Explosion-proof structure of power capacitor

Abstract

The application discloses an explosion-proof structure of a power capacitor and belongs to the technical field of capacitor safety protection. The structure comprises a capacitor body, a protection module, a monitoring protection module and a composite flame-retardant material layer. The capacitor body comprises a capacitor element and an electrode lead wire. The protection module is wrapped outside the capacitor body and comprises a flame-retardant insulating shell, an inert gas encapsulation filling layer, a self-healing medium assembly, an internal fuse arc extinguishing unit and a heat-conducting heat-dissipating layer. The composite flame-retardant material layer comprises, from inside to outside, a phase change heat-absorbing layer, a flame-retardant heat-insulating layer and an insulating protection layer. The monitoring protection module is integrated on the protection module and comprises a temperature sensing unit, a voltage monitoring unit, a current monitoring unit, a pressure sensing unit, a central processing unit and an electrical protection execution unit. The application realizes monitoring and early warning, active linkage and hierarchical protection full-process explosion-proof, has a reasonable structure, a mature process and mass production, is high in explosion-proof reliability and is suitable for the safety protection of various power capacitors.

Description

Technical Field

[0001] This application relates to the field of capacitor safety protection technology, and in particular to an explosion-proof structure for a power capacitor. Background Technology

[0002] Power capacitors are important reactive power compensation devices in power systems, widely used in power transmission and distribution networks, industrial power systems, and new energy power generation. With the continuous expansion of power system capacity and the increase in operating voltage levels, the safe operation of power capacitors has become an increasingly prominent issue.

[0003] Existing power capacitors have the following technical problems during operation: 1. Risk of explosion due to internal faults: When traditional power capacitors experience overvoltage, overcurrent or dielectric breakdown, a large amount of heat and gas will be generated inside, causing the internal pressure to rise sharply. When the pressure exceeds the shell's tolerance limit, an explosion accident is likely to occur, causing equipment damage and personal injury.

[0004] 2. Insufficient heat dissipation performance: The heat dissipation design of existing capacitors is relatively simple, usually relying solely on the natural heat dissipation of the casing. Under long-term high-load operation or high ambient temperature, heat accumulation can easily lead to excessively high internal temperature of the capacitor, accelerating dielectric aging and reducing service life.

[0005] 3. Lack of real-time monitoring and protection: Traditional capacitors lack comprehensive online monitoring functions and cannot sense key parameters such as internal temperature, pressure, voltage, and current in real time. They have weak fault early warning capabilities and are often only discovered after a fault occurs, thus failing to achieve proactive protection.

[0006] 4. Limited flame retardant performance: The existing capacitor casing material has a low flame retardant rating. When an internal fault occurs, the casing is prone to burning or melting, which cannot effectively prevent the spread of flames and increases the risk of fire.

[0007] 5. Insufficient self-healing ability: The dielectric material of traditional capacitors cannot effectively heal itself after local breakdown, which leads to the expansion of the fault range and eventually causes overall failure.

[0008] While some improvements have been made to address the aforementioned issues, such as adding pressure relief valves or using flame-retardant materials, these are mostly single protective measures and lack a systematic and comprehensive explosion-proof design, thus failing to fundamentally solve the safety hazards of power capacitors. Summary of the Invention

[0009] The present invention addresses the aforementioned problems in the prior art by providing an explosion-proof structure for power capacitors.

[0010] The objective of this invention is primarily achieved through the following approach: An explosion-proof structure for a power capacitor includes a capacitor body, a protective module, a monitoring and protection module, and a composite flame-retardant material layer. The capacitor body includes a capacitor element and electrode leads. The protective module is wrapped around the capacitor body to form all-round protection for the capacitor body. The composite flame-retardant material layer is attached between the protective module and the capacitor element to achieve intermediate protection of heat barrier, flame retardant insulation, and so on. The monitoring and protection module is integrated on the protective module and electrically connected to the capacitor body to realize real-time monitoring of the capacitor's operating status and fault intervention. The protection module includes a flame-retardant insulating shell, an inert gas encapsulation filling layer, a self-healing dielectric component, an internal fuse arc extinguishing unit, and a heat-conducting and heat dissipation layer. The components work together to form a hierarchical passive protection system. The composite flame-retardant material layer comprises, from the inside out, a phase change heat absorption layer, a flame-retardant heat insulation layer, and an insulating protective layer, which work together with the protective module to enhance the protective effect. The monitoring and protection module includes a temperature sensing unit, a voltage monitoring unit, a current monitoring unit, a pressure sensing unit, a central processing unit, and an electrical protection execution unit. These units work together to achieve real-time monitoring, signal processing, and fault intervention of the capacitor's operating status.

[0011] Preferably, the flame-retardant insulating shell is integrally injection molded from halogen-free flame-retardant engineering plastic. The engineering plastic is glass fiber reinforced PBT material with a heat distortion temperature of not less than 200°C, which can adapt to temperature changes during capacitor operation and prevent the shell from aging and breaking due to overheating. The shell surface is integrally molded with heat dissipation texture, which can effectively improve the heat dissipation efficiency of the shell, accelerate the dissipation of internal heat, help suppress the sudden rise of internal temperature, and further optimize the overall heat dissipation performance in conjunction with the heat-conducting heat dissipation layer.

[0012] Preferably, the inert gas encapsulation filling layer fills the gap between the flame-retardant insulating shell and the composite flame-retardant material layer, using high-purity nitrogen with a purity of not less than 99.99% and a filling pressure of 0.12-0.15 MPa. High-purity nitrogen can effectively block oxygen, inhibit combustion caused by internal faults, and absorb the heat generated by the fault, buffer internal pressure fluctuations, and delay the expansion of the fault. The inert gas encapsulation filling layer is also mixed with explosion-proof non-combustible filler. The filler is a mixture of vermiculite and perlite in a mixing ratio of 1:2. The filler particle size is 0.5-1mm, and the filling amount is 5%-8% of the inert gas filling volume. The mixture of vermiculite and perlite has good heat absorption, flame retardant and explosion suppression properties, which can further absorb fault energy, inhibit the spread of combustion, and improve the passive protection reliability of the protection module.

[0013] The pretreatment process for the above-mentioned vermiculite and perlite explosion-proof and non-combustible filler is as follows: Vermiculite and perlite are mixed at a mass ratio of 1:2 and then placed in a muffle furnace and dried at 200-250℃ for 2-3 hours to remove moisture; after cooling to room temperature, particles with a particle size of 0.5-1mm are screened out by vibrating sieve; before filling, the filler is dried again in a vacuum drying oven at 80-100℃ for 1 hour to ensure that the moisture content of the filler is ≤0.5%.

[0014] Preferably, the self-healing dielectric component uses a polypropylene film as the core dielectric of the capacitor element. The polypropylene film is a gradient film with a zinc-aluminum alloy coating deposited on its surface. The coating thickness gradually changes from the edge to the center, with an edge thickness of 0.1-0.15 μm and a center thickness of 0.05-0.08 μm. The gradient coating design balances current carrying capacity and self-healing performance. When a local breakdown occurs in the film, it can quickly achieve self-insulation repair, preventing local faults from escalating into overall faults. This solves the problem of insufficient self-healing ability in the prior art and extends the service life of the capacitor element.

[0015] The fabrication process of the aforementioned gradient thin film coating is as follows: Magnetron sputtering is employed, using a zinc-aluminum alloy target (Zn:Al=95:5); the thickness gradient is achieved by controlling the relative speed between the cathode target and the thin film, with a relative speed of 0.5-1 m / min at the film edge and 2-3 m / min at the center; alternatively, multi-target deposition can be used, with a high-power target (power density 3-5 W / cm²) at the edge and a low-power target (power density 1-2 W / cm²) at the center; the deposition vacuum is 1×10⁻⁶. -3 -5×10 -3 Pa, argon flow rate 50-100 sccm; edge thickness 0.1-0.15 μm, center thickness 0.05-0.08 μm, and the thickness of the transition region is linear or gradually changes with a curve.

[0016] Preferably, the internal fuse arc extinguishing unit is connected in series with the capacitor element. The internal fuse is wrapped with a quartz sand filling layer with a particle size of 0.1-0.3mm. When the capacitor element experiences overcurrent or breakdown fault, the internal fuse can quickly melt and cut off the fault circuit. At the same time, the quartz sand plays an arc extinguishing role, blocking the spread of the arc and preventing the fault from expanding further. The electrode leads and inner fuses are all fitted with heat shrink tubing made of cross-linked polyolefin material with a shrinkage ratio of 2:1. This effectively improves the insulation performance of the electrode leads and inner fuses, reduces partial discharge, prevents arcing at the leads, and further reduces potential faults.

[0017] Preferably, the heat-conducting and heat-dissipating layer is attached to the inner wall of the flame-retardant insulating shell and the outer side of the composite flame-retardant material layer. It is made of high thermal conductivity silicone material with a thermal conductivity of not less than 1.5 W / (m•K). It can quickly dissipate the heat generated by the capacitor element during operation and failure, suppress the sudden rise of internal temperature, solve the problem of insufficient heat dissipation performance in the prior art, and provide sufficient time for fault intervention of the monitoring and protection module. A thermally conductive insulating pad is also provided between the thermally conductive heat dissipation layer and the composite flame-retardant material layer. The pad is made of polytetrafluoroethylene and has a thickness of 0.2-0.3 mm. While achieving insulation and preventing partial discharge, it can improve the thermal conductivity efficiency, ensure that heat is quickly conducted to the thermally conductive heat dissipation layer, and further optimize the heat dissipation effect.

[0018] The above-mentioned high thermal conductivity silicone materials can be selected from: Shin-Etsu Chemical KE-1603 series (thermal conductivity 1.6W / (m•K)), Dow Corning SE4445 series (thermal conductivity 1.8W / (m•K)), Momentive TIA2604 series (thermal conductivity 2.0W / (m•K)) or domestic materials with equivalent performance.

[0019] Preferably, the phase change heat absorption layer is made of paraffin / polymer composite phase change material with a phase change temperature of 55-65℃ and a latent heat of phase change ≥100J / g. When the operating temperature of the capacitor element rises to the phase change temperature, the phase change heat absorption layer can absorb a large amount of heat, slow down the rate of internal temperature rise, and provide sufficient time for the monitoring and protection module to issue warnings and intervene. The flame-retardant and heat-insulating layer is made of modified graphene / polyolefin composite flame-retardant material, with a flame-retardant rating of UL94 V-0. It has good flame-retardant and heat-insulating properties, which can effectively block heat transfer and flame spread, solve the problem of limited flame-retardant performance in the prior art, and prevent the expansion of the fault. The insulating protective layer is made of polyimide material with a thickness of 0.1-0.2mm, which can improve the insulation performance between the capacitor element and the external structure, prevent partial discharge from causing faults, and further optimize the protection effect.

[0020] The specific composition and preparation process of the above-mentioned phase change heat absorption layer are as follows: the paraffin wax is selected from a mixture of n-alkanes with a carbon number range of C20-C30 and a melting point of 55-65℃; the polymer matrix is ​​high-density polyethylene (HDPE) or styrene-ethylene / butene-styrene block copolymer (SEBS); the mass ratio of paraffin wax to polymer is 7:3 to 8:2; it is prepared by melt blending, with a mixing temperature of 80-90℃ and a stirring speed of 500-800 rpm; to prevent paraffin wax leakage, 2%-3% of crosslinking agent (such as peroxide) is added for light crosslinking; the latent heat of phase change is ≥100J / g, and the thermal conductivity is ≥0.3W / (m•K); commercially available products that meet the requirements can be used, or the above formula can be prepared by oneself.

[0021] The specific composition and preparation process of the above flame-retardant and heat-insulating layer are as follows: Graphene is prepared by high-temperature reduction of graphene oxide, with a sheet size of 5-10μm and a thickness of 1-5nm; the polyolefin matrix is ​​a mixture of maleic anhydride-grafted polypropylene (MAPP) and linear low-density polyethylene (LLDPE) in a mass ratio of 3:2; the amount of graphene added is 3%-5% of the mass of the polyolefin matrix; 8%-10% of phosphorus-based flame retardants (such as ammonium polyphosphate) and 3%-5% of synergists (such as melamine cyanurate) are added; it is prepared by melt blending using a twin-screw extruder, with an extrusion temperature of 180-200℃ and a screw speed of 200-300rpm; the flame retardant rating reaches UL94V-0 level, and the oxygen index is ≥32%; commercially available products that meet the requirements can be used, or the above formula can be prepared by yourself.

[0022] The composite process of the above-mentioned flame-retardant material layer is as follows: During the preparation of the phase change heat-absorbing layer, the phase change material is coated onto an aluminum foil substrate with a thickness of 0.5-1 mm using a doctor blade coating method at a coating speed of 1-2 m / min and a drying temperature of 60-80℃. The flame-retardant heat-insulating layer is composited with the phase change heat-absorbing layer via hot pressing at a temperature of 150-180℃, a pressure of 2-5 MPa, and a time of 30-60 seconds. The insulating protective layer is composited with the flame-retardant heat-insulating layer using a pressure-sensitive adhesive or hot melt adhesive at a temperature of 120-150℃ and a pressure of 1-3 MPa. The overall thickness after composite is 1.0-1.5 mm, and the interlayer peel strength is ≥5 N / 25 mm.

[0023] Preferably, the temperature sensing unit is attached to the surface of the capacitor element, which can collect the operating temperature of the capacitor element in real time and accurately detect temperature anomalies. The pressure sensing unit is installed on the inner wall of the flame-retardant insulating shell and can collect the internal pressure of the inert gas encapsulation filling layer in real time to capture abnormal pressure fluctuations. The central processing unit is electrically connected to the temperature sensing unit, voltage monitoring unit, current monitoring unit, pressure sensing unit, and electrical protection execution unit, respectively. It is responsible for receiving the operating parameters collected by each sensing unit, processing and analyzing the data, judging the equipment operating status, and coordinating with the electrical protection execution unit to intervene in faults, thus solving the problem of lack of real-time monitoring and protection in the existing technology.

[0024] Preferably, the electrical protection execution unit includes a fast-cut-off switch and a discharge resistor circuit. The fast-cut-off switch uses a solid-state relay or thyristor switch with a response time of ≤10ms, fast response speed, no mechanical wear, and long service life. When the central processing unit determines that a serious fault has occurred, it can quickly cut off the power supply circuit of the capacitor element to prevent the fault from developing. The discharge resistor circuit can quickly release the residual charge of the capacitor element after cutting off the power supply circuit, avoid the residual charge from causing secondary faults, and improve the safety of fault handling.

[0025] The above-mentioned fast-cut-off switches can be selected from: Omron G3MB series solid-state relays (response time ≤ 5ms), Schneider Solido series solid-state relays (response time ≤ 8ms), Infineon thyristor modules (model: T1851N, response time ≤ 3ms) or domestic products with equivalent performance.

[0026] Preferably, the monitoring and protection module also includes a remote communication interface that supports RS485, CAN or wireless communication protocols. It can send the monitored operating parameters, early warning signals and fault information to an external monitoring system to realize remote monitoring, remote early warning and remote fault diagnosis, reduce operation and maintenance costs and adapt to the centralized management of large-scale power systems. The capacitor element has a shielding cap fitted on its gold-plated layer. The shielding cap is made of conductive metal material, which can effectively protect the gold-plated layer, reduce energy loss, improve the capacitor element's surge current resistance, and adapt to complex power grid conditions. The inner wall of the flame-retardant insulating shell is also provided with a polyimide insulating coating with a thickness of 0.1-0.2mm, which can further improve the insulation performance and high temperature resistance of the flame-retardant insulating shell, prevent the shell from aging and breaking due to local overheating, and extend the service life of the shell.

[0027] The temperature sensing unit mentioned above uses a PT100 platinum resistance temperature sensor, which can be selected from: Siemens Pt100 series (model: 6ES7 534-7QE00-0AB0), Omron E52 series (model: E52-CA15A D=3.2), Honeywell STD120 series, or domestic sensors with equivalent performance.

[0028] The pressure sensing unit mentioned above uses a piezoresistive pressure sensor with a measurement range of 0-0.5MPa and an accuracy of ±1%. It can be selected from Honeywell SSC series (model: SSCRRN005MDAA5), Tyco MEAS series (model: M5156-000005-050PG), Sensata Amphenol series (model: NPI-19A-005G) or domestic sensors with equivalent performance.

[0029] The aforementioned central processing unit uses an ARM Cortex-M4 microcontroller, which can be selected from: STMicroelectronics STM32F4 series (model: STM32F407VGT6), NXP Kinetis K4 series (model: MK40FX512VLL12), Microchip Technology SAM4E series, or domestic microcontrollers with equivalent performance.

[0030] The filling and sealing process of the above-mentioned inert gas encapsulation layer is as follows: Place the capacitor body in a vacuum drying oven, evacuate to ≤10Pa, and maintain for 2-4 hours to remove moisture; fill with high-purity nitrogen to 0.12-0.15MPa, with nitrogen purity ≥99.99% and dew point ≤-40℃; pre-dry the explosion-proof non-combustible filler (a mixture of vermiculite and perlite) at 200℃ for 2 hours, and add it at a volume ratio of 5%-8% after cooling; seal the gas filling port using laser welding or argon arc welding, and conduct a pressure test for 24 hours after sealing. A pressure drop ≤0.005MPa is considered qualified.

[0031] The installation process of the above-mentioned internal fuse arc extinguishing unit is as follows: the internal fuse uses an alloy wire with a diameter of 0.1-0.3mm (such as silver-copper alloy or copper-nickel alloy); the internal fuse is connected to the capacitor element electrode by ultrasonic welding or laser welding, the welding temperature is controlled at 300-400℃, and the welding time is 0.5-2 seconds; the quartz sand filling layer uses high-purity quartz sand (SiO2 content ≥99.9%) with a particle size of 0.1-0.3mm and a filling density of 1.5-1.8g / cm³; after the heat shrink tubing is installed, it is heated and shrunk with a hot air gun at a heating temperature of 120-150℃ and a shrinkage time of 10-30 seconds.

[0032] In summary, compared with the prior art, the present invention has the following beneficial technical effects: (1) The present invention forms an all-round explosion protection system from the inside out through the three-layer protection design of the protection module, the composite flame retardant material layer and the monitoring and protection module. The composite flame retardant material layer is composed of a phase change heat absorption layer, a flame retardant heat insulation layer and an insulating protection layer, which can play different protective functions at different temperature stages and effectively delay heat transfer and flame spread. (2) The protection module of the present invention adopts a hierarchical design. The flame-retardant insulating shell realizes external protection, the inert gas encapsulation filling layer realizes internal oxygen isolation, heat absorption and buffering, the self-healing medium component realizes local fault self-healing, the internal fuse arc extinguishing unit realizes fault rapid cut-off, the heat conduction and heat dissipation layer realizes heat rapid discharge, and combined with the phase change heat absorption, flame retardant heat insulation and insulation protection of the composite flame-retardant material layer, a multi-layer protection barrier is formed, which can prevent explosion accidents caused by various faults in all aspects, and is suitable for complex working conditions such as high voltage and high frequency. It fundamentally solves the problems of internal faults easily causing explosions, limited flame retardant performance and insufficient self-healing ability in the prior art. (3) The monitoring and protection module of the present invention responds quickly. It collects operating parameters such as temperature, voltage, current and pressure in real time through multiple sensing units. The central processing unit processes the data efficiently and the electrical protection execution unit intervenes quickly with a response time of ≤10ms. It can detect potential faults in advance and prevent the fault from escalating. The remote communication interface enables remote monitoring and fault diagnosis, reduces operation and maintenance costs, improves the intelligence level of power system operation, and solves the problems of lack of real-time monitoring and protection and weak fault early warning capabilities in the existing technology. (4) The heat dissipation performance of the present invention is greatly improved. The heat dissipation pattern of the heat-conducting heat dissipation layer and the flame-retardant insulating shell works together with the phase change heat absorption layer of the composite flame-retardant material layer to greatly improve the overall heat dissipation performance. This solves the problems of insufficient heat dissipation performance and heat accumulation accelerating the aging of the medium in the prior art, and effectively extends the service life of the power capacitor. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the module structure of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention. Example

[0035] like Figure 1 As shown, the present invention discloses a technical solution, an explosion-proof structure for a power capacitor, applicable to parallel capacitors in a 10kV high-voltage power system, comprising a capacitor body, a protection module, a monitoring and protection module, and a composite flame-retardant material layer.

[0036] The capacitor body includes a capacitor element and electrode leads. The capacitor element adopts a multi-layer polypropylene film wound structure, and the electrode leads are led out from both ends of the capacitor element for external circuit connection.

[0037] The protective module, which encloses the capacitor body, includes the following components: Flame-retardant and insulating shell: It is made of halogen-free flame-retardant glass fiber reinforced PBT material and is integrally injection molded. The heat distortion temperature is 210℃. The shell surface is integrally molded with heat dissipation texture. The width of the heat dissipation texture is 2mm, the depth is 1mm, and the spacing is 5mm, which effectively increases the heat dissipation area and improves the heat dissipation efficiency. The inner wall of the shell is coated with a 0.15mm thick polyimide insulating coating to further improve the insulation and high temperature resistance performance.

[0038] Inert gas encapsulation filling layer: Fills the gap between the flame-retardant insulating shell and the composite flame-retardant material layer, using high-purity nitrogen gas with a purity of 99.995% and a filling pressure of 0.13MPa; The inert gas encapsulation filling layer contains explosion-proof non-combustible filler, which is a mixture of vermiculite and perlite in a mixing ratio of 1:2, with a filler particle size of 0.8mm and a filling amount of 6% of the inert gas filling volume, uniformly mixed in the inert gas, further enhancing the heat absorption, flame retardancy, and explosion suppression effects.

[0039] Self-healing dielectric component: As the core dielectric of the capacitor element, a polypropylene film is used. This polypropylene film is a gradient film, with a zinc-aluminum alloy coating deposited on its surface. The coating thickness gradually changes from the edge to the center, with an edge thickness of 0.12 μm and a center thickness of 0.06 μm, ensuring good dielectric and self-healing properties. The coating is prepared using magnetron sputtering with a zinc-aluminum alloy target (Zn:Al=95:5), and the coating vacuum degree is 2×10⁻⁶. -3 Pa, argon flow rate is 80 sccm, the relative motion speed of the coating in the edge area is 0.8 m / min, and in the center area it is 2.5 m / min.

[0040] Internal fuse arc extinguishing unit: connected in series with the capacitor element, and wrapped with a quartz sand filling layer with a quartz sand particle size of 0.2mm; the electrode leads and the internal fuse are both fitted with heat shrink tubing, which is made of cross-linked polyolefin material with a shrinkage ratio of 2:1 and a thickness of 0.5mm, to improve insulation performance and reduce partial discharge.

[0041] Thermally conductive and heat dissipation layer: Adhered to the inner wall of the flame-retardant insulating shell and the outer surface of the composite flame-retardant material layer, it is made of high thermal conductivity silicone material with a thermal conductivity of 1.8 W / (m•K), and Dow Corning SE4445 series is selected; A thermally conductive insulating gasket is provided between the thermally conductive and heat dissipation layer and the composite flame-retardant material layer. The gasket is made of polytetrafluoroethylene material with a thickness of 0.25 mm, which achieves insulation and isolation while improving thermal conductivity.

[0042] A composite flame-retardant material layer is bonded between the protective module and the capacitor element, and from the inside out includes: Phase change heat absorption layer: Paraffin / polymer composite phase change material is used, with a phase change temperature of 60℃ and a latent heat of phase change of 120J / g. The paraffin is a mixture of C20-C30 n-alkanes, the polymer matrix is ​​HDPE, the mass ratio of paraffin to polymer is 7.5:2.5, and 2.5% peroxide crosslinking agent is added. When the internal temperature of the capacitor reaches 60℃, the phase change material absorbs heat and undergoes a phase change, effectively delaying the temperature rise.

[0043] Flame-retardant and heat-insulating layer: Utilizing modified graphene / polyolefin composite flame-retardant material, achieving a UL94 V-0 flame retardant rating. The graphene sheets are 8μm in size and 3nm in thickness, added at 4% of the polyolefin matrix mass. The polyolefin matrix is ​​a mixture of MAPP and LLDPE (mass ratio 3:2). 9% ammonium polyphosphate flame retardant and 4% melamine cyanurate synergist are added. This effectively blocks heat transfer and flame spread.

[0044] Insulation protection layer: Made of polyimide material with a thickness of 0.15mm, providing electrical insulation protection.

[0045] The monitoring and protection module is integrated into the protection module and electrically connected to the capacitor body, including: Temperature sensing unit: It is attached to the surface of the capacitor element and uses a PT100 platinum resistance temperature sensor, model Omron E52-CA15A D=3.2, with a measurement range of -40℃ to +150℃ and an accuracy of ±0.5℃.

[0046] Voltage monitoring unit: connected in parallel across the capacitor element, using a high-precision voltage transformer with a measurement accuracy of ±0.2%.

[0047] Current monitoring unit: connected in series with the electrode leads, using a Hall current sensor, with a measurement accuracy of ±0.5%.

[0048] Pressure sensing unit: Installed on the inner wall of the flame-retardant insulating housing, it adopts a piezoresistive pressure sensor, model Honeywell SSCRRN005MDAA5, with a measurement range of 0-0.5MPa and an accuracy of ±1%.

[0049] Central Processing Unit: Employs an ARM Cortex-M4 microcontroller, specifically an STMicroelectronics STM32F407VGT6, which is electrically connected to the temperature sensing unit, voltage monitoring unit, current monitoring unit, pressure sensing unit, and electrical protection actuator unit, and is responsible for data acquisition, analysis, and control decision-making.

[0050] Electrical protection actuator: includes a fast-cut-off switch and a discharge resistor circuit; the fast-cut-off switch uses a solid-state relay, model Omron G3MB-202P, with a response time of 8ms; the discharge resistor circuit uses a power resistor with a resistance of 10kΩ and a power of 50W to ensure rapid release of residual charge; the discharge resistor circuit consists of a 10kΩ, 50W discharge resistor and a controlled switch (such as a relay) connected in series, and this series branch is connected in parallel across the capacitor element. The controlled switch is controlled by the central processing unit. When the central processing unit issues a cut-off command, it first controls the fast-cut-off switch to disconnect the main circuit, and then, after a delay of 1-2ms, controls the controlled switch to close, connecting the discharge resistor and releasing the electrical energy stored inside the capacitor.

[0051] Remote communication interface: Supports RS485 communication protocol with a baud rate of 9600bps, and can send operating parameters and fault information to external monitoring systems to realize data communication with the host computer.

[0052] A shielding cap is fitted onto the gold plating layer of the capacitor element. The shielding cap is made of copper alloy and is 0.5mm thick, which protects the gold plating layer and reduces energy loss.

[0053] The working principle of this invention is as follows: Under normal operating conditions, the temperature sensing unit, voltage monitoring unit, current monitoring unit, and pressure sensing unit of the monitoring and protection module collect the operating temperature, operating voltage, operating current, and internal pressure of the inert gas encapsulation filling layer of the capacitor element in real time, and transmit the collected parameters to the central processing unit in real time. The central processing unit processes and analyzes the parameters. If all parameters are within the normal range, the capacitor operates normally. At this time, the phase change heat absorption layer of the composite flame-retardant material layer absorbs the heat generated by the operation of the capacitor element, delaying the temperature rise; the heat conduction and heat dissipation layer quickly conducts the heat to the flame-retardant insulating shell, and dissipates it to the outside through the heat dissipation pattern; the inert gas encapsulation filling layer blocks oxygen, forming normal protection; the insulating protective layer and the polyimide insulating coating improve the overall insulation performance and reduce the risk of partial discharge.

[0054] The system will activate its protection mechanism when the following abnormal conditions are detected: When a capacitor exhibits a minor abnormality (such as increased temperature, voltage / current fluctuations, or a slight increase in pressure), the central processing unit identifies the abnormal parameters and sends an early warning signal to the external monitoring system via a remote communication interface to alert maintenance personnel. If the abnormality worsens, the central processing unit will coordinate with the electrical protection execution unit to prepare for fault intervention.

[0055] When a serious fault occurs (such as a sudden temperature rise, pressure surge, or capacitor breakdown), the central processing unit immediately controls the fast-cut-off switch to quickly cut off the power supply circuit of the capacitor (response time 8ms). At the same time, the discharge resistor circuit releases the residual charge of the capacitor to prevent secondary faults. At this time, the internal fuse of the internal fuse arc extinguishing unit melts quickly, and the quartz sand filling layer blocks the arc spread. The self-healing dielectric component provides self-insulation and repair for the locally broken-down area. The inert gas encapsulation filling layer and explosion-proof non-combustible filler absorb the fault energy and suppress combustion. The flame-retardant heat insulation layer blocks the spread of flames. The flame-retardant insulating shell prevents the fault from spreading outward, comprehensively preventing the occurrence of an explosion. At the same time, the remote communication interface sends the fault information to the external monitoring system, which facilitates maintenance personnel to troubleshoot and repair the fault in a timely manner. Example

[0056] This embodiment is basically the same as Embodiment 1, except that the following parameters are adjusted: The filling pressure of the inert gas encapsulation layer was adjusted to 0.14 MPa, and the filling amount of the explosion-proof non-combustible filler was adjusted to 7%.

[0057] The coating edge thickness of the self-healing dielectric component was adjusted to 0.13 μm, and the center thickness was adjusted to 0.07 μm.

[0058] The phase change temperature of the phase change heat absorption layer was adjusted to 58℃, and the latent heat of phase change was adjusted to 110J / g.

[0059] The thermal conductivity of the heat-conducting and heat-dissipating layer was adjusted to 1.6 W / (m•K).

[0060] The fast-cut-off switch uses a thyristor switch with a response time of 6ms.

[0061] The remote communication interface supports the CAN communication protocol with a baud rate of 250kbps.

[0062] This embodiment is applicable to series capacitors in 35kV high-voltage power systems, and the other structures and functions are the same as in Embodiment 1. Example

[0063] This embodiment is basically the same as Embodiment 1, except that the following parameters are adjusted: The filling pressure of the inert gas encapsulation layer was adjusted to 0.15 MPa, and the filling amount of the explosion-proof non-combustible filler was adjusted to 8%.

[0064] The coating edge thickness of the self-healing dielectric component was adjusted to 0.15 μm, and the center thickness was adjusted to 0.08 μm.

[0065] The phase change temperature of the phase change heat absorption layer was adjusted to 65℃, and the latent heat of phase change was adjusted to 130J / g.

[0066] The thermal conductivity of the heat-conducting and heat-dissipating layer was adjusted to 2.0 W / (m•K).

[0067] The fast-cut switch uses a solid-state relay with a response time of 5ms.

[0068] The remote communication interface supports wireless communication protocols and uses LoRa technology, with a transmission distance of up to 5km.

[0069] The heat distortion temperature of the flame-retardant insulating shell is adjusted to 220℃.

[0070] This embodiment is applicable to filter capacitors in ultra-high voltage power systems, and the other structures and functions are the same as in Embodiment 1.

[0071] Performance testing: The following performance tests were performed on the explosion-proof structures of the power capacitors prepared in Examples 1-3: Explosion-proof performance Internal short circuit test pass pass pass Flame retardant rating UL94 test V-0 level V-0 level V-0 level Pressure resistance test 2.5 times the rated voltage pass pass pass Temperature rise test Continuous operation at rated current for 2 hours ≤35K ≤33K ≤30K Number of self-healing times self-healing due to dielectric breakdown ≥100 times ≥120 times ≥150 times Protection response time Fault Trigger to Disconnection ≤10ms ≤8ms ≤7ms Remote communication distance signal transmission 1km (RS485) 5km (CAN) 5km (wireless) Service life Accelerated aging test ≥15 years ≥18 years ≥20 years 1) Explosion-proof performance comparison test: An internal fault explosion-proof test was conducted according to GB / T 12747.1-2017 standard. A voltage of 2.5 times the rated voltage was applied until an internal fault occurred. Test results: In Example 1 of this invention, the maximum internal pressure was 0.28 MPa, the casing did not rupture, and no fire occurred; the maximum internal pressure of the traditional capacitor was 0.65 MPa, the casing ruptured, and a fire occurred; the explosion-proof structure of this invention can reduce the internal fault pressure by 57%, effectively preventing casing rupture and fire.

[0072] 2) Flame retardancy rating test: Using the UL94 test standard, all examples 1-3 achieved V-0 rating with an oxygen index ≥32%.

[0073] 3) Withstand voltage test: Apply 2.5 times the rated voltage. Examples 1-3 all passed the test without breakdown or flashover.

[0074] 4) Heat dissipation performance comparison test: Ambient temperature 25℃, rated current continuous operation for 2 hours; Test results: Surface temperature rise of Example 1 of the present invention ≤35K, maximum internal temperature ≤75℃, thermal equilibrium time 45 minutes; Surface temperature rise of traditional capacitor ≤55K, maximum internal temperature ≤95℃, thermal equilibrium time 70 minutes; The heat dissipation structure of the present invention reduces temperature rise by 36%, and the phase change material effectively absorbs peak heat.

[0075] 5) Self-healing performance comparison test: According to IEC 60831 standard, 1.5 times the rated voltage was applied to artificially create dielectric defects; Test results: Example 1 of this invention has ≥100 self-healing cycles, with a capacitance loss ≤0.5% after self-healing and a loss tangent ≤0.0015 after self-healing; Traditional self-healing capacitors have ≥50 self-healing cycles, with a capacitance loss ≤1.5% after self-healing and a loss tangent ≤0.003 after self-healing. The gradient plating design of this invention increases the number of self-healing cycles by 100% and results in better performance recovery after self-healing.

[0076] 6) Protection Response Time Test: Simulated overvoltage, overcurrent, overheat, and overvoltage faults. Test results: Overvoltage protection (120% rated voltage) response time 6ms, overcurrent protection (130% rated current) response time 8ms, overheat protection (85℃) response time 5ms, and pressure protection (0.3MPa) response time 7ms. The response time of the monitoring and protection system of this invention is far superior to the standard requirement (≤100ms), enabling rapid fault isolation.

[0077] (7) Remote communication distance test: signal transmission distance, Example 1 is 1km (RS485), Example 2 is 5km (CAN), Example 3 is 5km (wireless).

[0078] (8) Accelerated aging life test: According to GB / T 17702-2013 standard, the temperature was 70℃, the humidity was 85%RH, and 1.25 times the rated voltage was applied. Test results: After 1000 hours, the capacitance change of Example 1 of the present invention was ≤2%, the loss change was ≤30%, and the estimated service life was ≥20 years; after 1000 hours, the capacitance change of traditional capacitors was ≤5%, the loss change was ≤50%, and the estimated service life was ≥10 years. The structure of the present invention extends the service life of the capacitor by 100% and makes the failure mode safer.

[0079] Test results show that the explosion-proof structure for power capacitors provided by this invention meets or exceeds design requirements in terms of explosion-proof performance, flame retardant performance, electrical performance, heat dissipation performance, protection response speed, and service life. It has excellent comprehensive performance, can effectively solve various defects in the prior art, and is suitable for the use needs of power capacitors of different voltage levels and in different scenarios.

[0080] 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 and principle of this application should be covered within the scope of protection of this application.

Claims

1. An explosion-proof structure for a power capacitor, characterized in that: The capacitor includes a capacitor body, a protective module, a monitoring and protection module, and a composite flame-retardant material layer. The capacitor body includes a capacitor element and electrode leads. The protective module is wrapped around the outside of the capacitor body. The composite flame-retardant material layer is attached between the protective module and the capacitor element. The monitoring and protection module is integrated on the protective module and electrically connected to the capacitor body. The protective module includes a flame-retardant insulating shell, an inert gas encapsulation filling layer, a self-healing dielectric component, an internal fuse arc extinguishing unit, and a heat-conducting and heat dissipation layer. The composite flame-retardant material layer comprises, from the inside out, a phase change heat absorption layer, a flame-retardant heat insulation layer, and an insulating protective layer. The monitoring and protection module includes a temperature sensing unit, a voltage monitoring unit, a current monitoring unit, a pressure sensing unit, a central processing unit, and an electrical protection execution unit.

2. The explosion-proof structure of a power capacitor according to claim 1, characterized in that: The flame-retardant insulating shell is integrally injection molded from halogen-free flame-retardant engineering plastic. The engineering plastic is glass fiber reinforced PBT material with a heat distortion temperature of not less than 200°C. The shell surface is integrally molded with heat dissipation texture.

3. The explosion-proof structure of a power capacitor according to claim 2, characterized in that: The inert gas encapsulation filling layer fills the gap between the flame-retardant insulating shell and the composite flame-retardant material layer, using high-purity nitrogen with a purity of not less than 99.99%, and a filling pressure of 0.12-0.15 MPa; The inert gas encapsulation filling layer is also mixed with explosion-proof and non-flammable filler, which is a mixture of vermiculite and perlite in a mixing ratio of 1:

2. The filler particle size is 0.5-1mm, and the filling amount is 5%-8% of the inert gas filling volume.

4. The explosion-proof structure of a power capacitor according to claim 3, characterized in that: The self-healing media component uses a polypropylene film, which is a gradient film. A zinc-aluminum alloy coating is deposited on the surface of the film. The coating thickness gradually changes from the edge of the film to the center, with an edge thickness of 0.1-0.15 μm and a center thickness of 0.05-0.08 μm.

5. The explosion-proof structure of a power capacitor according to claim 4, characterized in that: The internal fuse arc extinguishing unit is connected in series with the capacitor element, and the internal fuse is wrapped with a quartz sand filling layer with a quartz sand particle size of 0.1-0.3mm. The electrode leads and the inner fuse are all fitted with heat shrink tubing, which is made of cross-linked polyolefin material with a shrinkage ratio of 2:

1.

6. The explosion-proof structure of a power capacitor according to claim 5, characterized in that: The heat-conducting and heat-dissipating layer is attached to the inner wall of the flame-retardant insulating shell and the outer side of the composite flame-retardant material layer. It is made of high thermal conductivity silicone material with a thermal conductivity of not less than 1.5 W / (m·K). A thermally conductive insulating pad is also provided between the thermally conductive heat dissipation layer and the composite flame-retardant material layer. The pad is made of polytetrafluoroethylene and has a thickness of 0.2-0.3 mm.

7. The explosion-proof structure of a power capacitor according to claim 1, characterized in that: The phase change heat absorption layer is made of paraffin / polymer composite phase change material with a phase change temperature of 55-65℃ and a latent heat of phase change ≥100J / g. The flame-retardant and heat-insulating layer is made of modified graphene / polyolefin composite flame-retardant material, with a flame-retardant rating of UL94 V-0. The insulating protective layer is made of polyimide material with a thickness of 0.1-0.2 mm.

8. The explosion-proof structure of a power capacitor according to claim 1, characterized in that: The temperature sensing unit is attached to the surface of the capacitor element; The pressure sensing unit is installed on the inner wall of the flame-retardant insulating housing; The central processing unit is electrically connected to the temperature sensing unit, voltage monitoring unit, current monitoring unit, pressure sensing unit, and electrical protection execution unit, respectively.

9. The explosion-proof structure of a power capacitor according to claim 8, characterized in that: The electrical protection execution unit includes a fast-cut-off switch and a discharge resistor circuit. The fast-cut-off switch adopts a solid-state relay or a thyristor switch with a response time ≤10ms.

10. The explosion-proof structure of a power capacitor according to claim 9, characterized in that: The monitoring and protection module also includes a remote communication interface that supports RS485, CAN or wireless communication protocols. A shielding cap is fitted onto the gold-plated layer of the capacitor element, and the shielding cap is made of conductive metal material; The inner wall of the flame-retardant insulating shell is also provided with a polyimide insulating coating with a thickness of 0.1-0.2 mm.

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