for calculating the resistive current component is as follows: in: Represents the resistive current component; This represents the effective value of the total leakage current; This represents the phase difference between the fundamental voltage wave and the fundamental leakage current wave.

[0054] The resistive current component obtained by separation It can reflect the internal performance changes of nano-modified SiC composite valve plate groups and ZnO valve plate groups.

[0055] The MCU (Microcontroller Unit) calculates the resistive current component. Recorded values ​​of the initial state of the protection device Comparisons were made to determine the performance changes of the composite nonlinear protection unit; Specifically, when the following is detected: At that time, the valve plate was determined to be in normal condition.

[0056] When detected: When the valve plate shows signs of aging, a warning message is output.

[0057] When detected: When the valve plate reaches the end of its service life, a maintenance and replacement prompt will be output.

[0058] The aforementioned state evaluation method based on resistive current changes can identify the performance degradation trend of internal nonlinear protection components in advance before a significant fault occurs in the protection device, thereby improving the operational reliability of the protection device.

[0059] The digital monitoring and processing module is also equipped with a status indicator unit, a local alarm unit, a 4G communication module, and an RS485 communication interface. The status indicator unit is used to display the current operating status of the protection device; the local alarm unit is used to provide on-site audible and visual alarms in abnormal conditions; the RS485 communication interface is used to realize data interaction between field devices; and the 4G communication module is used to realize remote wireless data transmission.

[0060] In addition, the low-voltage lightning surge integrated protection device of the present invention also includes a remote monitoring and alarm terminal; The remote monitoring and alarm terminal includes a background monitoring server, a mobile APP terminal, an SMS / voice broadcast module, and an operation and maintenance management platform; During the operation of the protection device, the digital monitoring and processing module uploads the collected operating parameters, protection action records, resistive current change trends and abnormal status information to the background monitoring server. The background monitoring server stores and analyzes the data to enable online monitoring of protection devices, abnormal alarms, valve life assessment, and operation and maintenance management.

[0061] This embodiment also provides a monitoring method for the above-mentioned low-voltage integrated overvoltage protection device, including the following steps: Step S1: The signal acquisition module collects the operating voltage, leakage current, number of protection actions, and action timestamp information of the protection device in real time according to the preset sampling period.

[0062] Step S2: The MCU (Digital Processing Unit) analyzes and processes the collected data.

[0063] Step S2-1: Use the adaptive digital filtering algorithm module to filter the acquired signal, and update the filter parameters through the LMS algorithm to obtain a pure fundamental signal.

[0064] Step S2-2: Use the resistive current separation algorithm module to extract the phase information of the fundamental voltage and fundamental current, and calculate the resistive current component. .

[0065] Step S2-3: Convert the resistive current component With initial value Compare them.

[0066] Step S3: When the detection result is within the normal range, continue monitoring; when the detection result exceeds the preset threshold, generate an abnormal alarm message and send it to the remote monitoring terminal through the local alarm unit or remote communication module.

[0067] Step S4: The remote monitoring terminal evaluates the operating status of the protection device based on the operating data, action records, and status analysis results uploaded by the protection device, and outputs the status monitoring results and maintenance prompts.

[0068] To visually demonstrate the advancements of this invention compared to existing technologies, three sets of comparative tests were conducted simultaneously on lightning strike and aging monitoring. The test conditions uniformly adopted the 400V low-voltage power distribution standard, and a new comparison table 2 was added to the test results. Comparative Example 1: Traditional single ZnO valve plate SPD, only configured with a single phase-to-ground branch, without isolation acquisition and online monitoring functions; Comparative Example 2: Only the nano-modified SiC valve plate is used as a protective element, with the same topology as the present invention, but without the ZnO composite parallel structure; Comparative Example 3: A traditional ZnO valve plate SPD is paired with a general single valve plate leakage current monitoring module, without adaptive filtering or resistive current diagnostic algorithm.

[0069] Table 2. Horizontal comparison of the performance of the present invention with three comparative examples. As shown in Table 2, although the pure SiC valve plate in Comparative Example 2 has a lower residual pressure, its current capacity is insufficient and it cannot withstand standard lightning strikes, thus lacking practical engineering value. The traditional ZnO products in Comparative Examples 1 and 3 have higher residual impact pressures, larger monitoring errors, and poor early warning reliability, making it impossible to balance rapid clamping with high-precision online monitoring.

[0070] Meanwhile, the two-level aging threshold of this invention is supported by complete accelerated aging test data: 100 sets of multi-frequency lightning strike accelerated aging tests were carried out on composite valve plates, and the resistive current decay curve was continuously monitored. The results showed that when the resistive current rose to 1.3 times the initial value, the nonlinear performance of the valve plate showed a significant decay; when it rose to 1.8 times the initial value, the residual voltage of the lightning strike exceeded the 1.6 pu safety limit, and the protective capability was lost. Therefore, the two-level layered alarm threshold is set, and the parameters are not set arbitrarily.

[0071] To verify the modification effect of nano-SiC on high-energy surge arrester valve plates and the optimal doping range, this embodiment sets up a nano-SiC composition gradient control experiment. The experiment uses nano-ZnO as the main phase and matching nano-additives, uniformly employing co-precipitation or coating processes to prepare composite powders. All process parameters, including molding and sintering, are fixed, and only the nano-SiC doping ratio is changed to ensure the uniqueness of the experimental variable.

[0072] Bi2O3 gas phase was continuously introduced into all samples during the sintering process to compensate for the volatilization of bismuth at high temperature, stabilize the composition of the grain boundary layer, eliminate the interference of grain boundary defect differences on the test results, and ensure that the performance difference is caused only by the change in SiC doping amount.

[0073] Microstructure, grain size, potential gradient, energy absorption density, residual voltage, and 100kA high-current impact performance were tested on SiC samples with different gradients. The results show that nano-SiC can be dispersed in ZnO grains and grain boundaries, inhibiting abnormal grain growth through grain pinning, refining grains, and improving microstructure uniformity.

[0074] When SiC doping is within the optimal range of this invention, the valve plate has fine and uniformly distributed grains, few internal defects, a stable potential gradient greater than 450V / mm, and an energy absorption density of not less than 200J / cm². 3 The valve plate has high density and excellent energy carrying capacity. After being subjected to a 100 kA high-energy lightning current impact, the component structure remains intact without cracking or breakdown. At the same time, it can maintain a low limiting overvoltage level, and has both excellent voltage stabilization performance and impact resistance.

[0075] If the SiC doping level is too low, the grain pinning effect is insufficient, resulting in coarse and uneven grains and an increase in internal defects. This leads to a decrease in potential gradient and energy absorption density, making the grains prone to microcracks under high current impact, and significantly deteriorating their withstand capability and voltage limiting performance. If the SiC doping level is too high, the nanoparticles are prone to agglomeration, introducing a large number of pores and interface defects, reducing sintering density, causing increased residual pressure and stress concentration. Under high current impact, this can easily lead to local breakdown or even overall failure.

[0076] In summary, under the co-precipitation / coating powder preparation combined with Bi2O3 bismuth-sintering process system of this invention, the nano-SiC doping in the preferred range can effectively refine the grains and compact the matrix, while simultaneously improving the valve plate potential gradient, energy absorption density and high current impact resistance. This solves the problems of low withstand voltage, weak energy resistance, easy breakage under high current and high residual voltage of traditional valve plates, and is suitable for the use requirements of high-energy lightning protection conditions.

[0077] Through the above embodiments, the present invention utilizes nano-modified SiC composite valve plates and ZnO zinc oxide valve plates to form a composite nonlinear protection structure, realizing rapid response and energy discharge for multiple types of overvoltages in low-voltage systems; at the same time, combined with digital acquisition, resistive current separation and intelligent diagnostic technology, it realizes online monitoring of the operating status and life prediction of the protection device, thereby improving the reliability and intelligence level of the low-voltage overvoltage protection device.

[0078] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape, principle and application direction of this application should be covered within the scope of protection of this application.

Claims

1. A low-voltage lightning surge integrated protection device based on nanocomposite valve plates, characterized in that, It includes an input module, an overvoltage protection module, a signal acquisition module, and a digital monitoring and processing module; The input module includes three phase lines L1, L2, L3, neutral line N, and protective grounding line PE, which are used to connect to the low-voltage power distribution system and complete the line connection and lightning protection grounding adaptation. The neutral line N is only used as a terminal block and is not connected to the overvoltage protection module. The overvoltage protection module is electrically connected to the input module and is provided with multiple sets of independent parallel lightning surge discharge branches. Each lightning surge discharge branch is equipped with a composite nonlinear protection unit. The composite nonlinear protection unit is composed of a parallel connection of a nano-modified SiC valve plate group and a ZnO zinc oxide valve plate group, forming a composite lightning protection structure with complementary characteristics. The signal acquisition module is weakly connected to and electrically isolated from the overvoltage protection module, and is used to acquire branch leakage current and line surge voltage signals under lightning protection conditions. The digital monitoring and processing module is electrically connected to the signal acquisition module, and is used to receive and analyze the acquired signals, determine the aging status of the valve plate lightning protection and the abnormal working condition of the line lightning, and realize the monitoring and alarm output of the device lightning protection status.

2. The low-voltage lightning surge integrated protection device based on nanocomposite valve plates according to claim 1, characterized in that, The lightning surge discharge branch includes a phase-to-phase overvoltage protection branch and a phase-to-ground overvoltage protection branch; The phase-to-phase protection branch is connected between any two phase lines to suppress phase-to-phase lightning induced overvoltage; the phase-to-ground lightning protection branch is connected between the phase line and the protective grounding wire to discharge line-to-ground direct lightning strikes and induced lightning surges. Each protective branch is independently connected in parallel, forming an independent overvoltage energy discharge channel.

3. The low-voltage lightning surge integrated protection device based on nanocomposite valve plates according to claim 2, characterized in that, The nano-modified SiC valve plate is made of nano-composite ceramic material, including nano-scale silicon carbide SiC functional powder, zinc oxide ZnO ceramic matrix material and nano-modifying additive Bi2O3. The nanoscale silicon carbide (SiC) functional powder is uniformly dispersed in the zinc oxide (ZnO) ceramic matrix, and a composite ceramic structure with nonlinear resistance characteristics is formed through nanocomposite modification and grain boundary regulation. The nano-modifying additive Bi2O3 is used to optimize the internal grain boundary structure of the composite ceramic material, thereby improving the nonlinear response capability and overvoltage impact resistance of the valve plate. The ZnO zinc oxide valve plate assembly is made of zinc oxide varistor material and is used to absorb and release energy under high amplitude overvoltage conditions.

4. The low-voltage lightning surge integrated protection device based on nanocomposite valve plate according to claim 3, characterized in that, The signal acquisition module includes a leakage current detection unit, a voltage acquisition unit, an action count detection unit, and a time recording unit. The leakage current detection unit is used to collect real-time leakage current signals of the lightning surge discharge branch; the voltage acquisition unit adopts a capacitor voltage divider structure to collect lightning surge voltage signals and normal operating voltage signals of the power distribution line; the action count detection unit is used to identify and count the number of protection actions caused by lightning impulses; the time recording unit is used to record the time information of the corresponding protection actions. The signal acquisition module is laid out using a low-voltage acquisition circuit, which is electrically isolated from the main lightning protection circuit.

5. The low-voltage lightning surge integrated protection device based on nanocomposite valve plate according to claim 4, characterized in that, The digital monitoring and processing module has a built-in software timestamp generation function, which is used to match the precise action time information for each lightning protection action. The digital monitoring and processing module includes a digital processing unit MCU, a data storage module, and a power supply module. The power module provides a stable power supply for the digital processing unit (MCU), the data storage module, and various low-voltage functional units; the digital processing unit (MCU) is used to receive and parse surge voltage, leakage current, and lightning action data; the data storage module is used to store the device's lightning protection operation parameters, lightning action history records, valve status data, and alarm information.

6. The low-voltage lightning surge integrated protection device based on nanocomposite valve plate according to claim 5, characterized in that, The digital processing unit (MCU) includes a signal filtering module and a resistive current analysis module. The signal filtering module uses the internally generated power frequency reference signal as a benchmark and employs the Least Mean Square Error (LMS) adaptive algorithm to iteratively update the filter weight coefficients in real time. The formula for updating the weight coefficients is as follows: In the formula, These are the filter weight coefficients; For adaptive step size; This is an error signal; Used as a reference input signal; The resistive current analysis module receives the filtered fundamental voltage signal and fundamental current signal, and extracts the phase difference between them. To achieve the calculation of resistive current components, The formula for calculating the resistive current component is as follows: in: Represents the resistive current component; This represents the effective value of the total leakage current; This represents the phase difference between the fundamental voltage and the fundamental leakage current. The MCU (Microcontroller Unit) calculates the resistive current component. Recorded values ​​of the initial state of the protection device Comparisons were made to determine the performance changes of the composite nonlinear protection unit; When detected: At that time, the valve plate was determined to be in normal condition; When detected: When the valve plate shows signs of aging, a warning message is output. When detected: When the valve plate reaches the end of its service life, a maintenance and replacement prompt will be output.

7. The low-voltage lightning surge integrated protection device based on nanocomposite valve plate according to claim 6, characterized in that, The digital monitoring and processing module also includes a status indication unit, a local alarm unit, a 4G wireless communication module, and an RS485 wired communication interface. The status indicator unit is used to display the lightning protection operation status of the device; the local alarm unit is used to output a local alarm when there is an abnormal lightning impact or the lightning protection performance of the valve plate exceeds the standard; the 4G wireless communication module and RS485 wired communication interface are used to upload lightning action data, valve plate lightning protection status, and alarm information to an external monitoring terminal; the RS485 wired communication interface is compatible with local debugging and field networking.

8. The low-voltage lightning surge integrated protection device based on nanocomposite valve plate according to claim 7, characterized in that, The low-voltage lightning surge protection device also includes a remote monitoring terminal, which communicates bidirectionally with the digital monitoring and processing module. The remote monitoring terminal includes a data management platform and a mobile communication terminal, which are used to receive lightning protection operation data uploaded by the device, and realize online monitoring of lightning action in low-voltage systems, lightning protection status assessment, abnormal alarms, and valve plate life prediction and maintenance management.

9. A comprehensive protection method for lightning surges in a low-voltage power distribution system, characterized in that, The low-voltage lightning surge integrated protection device based on nanocomposite valve plates as described in any one of claims 1 to 8 includes the following steps: S1. Collect terminal voltage signals, leakage current signals, number of protection actions, and action time information during the operation of the protection device through the signal acquisition module; S2. The collected data is processed and analyzed by the MCU (Microcontroller Unit). S3. When an abnormal operating state is detected, the corresponding level of status alarm information is sent to the remote monitoring terminal through the communication module. S4. The remote monitoring terminal evaluates the operating status of the protection device based on the operating data, action records, and status analysis results uploaded by the protection device, and outputs the status monitoring results and maintenance prompts.

10. The integrated lightning surge protection method for low-voltage power distribution systems according to claim 9, characterized in that, Step S2 specifically includes the following steps: S2-1. Perform digital filtering on the acquired voltage and leakage current signals to obtain voltage and current characteristic signals for state analysis. S2-2. Perform phase analysis based on the voltage characteristic signal and current characteristic signal to extract the resistive current component in the leakage current; S2-3. Compare the resistive current component with the preset aging criterion, and determine the operating status of the nanocomposite valve plate based on the comparison result. S2-4. Compare the acquired terminal voltage signal with the preset overvoltage criterion to determine the overvoltage type and the operating status of the composite nonlinear protection unit.

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