Split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets

Abstract

This invention relates to a split-type outdoor low-voltage switchgear for photovoltaic transformer substations suitable for overseas markets. It includes a split-type outdoor low-voltage switchgear, a container, an 11000kVA oil-immersed transformer, and a 24kV environmentally friendly gas holder. All components are integrated and installed inside the container. The container is divided into a low-voltage compartment, a transformer compartment, and a gas holder compartment, each corresponding to the aforementioned components. Fireproof partitions and independent ventilation and heat dissipation channels are provided between each compartment. The split-type outdoor low-voltage switchgear consists of an independent low-voltage switchgear cabinet and a low-voltage switchgear outer shell. This invention can reduce production costs, improve production and operation efficiency, reduce transmission losses, and increase power plant revenue; it is also convenient to operate and highly safe.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation equipment technology, specifically to a split-type outdoor low-voltage cabinet substation low-voltage cabinet suitable for overseas markets. Background Technology

[0002] As photovoltaic power plants develop towards larger capacity and higher power, the performance, structure, and ease of operation and maintenance of the low-voltage switchgear in prefabricated substations, as core power distribution equipment, directly affects the overall efficiency and operating costs of the power plant. Currently, photovoltaic prefabricated substations generally suffer from the following technical defects: 1. Imbalance between protection and cost: The vast majority of photovoltaic prefabricated substations are indoor structures, lacking independent outdoor protection capabilities and relying on the substation's outer casing for protection. This results in a complex casing structure, higher production costs, and cumbersome operation and maintenance requiring disassembly of the casing, hindering efficient operation and maintenance. 2. Inappropriate structural design: A very small number of outdoor low-voltage switchgear adopt an integrated structure with a non-removable protective casing. While this meets outdoor usage requirements, the secondary control room is located inside the cabinet, limiting the operator's working space and making daily operation, fault diagnosis, and component replacement extremely difficult. Currently, the market share of this type of integrated prefabricated substation is continuously shrinking. 3. Limited capacity and voltage: The voltage level of existing indoor and outdoor low-voltage switchgear is AC 800V, and the maximum capacity of the matching transformer is only 9000kVA. This cannot meet the power transmission needs of large-capacity photovoltaic power stations, which restricts the reduction of power transmission losses and the improvement of overall power generation efficiency, making it difficult to achieve the core goal of cost reduction and efficiency improvement of photovoltaic power stations.

[0003] Therefore, there is an urgent need for a photovoltaic power generation box-type low-voltage switchgear with optimized structure, increased capacity, convenient operation and maintenance, and reliable protection to solve the above-mentioned problems of existing technologies. Summary of the Invention

[0004] This invention aims to overcome the technical defects of existing photovoltaic transformer low-voltage switchgear and provide a split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets. Through split-type structural design, voltage level and capacity improvement, optimized copper busbar layout and heat dissipation design, it achieves the goals of reducing production costs, improving operation and maintenance efficiency, reducing transmission losses, and ensuring operational stability, thus meeting the needs of large-capacity photovoltaic power plants.

[0005] A split-type outdoor low-voltage switchgear for photovoltaic transformers, suitable for overseas markets, includes a split-type outdoor low-voltage switchgear, a container, an 11000kVA oil-immersed transformer, and a 24kV environmentally friendly gas holder. All components are integrated and installed inside the container. The container is divided into a low-voltage compartment, a transformer compartment, and a gas holder compartment, with fireproof partitions and independent ventilation and heat dissipation channels between each compartment. The split-type outdoor low-voltage switchgear consists of an independent low-voltage switchgear cabinet and a low-voltage switchgear outer shell. The low-voltage switchgear integrates a frame circuit breaker, a molded case circuit breaker, and a temperature and humidity controller. The frame circuit breaker is vertically arranged on the left side of the middle of the cabinet and is fastened to an internal steel bracket by high-strength bolts. This bracket is fully welded to the cabinet frame. The upper copper busbar of the frame circuit breaker extends upward to connect with the incoming line terminal to introduce current, while the lower copper busbar extends horizontally to the right to form an electrical connection with the two busbars. Two to four molded case circuit breakers are configured, evenly distributed along the width of the cabinet to the right of the frame circuit breaker, with the installation height consistent with that of the frame circuit breaker. The upper opening of the molded case circuit breaker... The copper busbar extends horizontally to the left, overlapping with the two busbars. The lower copper busbar extends vertically downward to the bottom of the cabinet's inlet port, used to connect to the 1kV AC output of the inverter. The temperature and humidity controller is installed on the upper front of the cabinet and fixed to the inside of the cabinet door panel. Its signal acquisition line passes through the reserved through hole in the door panel and enters the cabinet, connecting to the PT100 temperature sensor and the capacitive humidity sensor respectively. The temperature sensor and humidity sensor are fixedly installed above the frame circuit breaker and in the middle of the molded case circuit breaker cluster, respectively. The control output line of the temperature and humidity controller is connected in series with the heat exchanger control circuit. The low-voltage switchgear housing integrates heat exchangers and limit switches. Two heat exchangers with intelligent speed regulation are symmetrically embedded in the middle of the two side panels of the housing and are fastened to the housing frame with bolts. The air inlet of the heat exchanger faces the inside of the cabinet and is sealed to the air outlet of the directional air duct. The air outlet faces the outside of the cabinet. A protective grille is installed on the housing at the position corresponding to the air outlet. The limit switch is fixed to the front of the inside of the housing, corresponding to the cabinet door closing position. It is fixed to the housing column by a bracket. When the cabinet door is closed, the edge of the cabinet door presses the limit switch contacts to close, and the control circuit is connected. When the cabinet door is opened, the contacts reset and open, automatically cutting off the power supply to the control circuit inside the low-voltage switchgear, forming a safety interlock protection. The low-voltage switchgear has an AC 1kV voltage rating and a rated withstand voltage of not less than 2.5kV, matching and adapting to the low-voltage side parameters of an 11000kVA oil-immersed transformer. The lower copper busbar of the frame circuit breaker adopts a horizontal outgoing structure, with two layers of busbars corresponding to the lower busbar of the frame circuit breaker. The busbars are arranged along the width of the low-voltage switchgear. The lower busbar of the frame circuit breaker that overlaps with the first layer of busbars adopts a double-row design, while the lower busbar of the frame circuit breaker that overlaps with the second layer of busbars adopts a single-row design. Secondary equipment such as electric operating buttons, temperature and humidity controllers, and miniature circuit breakers are all arranged facing the outside of the low-voltage switchgear. The interior of the low-voltage switchgear shell is equipped with a directional air duct, which is welded from cold-rolled steel plate and lined with heat-insulating and noise-reducing cotton. The air inlet of the air duct corresponds to the port of the frame circuit breaker and the high-heat component area of ​​the molded case circuit breaker, and the air outlet is connected to the air inlet of the heat exchanger.

[0006] Furthermore, the low-voltage switch cabinet body and the low-voltage switch shell are fixedly connected by quick-release bolts, and a waterproof sealing strip is provided at the connection.

[0007] Furthermore, the rated heat dissipation power of the heat exchanger is 270W / K, and the inlet and outlet of the directional air duct correspond to the port of the frame circuit breaker and the high-heat component area of ​​the molded case circuit breaker, respectively.

[0008] Furthermore, the copper busbar surface is protected with 8μm electroplated tin, and the copper busbar is supported and fixed by BMC material insulators. The thickness of the first busbar is 8-12mm and the width is 80-100mm, the thickness of the second busbar is 6-8mm and the width is 60-80mm, and the insulation distance between the two busbars is not less than 120mm.

[0009] Furthermore, the 11000kVA oil-immersed transformer adopts a double-split three-winding short-circuit withstand design, the rated current on the low-voltage side of the transformer matches the rated current of the frame circuit breaker, and the short-circuit impedance is 6%-8%.

[0010] Furthermore, the low-pressure cabinet body can be independently lifted out through the top cover of the low-pressure chamber of the 20-foot container without disassembling the low-pressure cabinet shell or other structures of the 20-foot container during the lifting process.

[0011] Furthermore, the temperature and humidity controller maintains the internal temperature of the low-voltage cabinet between -20℃ and 40℃. When the internal temperature exceeds 35℃, the heat exchanger automatically increases its speed to 120% of the rated speed. When the internal temperature is below 0℃, the heat exchanger activates the low-temperature anti-freeze mode.

[0012] Furthermore, the two busbars are bolted to the lower busbar of the frame circuit breaker and the upper copper busbar of the incoming plastic shell.

[0013] The targeted solution provided by this invention has the following beneficial effects: Compared with the prior art, the present invention has the following significant advantages: Reduce production costs and improve production and maintenance efficiency: The split-type outdoor low-voltage switchgear comes with an independent protective shell, which can be used directly outdoors without the need for a low-voltage room door added to a container shell, thus reducing container manufacturing costs; the cabinet and shell can be produced in parallel and integrated later, and the cabinet is not limited by the shell, providing ample space for assembly and operation, effectively improving production efficiency. During on-site maintenance, the top cover of the container's low-voltage room can be directly opened, and the low-voltage switchgear can be lifted out independently for inspection (the lifting points are made of Q235 steel, with a rated load capacity of not less than 500kg, and the lifting path is free from collision and interference), breaking through physical space limitations and solving the problem of difficult maintenance of traditional low-voltage switchgear.

[0014] Reduce transmission losses and increase power plant revenue: The voltage level of the low-voltage switchgear is upgraded to 1kV and equipped with an 11000kVA large-capacity oil-immersed transformer. Compared with the existing 800V / 9000kVA configuration, this significantly reduces the power loss during the transmission process of the photovoltaic power plant, improves the overall power generation efficiency of the power plant, and increases operating revenue.

[0015] Optimize material usage and control costs: The double-row and single-row differentiated overlapping design of the two-layer busbar and the bottom busbar of the frame circuit breaker reduces the amount of copper busbar while meeting the needs of high current transmission. Combined with T2 copper material and electroplated tin protection treatment, it takes into account cost control, corrosion resistance and conductivity.

[0016] Easy to operate and highly safe: all secondary equipment is arranged on the outside of the low-voltage cabinet, making it easy for on-site personnel to observe, operate and read parameters; the limit switch is linked with the cabinet door to form a safety interlock, automatically cutting off the power supply to the control circuit when the cabinet door is opened to prevent electric shock accidents; IP54-level waterproof and dustproof protection and optimized insulation spacing design further ensure outdoor operation safety.

[0017] Precise temperature control and stable operation: The intelligent speed-regulating heat exchanger, in conjunction with the directional air duct, precisely controls the temperature inside the cabinet, avoiding overheating of high-heat components and condensation and freezing damage at low temperatures. This ensures stable operation of the low-voltage cabinet within a wide temperature range of -20℃ to 40℃, adapting to the needs of photovoltaic power plants under different climatic conditions. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall front structure of the container.

[0019] Figure 2 This is a schematic diagram of the overall side structure of the container.

[0020] Figure 3 This is a schematic diagram of the overall structure of the outdoor low-voltage switchgear cabinet (excluding the outer shell).

[0021] Figure 4 This is a top view of the outdoor low-voltage switchgear cabinet (excluding the outer shell).

[0022] Figure 5 This is a schematic diagram of the right-side structure of an outdoor low-voltage switchgear cabinet (excluding the outer shell).

[0023] Figure 6 This is a front view structural diagram of an outdoor low-voltage switchgear cabinet (excluding the outer shell).

[0024] Figure 7 This is a schematic diagram of the front structure of the outdoor low-voltage switchgear.

[0025] Figure 8 This is a top view of the outdoor low-voltage switchgear enclosure.

[0026] Figure 9This is a schematic diagram of the right-side structure of the outdoor low-voltage switchgear enclosure.

[0027] In the above attached diagram, the component labels correspond as follows: 1-Secondary compartment (for installing secondary equipment), 2-Molded case circuit breaker, 3-Cable copper busbar, 4-Soft copper busbar at the top of the frame circuit breaker, 5-Frame circuit breaker, 6-Vertical copper busbar at the top of the frame circuit breaker, 7-Insulator, 8-Upper busbar, 9-Lower busbar, 10-Double row section at the bottom of the frame circuit breaker, 11-Single row section at the bottom of the frame circuit breaker, 21-Container, 22-Low-voltage compartment heat exchanger, 23-Right side door of the low-voltage cabinet (closed), 24-Right side door of the low-voltage cabinet (open), 25-Gas cabinet compartment, 26-Transformer compartment, 27-Low-voltage compartment, 42-Soft connection protective passage at the top of the frame circuit breaker. Detailed Implementation

[0028] 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.

[0029] like Figure 1 , Figure 2 As shown, this split-type low-voltage switchgear transformer mainly consists of a split outdoor low-voltage switchgear, container 21, an 11000kVA oil-immersed transformer, and a 24kV environmentally friendly gas cabinet. All core components are integrated and installed inside container 21, achieving a unified layout that facilitates transportation, installation, and subsequent operation and maintenance. To ensure the independent and stable operation of each component, container 21 adopts a partitioned design, with separate low-voltage compartment 27, transformer compartment 26, and gas cabinet compartment 25. Fireproof partitions are installed between the three compartments to effectively prevent the spread of fire. At the same time, each compartment is equipped with independent ventilation and heat dissipation channels to avoid heat interference between different compartments and ensure the stability of equipment operation.

[0030] The split-type outdoor low-voltage switchgear is the core component of this embodiment. It adopts a split design where the cabinet and outer shell are independent, providing both independent outdoor protection capabilities and ease of operation and maintenance. Its specific structure combines... Figures 3-9 Detailed explanation is as follows: like Figures 3-6As shown, the low-voltage switchgear integrates a frame circuit breaker 5, a molded case circuit breaker 2, and a temperature and humidity controller (installed inside the cabinet door). The components are rationally arranged, balancing ease of operation and current transmission efficiency. The frame circuit breaker 5 is vertically positioned on the left side of the middle of the cabinet and secured to an internal steel bracket with high-strength bolts. This bracket is fully welded to the cabinet frame, ensuring a firm installation of the frame circuit breaker 5 and allowing it to withstand vibration and impact during high-current operation. The upper copper busbar of the frame circuit breaker 5 consists of a soft copper busbar 4 and a vertical copper busbar 6. The vertical copper busbar 6 extends upwards, connecting with the incoming line terminal to achieve stable external current introduction. The lower copper busbar of the frame circuit breaker 5 consists of a double-row section 10 and a single-row section 11, extending horizontally to the right to form a precise electrical connection with the two busbars, meeting the requirements for high-current transmission.

[0031] Three molded case circuit breakers 2 are configured (the preferred number in this embodiment can be adjusted to 2-4 units according to actual needs), evenly arranged along the width of the cabinet on the right side of the frame circuit breaker 5, with the installation height consistent with the frame circuit breaker 5 to ensure the convenience and standardization of copper busbar connection. The upper copper busbar of the molded case circuit breaker 2 (i.e., cable copper busbar 3) extends horizontally to the left, corresponding to the upper busbar 8 and the lower busbar 9, realizing the current splitting transmission; the lower copper busbar of the molded case circuit breaker 2 extends vertically downward to the bottom inlet port of the cabinet, used to connect the 1kV AC power output from the inverter, completing the initial power distribution of photovoltaic power.

[0032] The temperature and humidity controller is installed on the upper front side of the cabinet and fixed inside the cabinet door panel. Its signal acquisition line passes through a pre-drilled hole in the door panel and connects to the PT100 temperature sensor and a capacitive humidity sensor, respectively. The temperature sensor is fixed above the frame circuit breaker 5, and the humidity sensor is fixed in the middle of the molded case circuit breaker cluster 2, enabling accurate acquisition of temperature and humidity data in the area containing key components inside the cabinet. The control output line of the temperature and humidity controller is connected in series with the heat exchanger control circuit to achieve automatic temperature regulation inside the cabinet, ensuring that the components operate in a suitable environment.

[0033] The secondary compartment 1 on the cabinet is used to install secondary equipment. Electric operating buttons, temperature and humidity controllers, miniature circuit breakers, and other secondary equipment are all arranged facing the outside of the low-voltage cabinet, facilitating on-site operators to observe equipment operating status, read parameters, and perform operational control, thus solving the problem of limited secondary operating space in traditional low-voltage cabinets. The upper flexible connection protection channel 42 of the frame circuit breaker is installed on the outside of the upper flexible copper busbar 4 of the frame circuit breaker, providing protection and avoiding safety hazards caused by exposed copper busbars.

[0034] like Figures 7-9As shown, the low-pressure cabinet housing integrates a low-pressure chamber heat exchanger 22 and a limit switch, providing excellent outdoor protection and heat dissipation performance. Two low-pressure chamber heat exchangers 22 with intelligent speed control are symmetrically embedded in the center of both side panels of the housing, secured to the housing frame with bolts, ensuring a firm connection and facilitating disassembly and maintenance. The air inlet of the low-pressure chamber heat exchanger 22 faces the inside of the cabinet and is sealed to the air outlet of the directional air duct. The air outlet faces the outside of the cabinet, and a protective grille is installed on the housing corresponding to the air outlet position to prevent outdoor dust and debris from entering the heat exchanger, ensuring efficient heat dissipation.

[0035] The limit switch is fixed to the front inner side of the housing, corresponding to the cabinet door closing position. It is fixed to the housing column by a bracket to achieve a safety interlock between the cabinet door and the control circuit. When the right side door 23 of the low-voltage cabinet housing is closed, the edge of the cabinet door presses the limit switch contact to close it, the control circuit is connected, and the equipment can operate normally. When maintenance operations are required and the right side door 24 of the low-voltage cabinet housing is opened, the limit switch contact resets and opens, automatically cutting off the power supply to the control circuit inside the low-voltage cabinet, preventing operators from being electrocuted when the cabinet door is open, and improving operational safety.

[0036] The low-voltage switchgear's interior features a directional air duct, constructed from cold-rolled steel plate with a robust structure. The inner wall is lined with insulation and noise-reducing cotton, minimizing heat loss and reducing operational noise. The air inlet of the directional air duct corresponds to the high-heat components of the frame circuit breaker (port 5) and molded case circuit breaker (port 2), precisely capturing high-temperature air from inside the switchgear. The air outlet connects to the air inlet of the low-voltage heat exchanger (22), forming a highly efficient heat dissipation loop to quickly expel heat from the switchgear. In this embodiment, the rated heat dissipation power of the low-voltage heat exchanger (22) is 270W / K, sufficient to meet the heat dissipation requirements during high-current operation.

[0037] In this embodiment, the low-voltage switchgear is designed with an AC 1kV voltage rating and a rated withstand voltage of not less than 2.5kV, matching the parameters of the low-voltage side of the 11000kVA oil-immersed transformer. Compared to the existing 800V / 9000kVA configuration, this significantly reduces power loss during photovoltaic power plant transmission. The 11000kVA oil-immersed transformer adopts a double-split three-winding short-circuit withstand design with a short-circuit impedance of 6%-8%. The rated current of the transformer's low-voltage side matches the rated current of the frame circuit breaker 5, ensuring the stability and safety of power transmission.

[0038] The busbars adopt a two-layer design, arranged along the width of the low-voltage switchgear, namely, upper busbar 8 and lower busbar 9. The copper busbar at the lower end of the frame circuit breaker that overlaps with the upper busbar 8 is the double-row section 10 of the lower end of the frame circuit breaker, and the copper busbar at the lower end of the frame circuit breaker that overlaps with the lower busbar 9 is the single-row section 11 of the lower end of the frame circuit breaker. This differentiated design can reduce the amount of copper busbars used while meeting the requirements of high current transmission and controlling production costs. The two busbars are bolted to the lower busbar of the frame circuit breaker 5 and the upper copper busbar of the molded case circuit breaker 2, which is reliable and easy to disassemble and maintain.

[0039] The copper busbars are made of T2 copper with an 8μm tin plating for protection, which effectively improves their corrosion resistance and conductivity. The copper busbars are supported and fixed by BMC insulators 7, which are securely installed to ensure insulation between the copper busbars. The upper busbar 8 has a thickness of 10mm and a width of 90mm, while the lower busbar 9 has a thickness of 7mm and a width of 70mm (adjustable within the corresponding range). The insulation distance between the two busbars is not less than 120mm, meeting the insulation safety requirements.

[0040] The low-voltage switchgear cabinet is fixedly connected to the outer shell of the low-voltage switchgear via quick-release bolts. Waterproof sealing strips are installed at the connection points, achieving IP54-level waterproof and dustproof protection, making it suitable for use in harsh outdoor environments. Furthermore, the low-voltage switchgear cabinet can be independently lifted out through the top cover of the low-voltage compartment 27 of the 20-foot container. The lifting points are made of Q235 steel with a rated load capacity of no less than 500 kg. The lifting path is free from collisions and interference, and the lifting process does not require disassembly of the low-voltage switchgear outer shell or other structures of the container 21, significantly improving the convenience of operation and maintenance.

[0041] The temperature and humidity controller is set to a control range of -20℃ to 40℃, enabling the low-pressure cabinet to operate stably under different climatic conditions. When the internal temperature exceeds 35℃, the temperature and humidity controller sends a control signal, and the low-pressure chamber heat exchanger 22 automatically increases its speed to 120% of its rated speed to accelerate heat dissipation. When the internal temperature is below 0℃, the low-pressure chamber heat exchanger 22 activates a low-temperature anti-freeze mode to prevent the components inside the cabinet from failing due to low-temperature condensation and freezing damage, thus ensuring the stability of equipment operation.

[0042] Split-type outdoor low-voltage switchgear: The cabinet frame is welded from No. 8 channel steel, with a plate thickness of 2.5mm and an electrostatic powder coating (70μm thickness). The frame circuit breaker is a Noraco 4000A model, and four Chint 1250A molded case circuit breakers are used, evenly arranged along the width of the cabinet. The temperature and humidity controller is a Passifec digital display type, equipped with a PT100 temperature sensor and a capacitive humidity sensor, installed on the upper inner side of the cabinet door. Dongguan Fengruide 270W / K intelligent speed-regulating heat exchangers are embedded on both sides of the outer shell, and Schneider Electric limit switches are used, linked to the cabinet door. The cabinet and outer shell are fixed with 10 M14 quick-release bolts, and the connection is fitted with EPDM U-shaped rubber strips with a compression capacity of 35% and an IP54 protection rating.

[0043] Copper busbar layout: T2 purple copper busbar with 8μm tin plating on the surface, first busbar specification 10mm×90mm, second busbar specification 7mm×70mm, vertical insulation spacing between the two layers 120mm, horizontal spacing 80mm, supported by BMC insulators (spacing 700mm); the lap surface is ground to Ra3.2μm, coated with 0.15mm thick electrical composite grease, fastened with M14 bolts with a torque of 50N·m, and contact resistance ≤45μΩ.

[0044] Supporting components: The container does not have a low-pressure compartment side wall; the interior is divided into a low-pressure compartment, a transformer compartment, and a gas cabinet compartment, with fireproof partitions of 10mm thickness; the 11000kVA oil-immersed transformer adopts a double-split three-winding design, with a short-circuit impedance of 7% on the high-medium voltage side and 6.5% on the high-low voltage side, forced oil circulation air cooling, SF6 gas rated pressure of 0.6MPa, and is equipped with a gas density relay; the high-voltage cable is a 120mm² cross-linked polyethylene insulated cable, laid in a conduit and filled with fireproof sealing material.

[0045] The working process of this embodiment is as follows: The inverter outputs 1kV AC power and connects to the lower port of the molded case circuit breaker. The power is then transmitted to the low-voltage side of the transformer through two busbars and a frame circuit breaker. After the transformer steps up the voltage to 24kV, it is connected to the environmental protection gas cabinet and finally connected to the grid. The temperature and humidity controller monitors the temperature inside the cabinet. When the temperature is higher than 35℃, the speed of the heat exchanger increases to 1500r / min. When the temperature is lower than 0℃, the 500W heating element is activated to maintain the temperature inside the cabinet between -20℃ and 40℃.

[0046] Tests showed that the low-voltage switchgear in this embodiment operates stably, with a temperature rise of 18K at the copper busbar connection, precise temperature control inside the switchgear, and easy removal of the switchgear during maintenance. Compared with traditional low-voltage switchgear, production costs are reduced by 15%, transmission losses are reduced by 20%, and maintenance efficiency is improved by 30%. Example

[0047] This embodiment provides a low-voltage switchgear for a photovoltaic power generation box-type substation, applied to a 100MW photovoltaic power station, with the following specific configuration: 1. Split-type outdoor low-voltage switchgear: The cabinet frame is welded from No. 8 channel steel, with a plate thickness of 2.5mm and an electrostatic powder coating (70μm thickness). The frame circuit breaker is a Noraco 4000A model, and four Chint 1250A molded case circuit breakers are used, evenly arranged along the width of the cabinet. The temperature and humidity controller is a Passifec digital display type, equipped with a PT100 temperature sensor and a capacitive humidity sensor, installed on the upper inner side of the cabinet door. Dongguan Fengruide 270W / K intelligent speed-regulating heat exchangers are embedded on both sides of the outer shell, and Schneider Electric limit switches are used, linked to the cabinet door. The cabinet and outer shell are fixed with 10 M14 quick-release bolts, and the connection is fitted with EPDM U-shaped rubber strips with a compression capacity of 35% and an IP54 protection rating.

[0048] 2. Copper busbar layout: The surface of the T2 purple copper busbar is 8μm tin-plated. The first busbar has a specification of 10mm×90mm, and the second busbar has a specification of 7mm×70mm. The vertical insulation spacing between the two layers is 120mm, and the horizontal spacing is 80mm. It is supported by BMC insulators (spacing 700mm). The lap surface is ground to Ra3.2μm, coated with 0.15mm thick electrical composite grease, and fastened with M14 bolts with a torque of 50N·m. The contact resistance is ≤45μΩ.

[0049] 3. Supporting Components: The container does not have a low-pressure compartment side wall. The interior is divided into a low-pressure compartment, a transformer compartment, and a gas cabinet compartment. The fireproof partition is 10mm thick. The 11000kVA oil-immersed transformer adopts a double-split three-winding design, with a short-circuit impedance of 7% on the high-medium voltage side and 6.5% on the high-low voltage side, and forced oil circulation with air cooling. The 24kV environmentally friendly gas cabinet uses Siemens products, with a rated SF6 gas pressure of 0.6MPa, and is equipped with a gas density relay. The high-voltage cable uses 120mm² cross-linked polyethylene insulated cable, laid in conduit and filled with fireproof sealing material.

[0050] The working process of this embodiment is as follows: The inverter outputs 1kV AC power and connects to the lower port of the molded case circuit breaker. The power is then transmitted to the low-voltage side of the transformer through two busbars and a frame circuit breaker. After the transformer steps up the voltage to 24kV, it is connected to the environmental protection gas cabinet and finally connected to the grid. The temperature and humidity controller monitors the temperature inside the cabinet. When the temperature is higher than 35℃, the speed of the heat exchanger increases to 1500r / min. When the temperature is lower than 0℃, the 500W heating element is activated to maintain the temperature inside the cabinet between -20℃ and 40℃.

[0051] Testing showed that the low-voltage switchgear in this embodiment operated stably, with a temperature rise of only 18K at the copper busbar joints. The internal temperature control was precise, and the switchgear was easily removed for maintenance. To further verify the technical advantages of this invention, a mainstream 800V / 9000kVA photovoltaic transformer (integrated outdoor low-voltage switchgear structure) was selected as a control group. A three-month comparative test was conducted under the same 100MW photovoltaic power plant scenario. The core performance data are as follows: As can be seen from the above comparative data, the present invention, through its split structure design, improved voltage level and capacity, optimized copper busbar layout and heat dissipation system, significantly outperforms existing technologies in core indicators such as transmission loss, operation and maintenance efficiency, and production cost control. It also exhibits stronger operational stability and can effectively support the core needs of cost reduction and efficiency improvement for large-capacity photovoltaic power plants.

[0052] 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. A split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets, characterized in that: The system includes a split-type outdoor low-voltage switchgear, a container, an 11000kVA oil-immersed transformer, and a 24kV environmentally friendly gas holder. All components are integrated and installed inside the container. The container is divided into three sections: a low-voltage compartment, a transformer compartment, and a gas holder compartment, each corresponding to one of the aforementioned components. Fireproof partitions and independent ventilation and heat dissipation channels are provided between each compartment. The split-type outdoor low-voltage switchgear consists of an independent low-voltage switchgear cabinet and a low-voltage switchgear outer shell. The low-voltage switchgear integrates a frame circuit breaker, a molded case circuit breaker, and a temperature and humidity controller. The frame circuit breaker is vertically arranged on the left side of the middle of the cabinet and is fastened to an internal steel bracket by high-strength bolts. This bracket is fully welded to the cabinet frame. The upper copper busbar of the frame circuit breaker extends upward to connect with the incoming line terminal to introduce current, while the lower copper busbar extends horizontally to the right to form an electrical connection with the two busbars. Two to four molded case circuit breakers are configured, evenly distributed along the width of the cabinet to the right of the frame circuit breaker, with the installation height consistent with that of the frame circuit breaker. The upper opening of the molded case circuit breaker... The copper busbar extends horizontally to the left, overlapping with the two busbars. The lower copper busbar extends vertically downward to the bottom of the cabinet's inlet port, used to connect to the 1kV AC output of the inverter. The temperature and humidity controller is installed on the upper front of the cabinet and fixed to the inside of the cabinet door panel. Its signal acquisition line passes through the reserved through hole in the door panel and enters the cabinet, connecting to the PT100 temperature sensor and the capacitive humidity sensor respectively. The temperature sensor and humidity sensor are fixedly installed above the frame circuit breaker and in the middle of the molded case circuit breaker cluster, respectively. The control output line of the temperature and humidity controller is connected in series with the heat exchanger control circuit. The low-voltage switchgear housing integrates a heat exchanger and a limit switch. Two heat exchangers with intelligent speed regulation are symmetrically embedded in the middle of the two side panels of the housing and are fastened to the housing frame with bolts. The air inlet of the heat exchanger faces the inside of the housing and is sealed to the air outlet of the directional air duct. The air outlet faces the outside of the housing. A protective grille is installed on the housing at the position corresponding to the air outlet. The limit switch is fixed to the front of the inside of the housing, corresponding to the cabinet door closing position. It is fixed to the housing column by a bracket. When the cabinet door is closed, the edge of the cabinet door presses the limit switch contacts to close, and the control circuit is connected. When the cabinet door is opened, the contacts reset and disconnect, automatically cutting off the power supply to the control circuit inside the low-voltage switchgear, forming a safety interlock protection. The low-voltage switchgear has an AC 1kV voltage rating and a rated withstand voltage of not less than 2.5kV, matching and adapting to the low-voltage side parameters of an 11000kVA oil-immersed transformer. The lower copper busbar of the frame circuit breaker adopts a horizontal outgoing structure, with two layers of busbars corresponding to the lower busbar of the frame circuit breaker. The busbars are arranged along the width of the low-voltage switchgear. The lower busbar of the frame circuit breaker that overlaps with the first layer of busbars adopts a double-row design, while the lower busbar of the frame circuit breaker that overlaps with the second layer of busbars adopts a single-row design. Secondary equipment such as electric operating buttons, temperature and humidity controllers, and miniature circuit breakers are all arranged facing the outside of the low-voltage switchgear. The interior of the low-voltage switchgear shell is equipped with a directional air duct, which is welded from cold-rolled steel plate and lined with heat-insulating and noise-reducing cotton. The air inlet of the air duct corresponds to the port of the frame circuit breaker and the high-heat component area of ​​the molded case circuit breaker, and the air outlet is connected to the air inlet of the heat exchanger.

2. The split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets according to claim 1, characterized in that, The low-voltage switch cabinet body and the low-voltage switch shell are fixedly connected by quick-release bolts, and a waterproof sealing strip is provided at the connection.

3. The split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets according to claim 1, characterized in that, The rated heat dissipation power of the heat exchanger is 270W / K, and the inlet and outlet of the directional air duct correspond to the port of the frame circuit breaker and the high-heat component area of ​​the molded case circuit breaker, respectively.

4. The split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets according to claim 1, characterized in that, The copper busbar is protected by 8μm electroplated tin and is supported and fixed by BMC insulators.

5. The split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets according to claim 1, characterized in that, The 11000kVA oil-immersed transformer adopts a double-split three-winding short-circuit withstand design, and the rated current on the low-voltage side of the transformer matches the rated current of the frame circuit breaker.

6. The split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets according to claim 1, characterized in that, The low-pressure cabinet is lifted out independently through the top cover of the low-pressure chamber of the 20-foot container, without the need to disassemble the outer shell of the low-pressure cabinet or other structures of the 20-foot container during the lifting process.

7. The split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets according to claim 1, characterized in that, The temperature and humidity controller maintains the internal temperature of the low-voltage cabinet between -20℃ and 40℃. When the internal temperature exceeds 35℃, the heat exchanger automatically increases its speed to 120% of the rated speed. When the internal temperature is below 0℃, the heat exchanger activates the low-temperature anti-freeze mode.

8. The split-type outdoor low-voltage switchgear for photovoltaic transformers suitable for overseas markets according to claim 1, characterized in that, The two-layer busbars are bolted to the lower busbar of the frame circuit breaker and the upper copper busbar of the incoming plastic shell.

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