A 500kv transformer high-voltage outgoing line system and a method for installing the same

Abstract

The application relates to a 500kV transformer high-voltage outgoing line system, which comprises a grading tube connected with a grading ball at one end, characterized in that: the other end of the grading tube is fixedly connected with a tapered end head wrapped with a paper pulp insulation forming piece on the inside and the outside, the outer part of the tube body of the grading tube and the outer part of the paper pulp insulation forming piece at the coil side end head are uniformly coated with an insulation layer, one end of the grading tube is connected with the grading ball through a flange, and the grading tube and the grading ball are both non-current-carrying. In use, the scheme adopts a large-diameter grading tube and a grading ball outgoing line structure, a large-thickness insulation layer is wrapped outside the grading tube, three layers of molded insulation paper pulp pieces are arranged on the outer surface of the grading ball, the grading ball is connected with the grading tube through bolts, and an insulation support made of laminated paper board is fixed in an L-shaped lifting seat. The electrical performance is ensured, the mechanical strength requirements during transportation and operation are met, the installation is simple, and the manufacturing cost is obviously reduced.

Description

Technical Field

[0001] This invention relates to the field of ultra-high voltage transformer technology, specifically to a 500kV transformer high-voltage outgoing line system and its installation method. Background Technology

[0002] With the development of the global economy, the transmission capacity of power grids in various countries is constantly increasing, and power transformers are also developing towards larger capacity, ultra-high voltage (UHV), and green environmental protection. The 500kV UHV transmission technology has significant advantages, and the market demand for 500kV UHV transformers is gradually increasing, especially for three-phase integrated 500kV step-up transformers, which are seeing significant growth in demand in thermal power, hydropower, new energy, and pumped storage markets. To ensure the reliability of product insulation, all three-phase integrated 500kV UHV transformers adopt a high-voltage intermediate indirect outgoing line structure.

[0003] Traditional 500kV lead-out conductors mostly employ a Weidmann insulation structure. This structure uses multiple layers of corner rings and multiple layers of paper tubes to separate the oil gap. Its structure is complex, occupies a large space, and is inconvenient to operate. Furthermore, the electric field is concentrated at the lead-out conductor and the equalizing sphere, easily leading to partial discharge. Existing technology also includes a scheme using an L-shaped riser to install a 500kV formed lead-out conductor device. The advantage of this device is its good electrical performance, but the disadvantages are high procurement cost and poor mechanical strength.

[0004] Furthermore, in existing shielding structures for the high-voltage leads of 500kV transformers, the equalizing tubes are typically made of copper and short-circuited to the leads via equipotential bonding lines to maintain the same potential. While this structure provides some shielding, the high cost of copper tubes and the added complexity of the equipotential bonding lines further complicate the design. Additionally, the end treatment of existing equalizing tubes is relatively simple, typically only rounding the edges of the tube ends, leaving the problem of electric field concentration at the ends prominent, and the withstand voltage on the coil lead-out side needs further improvement.

[0005] In the face of fierce competition in the global transformer market, high quality and low price are the keys to market expansion. How to reduce the manufacturing cost of transformers while ensuring the reliability of product insulation and mechanical strength is a technical challenge faced by the R&D departments of every transformer manufacturer. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a 500kV transformer high-voltage outgoing line system and installation method, ensuring reliable insulation, high mechanical strength, and low manufacturing cost for the 500kV ultra-high voltage transformer high-voltage outgoing line system.

[0007] This invention is achieved through the following technical solution: a 500kV transformer high-voltage outgoing line system, comprising a voltage equalization pipe connected at one end to an voltage equalization ball, characterized in that: the other end of the voltage equalization pipe is fixedly connected to a conical end end wrapped with pulp insulation molding material on both the inner and outer sides; the outer surface of the voltage equalization pipe and the outer surface of the pulp insulation molding material at the coil-side end are uniformly covered with an insulating layer; one end of the voltage equalization pipe is connected to the voltage equalization ball through a flange; neither the voltage equalization pipe nor the voltage equalization ball carries current.

[0008] In this invention, the equalizing tube end adopts a tapered structure. Compared with the simple rounded corner treatment of the tube end in the prior art, the tapered end further increases the radius of curvature of the end electrode, effectively reducing the electric field concentration at the coil output end and significantly improving the dielectric strength of the weakest link in the output system. The inner and outer sides of the end are wrapped with pulp insulation molding parts, and are uniformly covered with an insulation layer with the tube body, forming a continuous and complete insulation barrier, avoiding electric field distortion at the end insulation steps or breaks, and improving the overall insulation reliability. Neither the equalizing tube nor the equalizing ball carries current, completely separating the shielding function from the conduction function. The equalizing tube is only used as a geometric field equalization element, simplifying the structural design. Combined with aluminum alloy material, the material cost is greatly reduced while ensuring electrical performance. The equalizing tube and the equalizing ball are connected by a flange, which is reliable and easy to assemble and maintain.

[0009] Preferably, the outer surface of the equalizing ball is first covered with a layer of conformal pulp insulation as a covering layer, and then two layers of conformal pulp molding are set. Each layer is supported by a pad and the oil gap is divided. The pads between each layer are evenly arranged along the circumferential direction and evenly arranged along the height direction. The pads are bonded and fixed to the pulp molding.

[0010] In this preferred embodiment, the outer surface of the equalizing ball adopts a three-layer insulation structure consisting of one layer of conformal pulp insulation and two layers of conformal pulp molding parts. This effectively increases the radius of curvature of the external electrodes of the equalizing ball, making the electric field distribution on the surface of the equalizing ball more uniform and improving the dielectric strength of the equalizing ball. The oil gaps are supported and divided by spacers (instead of support strips) between the layers. The spacers have a discrete distribution structure, which, compared with continuous strip support strips, provides a larger cross-sectional area for oil gap flow and smoother flow, which is conducive to the convection circulation and heat dissipation of insulating oil. At the same time, it facilitates the rapid dissipation of trace gases generated by partial discharge, reducing the risk of continuous development of partial discharge. The spacers are evenly arranged and bonded along the circumferential and height directions, ensuring that the spacing between each layer of molding parts is uniform and consistent. The electrical performance of the insulation structure is stable and reliable, and the bonding method makes it difficult for the spacers to shift during assembly.

[0011] Preferably, the pressure equalizing block and the pressure equalizing ball are provided with an L-shaped lifting seat on the outside, and the lifting seat is provided with a fixing structure to support the pressure equalizing pipe.

[0012] In this preferred embodiment, the L-shaped riser serves as an integrated load-bearing cavity, allowing the outgoing line system to be pre-assembled, positioned, and tested as a whole in the factory, reducing on-site installation procedures and errors, and ensuring consistent assembly accuracy. The L-shaped riser also acts as a boundary barrier for the insulating oil gap and a mechanical protective shell, combining insulation and protection functions. The fixed structure inside the riser provides reliable support for the equalizing pipe, ensuring that the equalizing pipe maintains its designed position during transportation and operation, and avoiding insulation failure caused by displacement.

[0013] Preferably, the fixing structure includes two clamping members that clamp the fixing tube circumferentially and are arranged opposite each other, a bracket bolted to the clamping members, and an angled member connecting the bracket and the wall of the rising seat tube. A fixing hole for the insulation layer to pass through is provided between the two clamping members. Both the bracket and the clamping members are made of insulating material.

[0014] In this preferred design, the two clamping components are arranged circumferentially opposite each other, clamping the equalizing pipe from both sides to form a stable clamp-like fixation. The force is symmetrical and uniform, avoiding the eccentric torque that may occur with unilateral fixation. The bracket, in conjunction with the angled component, transfers the clamping force to the riser pipe wall, forming a complete load transfer path. This provides high fixation rigidity and effectively resists transportation vibrations and short-circuit electromagnetic forces during operation. Fixing holes for the insulation layer to pass through are provided between the clamping components, allowing the clamping components to act directly on the outside of the equalizing pipe's insulation layer without damaging it, while also providing a large clamping area and low pressure. Both the bracket and the clamping components are made of insulating material (laminated cardboard), avoiding the introduction of floating potential or ground discharge hazards by metal clamping components, while also increasing the creepage distance and improving insulation reliability. Preferably, a base plate corresponding to the corner piece is welded to the wall of the riser tube, and the base plate is ground into a round ring without sharp corners or burrs.

[0015] In use, this preferred solution provides a precise installation reference surface for the fixing system, ensuring the installation position accuracy of the corner pieces, brackets, and clamps, thereby ensuring the centering of the equalizing pipe within the riser and making the electric field distribution more symmetrical and uniform. The base plate is ground smooth without sharp corners or burrs, eliminating electric field distortion points at metal protrusions and reducing the risk of partial discharge. The welded base plate and the riser pipe wall form an integral load-bearing component with high connection strength, capable of withstanding vibrations and mechanical impacts during operation.

[0016] As a preferred embodiment, the lead wire of the equalizing tube includes several stranded copper wires and a potential connection wire. Both the copper stranded wires and the potential connection wire are wrapped with insulating material. The potential connection wire does not carry current but is crimped together with the copper stranded wires and only serves to fix the potential.

[0017] In this preferred design, the lead wires are flexibly configured with single or multiple strands of soft copper stranded wire, allowing for selection of different quantities based on current carrying capacity requirements, avoiding over-design and reducing material costs. The potential connection wire and the copper stranded wire are crimped into the same terminal block, resulting in a more compact structure, reducing the number of connection nodes, and improving connection reliability. The potential connection wire only serves to fix the potential and does not carry the load current; its cross-sectional area can be much smaller than that of the copper stranded wire, ensuring potential stability while reducing material usage. Both the copper stranded wire and the potential connection wire are wrapped with a 2mm insulation layer, ensuring the insulation strength of the lead wire to the equalizing tube (ground potential or floating potential) and preventing internal breakdown.

[0018] Preferably, a conformal insulating pad is provided between the clamping member and the insulating layer. The conformal insulating pad is molded from multiple layers of insulating crepe paper. The side of the conformal insulating pad that is in contact with the outer circumferential surface of the equalizing tube is an arc-shaped surface with the same curvature as the tube body, and the other side is in contact with the inner arc surface of the clamping member. It is then bonded and fixed to the clamping member by an insulating adhesive. On the side of the conformal insulating pad that is in contact with the equalizing tube, a number of oil channel grooves are provided along the circumferential direction. Each oil channel groove is evenly distributed along the circumferential direction; each oil channel groove forms a channel that can accommodate insulating oil.

[0019] In this preferred embodiment, a conformal insulating pad is added between the clamping component and the insulating layer. The clamping force is first homogenized by the elastic pad before being transferred to the insulating layer. The conformal insulating pad reduces the risk of the insulating layer being crushed or scratched at the clamping point. The oil channel grooves contact the equalizing pipe in a discrete recessed form. The oil channel grooves provide a flow channel for the insulating oil, allowing the insulating oil to convect smoothly in the clamping area. The trace amounts of gas generated by partial discharge can also escape along the oil channel grooves, preventing the formation of oil flow dead zones or gas accumulation cavities at the clamping point. The rounded corners at the root of the oil channel grooves eliminate the sharp corners at the root of the grooves, avoiding the induction of partial discharge due to electric field concentration caused by structural abrupt changes.

[0020] Preferably, a molded corner ring is connected to the high-voltage coil. The molded corner ring is composed of two layers of irregularly shaped pulp molding parts and is located on the output side of the high-voltage coil, with the end located inside the molded corner ring.

[0021] In this preferred embodiment, the corner ring composed of two layers of irregularly shaped pulp molding parts is set on the high-voltage coil outlet side, which improves the dielectric strength of the outlet area in the middle of the high-voltage coil; the end is located inside the molding corner ring, and the corner ring forms an insulating barrier between the end and the outlet of the high-voltage coil, effectively isolating the electric field concentration area between components with different potentials; the molding corner ring and the end pulp molding parts cooperate with each other to form a multi-layer insulation protection on the coil outlet side, further strengthening the insulation reliability of the weakest link.

[0022] Preferably, the oil tank flange located at the coil is rounded to ensure a uniform electric field distribution on the potential side.

[0023] The large rounded corners of the oil tank flange eliminate the sharp angle structure of the flange edge, effectively reducing the electric field concentration caused by structural abrupt changes on the ground potential side, avoiding sharp-corner discharge on the ground potential side, and achieving dual optimization of the electric field distribution on the high and low voltage sides, ensuring uniform electric field distribution along the entire outgoing line path.

[0024] In particular, this solution employs a large-diameter equalizing pipe and its equalizing ball outlet structure. The equalizing pipe is covered with a thick insulation layer, and the outer surface of the equalizing ball is equipped with three layers of molded insulating paper pulp. The equalizing ball is connected to the equalizing pipe by bolts, and then fixed in an L-shaped riser seat using an insulating bracket made of laminated cardboard. This design ensures electrical performance while meeting the mechanical strength requirements for transportation and operation, and it is simple to install with a significant reduction in manufacturing costs.

[0025] An installation method for a 500kV transformer high-voltage outgoing line system includes the following steps: a. Fabricate 500kV high-voltage leads and potential connection wires; The lead wire is made of single or multiple soft copper stranded wires. One end is crimped to the lead wire of the coil, and the other end is crimped to the end of the terminal sleeve and connected together. The lead wire is wrapped with 2mm of insulation material. The potential connection wire is made of 8mm² soft copper stranded wire and wrapped with 2mm of insulation. One end of the potential connection wire is crimped into the terminal connected to the sleeve, and the other end is connected to a small terminal and an equalizing ball.

[0026] b. Before installing the high-voltage outgoing line system, the equalizing ball, equalizing pipe, angle fittings, brackets, clamps, and fixing bolts must be dried in advance; c. Securely connect the equalizing ball and the equalizing pipe together with bolts through the flange, place them in the L-shaped riser, and wrap the equalizing pipe with insulation at the two clamping positions in the horizontal and vertical directions; d. Install the angle bracket and support inside the L-shaped riser, and fix the equalizing pipe inside the L-shaped riser using clamping components; e. To ensure the installation accuracy and secure clamping of the equalizing pipe, first make a fine adjustment to center the equalizing pipe, and then fix the equalizing pipe. f. Install the 500kV transformer high-voltage outgoing line system on the oil tank, and connect the leads to the bushing end terminals.

[0027] In this preferred design, all insulating components are uniformly dried before installation to ensure that the moisture content of the insulating components meets the requirements for ultra-high voltage insulation, thus avoiding a decrease in insulation strength due to moisture introduction. The equalizing ball and equalizing pipe are pre-connected to the riser via flanges to form an integral assembly before being placed into the riser. This provides a large assembly and operation space with good visibility, reducing the difficulty of working at heights or in confined spaces. Insulation layers are wrapped at the clamping positions in both the horizontal and vertical directions, which not only increases the insulation strength at the clamping points but also acts as a buffer to prevent clamping. The main insulation layer was not scratched. The three-step process of "coarse positioning → fine adjustment → locking," involving fine-tuning the center before fixing, ensured the installation accuracy and centering of the equalizing tube. The assembly sequence of first installing the corner pieces and brackets, and finally the clamping pieces, was clear, easy to operate, and improved assembly efficiency and consistency. One end of the lead wire was crimped to the coil outlet, and the other end was connected to the bushing terminal. The potential connection wire was crimped to the same terminal as the lead wire and independently led out to the equalizing ball, achieving simultaneous completion of the lead wire's current-carrying function and the potential connection wire's potential-fixing function. This ensured reliable connection and facilitated testing and maintenance. The beneficial effects of this invention are as follows: This invention constructs a full-path insulation reinforcement system from the inside of the high-voltage lead to the ground potential side of the oil tank. The end of the equalizing tube adopts a conical structure with inner and outer pulp insulation molding parts, and is uniformly covered with an insulation layer with the outside of the tube body, which effectively increases the radius of curvature of the end electrode and solves the prominent problem of end electric field concentration in the prior art; the outer surface of the equalizing ball adopts a three-layer structure of one layer of conformal pulp insulation and two layers of conformal pulp molding parts, with uniformly arranged pads dividing the oil gaps between the layers. Compared with the support curtain structure, the oil gaps are more unobstructed, which is conducive to the circulation and heat dissipation of insulating oil and the dissipation of partial discharge gas, and also ensures the symmetrical and uniform distribution of the electric field; combined with two layers of irregularly shaped pulp molding corner rings on the high-voltage coil output side, as well as the large rounded corner treatment of the oil tank flange and the conformal shielding of the manhole cover, a full-path electric field optimization is formed from the high-voltage potential to the ground potential, which significantly improves the dielectric strength of each key part of the output system.

[0028] The L-shaped riser, acting as an integrated load-bearing cavity, works in conjunction with an insulating fixing system consisting of a laminated cardboard support, L-shaped corner pieces, and double clamping components. The installation process, involving grinding and smoothing the sharp corners of the base plate, fine-tuning for centering, and then tightening, provides reliable support and positioning for the equalizing pipe. The two clamping components, positioned circumferentially opposite each other, form a stable clamp-like fixation, ensuring symmetrical and uniform force distribution. The load is reliably transferred to the riser's pipe wall through the support and corner pieces, effectively resisting transportation vibrations and operational short-circuit electrodynamic forces, avoiding the risk of insulation failure caused by displacement. Furthermore, all fixing components are made of insulating materials, eliminating the potential for floating potential discharge introduced by metal parts while ensuring mechanical strength.

[0029] The equalizing tube and equalizing ball are explicitly non-current-carrying, completely separating the shielding function from the conductive function. Combined with the use of aluminum alloy material, material costs are significantly reduced while fully meeting the requirements for uniform electric field. The potential connection only serves to fix the potential and does not carry the load current, so its cross-sectional area can be much smaller than that of the current-carrying copper stranded wire, further reducing the amount of copper used. The lead wires adopt a flexible configuration of single or multiple soft copper stranded wires, which can be selected according to the current carrying capacity requirements, avoiding over-design. In addition, the overall pre-assembly in the factory reduces the cost of on-site rework. The superposition of cost control measures at all levels makes the manufacturing cost of this invention significantly lower than that of existing solutions using Weidmann molded insulation parts or copper shielding tubes. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the 500kV transformer high-voltage outgoing line system of the present invention; Figure 2 Schematic diagram of welding the base plate of the L-shaped riser seat; Figure 3 This is a schematic diagram of the equalizing pipe and insulation. Figure 4 This is a schematic diagram of an equalizing sphere and insulation. Figure 5 This is a schematic diagram of the fixed structure. Figure 6 A magnified schematic diagram of the end is provided; Figure 7 This is a schematic diagram of the conformal insulating pad in Example 2; As shown in the figure: 1. Equalizing pipe, 2. Elevator seat, 3. Lead wire, 4. Equalizing ball, 5. Hand hole, 6. Molded corner ring, 7. Oil tank flange, 8. Fixing structure, 20. Base plate, 21. Flange on equalizing pipe, 22. Insulation layer, 23. End, 24. Pulp insulation molding, 41. Covering layer, 42. Conformable pulp molding, 43. Gasket, 44. Flange on equalizing ball, 81. Bracket, 82. Clamping part, 83. Angle part, 821. Conformable insulation gasket, 822. Oil channel groove. Detailed Implementation

[0031] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0032] Example 1: See attached document Figure 1-6 The present invention discloses a 500kV transformer high-voltage outgoing line system and its installation method. The system includes an L-shaped riser 2, an equalizing pipe 1 disposed in the L-shaped riser 2, and an equalizing ball 4 connected to one end of the equalizing pipe 1.

[0033] One end of the equalizing tube 1 is connected to the equalizing ball 4 via a flange, and the other end is fixed to a conical end 23, which is wrapped with pulp insulating molded parts 24 on both the inner and outer sides. The outer surface of the equalizing tube 1 and the outer surface of the pulp insulating molded parts 24 at the end 23 are uniformly covered with an insulating layer 22. The equalizing tube 1 is made of aluminum alloy, and both its inner and outer surfaces are smooth and burr-free. Neither the equalizing tube 1 nor the equalizing ball 4 carries current; their main function is to increase the electrode shape, uniformly distribute the electric field, and improve the dielectric strength of the outgoing line system.

[0034] The equalizing tube 1 is made of aluminum alloy, with flanges and end caps 23 welded to both ends. The inner and outer surfaces must be smooth and burr-free. The flange circumference is evenly distributed with threaded holes for installing the equalizing ball 4. The end cap 23 is tapered with rounded corners. The coil-side end cap 23 is covered with a pulp insulation molding 24, and then completely wrapped with a thick insulation layer 22, which is mainly insulating crepe paper. The tapered end cap 23, combined with the rounded corners, further increases the radius of curvature of the end electrode, more effectively reducing the electric field concentration at the coil output end.

[0035] The equalizing sphere 4 is made of aluminum alloy and has a smooth overall shape. The outer surface of the equalizing sphere 4 is first covered with a layer of conformal pulp insulation as a covering layer 41, followed by two layers of conformal pulp moldings 42. Each layer is supported and separated by spacers 43. The spacers 43 are evenly distributed along the circumference and height of each layer, and are bonded to the pulp moldings. Compared to the support strip structure, the spacer 43 structure allows for smoother oil flow, facilitating the circulation and heat dissipation of the insulating oil and the rapid dissipation of gas generated by partial discharge.

[0036] The L-shaped riser seat 2 is welded from the riser seat 2 wall, flange, base plate 20, and manhole 5 flange. The riser seat 2 wall is formed by welding multiple rolled parts together. The base plate 20 has eight mounting structures for installing the fixing system, arranged in two groups along the horizontal and vertical directions respectively, with four structures in each group distributed circumferentially. Each mounting structure is a blind hole on the base plate 20, with four blind holes machined into each base plate 20. All weld lines on the riser seat 2 wall, flange, base plate 20, and manhole 5 flange are full and smooth, with no sharp corners or burrs on the inner wall. The blind hole design avoids the oil leakage risk associated with through holes, improving sealing reliability.

[0037] The riser 2 is equipped with a fixing system to support the equalizing pipe 1. The fixing system includes two clamping members 82 arranged opposite each other and clamping the pipe circumferentially, a bracket 81 bolted to the clamping members 82, and an angled member 83 connecting the bracket 81 and the pipe wall of the riser 2. A fixing hole for the insulating layer 22 to pass through is provided between the two clamping members 82. Both the bracket 81 and the clamping members 82 are made of insulating material. The bracket 81 and the clamping members 82 of the fixing system are made of laminated cardboard, and the fixing bolts are made of fiberglass. This structure ensures mechanical strength while avoiding the risk of floating potential discharge introduced by metal parts.

[0038] The lead 3 of the equalizing tube 1 consists of several stranded copper wires and a potential connection wire. Both the copper wires and the potential connection wire are wrapped with insulating material (2mm thick). The potential connection wire does not carry current but is crimped together with the copper wires, serving only to fix the potential. The cross-section of the stranded copper wires must meet the current carrying requirements. When there are multiple stranded copper wires, each pair of stranded copper wires is individually insulated and then the multiple groups of stranded copper wires are wrapped together as a whole.

[0039] A molded corner ring 6 is connected to the high-voltage coil. The molded corner ring 6 is composed of two layers of irregularly shaped pulp molded parts and is located on the output side of the high-voltage coil. The end 23 is located inside the molded corner ring 6. The oil tank flange 7 located at the coil has rounded corners to uniformly distribute the electric field on the potential side. The handhole 5 is equipped with a handhole 5 cover plate, which has a conformal shielding structure for uniformly distributing the electric field on the potential side.

[0040] This invention is illustrated using a three-phase integrated 500kV step-up transformer as an example. Before installation, it must be confirmed that all components of the L-shaped riser 2, equalizing pipe 1, equalizing ball 4, and fixing system have been processed and surface-treated, and that all insulating components have been dried.

[0041] Step 1: Fabricate 500kV high-voltage lead 3 and potential connection wire.

[0042] Lead 3 uses one or more strands of soft copper stranded wire, with the number and cross-sectional area determined according to the current carrying capacity requirements. When using multiple strands of soft copper stranded wire, each pair is individually insulated and wrapped. After each group is insulated, all groups are wrapped together into a single lead 3. The length of lead 3 is reserved according to the actual distance from the high-voltage coil outlet to the bushing terminal. One end is crimped to the coil outlet conductor using a cold-pressed connector, and the other end is crimped to a terminal for connection to the bushing. Lead 3 is wrapped with 2mm thick insulation material, which is made of semi-folded insulating crepe paper, with the wrapping tightness controlled between 167% and 200%.

[0043] The potential connection wire is made of 8mm² soft copper stranded wire and wrapped with 2mm thick insulation material. One end of the potential connection wire is crimped into the terminal block connected to the bushing (in the same terminal block as lead 3), and the other end is connected to a small terminal block for connection to the equalizing ball 4. The potential connection wire does not carry current and only serves to fix the potential.

[0044] During the fabrication of lead 3 and the potential connection, the crimping quality of all cold-pressed joints should be ensured. After crimping, a tensile test should be performed to ensure that the connection is firm and reliable.

[0045] Step 2: Drying of all components before installation of the high-voltage outgoing line system.

[0046] All insulating components, including the equalizing ball 4, equalizing tube 1, angle fitting 83, bracket 81, clamping component 82, and fixing bolts, must be dried before installation. The specific drying process is as follows: place each insulating component in a vacuum drying chamber and dry continuously at 105℃~115℃ for no less than 48 hours. The moisture content of the insulating components during the drying process should be controlled below 0.5%. After drying, each insulating component should be stored in a dry and clean environment for later use. The time from removing it from the drying chamber to completing installation should not exceed 4 hours to prevent the insulating components from absorbing moisture again.

[0047] Before drying, the equalizing tube 1 should first wrap the inner and outer sides of the coil end 23 with pulp insulation molding 24, and then uniformly cover the outside of the tube body and the outside of the pulp insulation molding 24 at the end 23 with insulation layer 22. The insulation layer 22 is wrapped with insulating crepe paper, with 10 to 12 layers and a total thickness of about 8 to 10 mm.

[0048] Step 3: Connect the equalizing ball 4 to the equalizing tube 1 and place it inside the L-shaped riser 2.

[0049] The equalizing ball 4 is securely connected to one end of the equalizing pipe 1 via a flange using bolts. The equalizing ball 4 has an inner flange or a mating flange corresponding to the flange at the end of the equalizing pipe 1. Stainless steel bolts are used for fastening, with the bolts evenly distributed around the circumference of the flange. The tightening torque must be controlled according to the design requirements to ensure a reliable connection without damaging the threads.

[0050] The connected equalizing ball 4 and equalizing tube 1 are placed in the predetermined position inside the L-shaped riser 2 according to the design drawings. Before placement, an insulating layer 22 should be pre-wrapped at the two clamping positions of the equalizing tube 1 in the horizontal and vertical directions. This insulating layer 22 serves as a buffer protection layer during clamping to prevent the clamping parts 82 from directly contacting the main insulating layer 22 of the equalizing tube 1, which could cause scratches or pressure damage.

[0051] Step 4: Install the corner piece 83, bracket 81 and clamping piece 82.

[0052] First, install the angled component 83 inside the L-shaped riser 2. The angled component 83 is fixedly connected to the base plate 20 welded to the pipe wall of the riser 2 by bolts. There are eight base plates 20 in total, divided into two groups, horizontal and vertical, with four in each group distributed in a circle. The angled component 83 is installed on the corresponding base plate 20 according to the actual position of the equalizing pipe 1.

[0053] After the corner piece 83 is installed, the bracket 81 is installed. The bracket 81 is an insulating bracket made of laminated cardboard. One end of the bracket 81 is connected to the corner piece 83 by bolts, and the other end extends towards the equalizing pipe 1. The structure and dimensions of the bracket 81 are determined according to the actual distance between the walls of the equalizing pipe 1 and the riser 2.

[0054] Finally, install the clamping components 82. The clamping components 82 are arc-shaped or V-shaped structures made of laminated cardboard. Two clamping components 82 are arranged opposite each other along the circumference of the equalizing pipe 1, forming a clamping structure. A fixing hole is provided between the two clamping components 82 for the insulation layer 22 to pass through. After the equalizing pipe 1 passes through the fixing hole, it is clamped from both sides by the two clamping components 82. The clamping components 82 are fixedly connected to the bracket 81 by bolts. When the clamping components 82 clamp the equalizing pipe 1, the clamping force should be uniform and moderate to avoid excessive local stress that could damage the insulation layer 22.

[0055] Step 5: Fine-tune the equalizing tube 1 to center it and fix it.

[0056] To ensure the installation accuracy and clamping stability of the equalizing pipe 1, its position should be fine-tuned before tightening all fixing bolts. During fine-tuning, a feeler gauge or vernier caliper should be used to measure the gap between the outer surface of the equalizing pipe 1 and the inner wall of the riser seat 2, measuring both horizontally and vertically. By adjusting the connection position of the angle bracket 83 to the base plate 20, the extension length of the bracket 81, and the clamping tightness of the clamping member 82, the equalizing pipe 1 should be centered within the L-shaped riser seat 2. The standard for centering is: the deviation between the axis of the equalizing pipe 1 and the theoretical center line of the inner cavity of the riser seat 2 should not exceed ±2mm.

[0057] After the equalizing pipe 1 is centered and adjusted, tighten all connecting bolts in sequence. First, tighten the connecting bolts between the clamping member 82 and the bracket 81, then tighten the connecting bolts between the bracket 81 and the angle member 83, and finally tighten the connecting bolts between the angle member 83 and the base plate 20. After all bolts are tightened, double nuts should be used for anti-loosening locking to prevent bolts from loosening due to operating vibration. The tightening torque should be controlled according to the design requirements, and a verification check should be performed after tightening.

[0058] Step 6: Install the outgoing line system onto the fuel tank and connect lead wire 3.

[0059] The assembled 500kV transformer high-voltage outgoing line system is hoisted onto the oil tank and connected to the oil tank flange 7 via the mounting flange at the bottom of the L-shaped riser 2, using bolts for secure connection. During installation, ensure a good seal between the riser 2 and the oil tank, and that the sealing ring is properly installed and free from twisting.

[0060] Lead 3 passes through the inside of the equalizing tube 1, and its terminal is connected to the end terminal of the bushing. Before connection, ensure that the length of lead 3 is appropriate, neither too tight nor too loose, and leave an appropriate bend allowance at the end terminal of the bushing to accommodate thermal expansion and contraction during transformer operation. One end of the potential connection wire is crimped into the same terminal as lead 3 and connected to the bushing, while the other end is connected to the equalizing ball 4 through a small terminal to fix the potential of the equalizing ball 4.

[0061] After the lead wire 3 is connected, install the molded corner ring 6 on the high voltage coil output side. The molded corner ring 6 is composed of two layers of irregularly shaped pulp molded parts. During installation, ensure that the end 23 is within the effective protection range of the molded corner ring 6. The position of the corner ring should be accurate and the fixation reliable.

[0062] After installation, a comprehensive inspection of the entire outgoing line system should be carried out, including: the tightness of all bolts, the cleanliness of the surface of the insulation components, the reliability of the lead wire 3 and the potential connection, and the centering position of the equalizing pipe 1. After confirming that everything is correct, the transformer should be vacuum-filled with oil and subjected to electrical tests.

[0063] Example 2: See attached document Figure 7 The difference between this embodiment and Embodiment 1 is that: A conformal insulating pad 821 is also provided between the clamping member 82 and the insulating layer 22. The conformal insulating pad 821 is molded from multiple layers of insulating crepe paper. The side of the conformal insulating pad 821 that is in contact with the outer circumferential surface of the equalizing pipe 1 is an arc-shaped surface with the same curvature as the pipe body. The other side is in contact with the inner arc surface of the clamping member 82 and is bonded and fixed to the clamping member 82 by an insulating adhesive. On the side of the conformal insulating pad 821 that is in contact with the equalizing pipe 1, at least a number of oil channel grooves 822 are provided along the circumferential direction. Each oil channel groove 822 is evenly distributed along the circumferential direction. Each oil channel groove 822 forms a channel that can accommodate insulating oil. The cross-section of the oil channel groove is an arc surface.

[0064] A conformal insulating pad is added between the clamping component and the insulating layer. The clamping force is first homogenized by the elastic pad before being transferred to the insulating layer. The conformal insulating pad reduces the risk of the insulating layer being crushed or scratched at the clamping point. The oil channel grooves contact the equalizing pipe in a discrete recessed form. The oil channel grooves provide a flow channel for the insulating oil, allowing the insulating oil to convect smoothly in the clamping area. The trace amounts of gas generated by partial discharge can also escape along the oil channel grooves, preventing the formation of oil flow dead zones or gas accumulation cavities at the clamping point. The rounded corners at the root of the oil channel grooves eliminate the sharp corners at the root of the grooves, avoiding the induction of partial discharge due to electric field concentration caused by structural abrupt changes.

[0065] Of course, the above description is not limited to the examples above. Technical features not described in this invention can be implemented by or using existing technology, and will not be repeated here. The above embodiments and drawings are only used to illustrate the technical solutions of this invention and are not intended to limit this invention. This invention has been described in detail with reference to preferred embodiments. Those skilled in the art should understand that any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention do not depart from the spirit of this invention and should also fall within the scope of protection of the claims of this invention.

Claims

1. A 500kV transformer high-voltage outgoing line system, comprising an equalizing pipe (1) with one end connected to an equalizing ball (4), characterized in that: The other end of the equalizing tube (1) is fixedly connected to a tapered end (23) which is wrapped with pulp insulating molding (24) on both the inner and outer sides. The outside of the tube body of the equalizing tube (1) and the outside of the pulp insulating molding (24) at the coil side end (23) are uniformly covered with an insulating layer (22). One end of the equalizing tube (1) is connected to the equalizing ball (4) through a flange. Neither the equalizing tube (1) nor the equalizing ball (4) carries current.

2. The 500kV transformer high-voltage outgoing line system according to claim 1, characterized in that: The outer surface of the equalizing ball (4) is first covered with a layer of conformable pulp insulation as a covering layer (41), and then two layers of conformable pulp molding parts (42) are set. Each layer is supported and the oil gap is divided by a pad (43). Each layer pad (43) is evenly set along the circumferential direction and evenly set along the height direction. The pad (43) is bonded and fixed on the pulp molding parts.

3. The 500kV transformer high-voltage outgoing line system according to claim 1, characterized in that: The equalizing block and equalizing ball (4) are provided with an L-shaped lifting seat (2) on the outside, and the lifting seat (2) is provided with a fixing structure (8) to support the equalizing tube (1).

4. The 500kV transformer high-voltage outgoing line system according to claim 3, characterized in that: The fixing structure (8) includes two clamping members (82) that clamp the fixing tube in the circumferential direction and are arranged opposite each other, a bracket (81) that is bolted to the clamping members (82), and an angle member (83) that connects the bracket (81) and the tube wall of the lifting seat (2). A fixing hole is provided between the two clamping members (82) for the insulation layer (22) to pass through. The bracket (81) and the clamping members (82) are both made of insulating material.

5. The 500kV transformer high-voltage outgoing line system according to claim 4, characterized in that: The riser (2) has a base plate (20) welded to the tube wall, which is connected to the corner piece (83). The base plate (20) is ground into a round ring without sharp corners or burrs.

6. The 500kV transformer high-voltage outgoing line system according to claim 4, characterized in that: The lead (3) of the equalizing tube (1) includes several soft copper stranded wires and a potential connection wire. Both the copper stranded wires and the potential connection wire are wrapped with insulating material. The potential connection wire does not carry current but is crimped together with the copper stranded wires and only serves to fix the potential.

7. The 500kV transformer high-voltage outgoing line system according to claim 5, characterized in that: A conformal insulating pad (821) is also provided between the clamping member (82) and the insulating layer (22). The conformal insulating pad (821) is molded from multiple layers of insulating crepe paper. The side of the conformal insulating pad (821) that is in contact with the outer circumferential surface of the equalizing tube (1) is an arc-shaped surface with the same curvature as the tube body. The other side is in contact with the inner arc surface of the clamping member (82) and is fixed to the clamping member (82) by an insulating adhesive. On the side of the conformal insulating pad (821) that is in contact with the equalizing tube (1), a number of oil channel grooves (822) are provided along the circumferential direction. Each oil channel groove (822) is evenly distributed along the circumferential direction. Each oil channel groove (822) forms a channel that can accommodate insulating oil.

8. The 500kV transformer high-voltage outgoing line system according to claim 1, characterized in that: A molding corner ring (6) is connected to the high-voltage coil. The molding corner ring (6) is composed of two layers of irregularly shaped pulp molding parts and is set on the output side of the high-voltage coil. The end (23) is located inside the molding corner ring (6).

9. The 500kV transformer high-voltage outgoing line system according to claim 1, characterized in that: The oil tank flange (7) located at the coil is rounded to ensure uniform electric field distribution on the potential side.

10. An installation method for a 500kV transformer high-voltage outgoing line system, characterized in that, Includes the following steps: a. Fabricate 500kV high-voltage lead wire (3) and potential connection wire; The lead wire (3) is made of single or multiple soft copper stranded wires. One end is crimped to the lead wire of the coil and the other end is crimped to the end of the sleeve of the terminal block and connected together. The lead wire (3) is wrapped with 2mm of insulation material. The potential connection wire is made of soft copper stranded wire with a cross section of 8mm and wrapped with 2mm of insulation. One end of the potential connection wire is crimped into the terminal block connected to the sleeve and the other end is connected to the small terminal block and the equalizing ball (4). b. Before installing the high-voltage outgoing line system, the equalizing ball (4), equalizing pipe (1), angle fitting, bracket (81), clamping fitting (82), and fixing bolts must be dried in advance; c. Securely connect the equalizing ball (4) and the equalizing pipe (1) together with bolts through the flange, place them in the L-shaped lifting seat (2), and wrap the insulation layer (22) at the two clamping positions of the equalizing pipe (1) in the horizontal and vertical directions. d. Install the angled parts and brackets (81) in the L-shaped riser (2) one after another, and fix the equalizing pipe (1) in the L-shaped riser (2) by clamping parts (82); e. To ensure the installation accuracy and secure clamping of the equalizing pipe (1), first make a fine adjustment to center the equalizing pipe (1), and then fix the equalizing pipe (1). f. Install the 500kV transformer high-voltage outgoing line system on the oil tank, and connect the lead (3) to the bushing end terminal.

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