On-site assembling method of super-high altitude extra-high voltage disintegrated AC transformer

Abstract

This invention discloses a method for on-site assembly of ultra-high altitude UHV AC transformers, belonging to the field of on-site assembly technology for UHV power transmission and transformation equipment. The method includes the following steps: S1, transformer body assembly; S2, vapor phase drying; S3, press-fitting; S4, final assembly, where the press-fitted transformer body is lifted and lowered into the oil tank, completing the tank assembly, sealing, external component assembly, vacuum oil impregnation, and static release processes; wherein the vacuum oil impregnation and static release processes employ a high-temperature, high-pressure, multi-stage stepped pressurization process; S5, finished product transfer: after passing inspection, the finished product is transferred to the factory via a rail flatcar or large-item transport vehicle. This solution, through a stepped pressurization process, improves the oil impregnation efficiency by 10% in high-altitude constant-pressure static release environments and by 30% in high-altitude atmospheric-pressure static release environments, while ensuring the quality of the insulating components' oil impregnation and without damaging the mechanical strength of the insulating components.

Description

Technical Field

[0001] This invention relates to the field of ultra-high voltage power transmission and transformation equipment on-site assembly technology, and in particular to a method for on-site assembly of an ultra-high altitude ultra-high voltage dismantled AC transformer. Background Technology

[0002] Currently, the traditional single-machine, single-station operation mode is widely used in the on-site assembly of UHV transformers in China. This mode is the mainstream construction method for on-site assembly of UHV transformers at present. The overall operation process relies on fixed single assembly stations, conventional tonnage lifting equipment, mobile weather drying systems, and conventional plant environment conditions to complete the entire process of transformer assembly, drying, oil filling, and static placement. However, in actual on-site assembly construction scenarios of UHV transformers in high-altitude areas, this traditional operation mode has exposed many unavoidable technical defects, which seriously restrict the construction efficiency, construction quality, and operational safety of on-site assembly of UHV transformers.

[0003] First, traditional assembly operations only have a single assembly station and adopt a sequential assembly method, which cannot support the parallel construction of multiple UHV transformers, significantly limiting the overall on-site assembly capacity and making it difficult to effectively compress the construction cycle.

[0004] Secondly, the 75t overhead crane configured on site has limited lifting capacity and insufficient lifting capacity. It can only meet the needs of hoisting small components and cannot adapt to the needs of transporting and hoisting large transformer bodies and the entire equipment of UHV transformers. Its operational adaptability is extremely poor.

[0005] Meanwhile, the existing drying operation uses a mobile meteorological drying system, which relies on the transformer's own oil tank as the drying container during the operation. However, the transformer oil tank has low heating power and poor overall insulation performance, which directly leads to the difficulty in achieving the required temperature control and pressure maintenance effect during the high vacuum stage of the drying operation. As a result, the quality of the drying operation cannot be guaranteed. Moreover, in high-altitude areas with even harsher air pressure and environmental conditions, this defect is further amplified, which not only seriously affects the construction effect of transformer insulation drying.

[0006] Meanwhile, the high altitude and low air pressure environment will significantly reduce the oil immersion efficiency of transformer insulation components, which may lead to insufficient or uneven oil immersion, resulting in substandard transformer insulation performance and potential safety hazards in equipment operation. This is a technical problem that urgently needs to be solved in the assembly of ultra-high voltage transformers in high-altitude areas.

[0007] Furthermore, the existing assembly process adopts a single-process serial operation mode, which makes the core construction processes such as assembly, drying, oiling, and static placement isolated and poorly connected. In addition, the auxiliary operations such as on-site material transfer, component unpacking, and finished product circulation lack systematic and standardized planning. The overall construction process is chaotic and disorderly, which further reduces construction efficiency and easily leads to loopholes in process connection and construction delays.

[0008] In addition, the assembly sites of ultra-high voltage transformers in high-altitude areas lack specialized environmental protection systems and are not equipped with dedicated oxygen generation and constant-temperature fresh air equipment. The oxygen content in the atmosphere at high altitudes is only about 64% of that at sea level. This not only affects the safety and efficiency of on-site construction personnel, but also makes it difficult to accurately control environmental indicators such as humidity and dust in extremely cold weather conditions. This makes it difficult to meet the process requirements of high-precision assembly and clean construction of ultra-high voltage transformers, which can easily lead to quality hazards such as residual impurities inside the transformer and substandard operating conditions. Overall, this reduces the construction quality and operational stability of on-site assembly of ultra-high voltage transformers. Summary of the Invention

[0009] The purpose of this invention is to provide a method for on-site assembly of ultra-high altitude UHV AC transformers, addressing the aforementioned shortcomings. This method solves the problems of short construction windows in high-altitude, extremely cold regions, low efficiency of traditional single-station assembly, and the inability to efficiently deliver multiple UHV transformers simultaneously. It also solves the problems of poor insulation and heating performance, long drying cycles, and unstable drying quality of mobile vapor phase drying systems in high-altitude, extremely cold regions. Furthermore, it addresses the challenge of low air pressure at high altitudes affecting the oil impregnation efficiency of product insulation components. Additionally, it addresses the issues of poor working conditions for personnel in high-altitude, low-oxygen, and low-temperature environments, and substandard factory process environments (temperature, humidity, dust), which affect personal safety and product assembly quality. Finally, it resolves the problems of lack of functional zoning in on-site workshops, disordered material and finished product flow, and poor process coordination.

[0010] This invention is achieved through the following scheme: A method for on-site assembly of an ultra-high altitude UHV AC transformer for disassembly includes the following steps: S1, the assembly process of the device body, includes tooling leveling and positioning process, core assembly process, complete coil assembly process, upper yoke and iron insertion assembly process, lead wire assembly process and wire welding test process. S2, vapor phase drying process: The assembled reactor body is carried on a rail flatcar into a fixed vapor phase drying tank to complete the drying treatment of the reactor body and other insulating components. S3, Pressing process: After drying, the vessel body is taken out of the furnace and transferred to the pressing station to carry out vessel body fastening and pressing operations. S4, final assembly process: The press-fitted vessel body is lifted and lowered into the oil tank, and the oil tank is closed, sealed, external components are assembled, vacuum oil immersion and static release processes are completed; the vacuum oil immersion and static release process adopts a high temperature and high pressure multi-stage stepped pressurization process for vacuum oil immersion and static release. S5, Finished Product Transfer and Offline: After passing inspection, the finished product is transferred out of the factory via a rail flatcar or heavy-duty transport vehicle.

[0011] In S4, the vacuum impregnation and settling process is generally as follows: After assembly, vacuuming begins. The vacuum level should not exceed 30 Pa, and timing should begin. The vacuum level should be maintained for at least 96 hours before oil filling begins. The oil temperature should be controlled at around 60℃, and the oil filling rate should be controlled at 5000 L / h. Vacuuming should continue during oil filling, and the vacuum level should not exceed 30 Pa to ensure that air released from the oil during the oil filling process does not affect the quality of the oil immersion of the insulating components. When the oil level reaches the middle mark of the oil conservator, oil filling is stopped. The oil conservator is then pressurized by venting the breather to a pressure of 35 kPa. The pressure at the bottom of the transformer main tank should not exceed 120 kPa. The main body is then pressurized and allowed to stand for 120 hours.

[0012] Introducing the high-pressure climate pressure fluctuation factor J; examining the typical diurnal variation ΔJ of the plateau climate pressure changes at the target location; the high-pressure climate pressure fluctuation factor J = 1.5ΔJ; the depressurization pressure is P. d =△P+J; Additional pressure needs to be added △P= P0-P, where P0=101.325kPa and P is the atmospheric pressure at the target location.

[0013] In S4, the specific steps are as follows: S41, the first stage, the immersion period, lasts 0-24 hours, with inflation pressure controlled at 1 / 4 to 3 / 8P. d ; S42, the second stage, the main acceleration period, lasting 24-96 hours, during which the inflation pressure rises to P. d It has entered the core oil immersion stage; S43, the third stage, the deep pressure holding period, lasting 96-120 hours: the pressure is reduced to 1 / 2P. d It can be kept for 24 hours.

[0014] The S1 tooling leveling and positioning process is as follows: Leveling is carried out according to the spacing between the iron core feet and the temporary pads placed on the iron core frame during the assembly process; each pad is required to be parallel to each other, and the flatness of each pad is checked and adjusted with a laser line gauge, and the overall flatness of the pads is not greater than 2mm. The core assembly process in S1 is as follows: unpack the core transport box in sequence and assemble the U-shaped core frame, ensuring that the marking lines between the frames are aligned; after the core frame is assembled, install the core insulation components and shielding.

[0015] The complete coil assembly process in S1 is as follows: after unpacking the coil transport box, use a crane to lift out the complete coil set and assemble it onto the corresponding iron core column in sequence; the coil protrusion position should be aligned with the corresponding position marking line of the iron core.

[0016] The assembly process for the upper yoke in S1 is as follows: After the entire coil assembly is completed, the upper yoke shield is installed, the yoke is inserted, and the clamps are installed. The dustproof shed is closed and the diffused oxygen generator is turned on to increase the local oxygen content in the work area to more than 19.5%.

[0017] The lead assembly process in S1 is as follows: unpack the lead transport box, take out each part of the lead and wire clamps from the transport box in sequence, and reinstall them on the device body.

[0018] This method is applied to an assembly system, which includes a component unpacking and transfer area, a shell drying area, a shell assembly area, a shell pressing area, and a final assembly area. The entrance to the component unpacking and transfer area is connected to the factory entrance, and the exit of the component unpacking and transfer area is connected to the entrance of the device assembly area; the exit of the device assembly area is connected to the entrance of the device pressing area; the device pressing area is equipped with two flow ports, the first flow port of the device pressing area is connected to the device drying area, and the first flow port of the device pressing area is connected to the final assembly area; the final assembly area is connected to the factory exit.

[0019] The assembly area of ​​the reactor body is housed within a dustproof shed. A fixed vapor phase drying system is installed in the reactor body drying area. A movable transfer flatcar is installed in the reactor body pressing area. A vacuum oil injection unit is located in the final assembly area. A lifting assembly rack is installed in the reactor body assembly area.

[0020] The operation methods for S1~S5 are as follows: After the first product module was in place, unpacking began in the component unpacking and transfer area. The module was hoisted to the reactor body assembly area for assembly. The module packaging boxes were unpacked, sealed, and transferred out immediately. By the 13th day, the U-shaped iron core frame, the main modules of the complete coil set, the top iron core laminations, and the lead wires had all been unpacked and transferred to the site. From the 14th to the 18th day, the first reactor body assembly was completed, and at the same time, the second product module was transferred to the component unpacking and transfer area to begin unpacking. From the 19th to the 26th day, the first product was hoisted out of the reactor body assembly area and transported to the reactor body drying area for furnace drying, while the second product module was hoisted into the reactor body assembly area to begin reactor body assembly. On the 27th day, the first unit was unloaded from the furnace and transferred to the reactor body pressing area. On the 28th day, the first product is hoisted to the general assembly area for unpacking and subsequent vacuum treatment. On the 31st day, the unpacking of the second product module is completed in the component unpacking and transfer area. From the 32nd to the 36th day, the second product completes the body assembly, while the third module is transferred to the component unpacking and transfer area. From the 37th to the 44th day, the second product is hoisted out of the body assembly area and transported to the body drying area for furnace drying. At the same time, the third product module is hoisted into the body assembly area to begin body assembly. On the 45th day, the vacuum treatment of the first product is completed, and it is ready for transfer. At this time, the second product is in the furnace unloading and body pressing stage, and the third product is in the body assembly stage.

[0021] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. Significantly improves construction efficiency and adapts to short construction windows: The three-station assembly line mode shortens the assembly cycle of a single transformer body to 18 days and the total assembly cycle of a single unit to 45 days; the total construction period for the cyclic assembly of 7 UHV transformers is only about 145 days. Compared with the traditional single-station single-unit assembly mode, the efficiency is significantly improved, perfectly adapting to the extremely short construction windows in high-altitude areas and meeting the requirements for efficient delivery of multiple pieces of equipment at the same time.

[0022] 2. The fixed vapor phase drying system has superior heat preservation, heating and pressure holding performance compared to traditional mobile drying systems, and the total drying time is reduced by 30% compared to the original technology; at the same time, the vacuum degree and temperature control accuracy are higher, the transformer body is thoroughly dried, and the insulation performance of the UHV transformer is effectively guaranteed.

[0023] 3. The 2×200t heavy-duty overhead crane combination has strong lifting capacity and can complete the entire process of heavy operations such as core assembly, furnace loading, lowering of the furnace body into the box, and loading of the main body onto the vehicle. It solves the problem of insufficient tonnage of the traditional 75t overhead crane and greatly improves the stability and safety of the lifting operation. With the addition of high-strength synthetic fiber slings, the lifting process is further optimized.

[0024] 4. The oxygen generation system increases the oxygen content in the work area to a safe and comfortable range, completely solving the problems of decreased physical strength and low work efficiency caused by high-altitude hypoxia; the central air conditioning and dustproof shed ensure that the temperature, humidity and dust index of the factory are equivalent to the factory standard, eliminating the impact of low temperature, dust and high humidity on the assembly accuracy and insulation performance of transformers.

[0025] 5. By renovating the existing spare parts warehouse, the factory can maximize the utilization of on-site resources; standardized functional zoning and flow routes can eliminate waiting time for material unpacking, storage, and transfer, making process connections smoother and significantly improving the standardization of on-site management.

[0026] 6. This solution uses a stepped pressure testing process to improve the oil impregnation efficiency by 10% (e.g., 40 kPa) in high-altitude constant pressure static discharge environment and by 30% in high-altitude normal pressure static discharge environment, while ensuring the quality of oil impregnation and not damaging the mechanical strength of the insulation components. Attached Figure Description

[0027] Figure 1 This is a flowchart of the assembly process of the device body in this invention; Figure 2 This is a schematic diagram of the three-station assembly line operation and logistics transfer in this invention; Figure 3 This is a Gantt chart of the two-zone, three-station assembly mode in this invention; Attached reference numerals: 1. Component unpacking and transfer area; 2. Shell drying area; 3. Shell assembly area; 4. Final assembly area; 5. Shell pressing area; 6. Dustproof shed; 7. Fixed vapor phase drying system; 8. Transfer flatcar; 9. Vacuum oil injection unit; 10. Lifting assembly rack. Detailed Implementation

[0028] All features disclosed in this specification, or steps in all methods or processes disclosed herein, may be combined in any way, except for mutually exclusive features and / or steps.

[0029] Any feature disclosed in this specification (including any appended claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0030] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a predetermined orientation, or be constructed and operated in a predetermined orientation. Therefore, they should not be construed as limitations on this invention.

[0031] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0032] Example 1 like Figures 1-3 As shown, the present invention provides a technical solution: A method for on-site assembly of an ultra-high altitude UHV AC transformer for disassembly includes the following steps: S1, the assembly process of the device body, includes tooling leveling and positioning process, core assembly process, complete coil assembly process, upper yoke and iron insertion assembly process, lead wire assembly process and wire welding test process. The tooling leveling and positioning process is as follows: leveling is carried out according to the spacing between the iron core feet and the temporary pads placed on the iron core frame during the assembly process; each pad is required to be parallel to each other, and the flatness of each pad is checked and adjusted with a laser ink line meter, and the overall flatness of the pads is not greater than 2mm. The core assembly process is as follows: unpack the core transport box in sequence and assemble the U-shaped core frame, ensuring that the marking lines between the frames are aligned; after the core frame is assembled, install the core insulation components and shielding. The complete coil assembly process is as follows: after unpacking the coil transport box, use an overhead crane to lift out the complete coil set and assemble it onto the corresponding iron core column in sequence; the coil protrusion position should be aligned with the corresponding position marking line of the iron core; The assembly process of inserting the iron yoke is as follows: After the entire coil assembly is completed, the iron yoke shield is installed and the iron yoke is inserted and the clamps are installed. This process is a physically demanding process. In order to prevent the low oxygen environment from affecting the operator's work efficiency, the dustproof shed is closed and the diffused oxygen generator is turned on to increase the local oxygen content in the work area to more than 19.5% to ensure the efficiency, quality and comfort of the process. The lead assembly process is as follows: unpack the lead transport box, take out each lead and wire clamp in sequence from the transport box, and reinstall them onto the transformer body. This mainly includes the assembly of high-voltage inter-station connections, medium- and low-voltage leads, and neutral point leads. All electrical connections are mechanical connections using metal bolts, which must be tightened with a torque wrench, and the tightening torque must meet the requirements of Table 1. Table 1. Tightening Torque Requirements;

[0033] The wire bonding test procedure is as follows: conduct semi-finished product tests according to relevant standards; The more specific steps of the assembly process are as follows: leveling the assembly station, placing the first U-shaped iron core, placing the second U-shaped iron core, placing the third U-shaped iron core, inserting the first integral coil, inserting the second integral coil, installing the clamps, installing the yoke laminations, and installing the leads, such as... Figure 1 As shown.

[0034] S2, the vapor phase drying process, involves the assembled reactor body being transported by a rail flatcar into a stationary vapor phase drying tank to complete the drying treatment of the reactor body and other insulating components. The drying parameters are set the same as those used in the plant. Benefiting from the better heat and pressure retention capabilities of the stationary vapor phase drying system, the processing time is reduced by 30% compared to a mobile vapor phase drying system. Table 2. Vapor phase drying parameters;

[0035] S3, Pressing process: After drying, the vessel body is taken out of the furnace and transferred to the pressing station to carry out vessel body fastening and pressing operations. S4, final assembly process: the press-fitted vessel body is lifted and lowered into the oil tank, and the oil tank is closed, sealed, external components are assembled, vacuum oil immersion and static placement processes are completed. In the vacuum oil impregnation and settling process, a multi-stage stepped pressurization process with high temperature and high pressure is used for vacuum oil impregnation and settling. Specifically, after assembly, vacuuming begins, and timing begins when the vacuum level is no greater than 30 Pa. This vacuum is maintained for at least 96 hours before oil injection begins. The oil temperature is controlled at approximately 60℃, and the oil injection rate is controlled at 5000 L / h. Vacuuming continues during oil injection, ensuring the vacuum level does not exceed 30 Pa to prevent air release from the oil from affecting the immersion quality of the insulating components. Oil injection stops when the oil level reaches the middle mark of the oil conservator. The oil conservator is then pressurized through a breather pipe to a pressure of 35 kPa, ensuring the transformer main tank bottom pressure does not exceed 120 kPa. The main body is then pressurized and allowed to stand for 120 hours.

[0036] In high-altitude areas, the temperature difference between day and night is large, and the nighttime temperature is low. To prevent the temperature from dropping too quickly during the static storage period, which would affect the viscosity (μ) of the insulating oil and thus the oil impregnation efficiency, the following insulation strategy was adopted: the oil filling temperature was moderately increased to 60℃ during the oil filling period; an insulation layer was laid on the oil pipeline to prevent the oil temperature from dropping; air conditioners and dry air generators were placed around the main body of the oil tank during static storage and kept in hot air mode all day, while the main inlets and outlets were closed to form a stable hot air field around the oil tank. The local temperature during the day was 30-40℃ and at night it was 20-30℃, which effectively slowed down the rate of oil temperature drop during static storage.

[0037] In the above steps, a high-pressure climate pressure fluctuation factor J is introduced. Because plateau climate pressure changes involve a combination of typical diurnal variations and non-periodic variations, it is necessary to check the typical diurnal variation ΔJ of the plateau climate pressure at the target location. To prevent this fluctuation from affecting the pressurization quality, the high-pressure climate pressure fluctuation factor J = 1.5ΔJ; the pressurization pressure is P. d =△P+J; The air pressure value at high altitudes is P=P0×e H / h To achieve an oil immersion efficiency at high altitudes that is no less than that in plains areas, additional pressure needs to be applied ΔP = P0 - P, where P0 = 101.325 kPa and P is the atmospheric pressure at the target location. To prevent constant pressure from causing "surface sealing" due to excessively rapid initial oil immersion, which would lead to decreased efficiency later, a multi-stage stepped pressurization process was developed, with different pressure values ​​used in each stage.

[0038] Specifically: S41, the first stage, the immersion period, lasts 0-24 hours, with inflation pressure controlled at 1 / 4 to 3 / 8P. d The aim is to initiate the process gently during the immersion period, avoiding any shock. S42, the second stage, the main acceleration period, lasting 24-96 hours, during which the inflation pressure rises to P. d It has entered the core oil immersion stage; S43, the third stage, the deep pressure holding period, lasting 96-120 hours: the pressure is reduced to 1 / 2P. dThe pressure is maintained for 24 hours. The purpose of this pressure reduction stage is to release elastic stress, promote the penetration of oil into finer pores, and prevent residual deformation of the insulating components.

[0039] This solution uses a stepped pressure testing process to improve the oil immersion efficiency by 10% (e.g., 40 kPa) in high-altitude constant pressure static discharge environments and by 30% in high-altitude normal pressure static discharge environments, while ensuring the quality of oil immersion and not damaging the mechanical strength of the insulation components.

[0040] For example: Taking an altitude of 3400m as a typical example: the working point air pressure is 66.7kPa, with a pressure difference of 34.3kPa compared to sea level, ΔP is calculated to be 35kPa, and the actual pressurization is 40kPa. In the first stage (immersion period, 0-24h), the inflation pressure is controlled at 10-15kPa, with the tank bottom pressure at approximately 100kPa. The purpose is a gentle start-up during the immersion period to avoid shock. In the second stage (main acceleration period, 24-96h), the inflation pressure rises to 40kPa (Pd), with the tank bottom pressure at approximately 120kPa, entering the core oil immersion stage. In the third stage (deep pressure holding period, 96-120h): the pressurization pressure is reduced to 25kPa (1 / 2Pd), with the tank bottom pressure at 105kPa, maintained for 24 hours. The purpose of this pressure reduction is to release elastic stress, promote oil penetration into finer pores, and prevent residual deformation of the insulating components.

[0041] S5, Finished Product Transfer and Offline: After passing inspection, the finished product is transferred out of the factory via a rail flatcar or heavy-duty transport vehicle.

[0042] This solution is also based on an assembly system, which includes a component unpacking and transfer area 1, a vessel drying area 2, a vessel assembly area 3, a vessel pressing area 5, and a final assembly area 4. The entrance to the component unpacking and transfer area 1 is connected to the factory entrance, and the exit of the component unpacking and transfer area 1 is connected to the entrance of the body assembly area 3; the exit of the body assembly area 3 is connected to the entrance of the body pressing area 5; the body pressing area 5 is provided with two flow ports, the first flow port of the body pressing area 5 is connected to the body drying area 2, and the first flow port of the body pressing area 5 is connected to the final assembly area 4; the final assembly area 4 is connected to the factory exit. The assembly area 3 is housed within a dustproof shed 6; a fixed vapor phase drying system 7 is installed in the drying area 2; a movable transfer flatcar 8 is installed in the pressing area 5; a vacuum oil injection unit 9 is located in the final assembly area 4; and a lifting assembly rack 10 is installed in the assembly area 3. In this embodiment, the following components are also used in the above assembly system: The large-tonnage lifting system includes two 200t double-girder overhead cranes in the plant, with a maximum combined lifting capacity of 370t, meeting the needs of the entire lifting and transportation process. The maximum lifting capacity for module transfer and assembly is 75t; during this stage, both cranes operate independently, simultaneously handling the transfer, unpacking, and assembly of modules. The assembled vessel body weighs approximately 320t, and during furnace transfer and unpacking, it is lifted using a combination of the two cranes and a 400t lifting beam. The main assembly, weighing approximately 340t, is also lifted and loaded onto the truck using a combination of the two cranes.

[0043] Fixed vapor phase drying system: A fixed vapor phase drying tank is arranged on one side of the pressing station, using an electrically heated heat transfer oil mode. The tank body is quickly moved in and out of the tank using a rail flatcar, with the overall processing time controlled within 7-8 days. Mobile vapor phase drying system uses the product's own oil tank as the drying tank. Although it is externally covered with heating tape and asbestos blankets, its tank wall heating and insulation effects are only sufficient for processing requirements in plains areas. The fixed vapor phase drying system is equipped with an independent drying tank with high-power heating and excellent insulation performance, ensuring processing quality in high-altitude areas. The mobile vapor phase drying system requires 3 days for main body lifting, system module transfer, assembly, and disassembly. The fixed vapor phase drying system's equipment preparation and product assembly are carried out concurrently. Product loading and unloading are achieved through a combination of 2×200t overhead cranes and transfer flatcars for efficient transport.

[0044] Dustproof room and oxygen supply system: A sealed dustproof shed is set up in the assembly area of ​​the equipment body to control the dust fall in the plant to ≤25mg / ㎡. d. Multiple diffused oxygen generators are installed in the dust-proof shed heavy physical work positions (equipment assembly positions) and rest areas. Each oxygen generator has an oxygen flow rate of 50L / min and an oxygen concentration of 93%, which will increase the local oxygen content in the work area to more than 19.5%, solve the problem of hypoxia at high altitudes, and ensure the personnel's work capacity and product assembly process requirements from an environmental perspective.

[0045] High-altitude operating environment protection system: The factory is equipped with a central air conditioning fresh air system. In an outdoor low temperature environment of -10℃, the indoor temperature can be maintained above 10℃ and the ambient humidity ≤75%.

[0046] This innovative solution sets up three independent workstations for transformer body assembly, transformer body pressing, and main body assembly, as well as two independent work areas for component unpacking and vapor phase drying. This breaks down the entire process of a single transformer into parallel and interconnected assembly line operations. When the previous product enters the drying process, the next product can simultaneously undergo transformer body assembly. The component unpacking area and vapor phase drying area operate independently in coordination with the product assembly process, enabling continuous construction of multiple products and significantly improving work efficiency.

[0047] The operation methods for S1~S5 in this plan are as follows: Taking a complete 45-day cycle as an example, after the first product module is in place, unpacking begins in the component unpacking area. The module is hoisted to the body assembly area 3 for assembly. The module packaging boxes are unpacked, sealed, and transferred out simultaneously. By day 13, the U-shaped iron core frame, the main modules of the complete coil set, the top iron core laminations, and the lead wires have all been unpacked and transferred to the site. From day 14 to day 18, the first unit completes the body assembly work, while the second product module is transferred to the component unpacking area. From day 19 to day 26, the first product is hoisted out of body assembly area 3 and placed in the furnace for drying, while the second product module is hoisted into body assembly area 3 to begin body assembly. On day 27, the first unit is unloaded and transported. On the 28th day, the first product is hoisted to the final assembly station for unpacking and subsequent vacuum treatment; on the 31st day, the unpacking of the second product module is completed in the unpacking area; from the 32nd to the 36th day, the second product completes its body assembly, while the third module is transferred to the unpacking area; from the 37th to the 44th day, the second product is hoisted from body assembly area 3 into the furnace for drying, while the third product module is hoisted into body assembly area 3 to begin body assembly; on the 45th day, the first product completes vacuum treatment and is ready for transfer. At this point, the second product is in the furnace unloading and body pressing stage, and the third product is in the body assembly stage, as detailed below. Figure 3 As shown in the figure, different colors represent the time taken by different numbers of units.

[0048] With each cycle lasting 18 days, three products were put into production one after another. Benefiting from the reasonable spatial layout of two zones and three workstations, the large-tonnage and efficient transfer capacity of the 2×200t overhead cranes, and the efficient and high-quality processing capacity of the fixed vapor phase drying system, the production of products in the plant was carried out in a high-quality, efficient, and orderly manner.

[0049] This solution, designed to meet the requirements of the two-zone, three-station assembly line process and high-altitude conditions of this invention, integrates for the first time a complete set of equipment systems, including 2×200t heavy-duty overhead cranes, a fixed vapor phase drying system, a diffused oxygen generation system, and a constant-temperature fresh air system. This ensures the successful implementation of the process innovation across all aspects, including transfer efficiency, drying efficiency, and assembly efficiency.

[0050] Innovative site layout: The spare parts warehouse features an integrated functional zoning layout for the component unpacking area, vapor phase drying area, and assembly area, along with standardized material and finished product flow lines to ensure efficient material and waste transfer and meet product assembly requirements.

[0051] Process parameter innovation: Benefiting from the fixed vapor phase drying system, the drying parameters were innovatively applied in the high-altitude environment, with the settings set at the headquarters manufacturing level, which significantly improved the drying quality and efficiency of products assembled on-site; for high-altitude and low-pressure environments, a pressurized static release process was pioneered, which enabled the internal pressure of the oil tank to reach the conventional atmospheric pressure during the static release stage, which significantly improved the oil immersion quality and efficiency of products assembled on-site.

[0052] Example 2 Current UHV transformer on-site assembly generally adopts a single-station, full-process serial operation approach. Using a single transformer as the work unit, all processes—including transformer body assembly, drying, pressing, final assembly, and oil filling—are completed sequentially at the same station. Once one transformer is finished and moved out, the next one is started. This approach only considers the product assembly logic and fails to take into account on-site constraints such as high altitude, extreme cold, low oxygen levels, short construction windows, limited space, and insufficient personnel physical strength. This results in problems such as concentrated processes and significant downtime, and represents a common on-site assembly design model for plains areas.

[0053] This invention addresses the challenges of working in high-altitude, extremely cold regions, specifically the four major pain points of concentrated delivery of multiple pieces of equipment, short effective construction time, harsh working environments, and reduced work capabilities of personnel at high altitudes. It proposes a novel integrated design approach, using workstations as work units to spatially decompose the processes for the same product, streamlining workflows through workstation allocation and environmental control. The core design comprises four dimensions: 1. Process breakdown; Based on the work content, equipment dependence, labor intensity, and time consumption, the complete transformer assembly process is divided into three independent process modules: transformer body assembly, transformer body drying and pressing, and main body assembly and oil injection. Each module corresponds to a dedicated workstation. The disassembly of the transport box and the drying of the transformer body are set up in separate work areas, realizing physical zoning of the process and parallel operation, breaking the single-workstation full-process operation mode.

[0054] 2. Workstation separation; Dedicated spaces and equipment are matched according to the operational characteristics of each process: heavy-duty, high-precision vessel assembly operations are arranged in constant-temperature, oxygen-enriched, and dust-proof sheds. The drying area is adjacent to the vessel pressing station, where the vessel's pre-furnace preparation and outgoing pressing can be completed on the transfer flatcar, shortening the vessel's exposure time and ensuring product processing efficiency and quality. The final assembly workers are located in an open area adjacent to the transfer channel, realizing "specialized workstations for specialized processes".

[0055] 3. Beat design; By statistically analyzing the standard operating time of each process, and taking the longest assembly process, the body assembly, at 18 days as the benchmark cycle time for the production line, the progress of the preceding and following processes is dynamically matched to eliminate problems such as waiting at workstations, idle personnel, and idle equipment, and to maximize the use of short construction windows.

[0056] 4. Suitable for high-altitude environments; Given the high-altitude environment characterized by low air pressure, low temperature, low oxygen, and large diurnal temperature variations, a fresh air system and a ventilation system have been added to ensure that the environmental standards inside the workshop and dust-proof shed are basically aligned with those in plains areas, reducing the impact of the high-altitude environment on product assembly efficiency and quality. Specialized processes have been added to eliminate the impact of low air pressure on the oil impregnation of product insulation components.

[0057] This solution can significantly improve construction efficiency and is suitable for short construction windows. By adopting a three-station assembly line mode, the assembly cycle of a single transformer body is shortened to 18 days, and the total assembly cycle of a single unit is 45 days, as shown in Table 3. The total construction period for the cyclic assembly of 7 UHV transformers is only about 145 days. Compared with the traditional single-station single-unit assembly mode, the efficiency is significantly improved. It is perfectly adapted to the extremely short construction window in high-altitude areas and meets the requirements for efficient delivery of multiple devices at the same time.

[0058] Table 3. Assembly and processing cycle of a single product;

[0059] Example 3 A State Grid 1000kV UHV AC transformer on-site assembly project: 1. Basic conditions for the project: Project Location: A location in Sichuan Province, at an altitude of 3450m, with an atmospheric oxygen content of 64% of that at sea level and an average annual minimum temperature of -20.6℃, which is a typical high-altitude extremely cold environment. The available construction site is limited, and the effective construction window is short. It is necessary to complete the on-site assembly, commissioning and delivery of 7 1000kV UHV main transformers simultaneously.

[0060] 2. Implementation of the plan: 2.1 Factory Renovation and Layout: Utilizing the existing spare parts warehouse within the station, the assembly plant was transformed using a serial integrated model, dividing it into a component disassembly and assembly area, a body assembly area, a pressing area, a final assembly area, and a vapor phase drying area on the west side.

[0061] 2.2 Equipment Installation and Commissioning: Two 200t double-girder overhead cranes are installed in the plant, and the parallel lifting function of the two cranes is being tested. A horizontal fixed vapor phase dryer and supporting evaporator, condenser and heat transfer oil heating system are arranged on the west side. A dustproof shed is assembled on the body and multiple 50L / min diffused oxygen generators are arranged in the rest room. The whole plant is equipped with central air conditioning fresh air and dust monitoring devices.

[0062] 2.3 Implementation of assembly line process: Construction is strictly organized according to the two-zone, three-station assembly line process of this invention: when the first transformer enters the body assembly station, subsequent equipment queues up and flows in sequence, one entering the drying process and another undergoing pressing, forming a continuous cycle operation. The unpacking area and the drying area operate independently to meet the product assembly and processing requirements.

[0063] 2.4 Implementation of Environmental Control Measures: During operation, the sealed dustproof shed remains closed, and the oxygen generator runs continuously to maintain the oxygen content at the workstation above 19.5%. The fresh air system operates around the clock, the indoor temperature remains stable above 10℃, the humidity is ≤75%, and the dustfall is controlled at 25mg / ㎡. Within d.

[0064] 2.5 Innovative Process Applications: The Ganzi station is equipped with a fixed vapor phase drying system. The drying parameters are set according to the manufacturing standards of the headquarters. The overall drying time is 7 days, which is more than 30% shorter than the drying time of traditional on-site assembled products. During the static storage period, a pressurized static storage process is implemented. The pressure on the top of the tank is 62 kPa, so that the internal pressure of the oil tank reaches the normal atmospheric pressure during the static storage stage. The actual static storage time is 6 days, which is more than 25% shorter than the static storage time of traditional on-site assembled products.

[0065] 3. Implementation Results: 3.1 The assembly cycle for a single transformer body is 18-19 days, the total assembly cycle for a single transformer is 45 days, and the total construction period for all 7 transformers to be assembled is 145 days, strictly matching the project schedule.

[0066] 3.2 The stationary vapor phase drying system operates stably, and the drying time is shortened by 30% compared with the traditional mobile system. The drying quality of the entire equipment meets the standards. 3.3200t overhead crane completed all heavy component hoisting operations without any safety incidents throughout the process; 3.4 The problems of oxygen deficiency and physical exhaustion among workers have been completely resolved, and the efficiency of heavy physical labor processes has been stabilized; 3.5 The existing spare parts warehouse on site was fully utilized, the site resource utilization rate was maximized, the material flow was smooth, and there was no long-term stagnation. All 3.67 UHV transformers were delivered on schedule, and all on-site handover tests passed on the first attempt, with product operating indicators meeting design requirements. This case fully verifies the feasibility, stability, and advanced nature of the process design, technology design, equipment, layout, and environmental control scheme of this invention in high-altitude, extremely cold, and ultra-high voltage engineering projects, and can be widely promoted and applied.

[0067] This solution addresses the challenge of short working windows in high-altitude and extremely cold regions by developing a two-zone, three-station on-site assembly process for ultra-high voltage transformers. This process enables multiple machines to operate in a cyclical, sequential manner, increasing production efficiency by 2.2 times and achieving efficient delivery of a series of products in a short time.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for on-site assembly of an ultra-high altitude UHV AC transformer, characterized in that: Includes the following steps: S1, the assembly process of the device body, includes tooling leveling and positioning process, core assembly process, complete coil assembly process, upper yoke and iron insertion assembly process, lead wire assembly process and wire welding test process. S2, vapor phase drying process: The assembled reactor body is carried on a rail flatcar into a fixed vapor phase drying tank to complete the drying treatment of the reactor body and other insulating components. S3, Pressing process: After drying, the vessel body is taken out of the furnace and transferred to the pressing station to carry out vessel body fastening and pressing operations. S4, final assembly process: The press-fitted vessel body is lifted and lowered into the oil tank, and the oil tank is closed, sealed, external components are assembled, vacuum oil immersion and static settling are completed; the vacuum oil immersion and static settling process adopts a multi-stage stepped pressurization process. S5, Finished Product Transfer and Offline: After passing inspection, the finished product is transferred out of the factory via a rail flatcar or heavy-duty transport vehicle.

2. The method for on-site assembly of an ultra-high altitude UHV AC transformer according to claim 1, characterized in that: In S4, the vacuum impregnation and settling process is generally as follows: After assembly, vacuuming begins, with the vacuum level not exceeding 30 Pa. Timing starts at this point and the vacuum is maintained for at least 96 hours before oil injection begins. The oil temperature is controlled at 60℃, and the oil injection rate is controlled at 5000 L / h. Vacuuming continues during oil injection, with the vacuum level not exceeding 30 Pa, to ensure that air released from the oil during the injection process does not affect the quality of the oil immersion of the insulating components. When the oil level reaches the middle mark of the oil conservator, oil injection is stopped. The oil conservator is then pressurized through the breather pipe to a pressure of 35 kPa, ensuring that the pressure at the bottom of the transformer main tank does not exceed 120 kPa. The main body is then pressurized and allowed to stand for 120 hours.

3. The method for on-site assembly of an ultra-high altitude UHV AC transformer according to claim 2, characterized in that: Introducing the high-pressure climate pressure fluctuation factor J; examining the typical diurnal variation ΔJ of the plateau climate pressure changes at the target location; the high-pressure climate pressure fluctuation factor J = 1.5ΔJ; the depressurization pressure is P. d =△P+J; Additional pressure needs to be added △P= P0-P, where P0=101.325kPa and P is the atmospheric pressure at the target location.

4. The method for on-site assembly of an ultra-high altitude UHV AC transformer according to claim 3, characterized in that: In S4, the specific steps are as follows: S41, the first stage, the immersion period, lasts 0-24 hours, with inflation pressure controlled at 1 / 4 to 3 / 8P. d ; S42, the second stage, the main acceleration period, lasting 24-96 hours, during which the inflation pressure rises to P. d It has entered the core oil immersion stage; S43, the third stage, the deep pressure holding period, lasting 96-120 hours: the pressure is reduced to 1 / 2P. d It can be kept for 24 hours.

5. The method for on-site assembly of an ultra-high altitude UHV AC transformer according to claim 1, characterized in that: The S1 tooling leveling and positioning process is as follows: Leveling is carried out according to the spacing between the iron core feet and the temporary pads placed on the iron core frame during the assembly process; each pad is required to be parallel to each other, and the flatness of each pad is checked and adjusted with a laser line gauge, and the overall flatness of the pads is not greater than 2mm. The core assembly process in S1 is as follows: unpack the core transport box in sequence and assemble the U-shaped core frame, ensuring that the marking lines between the frames are aligned; after the core frame is assembled, install the core insulation components and shielding.

6. A method for on-site assembly of an ultra-high altitude UHV AC transformer according to any one of claims 1 to 5, characterized in that: The complete coil assembly process in S1 is as follows: after unpacking the coil transport box, use a crane to lift out the complete coil set and assemble it onto the corresponding iron core column in sequence; the coil protrusion position should be aligned with the corresponding position marking line of the iron core.

7. A method for on-site assembly of an ultra-high altitude UHV AC transformer according to any one of claims 1 to 5, characterized in that: The assembly process of the upper iron yoke in S1 is as follows: After the entire coil assembly is completed, the upper iron yoke shield is installed and the iron yoke is inserted and the clamps are installed. The dustproof shed is closed and the diffuse oxygen generator is turned on to increase the local oxygen content in the work area to more than 19.5%. The lead assembly process in S1 is as follows: unpack the lead transport box, take out each part of the lead and wire clamps from the transport box in sequence, and reinstall them on the device body.

8. The method for on-site assembly of an ultra-high altitude UHV AC transformer according to claim 1, characterized in that: This method is applied to an assembly system, which includes a component unpacking and transfer area (1), a vessel drying area (2), a vessel assembly area (3), a vessel pressing area (5), and a final assembly area (4). The entrance to the component unpacking and transfer area (1) is connected to the factory entrance, and the exit of the component unpacking and transfer area (1) is connected to the entrance of the body assembly area (3); the exit of the body assembly area (3) is connected to the entrance of the body pressing area (5); the body pressing area (5) is provided with two flow ports, the first flow port of the body pressing area (5) is connected to the body drying area (2), and the first flow port of the body pressing area (5) is connected to the final assembly area (4); the final assembly area (4) is connected to the factory exit.

9. A method for on-site assembly of an ultra-high altitude UHV AC transformer according to claim 8, characterized in that: The assembly area (3) is housed in a dustproof shed (6), and a fixed vapor phase drying system (7) is installed in the drying area (2); a movable transfer flatcar (8) is installed in the pressing area (5); a vacuum oil injection unit (9) is installed in the final assembly area (4); and a lifting assembly rack (10) is installed in the assembly area (3).

10. The method for on-site assembly of an ultra-high altitude UHV AC transformer according to claim 1, characterized in that: The operation methods for S1~S5 are as follows: After the first product module is in place, unpacking begins in the component unpacking and transfer area (1). The module is hoisted to the body assembly area (3) for assembly. The module packaging boxes are unpacked, sealed, and transferred out. By the 13th day, the U-shaped iron core frame, the main modules of the complete coil have been assembled, and the iron core plates and leads have been unpacked and transferred to the site. From the 14th to the 18th day, the first unit completes the body assembly work, and the second product module is transferred to the component unpacking and transfer area (1) to begin unpacking. From the 19th to the 26th day, the first product is hoisted out of the body assembly area (3) and transported to the body drying area (2) for furnace drying. At the same time, the second product module is hoisted into the body assembly area (3) to begin body assembly. On the 27th day, the first unit is taken out of the furnace and transferred to the body pressing area. (5) Press fitting is performed; on the 28th day, the first product is hoisted to the general assembly area (4) for unpacking and subsequent vacuum treatment; on the 31st day, the second product module is unpacked in the component unpacking and transfer area (1); from the 32nd to the 36th day, the second product completes the body assembly, and the third module is transferred to the component unpacking and transfer area (1); from the 37th to the 44th day, the second product is hoisted away from the body assembly area (3) and transported to the body drying area (2) for furnace drying, while the third product module is hoisted into the body assembly area (3) to begin body assembly; on the 45th day, when the vacuum treatment of the first product is completed, it is ready to be transferred out. At this time, the second product is in the furnace exit and body press fitting stage, and the third product is in the body assembly stage.

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