An automatically adjustable overvoltage circuit protection device and its usage method

Abstract

This invention relates to an automatically adjustable overvoltage circuit protection device and its usage method, belonging to the field of power system technology. The device includes: a cabinet comprising five isolated independent compartments: a control module compartment, a high-voltage compartment, a nonlinear component compartment, a busbar compartment, and a cable compartment; a nonlinear damping unit, disposed within the nonlinear component compartment, consisting of a parallel combination of a high-energy silicon carbide valve plate and a low-field-strength zinc oxide valve plate, used to simultaneously achieve voltage clamping and damping oscillation functions; a self-recovering current limiting unit, connected in series with the nonlinear damping unit, including a PTC thermistor, used to automatically increase the resistance value to achieve current limiting during overcurrent and automatically recover after the fault is cleared; and an intelligent control unit, disposed within the control module compartment, electrically connected to the nonlinear damping unit and the self-recovering current limiting unit, used to monitor the system status in real time and generate control commands.

Description

Technical Field

[0001] This invention relates to an automatically adjustable overvoltage circuit protection device and its usage method, belonging to the field of power system technology. Background Technology

[0002] In power systems, overvoltage is one of the main factors leading to equipment damage, system outages, and even fires and explosions. Common types of overvoltage include resonant overvoltage, switching overvoltage, arcing grounding overvoltage, and lightning overvoltage. Traditional protection methods mainly rely on equipment such as zinc oxide surge arresters, arc suppression coils, and discharge gaps, but these devices have the following shortcomings:

[0003] The drawbacks of zinc oxide surge arresters include: limited current carrying capacity (small capacity), high residual voltage, and frequent explosion damage; due to material limitations, it is impossible to further reduce the protection voltage amplitude, making it difficult to improve the safety performance index of the equipment operating in the system.

[0004] The drawbacks of surge arresters with discharge gaps: Although the presence of discharge gaps achieves zero charge rate for the zinc oxide varistors, it also cuts off the damping path of resonance, resulting in the inability to suppress resonant overvoltages and limiting their functionality.

[0005] The drawbacks of surge arresters with fuses: once the fuse blows, the protective function is immediately lost, requiring a power outage for manual replacement, making intelligent operation impossible and increasing maintenance costs.

[0006] The drawbacks of arc suppression coils are: large size, inconvenient installation, and high cost; although they can compensate for capacitor current, they cannot eliminate arc grounding overvoltage, and when the inductor and capacitor are not properly matched, they may cause resonant overvoltage.

[0007] Defects of harmonic suppression devices: Traditional harmonic suppression devices mostly use linear resistors, which will generate large energy consumption when connected to the system for a long time, and cannot withstand the heat accumulation caused by continuous oscillation, making them prone to thermal collapse.

[0008] Statistics show that the economic losses caused by various accidents due to system overvoltage in my country reach hundreds of billions of yuan annually. Especially in industries with extremely high requirements for power supply stability, such as petrochemicals and chip manufacturing, even a brief voltage fluctuation can lead to economic losses of millions or even tens of millions of yuan. Therefore, developing an integrated, intelligent, and automatically adjustable overvoltage protection device has become an urgent need for the safe operation of power systems.

[0009] In recent years, some intelligent overvoltage protection devices have emerged. For example, Chinese Patent Publication No. CN 119482295A discloses an intelligent power supply protection device that can dynamically adjust overvoltage and undervoltage protection thresholds based on the load power curve. However, this technology is mainly applied to low-voltage power supply protection and does not address overvoltage identification and suppression in high-voltage power systems, particularly neglecting the damping problem of resonant overvoltages. Furthermore, while existing technologies employ PTC self-resetting fuses for protection, these are mostly used in low-voltage circuits and do not work in conjunction with nonlinear resistive materials to compensate for negative resistance characteristics. Summary of the Invention

[0010] The purpose of this invention is to provide an automatically adjustable overvoltage circuit protection device and its usage method, which solves the problems of low current carrying capacity and high residual voltage of traditional surge arresters, significantly improves the energy capacity of the device, reduces the protection voltage amplitude, solves the problem that the discharge gap cannot suppress resonant overvoltage, achieves a gapless design, and has a strong damping resonance function, and solves the problem that fuses need to be replaced manually, achieves self-recovering current limiting protection, and meets the requirements of unattended intelligent operation.

[0011] The present invention provides an automatically adjustable overvoltage circuit protection device, comprising:

[0012] The cabinet includes five isolated independent compartments located within the cabinet: a control module compartment, a high-voltage compartment, a nonlinear component compartment, a busbar compartment, and a cable compartment.

[0013] The nonlinear damping unit, located in the nonlinear component compartment, is composed of a high-energy silicon carbide valve plate and a low-field-strength zinc oxide valve plate connected in parallel, and is used to simultaneously realize the dual functions of voltage clamping and damping oscillation.

[0014] The self-recovering current limiting unit is connected in series with the nonlinear damping unit and includes a PTC thermistor, which is used to automatically increase the resistance value to achieve current limiting when there is an overcurrent and automatically recover after the fault is cleared.

[0015] The intelligent control unit is located in the control module compartment and is electrically connected to the nonlinear damping unit and the self-recovering current limiting unit. It is used to monitor the system status in real time and generate control commands.

[0016] The five-compartment independent design achieves physical isolation between high and low voltage. The control module compartment can be electromagnetically shielded to prevent strong electric field interference. The high-voltage compartment and busbar compartment can be equipped with explosion-proof pressure relief channels, fundamentally solving the safety hazards of strong and weak current interference and fault propagation in traditional devices. It integrates four major functions—damped oscillation (SiC), voltage clamping (ZnO), self-resetting current limiting (PTC), and intelligent control—into one unit, replacing the protection functions that traditional devices (surge arrester + arc suppression coil + harmonic suppression device + fuse) require, greatly simplifying system configuration. The parallel connection of SiC and ZnO simultaneously achieves damping and clamping, solving the functional separation problem of traditional surge arresters only limiting voltage and not damping resonance, and traditional harmonic suppression devices only suppressing harmonics and not limiting voltage. The intelligent control unit provides a hardware platform for subsequent overvoltage identification and parameter adjustment, upgrading the device from passive protection to active protection. The PTC self-resetting characteristic replaces traditional fuses, eliminating the need for manual replacement during power outages, meeting the requirements of unattended substations.

[0017] Preferably, the PTC thermistor is used to compensate for the negative resistance characteristic of the low-field-strength zinc oxide valve plate; during normal operation, the PTC thermistor is in a low-resistance state and the low-field-strength zinc oxide valve plate is in a high-resistance state; in the event of an overcurrent fault, the PTC thermistor rapidly heats up and its resistance surges, achieving current limiting protection, while the low-field-strength zinc oxide valve plate nonlinearly conducts, achieving voltage clamping.

[0018] Traditional ZnO exhibits negative resistance (resistance decreases with increasing temperature), easily leading to a vicious cycle of increased leakage current → increased temperature → further decrease in resistance, ultimately resulting in thermal collapse and explosion. The positive temperature characteristic of the PTC (Polythermal Thyristor) forms a negative feedback loop: as temperature rises, the PTC resistance increases, limiting current and breaking the vicious cycle. The PTC current-limiting protection reduces the peak current surge experienced by the ZnO varistor, decreasing heat accumulation. Experiments have shown that this increases the number of surges ZnO can withstand from 5-8 to over 20. After the fault is cleared, the PTC automatically cools and returns to low resistance, requiring no manual intervention, unlike the one-time protection of traditional fuses. During normal operation, the PTC has low resistance (milliohms), ZnO has high resistance (megaohms), the device leakage current is extremely small (microamperes), and it generates almost no energy consumption or heat.

[0019] Preferably, the intelligent control unit includes:

[0020] A multi-channel high-speed data acquisition module is used to acquire three-phase voltage, three-phase current, zero-sequence voltage, zero-sequence current and PT neutral point current in real time.

[0021] The harmonic analysis module, connected to the data acquisition module, is used to perform spectrum analysis on the acquired signal to obtain the content characteristics of 1 / 4, 1 / 3, 1 / 2 frequency divisions and the 1st to 31st harmonics.

[0022] An overvoltage identification module, connected to the harmonic analysis module, is used to automatically identify the overvoltage type based on the harmonic content characteristics combined with voltage amplitude and waveform distortion rate. The overvoltage types include resonant overvoltage, switching overvoltage, arc grounding overvoltage, and lightning overvoltage.

[0023] The parameter adjustment module, connected to the overvoltage identification module, is used to generate control commands based on the identified overvoltage type and dynamically adjust the current limiting threshold of the self-recovering current limiting unit and the access depth of the nonlinear damping unit.

[0024] Multi-channel synchronous sampling at a 20kS / s sampling rate enables complete capture of microsecond-level overvoltage transients, providing a data foundation for accurate identification. Harmonic analysis covers 1 / 4, 1 / 3, and 1 / 2 frequency divisions, as well as harmonics from 1 to 31, capturing typical spectral characteristics of resonant overvoltages (such as 1 / 2 frequency division resonance) and distinguishing different types of overvoltages. After identifying four overvoltage types, different protection strategies can be implemented for different types (such as activating SiC during resonance and ZnO during lightning strikes), avoiding the limitations of "one-size-fits-all" protection. Dynamic adjustment of the current limiting threshold and connection depth allows the device to adapt to changes in system operation (such as changes in capacitor current and load), maintaining optimal protection performance.

[0025] Preferably, the overvoltage identification module adopts a hierarchical identification strategy of multi-feature fusion: first, it uses the voltage amplitude for coarse classification, and then combines the harmonic content features and waveform distortion rate for fine identification.

[0026] A hierarchical strategy avoids misjudgment based on a single feature. For example, a high voltage amplitude alone could be due to lightning strikes or operational overvoltages; only by considering the waveform rise time can this be distinguished. Similarly, a high harmonic content alone could be due to resonance or arcing grounding; only by considering the transient frequency can this be differentiated. First, coarse classification narrows the candidate range, followed by fine identification, reducing computational resource consumption and improving response speed. The hierarchical framework facilitates the subsequent addition of new overvoltage types (such as ferroresonant resonance, open-circuit resonance, etc.); simply add the corresponding rules to the fine identification layer.

[0027] Preferably, the nonlinear component compartment is located at the lower rear of the cabinet and has an independent heat dissipation channel; the control module compartment is located at the upper front of the cabinet and has a metal shielding layer between it and the high-voltage compartment.

[0028] The nonlinear components (SiC, ZnO) are the main heat-generating parts, located at the rear bottom with independent heat dissipation channels. Utilizing the principle of rising hot air to create natural convection, they effectively dissipate heat without a fan, improving long-term operational reliability. The metal shielding layer between the control module and the high-voltage compartment effectively blocks electromagnetic interference from the strong electric field to the weak electrical control circuit, ensuring sampling accuracy and control reliability.

[0029] Preferably, it also includes a fault recording and data analysis unit, which is connected to the intelligent control unit, for recording voltage and current waveforms before, during, and after an overvoltage event, as well as waveform playback, data analysis, and event tracing.

[0030] Recording waveforms before, during, and after an event allows for analysis of the causes of overvoltage (such as whether it is due to circuit breaker reignition or the distance from the lightning strike point), providing data support for power grid operation analysis.

[0031] Preferably, the high-energy silicon carbide valve plate is made of nanoscale material with an electric field strength ≤25V / mm, and its resistance value decreases sharply with the increase of voltage; the low-electric-field-strength zinc oxide valve plate is made of high-energy material with a residual voltage ≤20kV.

[0032] Traditional SiC has a field strength of approximately 100V / mm, while this invention's is ≤25V / mm. This means that the valve plate thickness can be reduced by 75% at the same voltage, resulting in a smaller size and lower cost. Traditional 10kV surge arresters have a residual voltage of approximately 32.4kV, while this invention's is ≤20kV, a reduction of 38%. This significantly reduces the overvoltage stress on the protected equipment and extends insulation life. The nano-scale powder increases the total depletion layer area, improving current carrying capacity, while also resulting in a higher nonlinear coefficient and superior protection characteristics.

[0033] Preferably, the nonlinear damping unit achieves megajoule-level current carrying capacity using the following features:

[0034] The zinc oxide valve plate is made of nanoparticles with a particle size of 40-50nm, which are modified by Fe³⁺ and Ag⁺ ion doping.

[0035] The valve plate is manufactured by microwave sintering process and has a microstructure with uniform grain size and low porosity.

[0036] The nonlinear damping unit adopts a multi-core parallel structure, including at least four mutually insulated and independent valve plate groups;

[0037] The valve plate is coated with an organic insulating coating modified by nanocomposite powder.

[0038] Traditional surge arresters have a current-carrying capacity in the kilojoule range, while this invention reaches the megajoule range (a 5-10 times improvement), capable of withstanding high-energy continuous overvoltages such as resonant overvoltages and arc grounding overvoltages, solving the industry problem of thermal breakdown in traditional devices. Microwave sintering results in uniform grain size (average 5μm) and a porosity of <2%, significantly improving current-carrying capacity and aging stability compared to traditional sintering. Multi-core parallel connection with independent insulation for each core avoids current concentration, ensuring that a single core failure does not affect overall operation, thus improving reliability. The nanocomposite coating increases the side current surge resistance from 45kA to 65kA, reaching international advanced levels and eliminating surface flashover. A 2ms square wave with 400A absorbs ≥400 kilojoules of energy over 20 cycles, continuously suppressing resonant overvoltages for several seconds without damage, truly achieving "flexible suppression."

[0039] The present invention provides a method for using the above-described automatically adjustable overvoltage circuit protection device, comprising the following steps:

[0040] Step S1: After the system is powered on, the intelligent control unit performs a self-test and enters the monitoring mode after confirming that each module is working normally.

[0041] Step S2: The multi-channel high-speed data acquisition module acquires the voltage and current signals of the power system in real time;

[0042] Step S3: The harmonic analysis module performs harmonic analysis on the acquired signal to obtain the harmonic content characteristics;

[0043] Step S4: The overvoltage identification module automatically identifies the overvoltage type based on the harmonic content characteristics combined with the voltage amplitude and waveform distortion rate. The overvoltage types include resonant overvoltage, switching overvoltage, arc grounding overvoltage, and lightning overvoltage.

[0044] Step S5: The parameter adjustment module generates control commands based on the identified overvoltage type, and controls the nonlinear damping unit and / or self-recovering current limiting unit to perform corresponding protection actions;

[0045] Step S6: The fault recording and data analysis unit records overvoltage event information, generates an event log, and uploads it to the dispatch center via the communication interface; when a severe overvoltage event is detected, an alarm signal is automatically issued.

[0046] Preferably, in step S5, the specific method for performing the protection action is as follows:

[0047] When a resonant overvoltage is detected, a high-energy silicon carbide valve is preferentially activated to suppress system oscillations by utilizing its nonlinear damping characteristics.

[0048] When an operational overvoltage or lightning overvoltage is detected, the low field strength zinc oxide valve plate is put into operation first, and its fast clamping characteristics are used to limit the overvoltage to a safe range.

[0049] When an arc grounding overvoltage is detected, both high-energy silicon carbide varistors and low-field-strength zinc oxide varistors are simultaneously activated, so that the two together absorb the arc energy and suppress arc reignition.

[0050] Different types of overvoltages have different physical natures, and differentiated protection strategies optimize protection effectiveness. For example, the core issue of resonant overvoltage is the continuous oscillation, making damping more important than clamping; the core issue of lightning overvoltage is the excessively high amplitude, making clamping more urgent than damping. SiC and ZnO each have their advantages (SiC excels at short-duration oscillations, while ZnO excels at transient oscillations), and differentiated application allows both to leverage their strengths and mitigate their weaknesses, avoiding overload of a single device. Arc grounding involves both high amplitude and intermittent transients; simultaneously applying SiC and ZnO effectively suppresses arc reignition through a triple effect: SiC dampens transient oscillations, ZnO clamps the overvoltage amplitude, and both absorb arc energy. This avoids unnecessary device application (e.g., applying only SiC during resonance without ZnO), reducing unnecessary energy consumption and device losses.

[0051] An automatically adjustable overvoltage circuit protection device and its usage method have the following beneficial effects:

[0052] 1. Structural Innovation: The five-compartment independent space design achieves electromagnetic shielding, high and low voltage isolation, and explosion-proof pressure relief, significantly improving the safety and reliability of the equipment.

[0053] 2. Collaborative material innovation: SiC and ZnO are combined in parallel to achieve both damped oscillation and voltage clamping; PTC compensates for the negative resistance of ZnO to achieve self-recovering current limiting, solving the problem of traditional fuses requiring manual replacement.

[0054] 3. Intelligent identification innovation: The overvoltage identification method based on harmonic analysis can accurately distinguish between four types of overvoltage: resonance, switching, arcing, and lightning strike, and implement differentiated protection to avoid false operation.

[0055] 4. Superior performance: Through the comprehensive application of technologies such as nanomaterials, microwave sintering, multi-core parallel connection, and PTC synergy, the current carrying capacity reaches the megajoule level (2ms square wave current carrying capacity ≥400A 20 times, cumulative absorbed energy ≥400 kilojoules, ultimate capacity ≥1 megajoule), residual voltage is reduced by more than 90%, protection voltage amplitude is reduced by more than 50%, and resonance suppression time is ≤5ms.

[0056] 4. Significant economic benefits: The cost of the device is only 35%-50% of that of traditional equipment, and its widespread application can greatly reduce economic losses caused by overvoltage. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the internal structure of an automatically adjustable overvoltage circuit protection device according to the present invention.

[0058] Figure 2 This is a front view of the automatically adjustable overvoltage circuit protection device described in this invention.

[0059] Figure 3 This is a circuit connection diagram of a nonlinear damping unit according to the present invention.

[0060] Figure 4 This is a comparison diagram of actual test waveforms as described in this invention;

[0061] Figure 5 This is a characteristic curve of a high-energy silicon carbide valve plate according to the present invention;

[0062] Figure 6 This is a characteristic curve of a high-energy, low-residual-pressure zinc oxide valve plate according to the present invention;

[0063] Figure 7 This is a characteristic curve diagram of a SiC and ZnO parallel component according to the present invention;

[0064] Figure 8 This is a schematic diagram of a multi-core parallel structure according to the present invention.

[0065] In the diagram: 1. Intelligent control unit; 2. Control module compartment; 3. Isolation trolley; 4. High voltage compartment; 5. Cable compartment; 6. Busbar compartment; 7. Primary busbar; 8. Disconnecting switch; 9. Cabinet; 10. Nonlinear component; 11. Nonlinear component compartment; 12. Human-machine interaction and communication unit. Detailed Implementation

[0066] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0067] like Figures 1-8 As shown, the present invention proposes an automatically adjustable overvoltage circuit protection device, including a cabinet 9, a nonlinear damping unit 10, a self-recovering current limiting unit, and an intelligent control unit 1.

[0068] Cabinet 9 adopts a removable handcart structure, with five mutually isolated independent compartments inside:

[0069] Control module compartment 2: Located at the front of cabinet 9, it houses the intelligent control unit 1 and adopts an electromagnetic shielding design to prevent strong electric field interference;

[0070] High-voltage compartment 4: accommodates the isolation trolley 3, serves as the disconnecting switch 8 for the high-voltage section to be deactivated and put into operation, and is equipped with an explosion-proof pressure relief channel;

[0071] Nonlinear component compartment 11: Located at the rear and lower part of cabinet 9, it houses nonlinear damping unit 10 and has an independent heat dissipation channel;

[0072] Busbar compartment 6: accommodates primary busbar 7, is always energized, and is equipped with an explosion-proof pressure relief passage;

[0073] Cable compartment 5: accommodates incoming and outgoing cables, facilitating wiring and maintenance.

[0074] The nonlinear damping unit consists of a high-energy silicon carbide (SiC) valence plate and a low-field-strength zinc oxide (ZnO) valence plate connected in parallel. The high-energy silicon carbide valence plate is made of nanoscale materials with a field strength ≤25V / mm. Its resistance decreases sharply with increasing voltage, thus acting as a damping oscillator in the system. The low-field-strength zinc oxide valence plate is made of high-energy materials with extremely low residual voltage (≤20kV for a 10kV system). It is used to quickly conduct when the voltage exceeds the threshold, clamping the overvoltage within a safe range. When the two are connected in parallel, they simultaneously possess the dual functions of damping oscillation and voltage clamping.

[0075] To achieve megajoule-level current handling capacity, the nonlinear damping unit employs the following innovative design:

[0076] Nanomaterial formulation: The zinc oxide valve plate uses nanoparticles with a particle size of 40-50nm, which are modified by Fe³⁺ and Ag⁺ ion doping to optimize the grain boundary barrier characteristics, thereby increasing the total area of ​​the depletion layer per unit volume and increasing the flow rate by more than 33%; the silicon carbide valve plate uses a composite formulation containing silicon carbide, conductor and insulator, with an energy absorption density >40J / cm³.

[0077] Microwave sintering process: The valve plate blank is sintered by microwave to obtain a dense microstructure with uniform grain size and low porosity, which significantly improves the flow capacity and aging stability.

[0078] Multi-core parallel structure: It adopts a four-core five-column parallel design, with each column resistor being insulated and independent from each other. The total current capacity is four times that of a single column, with a theoretical limit of 1.6 megajoules. At the same time, the current distribution of each column is ensured to be uniform through current sharing design.

[0079] Side high current impact resistant coating: The side of the valve plate is coated with a nano-composite powder modified organic insulating varnish, which improves the high current impact resistance to more than 65kA.

[0080] The self-recovering current-limiting unit is connected in series with the nonlinear damping unit, including a PTC thermistor. The PTC thermistor has a positive temperature coefficient characteristic, used to compensate for the negative resistance characteristic of the ZnO varistor. Under normal operation, the PTC is in a low-resistance state, and the ZnO is in a high-resistance state, resulting in minimal system losses. When an overcurrent occurs, the PTC rapidly heats up, and its resistance surges, limiting the fault current. Simultaneously, the ZnO nonlinearly conducts, clamping the overvoltage. After the fault is cleared, the PTC automatically cools down and returns to its low-resistance state, requiring no manual replacement. The current-limiting protection function of the PTC limits the current surges experienced by the ZnO varistor to a safe range, enabling it to withstand more surges. This is a key synergistic mechanism for achieving megajoule-level cumulative current carrying capacity.

[0081] The intelligent control unit 1 is located within the control module compartment 2 and includes:

[0082] Multi-channel high-speed data acquisition module: sampling rate ≥20kS / s, supports eight-channel synchronous sampling, and real-time acquisition of three-phase voltage, three-phase current, zero-sequence voltage, zero-sequence current and PT neutral point current;

[0083] Harmonic analysis module: Performs spectrum analysis on the acquired signal to obtain the content characteristics of 1 / 4, 1 / 3, 1 / 2 frequency divisions and the 1st to 31st harmonics;

[0084] Overvoltage identification module: Automatically identifies overvoltage types (resonance overvoltage, switching overvoltage, arcing grounding overvoltage, lightning overvoltage) based on harmonic content characteristics combined with voltage amplitude and waveform distortion rate.

[0085] Parameter adjustment module: Generates control commands based on the identified overvoltage type, and dynamically adjusts the current limiting threshold of the self-recovering current limiting unit and the connection depth of the nonlinear damping unit (such as activating SiC alone, ZnO alone, or both).

[0086] The device also integrates a fault recording and data analysis unit to record voltage and current waveforms before, during, and after an overvoltage event, supporting waveform playback, data analysis, and event tracing. The human-machine interaction and communication unit 12 is equipped with a touch screen, control buttons, indicator lights, and a USB / Ethernet communication interface, supporting local operation and remote monitoring.

[0087] The usage method is as follows:

[0088] The method of using the device of the present invention includes the following steps:

[0089] S1: After the system is powered on, the intelligent control unit checks the status of each module and enters the monitoring mode after confirming that everything is normal.

[0090] S2: Multi-channel high-speed data acquisition module acquires voltage and current signals of the power system in real time;

[0091] S3: The harmonic analysis module performs harmonic analysis on the acquired signal to obtain harmonic content characteristics;

[0092] S4: The overvoltage identification module automatically identifies the overvoltage type based on the harmonic content characteristics combined with the voltage amplitude and waveform distortion rate;

[0093] S5: The parameter adjustment module generates control commands based on the identified overvoltage type, and controls the nonlinear damping unit and / or self-recovering current limiting unit to perform corresponding protection actions (SiC valve plate damping oscillation is activated during resonant overvoltage; ZnO valve plate clamping is activated during operation or lightning strike overvoltage; SiC and ZnO are activated simultaneously to absorb energy during arc grounding overvoltage).

[0094] S6: The fault recording and data analysis unit records overvoltage event information, generates an event log, and uploads it to the dispatch center via the communication interface; when a severe overvoltage event is detected, an alarm signal is automatically issued.

[0095] Example 1: 10kV System Application

[0096] Taking a 10kV neutral point ungrounded system as an example, the device of this invention is installed inside a high-voltage switchgear and connected in parallel with primary busbar 7. The main parameters of the device are as follows:

[0097] Table 1 10kV Parameter Table

[0098]

[0099] Detailed Explanation of Flow Capacity Implementation:

[0100] In this embodiment, the nonlinear damping unit 10 employs the following techniques to achieve megajoule-level current carrying capacity:

[0101] Nanomaterial formulation:

[0102] Zinc oxide valve plates: Made from nano-ZnO powder with a particle size of 40-50 nm, and modified by adding 0.5 mol% Fe2O3 and 0.2 mol% Ag2O. The powder is uniformly dispersed through high-energy ball milling, achieving a specific surface area of ​​3569 m² / g.

[0103] Silicon carbide valve plate: made of SiC micro powder mixed with organosilicon resin and conductive carbon black in a mass ratio of 100:15:3, with an insulation resistance of about 10¹² Ω·cm, a nonlinear coefficient of about 10, and an energy absorption density of 45J / cm³.

[0104] Microwave sintering process:

[0105] The formed valve plate blank was placed in a microwave sintering furnace and heated to 1100℃ at a rate of 15℃ / min, held at that temperature for 30 minutes, and then allowed to cool naturally. Microwave sintering resulted in uniform grain size (average 5μm) and porosity of <2%, improving flow capacity by 40% compared to traditional sintering.

[0106] Multi-core parallel structure:

[0107] It adopts a four-core parallel design, with each core consisting of 10 valve plates connected in series. The current is led out through an independent low-voltage terminal block between the cores to ensure balanced current distribution. The single-core 2ms square wave current capacity is 120A, and the total capacity of the four cores in parallel is 480A, which meets the ≥400A requirement.

[0108] Side high current impact resistant coating:

[0109] Nano-Al₂O₃ powder (40nm) was surface-treated with a silane coupling agent, mixed with organosilicon resin, and coated onto the side of a valve plate. After curing, it formed an insulating layer with a thickness of 0.2mm. No flashover was observed under impulse current testing at 65kA.

[0110] PTC Collaborative Protection:

[0111] A PTC thermistor with a Curie point of 120℃ was selected and connected in series with a nonlinear damping unit. In a 400A, 2ms square wave continuous impact test, the PTC started to limit the current after the third impact, reducing the peak current flowing through the ZnO valve plate to below 300A and keeping the valve plate temperature rise below 40℃, ensuring normal operation after 20 impacts.

[0112] Flow capacity verification:

[0113] A 2ms square wave current with a peak value of 400A was applied 20 times consecutively using an impulse current generator, with a 1-minute interval between each application. The test results are as follows:

[0114] First impact: residual voltage 24.3kV, absorbed energy 9.72 kilojoules.

[0115] The 10th impact: residual voltage 24.5 kV, absorbed energy 9.80 kilojoules.

[0116] 20th impact: residual voltage 24.8 kV, absorbed energy 9.92 kilojoules.

[0117] The device absorbed a total of 195.6 kilojoules of energy over 20 cycles without any damage, and the temperature rise was ≤40℃. Based on this, the device's ultimate current carrying capacity can reach over 1.2 megajoules, which is 5-8 times that of traditional surge arresters.

[0118] Resonance suppression effect:

[0119] The simulation system experienced ferroresonance, resulting in significant periodic oscillations in the voltage waveform with a harmonic content as high as 15%. After the device was put into operation, the oscillation waveform completely disappeared within 5ms, and the voltage returned to a sinusoidal waveform, demonstrating a significant suppression effect (see...). Figure 4 ).

[0120] Example 2: 35kV System Application

[0121] Taking a 35kV neutral point grounded system via an arc suppression coil as an example, the device parameters are adjusted accordingly as follows:

[0122] Table 2 35kV Parameter Table

[0123]

[0124] The nonlinear damping unit 10 adopts a six-core parallel design, increasing the number of valve plates per core to 15, while maintaining the total current carrying capacity in the megajoule range. The operating effect is similar to that of Example 1, and will not be repeated here.

[0125] Example 3: Harmonic Identification Verification

[0126] Four overvoltage simulation scenarios are set up:

[0127] Resonant overvoltage: A 1 / 2 frequency division resonance is generated by matching the adjustable inductor with the system capacitance;

[0128] Operational overvoltage: generated by switching off unloaded lines via circuit breakers;

[0129] Arc ground overvoltage: simulated using an intermittent arc generator;

[0130] Lightning overvoltage: simulated using an impulse voltage generator.

[0131] The harmonic analysis module of the intelligent control unit 1 acquires waveforms in real time, and the overvoltage identification module automatically identifies overvoltages using the following rules:

[0132] Table 3 Overvoltage Identification Module Rules

[0133]

[0134] The test showed that the recognition accuracy was 100% and the corresponding protection strategy was executed correctly.

[0135] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An automatically adjustable overvoltage circuit protection device, characterized in that, include: The cabinet (9) includes five independent compartments that are isolated from each other, namely the control module compartment (2), the high voltage compartment (4), the nonlinear component compartment (11), the busbar compartment (6), and the cable compartment (5). The nonlinear damping unit (10) is located in the nonlinear component compartment (11) and is composed of a high-energy silicon carbide valve plate and a low-field-strength zinc oxide valve plate connected in parallel. It is used to simultaneously realize the dual functions of voltage clamping and damping oscillation. The self-recovering current limiting unit is connected in series with the nonlinear damping unit (10), including a PTC thermistor, which is used to automatically increase the resistance value to achieve current limiting when there is an overcurrent, and automatically recover after the fault is eliminated; The intelligent control unit (1) is located in the control module compartment (2) and is electrically connected to the nonlinear damping unit (10) and the self-recovering current limiting unit. It is used to monitor the system status in real time and generate control commands.

2. The automatically adjustable overvoltage circuit protection device according to claim 1, characterized in that, The PTC thermistor is used to compensate for the negative resistance characteristic of the low-field-strength zinc oxide valve. During normal operation, the PTC thermistor is in a low-resistance state, and the low-field-strength zinc oxide valve is in a high-resistance state. In the event of an overcurrent fault, the PTC thermistor rapidly heats up and its resistance surges, achieving current limiting protection. At the same time, the low-field-strength zinc oxide valve is nonlinearly turned on, achieving voltage clamping.

3. The automatically adjustable overvoltage circuit protection device according to claim 1, characterized in that, The intelligent control unit (1) includes: A multi-channel high-speed data acquisition module is used to acquire three-phase voltage, three-phase current, zero-sequence voltage, zero-sequence current and PT neutral point current in real time. The harmonic analysis module, connected to the data acquisition module, is used to perform spectrum analysis on the acquired signal to obtain the content characteristics of 1 / 4, 1 / 3, 1 / 2 frequency divisions and the 1st to 31st harmonics. An overvoltage identification module, connected to the harmonic analysis module, is used to automatically identify the overvoltage type based on the harmonic content characteristics combined with voltage amplitude and waveform distortion rate. The overvoltage types include resonant overvoltage, switching overvoltage, arc grounding overvoltage, and lightning overvoltage. The parameter adjustment module is connected to the overvoltage identification module and is used to generate control commands according to the identified overvoltage type to dynamically adjust the current limiting threshold of the self-recovering current limiting unit and the access depth of the nonlinear damping unit (10).

4. The automatically adjustable overvoltage circuit protection device according to claim 3, characterized in that, The overvoltage identification module adopts a hierarchical identification strategy that integrates multiple features: first, it uses voltage amplitude for coarse classification, and then combines harmonic content features and waveform distortion rate for fine identification.

5. The automatically adjustable overvoltage circuit protection device according to claim 1, characterized in that, The nonlinear component compartment (11) is located at the rear lower part of the cabinet (9) and has an independent heat dissipation channel; the control module compartment (2) is located at the front upper part of the cabinet (9) and has a metal shielding layer between it and the high voltage compartment (4).

6. The automatically adjustable overvoltage circuit protection device according to claim 1, characterized in that, It also includes a fault recording and data analysis unit, which is connected to the intelligent control unit (1) and is used to record the voltage and current waveforms before, during and after the overvoltage event, as well as waveform playback, data analysis and event tracing.

7. The automatically adjustable overvoltage circuit protection device according to claim 1, characterized in that, The high-energy silicon carbide valve plate is made of nanoscale materials with an electric field strength ≤25V / mm, and its resistance value decreases sharply with the increase of voltage; the low-electric-field-strength zinc oxide valve plate is made of high-energy materials with a residual voltage ≤20kV.

8. The automatically adjustable overvoltage circuit protection device according to claim 1, characterized in that, The nonlinear damping unit (10) achieves megajoule-level current carrying capacity using the following features: The zinc oxide valve plate is made of nanoparticles with a particle size of 40-50nm, which are modified by Fe³⁺ and Ag⁺ ion doping. The valve plate is manufactured by microwave sintering process and has a microstructure with uniform grain size and low porosity. The nonlinear damping unit (10) adopts a multi-core parallel structure, including at least four mutually insulated and independent valve plate groups; The valve plate is coated with an organic insulating coating modified by nanocomposite powder.

9. A method of using an automatically adjustable overvoltage circuit protection device according to any one of claims 1 to 8, characterized in that, Includes the following steps: Step S1: After the system is powered on, the intelligent control unit (1) performs a self-test and enters the monitoring mode after confirming that each module is working normally. Step S2: The multi-channel high-speed data acquisition module acquires the voltage and current signals of the power system in real time; Step S3: The harmonic analysis module performs harmonic analysis on the acquired signal to obtain the harmonic content characteristics; Step S4: The overvoltage identification module automatically identifies the overvoltage type based on the harmonic content characteristics combined with the voltage amplitude and waveform distortion rate. The overvoltage types include resonant overvoltage, switching overvoltage, arc grounding overvoltage, and lightning overvoltage. Step S5: The parameter adjustment module generates control commands based on the identified overvoltage type, and controls the nonlinear damping unit (10) and / or the self-recovering current limiting unit to perform corresponding protection actions; Step S6: The fault recording and data analysis unit records overvoltage event information, generates an event log, and uploads it to the dispatch center via the communication interface; when a severe overvoltage event is detected, an alarm signal is automatically issued.

10. The method of use according to claim 9, characterized in that, In step S5, the specific method for performing the protection action is as follows: When a resonant overvoltage is detected, a high-energy silicon carbide valve is preferentially activated to suppress system oscillations by utilizing its nonlinear damping characteristics. When an operational overvoltage or lightning overvoltage is detected, the low field strength zinc oxide valve plate is put into operation first, and its fast clamping characteristics are used to limit the overvoltage to a safe range. When an arc grounding overvoltage is detected, both high-energy silicon carbide varistors and low-field-strength zinc oxide varistors are simultaneously activated, so that the two together absorb the arc energy and suppress arc reignition.

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