A cascade type gas-insulated grounding reactor

Abstract

The application discloses a cascade type gas insulated grounding reactor and belongs to the technical field of the reactor. The grounding reactor comprises a high potential module, a low voltage potential module and an insulation support module which are sequentially connected from top to bottom. The low voltage potential module comprises a shell, two coils, an iron core assembly and an insulation support. The shell is at ground potential, is filled with sulfur hexafluoride insulation gas inside, and the two coils are connected in series. The iron core assembly is at intermediate potential and is connected with the internal lead-out wires of the two coils respectively. The iron core assembly is insulatedly connected with the shell through the insulation support, so that the iron core assembly is suspended in the shell. The shell is set at ground potential, so that the safety of the equipment is remarkably improved. The cascade structure of the two coils connected in series reduces the voltage grade of the single coil, improves the heat dissipation condition, and solves the problems of the single-stage reactor, such as large volume, serious heating and poor heat dissipation performance.

Description

Technical Field

[0001] This invention belongs to the field of reactor technology, and particularly relates to a cascade gas-insulated grounding reactor. Background Technology

[0002] As offshore wind power develops towards deep-sea, large-scale, and clustered directions, flexible DC transmission technology has become the optimal choice for long-distance power transmission. In offshore wind power flexible DC systems, grounding reactors are connected between the DC side neutral point and the ground. They are used to construct the neutral point reference potential, limit the rise rate and amplitude of the single-pole ground fault current, suppress switching overvoltage and lightning overvoltage, and dampen the resonance that may occur between the DC line and the converter station equipment. They are key equipment to ensure the safety of the DC side, quickly isolate faults, and ensure the reliable grid connection and power transmission of the entire wind farm.

[0003] Currently, existing gas-insulated reactors mainly adopt a single-stage structure. For ultra-high voltage gas-insulated reactors, the high-voltage coil of a single-stage gas-insulated iron-core reactor needs to be made large enough to carry the rated voltage, which leads to a corresponding increase in the size of the insulating bushing and shell. This large-volume structure not only results in a higher voltage load on the high-voltage coil and serious heat generation problems, but also poor heat dissipation due to the dense winding of the high-voltage coil.

[0004] To address the aforementioned issues, a gas-insulated cascade core reactor, authorized by publication number CN112103050B, employs a cascade structure in which a high-voltage potential module, an intermediate potential module, and a low-voltage potential module are connected sequentially from top to bottom. However, this existing technology has the following shortcomings: (1) Its shell is part of the intermediate potential module and is at the intermediate potential rather than the ground potential. This design is not convenient for calculating the insulation distance between various equipment in the power station, has poor safety performance, and increases the difficulty of overall insulation coordination of the power station.

[0005] (2) Its products have a high center of gravity and weak seismic resistance, making it difficult to meet the State Grid's 0.5g seismic resistance requirements. In application scenarios with high seismic performance requirements, such as active seismic areas or offshore wind power platforms, there are potential safety hazards.

[0006] (3) Its equipment needs to be assembled by module docking on site. The installation process is complicated and the construction period is long, which is not conducive to projects such as offshore wind power that have strict requirements on the construction period.

[0007] Therefore, there is an urgent need to design a cascade gas-insulated grounding reactor to solve the problems mentioned above. Summary of the Invention

[0008] The purpose of this invention is to provide a cascade gas-insulated grounding reactor, which has the advantages of high safety performance, low center of gravity, and strong shock resistance, and solves the problems mentioned in the background art.

[0009] To achieve the above objectives, the specific technical solution of the cascade gas-insulated grounding reactor of the present invention is as follows: A cascaded gas-insulated grounding reactor includes a high-potential module, a low-potential module, and an insulation support module connected in sequence from top to bottom. The high-potential module is used to introduce external high voltage into the reactor; The low-voltage potential module includes a housing, two coils, a core assembly, and an insulating support. The housing is at ground potential and is filled with sulfur hexafluoride insulating gas. The two coils are connected in series. The core assembly is at intermediate potential and is connected to the internal leads of the two coils respectively. The core assembly is insulated from the housing through an insulating support, so that the core assembly is suspended in the housing. The insulating support module is used to support and fix the housing to the mounting base.

[0010] Furthermore, the insulating support includes a bottom insulating support and a side insulating support. The core assembly is connected to the bottom of the housing through the bottom insulating support and to the side wall of the housing through the side insulating support, so that the core assembly is constrained in both the horizontal and vertical directions.

[0011] Furthermore, multiple mounting plates are fixedly connected to the side wall of the housing, and there are multiple side insulating supports. The multiple side insulating supports are evenly distributed along the direction perpendicular to the iron core. One end of the multiple side insulating supports is fixedly connected to its corresponding mounting plate, and the end of the multiple side insulating supports away from the mounting plate is assembled and connected to the iron core. Each side insulating support has a semi-circular shield on the side facing the coil.

[0012] Furthermore, the low-voltage potential module also includes two insulating support cylinders and two coil equalizing rings. The two coils are wound on the corresponding insulating support cylinders, and the two insulating support cylinders are fixed to both ends of the core assembly. Ventilation holes are provided on the circumference of the two insulating support cylinders. The two coil equalizing rings are respectively fitted onto the ends of the corresponding coils.

[0013] Furthermore, the low-voltage potential module also includes a grounding terminal, a lower terminal plate, and a grounding block. The grounding terminal is molded with resin through an insert, insulated and fixed to the housing, and is detachably connected to the lower terminal plate through the grounding block. When measuring insulation resistance, remove the grounding block to electrically disconnect the grounding terminal from the lower terminal block; During normal operation, the grounding block connects the grounding terminal, the lower terminal plate, and the housing to the same potential.

[0014] Furthermore, the high-potential module includes a high-voltage terminal block, a composite bushing, a vented basin-type insulator, a high-potential shield, and a high-voltage lead wire. The high-voltage terminal block is fixed to the top of the composite bushing for connecting external high-voltage conductors. The lower end of the composite bushing is sealed to the vented basin-type insulator, which is fixed to the top of the housing and isolates the internal air chamber from the outside. The high-potential shield is located below the vented basin-type insulator to uniformly distribute the electric field around the high-voltage lead wire. The starting end of the high-voltage lead wire is electrically connected to the high-voltage terminal block, and the end of the high-voltage lead wire passes through the high-potential shield and extends into the housing for connecting to the leads of the two coils.

[0015] Furthermore, a contact assembly is provided at the lower end of the high-voltage terminal block, and the upper end of the high-voltage lead wire is connected to the high-voltage terminal block through the contact assembly. An exhaust hole is provided at the top of the high-voltage terminal block for internal gas circulation and heat dissipation.

[0016] Furthermore, a bushing equalizing ring is provided inside the composite bushing, and a terminal plate equalizing ring is provided on the upper surface of the high-voltage terminal plate.

[0017] Furthermore, the insulation support module includes multiple support insulators and insulating sleeves. The upper ends of the multiple support insulators are fixedly connected to the bottom of the housing, and the lower ends of the multiple support insulators are used to be fixedly connected to the mounting foundation to support the reactor. The insulating sleeve is fixedly connected to the housing and communicates with the air chamber inside the housing.

[0018] Furthermore, a density relay is installed at the bottom of the insulating sleeve to monitor the density of sulfur hexafluoride insulating gas inside the housing. The density relay maintains ground potential with the housing.

[0019] The present invention has the following advantages: by setting the shell to ground potential, compared with the solution of the shell being at intermediate potential in the prior art, the safety of the equipment is significantly improved. At the same time, it is convenient to calculate the insulation distance between various devices in the power station. By using sulfur hexafluoride insulating gas, its high insulation strength is fully utilized, and the size of the equipment is greatly reduced while ensuring reliable insulation. Through the cascade structure of two coils connected in series, the voltage level of a single coil is reduced, the heat dissipation conditions are improved, and the problems of large size, serious heat generation and poor heat dissipation performance of single-stage reactors are solved. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the grounding reactor of the present invention; Figure 2 This is a schematic diagram of the low-voltage potential module of the present invention. Figure 1 ; Figure 3 This is a schematic diagram of the low-voltage potential module of the present invention. Figure 2 ; Figure 4This is a schematic diagram of the high-potential module of the present invention; Figure 5 This is a schematic diagram of the low-voltage potential module and the insulation support module of the present invention; The markings in the diagram are as follows: 1. High-potential module; 11. High-voltage terminal block; 12. Terminal block equalizing ring; 13. Composite bushing; 14. Bushing equalizing ring; 15. Contact assembly; 16. Vent basin insulator; 17. High-potential shield; 18. High-voltage lead-out wire; 2. Low-voltage module; 21. Coil equalizing ring; 22. Coil; 23. Insulating support cylinder; 24. Core assembly; 25. Insulating support component; 251. Bottom insulating support; 252. Side insulating support; 253. Mounting plate; 26. Housing; 27. Grounding terminal; 28. Lower terminal block; 29. ​​Grounding block; 3. Insulating support module; 31. Support insulator; 32. Insulating bushing; 33. Density relay. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0023] The following is a reference to the appendix. Figure 1 To be continued Figure 5 This invention describes a cascade gas-insulated grounding reactor.

[0024] A cascaded gas-insulated grounding reactor includes a high-potential module 1, a low-potential module 2, and an insulation support module 3 connected sequentially from top to bottom. The high-potential module 1 is used to introduce external high voltage into the reactor. It is the interface between the entire reactor equipment and the external high voltage system. The top of the high-potential module 1 is connected to the external high voltage wire, and the bottom is sealed to the top of the housing 26 of the low-potential module 2. It introduces external high voltage power into the housing 26 to power the two series coils 22.

[0025] The low-voltage potential module 2 includes a housing 26, two coils 22, a core assembly 24, and an insulating support. The housing 26 is at ground potential, meaning it is directly connected to the earth and is in a zero-potential state. It is filled with sulfur hexafluoride insulating gas, utilizing the excellent insulating properties of sulfur hexafluoride to achieve reliable insulation with a small electrical clearance, thereby effectively reducing the size of the reactor equipment. The two coils 22 are connected in series to form a cascade structure, allowing each coil 22 to share half of the system voltage, reducing the insulation requirements and heat generation of a single coil 22. The core assembly 24 is at an intermediate potential, meaning its potential is between the high potential and the ground potential. The core assembly 24 is connected to the internal leads of the two coils 22 to form a complete electromagnetic circuit. The core assembly 24 is insulated from the housing 26 through an insulating support 25, allowing it to float within the housing 26 without direct contact, thus achieving stable maintenance of the intermediate potential.

[0026] The insulation support module 3 is used to support and fix the housing 26 to the mounting base, bear the weight of the entire reactor, and firmly fix the reactor equipment to the ground or mounting platform.

[0027] This reactor significantly improves equipment safety by setting the casing 26 to ground potential, compared to the existing technology where the casing 26 is at an intermediate potential. It also facilitates the calculation of insulation distances between various devices in the power station. By using sulfur hexafluoride insulating gas, its high insulation strength is fully utilized, resulting in a substantial reduction in equipment size while ensuring reliable insulation. The cascade structure of two coils 22 connected in series lowers the voltage level of a single coil 22, improves heat dissipation, and solves the problems of large size, severe heat generation, and poor heat dissipation performance associated with single-stage reactors.

[0028] The shell 26 adopts an aluminum alloy welded structure, which, through simulation calculations, has been verified to meet the strength requirements of three times the design pressure. The shell 26 adopts a three-section structure, mainly for ease of installation. Each section can be processed separately in the factory and then assembled and welded together. The joint of the shell 26 adopts a double EPDM sealing structure to form a double sealing barrier with an annual leakage rate of less than 0.1%, ensuring the long-term stable sealing performance of sulfur hexafluoride gas inside the shell 26.

[0029] The housing 26 is positioned low, with the overall center of gravity lower than the core assembly 24, which significantly lowers the center of gravity of the entire reactor. This low center of gravity design gives the reactor superior seismic performance, meeting the State Grid's 0.5g seismic requirements. It is suitable for applications with strict seismic performance requirements, such as seismically active areas and offshore wind power platforms.

[0030] The core assembly 24 adopts a laminated form, which is made of silicon steel sheets and has good magnetic permeability. An air gap is added between the upper and lower core columns of the core assembly 24 to prevent magnetic saturation and ensure the linearity of the reactor under different operating conditions. There is a casting insulating cylinder inside the core to cast the iron disc into one piece. At the same time, four screws are inserted between the two insulating cylinders and connected to the clamps of the core assembly 24. Under this dual action, the air gap of the core columns remains stable, ensuring the performance stability of the reactor throughout its entire life cycle, while reducing core vibration and lowering operating noise.

[0031] A core shield is installed on the outside of the core assembly 24 to homogenize the electric field at sharp corners such as clamps and prevent partial discharge.

[0032] The insulating support 25 includes a bottom insulating support 251 and a side insulating support 252. The bottom insulating support 251 is disposed between the core assembly 24 and the bottom of the housing 26. The core assembly 24 is connected to the bottom of the housing 26 through the bottom insulating support 251, bearing the vertical load of the core assembly 24 and providing reliable support for the core assembly 24 in the vertical direction. The side insulating support 252 is disposed between the core assembly 24 and the side wall of the housing 26. The core assembly 24 is connected to the side wall of the housing 26 through the side insulating support 252, constraining and positioning the core assembly 24 in the horizontal direction.

[0033] Through the combined action of the bottom insulating support 251 and the side insulating support 252, the core assembly 24 is effectively constrained in both the horizontal and vertical directions, ensuring the positional stability of the core assembly 24 during transportation, installation, and operation. Simultaneously, both the bottom insulating support 251 and the side insulating support 252 are made of insulating material, effectively isolating the electrical connection between the intermediate potential core assembly 24 and the ground potential housing 26 while providing mechanical support, thus ensuring insulation reliability.

[0034] The bottom insulating support 251 preferably adopts an epoxy casting structure, which has good mechanical strength and insulation performance. The connection part of the bottom insulating support 251 is provided with a metal insert. The insert and bolts cooperate to achieve a reliable connection with the core assembly 24 and the housing 26. The structure of the insert is optimized to ensure the connection strength without affecting the insulation performance.

[0035] Preferably, the specific number of bottom insulating supports 251 is two, and the two bottom insulating supports 251 are fixedly connected to the core assembly 24. In other embodiments of the present invention, the number of bottom insulating supports 251 may be more than two.

[0036] A pad is provided between the bottom insulating support 251 and the housing 26. Specifically, the pad is made of metal and has countersunk holes on both sides. One side of the pad is connected to the bottom insulating support 251 by bolts, and the other side is connected to the housing 26 by bolts. The countersunk hole design allows the bolt head to be completely recessed into the pad, ensuring the flatness of the mounting surface and preventing the bolt head from protruding and causing local electric field concentration. The main function of the pad is to provide a flat mounting reference surface for the bottom insulating support 251, which facilitates the bolt fixing between the bottom insulating support 251 and the housing 26. At the same time, it disperses the pressure transmitted from the bottom insulating support 251 to the housing 26, preventing local stress concentration from damaging the housing 26.

[0037] Multiple mounting plates 253 are fixedly connected to the side wall of the housing 26. The multiple mounting plates 253 are arranged circumferentially along the side wall of the housing 26 to provide mounting bases for the side insulation supports 252. There are multiple side insulation supports 252, which are evenly distributed in a direction perpendicular to the core. One end of the multiple side insulation supports 252 is fixedly connected to its corresponding mounting plate 253, and the end of the multiple side insulation supports 252 away from the mounting plate 253 is connected to the core assembly 24, thereby forming a uniform support network around the core assembly 24.

[0038] The specific number of mounting plates 253 is the same as the specific number of side insulating supports 252. Preferably, the specific number of mounting plates 253 and side insulating supports 252 is eight. The eight side insulating supports 252 are evenly distributed along the direction perpendicular to the core, so that the core assembly 24 is subjected to a balanced constraint force in the horizontal direction. This satisfies the insulation requirements between the intermediate potential of the core and the ground potential of the shell 26, and also plays a supporting and vibration-damping role, reducing the vibration of the core during operation. At the same time, the evenly distributed side insulating supports 252 also determine the shape of the product during transportation, that is, the side insulating supports 252 are perpendicular to the vertical direction, ensuring transportation stability. In other embodiments of the invention, the number of mounting plates 253 and side insulating supports 252 may also be other.

[0039] Each side insulation support 252 has a semi-circular shield on the side facing the coil 22. The semi-circular shield is made of aluminum and is formed into a semi-circular arc structure by spinning or stamping. It is fixedly installed on the side of the side insulation support 252. The semi-circular shield is set towards the coil 22. Its function is to uniformly distribute the electric field between the coil 22 and the core assembly 24, shield the sharp corner effect of metal parts such as mounting screws and nuts, and prevent local electric field concentration from causing discharge or excessive partial discharge.

[0040] The low-voltage potential module 2 also includes two insulating support cylinders 23 and two coil 22 equalizing rings. The two coils 22 are wound on the corresponding insulating support cylinders 23. The insulating support cylinders 23 are made of insulating materials (such as epoxy glass fiber composite material) to provide a skeleton and support for the coils 22. The two insulating support cylinders 23 are fixed to both ends of the core assembly 24. Specifically, the two insulating support cylinders 23 are installed and connected to the core assembly 24 by bolts.

[0041] Ventilation holes are provided on the circumference of the two insulating support cylinders 23. The ventilation holes are arranged at intervals along the axial and circumferential directions of the insulating support cylinders 23, which facilitates the free flow of gas inside the shell 26 inside and outside the insulating support cylinders 23, promotes heat exchange, and reduces the temperature rise inside the core.

[0042] Two equalizing rings for coils 22 are respectively fitted onto the corresponding ends of coils 22. The equalizing rings are preferably made of 304 stainless steel and are formed by joining two semi-circular rings together. The joint of the semi-circular rings is grooved, and a connecting plate is welded inside. The two semi-circular rings are fastened together by screws, so that the equalizing rings for coils 22 are tightly held at the ends of coils 22. The function of the equalizing rings for coils 22 is to even out the electric field distribution at the ends of coils 22, prevent electric field concentration at sharp corners, and improve insulation performance.

[0043] Two coils 22 are located at opposite ends of the core assembly 24 and are connected in series. The two coils 22 are the first coil 22 and the second coil 22, respectively. The starting end of the first coil 22 is electrically connected to the lower end of the high-voltage lead 18 to receive high-voltage power from the high-potential module 1, and the end of the first coil 22 is electrically connected to the internal lead of the core assembly 24. The starting end of the second coil 22 is electrically connected to the internal lead of the core assembly 24, and the end of the second coil 22 is electrically connected to the grounding terminal 27. Finally, it is connected to the housing 26 at the same potential through the grounding block 29. The two coils 22 form a series circuit connected end to end through the core assembly 24. The core assembly 24 serves as an intermediate potential node and is connected to the leads of both coils 22, so that the system voltage is evenly distributed across the two coils 22. Through this series connection, the system voltage is distributed across the two coils 22, with each coil 22 bearing only half of the voltage, thereby reducing the insulation requirements and heat generation of a single coil 22 and achieving the effect of cascade voltage sharing.

[0044] The coil 22 is made of copper enameled wire with a diameter of 0.8mm wound together, with two layers of diamond-shaped adhesive film between the layers. The coil 22 is wound around the insulating support cylinder 23 from the inside out. To prevent the coil 22 from loosening and falling off, the ends of each layer of wire are fixed with high-temperature double-sided tape. After the coil 22 is wound, it is cured in a high-temperature oven. The gaps between the diamond dots are used for venting during the curing process and serve as tiny heat dissipation channels during equipment operation, which helps to dissipate heat and improves the heat dissipation performance of the coil 22.

[0045] The low-voltage potential module 2 also includes a grounding terminal 27, a lower terminal plate 28, and a grounding block 29. The grounding terminal 27 is molded with resin through an insert and is insulated and fixed to the housing 26. That is, the grounding terminal 27 and the housing 26 are isolated by insulating material to achieve electrical insulation. The grounding terminal 27 and the lower terminal plate 28 are detachably connected through the grounding block 29. The grounding block 29 is a conductive connector that forms an electrical path between the grounding terminal 27 and the lower terminal plate 28 under normal connection conditions.

[0046] When measuring insulation resistance, remove the grounding block 29 to electrically disconnect the grounding terminal 27 from the lower terminal plate 28. At this time, the insulation resistance between the grounding terminal 27 and the housing 26 can be measured separately, which facilitates the detection of the integrity of the insulation structure of the grounding terminal 27.

[0047] During normal operation, the grounding block 29 connects the grounding terminal 27, the lower terminal plate 28, and the housing 26 to the same potential, ensuring that the grounding terminal 27 is at ground potential and meeting the system's grounding requirements.

[0048] The detachable connection design of the grounding block 29 facilitates the periodic testing of insulation resistance without affecting normal operation, and solves the problem that the grounding terminal 27 is fixedly connected to the housing 26 in the traditional structure and the insulation resistance cannot be measured separately.

[0049] The high-potential module 1 includes a high-voltage terminal block 11, a composite bushing 13, a vented basin insulator 16, a high-potential shield 17, and a high-voltage lead wire 18.

[0050] The high-voltage terminal block 11 is fixed to the top of the composite bushing 13 and is used to connect the external high-voltage conductor. The high-voltage terminal block 11 is preferably made of aluminum alloy material and is integrally welded with the aluminum alloy round flange and the internal conductive tube, which has good conductivity and mechanical strength.

[0051] The lower end of the composite bushing 13 is sealed to the ventilated basin insulator 16 to form a closed insulation channel. The ventilated basin insulator 16 is fixed to the top of the housing 26 and isolates the internal air chamber of the housing 26 from the outside, playing a dual role of sealing and insulation. The ventilated basin insulator 16 preferably adopts an external aluminum alloy ring structure, which has the characteristics of UV protection and anti-aging, and at the same time significantly enhances the mechanical strength of the entire basin insulator.

[0052] The high-potential shield 17 is located below the ventilated basin insulator 16. The high-potential shield 17 is made of aluminum tube and spun cover welded together. The main function of the high-potential shield 17 is to shield the high-voltage lead 18, so that the electric field lines around the high-voltage lead 18 are evenly distributed, preventing internal discharge and reducing the level of partial discharge.

[0053] The starting end of the high voltage lead 18 is electrically connected to the high voltage terminal block 11. The end of the high voltage lead 18 passes through the high potential shield 17 and extends into the housing 26 for connection with the lead ends of the two coils 22. The high voltage lead 18 is preferably made of copper wire with an insulating outer sheath and is arranged in a spiral shape, which is convenient for installation and can prevent discharge between the shield and the high voltage lead 18 under lightning strike.

[0054] A bushing equalizing ring 14 is provided inside the composite bushing 13 to equalize the electric field distribution inside the composite bushing 13, eliminate the sharp corner effect, improve insulation performance, and optimize equipment size. A terminal plate equalizing ring 12 is provided on the upper surface of the high voltage terminal plate 11. The terminal plate equalizing ring 12 adopts a welded structure of aluminum alloy tube and aluminum alloy plate and is bolted to the upper surface of the high voltage terminal plate 11 to optimize the electric field distribution, prevent the equipment from causing insulation faults due to electric field distortion, suppress corona discharge, reduce partial discharge, eliminate sharp discharge, and at the same time shield the influence of external electromagnetic field on the bushing itself to a certain extent, and protect the bushing end from external mechanical stress damage.

[0055] The lower end of the high voltage terminal block 11 is provided with a contact assembly 15. The upper end of the high voltage lead 18 is connected to the high voltage terminal block 11 through the contact assembly 15. The contact assembly 15 is preferably made of aluminum alloy machined parts and is provided with a polytetrafluoroethylene guide ring and spring contact finger inside to ensure reliable insertion and good contact.

[0056] An exhaust port is provided on the top of the high-voltage terminal board 11. The exhaust port passes through the conductive tube of the high-voltage terminal board 11, which facilitates the internal gas circulation, promotes heat convection with the outside, and assists in heat dissipation.

[0057] The insulation support module 3 includes multiple support insulators 31. The upper ends of the multiple support insulators 31 are fixedly connected to the bottom of the housing 26, and the lower ends of the multiple support insulators 31 are fixedly connected to the mounting foundation to support the entire reactor. Specifically, the upper ends of the multiple support insulators 31 are fixedly connected to the bottom of the housing 26 by bolts. The number of support insulators 31 is preferably six, which are evenly distributed around the bottom of the housing 26 to make the housing 26 bear force evenly. The support insulators 31 are made of high-strength insulating material and have both good mechanical load-bearing capacity and insulation performance.

[0058] The insulation support module 3 also includes an insulation sleeve 32, which is fixedly connected to the housing 26 and communicates with the gas chamber inside the housing 26. The function of the insulation sleeve 32 is to provide a communication interface between the gas chamber inside the housing 26 and the outside, so as to facilitate the installation of monitoring equipment and the performance of gas maintenance operations.

[0059] A density relay 33 is installed at the bottom of the insulating sleeve 32 to monitor the density of sulfur hexafluoride insulating gas inside the housing 26. The density relay 33 is kept at ground potential with the housing 26 to ensure the accuracy of the measurement by the density relay 33. When the density of sulfur hexafluoride gas inside the housing 26 is lower than the set threshold, the density relay 33 issues an alarm signal to remind maintenance personnel to replenish the gas in time or check for leaks, so as to ensure that the insulation performance of the equipment is always in a reliable state.

[0060] This cascade gas-insulated grounding reactor is particularly suitable for offshore wind power flexible DC transmission projects. It is connected between the DC side neutral point and the ground to limit the rise rate and amplitude of fault current in DC side single-pole grounding faults, suppress switching overvoltage and lightning overvoltage, dampen resonance, and construct a stable neutral point reference potential. At the same time, it can also be widely used in onshore flexible DC back-to-back interconnection projects, urban power grid flexible DC transmission and other fields.

[0061] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A cascade gas-insulated grounding reactor, characterized in that, It includes a high-potential module, a low-potential module, and an insulating support module connected sequentially from top to bottom; The high-potential module is used to introduce external high voltage into the reactor; The low-voltage potential module includes a housing, two coils, a core assembly, and an insulating support. The housing is at ground potential and is filled with sulfur hexafluoride insulating gas. The two coils are connected in series. The core assembly is at intermediate potential and is connected to the internal leads of the two coils respectively. The core assembly is insulated from the housing through an insulating support, so that the core assembly is suspended in the housing. The insulating support module is used to support and fix the housing to the mounting base.

2. The cascade gas-insulated grounding reactor according to claim 1, characterized in that, The insulating support includes a bottom insulating support and a side insulating support. The core assembly is connected to the bottom of the housing through the bottom insulating support and to the side wall of the housing through the side insulating support, so that the core assembly is constrained in both the horizontal and vertical directions.

3. The cascade gas-insulated grounding reactor according to claim 2, characterized in that, Multiple mounting plates are fixedly connected to the side wall of the housing. There are multiple side insulating supports, which are evenly distributed along the direction perpendicular to the iron core. One end of each side insulating support is fixedly connected to its corresponding mounting plate, and the end of each side insulating support away from the mounting plate is assembled and connected to the iron core. Each side insulating support has a semi-circular shield on the side facing the coil.

4. The cascade gas-insulated grounding reactor according to claim 1, characterized in that, The low-voltage potential module also includes two insulating support cylinders and two coil equalizing rings. The two coils are wound on the corresponding insulating support cylinders, and the two insulating support cylinders are fixed to the two ends of the iron core assembly. Ventilation holes are provided on the circumference of the two insulating support cylinders. The two coil equalizing rings are respectively fitted onto the ends of the corresponding coils.

5. The cascade gas-insulated grounding reactor according to claim 1, characterized in that, The low-voltage potential module also includes a grounding terminal, a lower terminal plate, and a grounding block. The grounding terminal is molded with resin through an insert, insulated and fixed to the housing, and is detachably connected to the lower terminal plate through the grounding block. When measuring insulation resistance, remove the grounding block to electrically disconnect the grounding terminal from the lower terminal block; During normal operation, the grounding block connects the grounding terminal, the lower terminal plate, and the housing to the same potential.

6. The cascade gas-insulated grounding reactor according to claim 1, characterized in that, The high-potential module includes a high-voltage terminal block, a composite bushing, a vented basin-type insulator, a high-potential shield, and high-voltage leads. The high-voltage terminal block is fixed to the top of the composite bushing and is used to connect to the external high-voltage conductor. The lower end of the composite bushing is sealed to the vented basin-type insulator, which is fixed to the top of the housing and isolates the internal air chamber from the outside. The high-potential shield is located below the vented basin-type insulator to uniformly distribute the electric field around the high-voltage leads. The starting end of the high-voltage leads is electrically connected to the high-voltage terminal block, and the end of the high-voltage leads passes through the high-potential shield and extends into the housing to connect to the leads of the two coils.

7. The cascade gas-insulated grounding reactor according to claim 6, characterized in that, The lower end of the high-voltage terminal block is equipped with a contact assembly, and the upper end of the high-voltage lead wire is connected to the high-voltage terminal block through the contact assembly. The upper part of the high-voltage terminal block is equipped with an exhaust hole for internal gas circulation and heat dissipation.

8. The cascade gas-insulated grounding reactor according to claim 6, characterized in that, A bushing equalizing ring is provided inside the composite bushing, and a terminal plate equalizing ring is provided on the upper surface of the high-voltage terminal plate.

9. The cascade gas-insulated grounding reactor according to claim 1, characterized in that, The insulation support module includes multiple support insulators and insulating sleeves. The upper ends of the multiple support insulators are fixedly connected to the bottom of the housing, and the lower ends of the multiple support insulators are fixedly connected to the mounting foundation to support the reactor. The insulating sleeves are fixedly connected to the housing and communicate with the air chamber inside the housing.

10. The cascade gas-insulated grounding reactor according to claim 9, characterized in that, A density relay is installed at the bottom of the insulating sleeve to monitor the density of sulfur hexafluoride insulating gas inside the housing. The density relay maintains ground potential with the housing.

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