Long pipeline gil thermal expansion and contraction bellows compensation structure and optimization method thereof

Abstract

The application belongs to the technical field of ultra-high voltage power transmission, and particularly relates to a long-pipeline GIL thermal expansion and contraction corrugated pipe compensation structure and an optimization method thereof, which comprises a supporting part, a metal shell and a corrugated pipe lining, the supporting part comprises a fixed base, clamping tables are formed on the two sides of the fixed base, uniform distribution positioning grooves are formed on the outer side walls of the clamping tables, a plurality of inner supporting plates are clamped on the outer sides of the clamping tables through the positioning grooves, the plurality of inner supporting plates form a closed loop structure, and a sealing gasket is arranged between each inner supporting plate, the corrugated pipe lining is used, the inner side flexible insulation layer improves the insulation performance and is self-adaptive to the shell expansion and contraction, and the outer side metal layer provides support. The inner and outer air pressures are balanced, high-pressure nitrogen is used to prevent insulation gas leakage. The modular design is convenient for maintenance and reduces the air tightness requirement. The overall thermal compensation amount is evenly divided into each module, and the stability is enhanced through the fixed supporting part. The air pressure monitoring and nitrogen supplement device is equipped, sealing faults are diagnosed in real time, and the leakage detection process is simplified.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high voltage power transmission technology, specifically relating to the GIL thermal expansion corrugated pipe compensation structure for long pipelines and its optimization method. Background Technology

[0002] Gas-insulated metal-enclosed transmission lines (GILs) are electrical equipment used to transmit extremely high voltages and enormous currents. Their core structure consists of a central aluminum conductor and a coaxial aluminum outer shell. High-pressure insulating gas is filled between the conductor and the shell; traditionally, sulfur hexafluoride (SF6) is used, but increasingly, mixtures of SF6 with nitrogen or other environmentally friendly gases are employed to maintain strong insulation capabilities.

[0003] The most significant characteristic of GIL (Gas Insulator Line) lies in its superior power transmission capacity. A single circuit can carry several gigawatts of power, sufficient to meet the electricity needs of large cities. Because its conductors and insulation system are completely sealed within a grounded metal casing, it possesses extremely high operational reliability and safety. It is unaffected by any external environmental conditions such as harsh weather, pollution, humidity, or salt spray, while the metal casing also forms complete electromagnetic shielding, preventing electromagnetic field leakage. Furthermore, GIL has lower transmission losses than traditional power cables, resulting in energy savings, and it can operate virtually maintenance-free throughout its design life. It is primarily used in critical applications where overhead lines or power cables cannot perform their functions, such as outgoing lines from large hydroelectric and nuclear power plants, underground transmission lines crossing rivers, mountains, airports, or sensitive areas such as city centers, and for connecting critical equipment within high-voltage substations.

[0004] When existing GILs are in use, the metal casing is prone to thermal expansion and contraction due to changes in external temperature or internal circuit temperature. This can cause stress concentration at the weld seams of the metal casing and even affect the sealing performance of the metal casing, leading to leakage of insulating gas.

[0005] To address the aforementioned issues, this application proposes a long pipeline GIL thermal expansion corrugated pipe compensation structure and its optimization method. Summary of the Invention

[0006] To address the problems mentioned in the background section, this invention provides a long pipeline GIL thermal expansion bellows compensation structure and its optimization method, which features the characteristics of preventing leakage of insulating gas and compensating for the thermal expansion and contraction of the bellows.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a long pipeline GIL thermal expansion corrugated pipe compensation structure, comprising a support part, a metal outer shell, and a corrugated pipe liner. The support part includes a fixed base, on both sides of which are formed locking platforms. The outer side wall of each locking platform has evenly distributed positioning grooves. Several inner support plates are engaged with the outer side of the locking platforms through the positioning grooves. These inner support plates form a closed-loop structure, and a sealing gasket is provided between each inner support plate. Sealing plates are formed at both ends of the corrugated pipe liner. A first connecting hole is formed on the surface of each sealing plate. The end face of the support plate is provided with a second connecting hole. The corrugated pipe liner is fixed to the inner support plate by bolts. The bolts pass through the first connecting hole and the second connecting hole and extend into the fixed base. The outer side of the inner support plate is provided with the same number of hoop plates. Several fixing bolts are installed on the surface of each hoop plate. The fixing bolts pass through the hoop plate and the inner support plate and extend into the mounting bracket. The hoop plate and the inner support plate form a gap to accommodate the end face of the metal shell. An insulating bracket is fixed to the inner side wall of the fixed base. A power transmission wire passes through the insulating bracket.

[0008] As a preferred embodiment of the long pipeline GIL thermal expansion corrugated pipe compensation structure of the present invention, the end face of the metal shell is fixed with a lug corresponding to the hoop plate, and a pre-tension spring is engaged on each lug. Both ends of the pre-tension spring are annular structures, and the other end of the pre-tension spring is penetrated by one of the fixing bolts.

[0009] As a preferred embodiment of the GIL thermal expansion corrugated pipe compensation structure for long pipelines of the present invention, the inner lining of the corrugated pipe is filled with an insulating gas, wherein the insulating gas is... and Mix at a ratio of 1:4.

[0010] As a preferred embodiment of the long pipeline GIL thermal expansion corrugated pipe compensation structure of the present invention, the corrugated pipe liner has at least a two-layer structure, with the outer side of the corrugated pipe liner being made of metal and the inner side being made of flexible insulating composite material.

[0011] As a preferred embodiment of the long pipeline GIL thermal expansion corrugated pipe compensation structure of the present invention, a pressurizing pipe is installed on the middle outer wall of each of the metal shells. The pressurizing pipe is connected between the metal shell and the corrugated pipe lining. The pressurizing pipe is connected to a nitrogen pipeline. The gas pressure of the nitrogen pipeline is the same as the gas pressure of the insulating gas in the corrugated pipe lining.

[0012] As a preferred embodiment of the long pipeline GIL thermal expansion corrugated pipe compensation structure of the present invention, the bottom of the support is fixed with an anchor pile foundation, and the anchor pile foundation is fixed in the foundation pit.

[0013] As a preferred embodiment of the long pipeline GIL thermal expansion corrugated pipe compensation structure of the present invention, the included angle between the two end faces of the fixed base is 0° to 90°.

[0014] Optimization method for GIL thermal expansion corrugated pipe compensation structure in long pipelines

[0015] This includes S1, estimating the maximum temperature difference based on the ambient temperature difference at the location where GIL is laid and the line load temperature;

[0016] S2. Design compensation based on the maximum temperature difference, and add design margin on this basis;

[0017] S3. Based on the length of the transmission line, the GIL is divided into several units, and the compensation amount is evenly distributed to each unit.

[0018] S4. Test the sealing performance during installation. Judge the airtightness of GIL by the rate of gas pressure loss in the nitrogen pipeline.

[0019] S5. Maintenance and optimization after long-term use.

[0020] As a preferred optimization method for the long pipeline GIL thermal expansion corrugated pipe compensation structure of the present invention, S5 involves periodic airtightness and insulation performance testing, monitoring the pressure inside and outside the corrugated pipe lining, determining the replacement time of the seals in the corrugated pipe lining and the support section based on the nitrogen pipeline pressure loss rate and the pressure values ​​inside and outside the corrugated pipe lining, and adjusting the replacement time based on the insulating gas concentration inside the corrugated pipe lining. Replenish.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] This invention utilizes a composite bellows liner. The flexible insulating composite material on the inner side of the bellows liner improves the insulation performance of the gas insulating oil (GIL) while adapting to the length of the GIL's metal outer shell for expansion and contraction compensation. The metal material on the outer side of the bellows liner provides sufficient support. Simultaneously, the internal and external air pressures of the bellows liner are the same. High-pressure nitrogen gas on the outer side of the bellows liner prevents leakage of the insulating gas inside. Specifically, the gap between the bellows liner and the GIL's metal outer shell is filled with high-pressure nitrogen gas at the same working pressure as the insulating gas inside the bellows liner, artificially creating a pressure balance environment. According to fluid mechanics principles, when the air pressure on both sides of the bellows liner remains balanced, the insulating gas inside the liner loses its main driving force for outward leakage. The modular installation facilitates subsequent maintenance compared to traditional welding connections and reduces the requirements for airtightness, greatly minimizing the impact of airtightness on the GIL's insulation performance.

[0023] This invention abandons the welding connection method heavily relied upon in traditional GIL systems, instead adopting a highly standardized modular assembly concept. Core components such as the support section, inner support plate, hoop plate, and bellows liner are securely connected using precise mechanical design and positioning structures such as clamps and positioning grooves, along with bolts, and multiple sealing rings are installed at each interface. This modular installation method not only simplifies the on-site construction process and improves installation accuracy and efficiency, but more importantly, when a component in the system, such as the bellows liner or seals, needs replacement or repair, targeted partial disassembly and repair can be performed, avoiding the overall cutting, re-welding, and the subsequent more complex gas handling and vacuum reprocessing processes required by traditional welded structures. The combination of modular design and pressure balancing technology constitutes a more maintenance-friendly GIL system, significantly reducing the overall lifecycle maintenance costs and complexity.

[0024] This invention utilizes a gas pressure monitoring device, combined with nitrogen replenishment, to monitor in real time whether each GIL unit has a sealing problem, quickly eliminate faults, and reduce the difficulty of leak detection. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0026] Figure 1 This is a schematic diagram of the structure of the present invention;

[0027] Figure 2 For the present invention Figure 1 Enlarged structural diagram at point A;

[0028] Figure 3 This is a schematic diagram of the front structure of the present invention;

[0029] Figure 4 This is a schematic diagram of the structure of the hoop plate and the inner support plate in this invention;

[0030] Figure 5 For the present invention Figure 4 Enlarged structural diagram at point B;

[0031] Figure 6 This is a partial cross-sectional view of the present invention;

[0032] Figure 7 This is a schematic diagram of the left-side structure of the present invention;

[0033] Figure 8 This is a schematic diagram illustrating the usage state of the present invention;

[0034] Figure 9 This is a schematic diagram of the support structure in Embodiment 2 of the present invention;

[0035] In the diagram: 1. Support; 101. Mounting plate; 102. Positioning groove; 103. Fixing bolt; 104. Insulating bracket; 111. Fixing base; 2. Anchor pile; 3. Hoop plate; 4. Metal shell; 401. Hanging lug; 402. Pressurizing pipe; 5. Power transmission line; 6. Corrugated pipe liner; 601. Sealing plate; 602. First connecting hole; 7. Inner support plate; 701. Second connecting hole; 8. Preload spring. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] like Figures 1 to 8 As shown;

[0039] The long pipeline GIL thermal expansion bellows compensation structure includes a support part 1, a metal outer shell 4, and a bellows liner 6. The support part 1 includes a fixed base 111, with locking platforms 101 formed on both sides of the fixed base 111. The outer side wall of the locking platform 101 has evenly distributed positioning grooves 102. Several inner support plates 7 are engaged with the outer side of the locking platform 101 through the positioning grooves 102. The several inner support plates 7 form a closed loop structure. A sealing gasket is provided between each inner support plate 7. Sealing plates 601 are formed at both ends of the bellows liner 6. The surface of the sealing plate 601 has a first connection hole 602. The end face of the inner support plate 7 is... A second connecting hole 701 is provided. The corrugated pipe liner 6 is fixed to the inner support plate 7 by bolts. The bolts pass through the first connecting hole 602 and the second connecting hole 701 and extend into the fixed base 111. The same number of hoop plates 3 are provided on the outer side of the inner support plate 7. Several fixing bolts 103 are installed on the surface of each hoop plate 3. The fixing bolts 103 pass through the hoop plate 3 and the inner support plate 7 and extend into the mounting plate 101. The hoop plate 3 and the inner support plate 7 form a gap to accommodate the end face of the metal shell 4. An insulating bracket 104 is fixed on the inner side wall of the fixed base 111. A power transmission wire 5 passes through the insulating bracket 104.

[0040] Furthermore:

[0041] In an optional embodiment, the end face of the metal shell 4 is fixed with a lug 401 corresponding to the hoop 3. Each lug 401 is fitted with a preload spring 8. Both ends of the preload spring 8 are annular structures, and the other end of the preload spring 8 is penetrated by one of the fixing bolts 103.

[0042] Furthermore:

[0043] In an optional embodiment, the bottom of the support 1 is fixed with an anchor pile 2, which is fixed in the foundation pit.

[0044] In this embodiment: During installation, the anchor pile 2 is first inserted into the underground foundation pit. Concrete pouring securely fixes the anchor pile 2 to the pit. Then, the inner support plate 7 is attached to the outside of the mounting platform 101, and the inner support plate 7 is secured in the positioning groove 102, which serves for positioning and temporary fixation. Next, the first connecting hole 602 on one end of the corrugated pipe liner 6's sealing plate 601 is aligned with the second connecting hole 701. Bolts are passed through both the sealing plate 601 and the inner support plate 7, and finally fixed to the side of the fixing base 111. Sealing washers are installed between the bolts and the sealing plate 601, and similarly between the sealing plate 601 and the inner support plate 7. Sealing gaskets are placed between multiple inner support plates 7. When the bolts are tightened, the inner support plates 7... The inner support plate 7 and the sealing plate 601 are in an interference fit. The inner support plate 7 and the sealing plate 601 bear the positive pressure of the bolts. Then, the hoop plate 3 is fitted onto the outside of the fixed base 111 corresponding to the inner support plate 7. First, one of the fixing bolts 103 is passed through the annular end of the preload spring 8. Then, the fixing bolts 103 are tightened one by one to complete the assembly of the present invention. The preload spring 8 pulls the two ends of the metal shell 4 to put it in a preloaded state, which improves the stability of the metal shell 4 and avoids the problem of not being able to connect due to the drooping caused by gravity when connecting to another set of support parts 1. After the two support parts 1 are installed, the preload springs 8 on both sides pull the metal shell 4 to put it in the middle position. When the external temperature changes, the metal shell 4 expands and contracts, but it can still always be in the middle position, making full use of the thermal expansion compensation.

[0045] Furthermore:

[0046] In an optional embodiment, the bellows liner 6 is filled with an insulating gas, the insulating gas being... and Mix at a ratio of 1:4.

[0047] In this embodiment: through this design, the insulating gas is a mixed gas, reducing... It is practical, reduces environmental pollution, and has little impact on overall insulation performance.

[0048] Furthermore:

[0049] In one optional embodiment, the bellows liner 6 has at least a two-layer structure, with the outer side of the bellows liner 6 being made of metal and the inner side being made of flexible insulating composite material.

[0050] In this embodiment: Through this design, the flexible insulating composite material on the inner side of the bellows liner can improve the insulation performance of the GIL while adapting to the length of the GIL metal shell for expansion and contraction compensation, and the metal material on the outer side of the bellows liner provides sufficient support.

[0051] Furthermore:

[0052] In an optional embodiment, a pressurizing pipe 402 is installed on the middle outer side wall of each metal housing 4. The pressurizing pipe 402 connects the metal housing 4 and the corrugated pipe liner 6. The pressurizing pipe 402 is connected to a nitrogen pipeline. The gas pressure in the nitrogen pipeline is the same as the gas pressure of the insulating gas in the corrugated pipe liner 6.

[0053] In this embodiment: Since the insulating gas inside the GIL is at a high pressure, the present invention balances the pressure by introducing nitrogen gas of the same pressure into the gap between the metal shell 4 and the bellows liner 6, so that the insulating gas inside the bellows liner 6 will not easily overflow to the outside of the bellows liner 6. That is, there is no pressure difference between the inside and outside of the bellows liner 6. At this time, the insulating gas is difficult to leak, which greatly reduces the requirements for the airtightness of the GIL. Moreover, nitrogen is a stable, harmless and readily available gas. Even if a leak occurs, it is easy to deal with. Nitrogen gas is injected into the outside of the bellows liner 6 by an external gas pump, and the nitrogen gas pressure is monitored in real time, which can prevent the loss of insulating gas and facilitate later maintenance and repair.

[0054] It should be noted that a pressure relief valve and a pressure sensor are installed between the nitrogen pipeline and the pressurization pipe 402. The pressure sensor is located near the metal casing 4, and the control valve is located near the nitrogen pipeline. The pressure sensor can be used to determine the nitrogen pressure inside the metal casing 4, and the control valve can be used to control whether the flow into the metal casing 4 is connected to the nitrogen pipeline.

[0055] Example 2

[0056] When the GIL design is not a straight line, multiple inflection points are required to realize complex transmission lines. The included angle between the two end faces of the fixed base 111 can be 0° to 90°.

[0057] In this embodiment: as follows Figure 9 As shown, the fixed base 111 can be designed as an arc, so that the two end faces of the support part 1 form an angle, while ensuring that the transmission conductor 5 is always on the axis of the device. This design makes the transmission line form of the present invention more diverse and more suitable for actual installation needs, avoids digging straight foundation pits and increasing construction difficulty. Moreover, since the insulating bracket 104 is fixed at the fixed base 111, the fixed base 111, as the main load-bearing body, can withstand the large traction force at the inflection point of the transmission conductor 5, further improving the stability of the present invention.

[0058] This invention also proposes an optimization method for a long pipeline GIL thermal expansion corrugated pipe compensation structure.

[0059] Including: S1, estimating the maximum temperature difference based on the ambient temperature difference at the location where GIL is laid and the line load temperature;

[0060] S2. Design compensation based on the maximum temperature difference, and add design margin on this basis;

[0061] S3. Based on the length of the transmission line, the GIL is divided into several units, and the compensation amount is evenly distributed to each unit.

[0062] S4. Test the sealing performance during installation. Judge the airtightness of GIL by the rate of gas pressure loss in the nitrogen pipeline.

[0063] S5. Maintenance and optimization after long-term use.

[0064] In an optional embodiment, S5 involves periodic airtightness and insulation performance testing, monitoring the pressure inside and outside the bellows liner 6, and determining the replacement time of the seals in the bellows liner 6 and support 1 based on the nitrogen pipeline pressure loss rate and the pressure values ​​inside and outside the bellows liner 6, and adjusting the replacement time based on the insulating gas concentration inside the bellows liner 6. Replenish.

[0065] The overall workflow of this invention is as follows: This invention provides a thermally expandable corrugated pipe compensation structure for long-distance gas-insulated metal-enclosed transmission lines (GIL). The structure uses a support 1 as a fixed foundation, which is stabilized within the foundation pit by anchor piles 2 at its bottom. The fixed base 111 of the support 1 has clamping platforms 101 on both sides. A modular clamping system is formed by combining inner support plates 7, hoop plates 3, and fixing bolts 103 to reliably connect and seal the corrugated pipe liner 6 and the metal outer shell 4. The corrugated pipe liner 6 adopts a composite structure of outer metal and inner flexible insulating composite material, aiming to optimize its internal electric field distribution while undertaking the mechanical compensation function for thermal expansion and contraction. The structure innovatively introduces a pressure balance system, injecting nitrogen gas at the same pressure as the internal insulating gas into the gap between the metal outer shell 4 and the corrugated pipe liner 6 through a pressurization pipe 402, thereby eliminating pressure differences and fundamentally suppressing the outward leakage tendency of the insulating gas. Furthermore, the pre-tensioning spring 8, connected between the lug 401 of the metal housing 4 and the fixing bolt 103, enables pre-tensioning and automatic alignment of the pipeline, which helps to balance the use of compensation. This structure can also adapt to non-linear laying paths by changing the included angle between the two end faces of the fixing base 111 from 0° to 90°.

[0066] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A long pipeline GIL thermal expansion corrugated pipe compensation structure, characterized in that: The device includes a support (1), a metal shell (4), and a corrugated pipe liner (6). The support (1) includes a fixed base (111). The fixed base (111) has mounting brackets (101) formed on both sides. The outer side wall of the mounting brackets (101) is provided with evenly distributed positioning grooves (102). Several inner support plates (7) are engaged with the outer side of the mounting brackets (101) through the positioning grooves (102). The several inner support plates (7) form a closed loop structure. A sealing gasket is provided between each inner support plate (7). The two ends of the corrugated pipe liner (6) are formed with sealing plates (601). The surface of the sealing plate (601) is provided with a first connecting hole (602). The end face of the inner support plate (7) is provided with a second connecting hole (701). The corrugated pipe liner (6) is fixed to the inner support plate (7) by bolts. The bolts pass through the first connecting hole (602) and the second connecting hole (701) and extend... Inside the fixed base (111), the same number of hoop plates (3) are provided on the outer side of the inner support plate (7). Several fixing bolts (103) are installed on the surface of each hoop plate (3). The fixing bolts (103) pass through the hoop plate (3) and the inner support plate (7) and extend into the mounting plate (101). The hoop plate (3) and the inner support plate (7) form a gap to accommodate the end face of the metal shell (4). An insulating bracket (104) is fixed on the inner side wall of the fixed base (111). A power transmission wire (5) passes through the insulating bracket (104). The end face of the metal shell (4) is fixed with a hanging ear (401) corresponding to the hoop plate (3). A pre-tightening spring (8) is engaged on each hanging ear (401). Both ends of the pre-tightening spring (8) are annular structures. The other end of the pre-tightening spring (8) is penetrated by one of the fixing bolts (103).

2. The long pipeline GIL thermal expansion corrugated pipe compensation structure according to claim 1, characterized in that: The corrugated pipe liner (6) is filled with insulating gas, which is a mixture of SF6 and N2 in a ratio of 1:

4.

3. The long pipeline GIL thermal expansion corrugated pipe compensation structure according to claim 2, characterized in that: The corrugated pipe liner (6) has at least two layers, with the outer side of the corrugated pipe liner (6) being made of metal and the inner side being made of flexible insulating composite material.

4. The long pipeline GIL thermal expansion corrugated pipe compensation structure according to claim 3, characterized in that: Each of the metal shells (4) has a pressurizing pipe (402) installed on the middle outer side wall. The pressurizing pipe (402) is connected between the metal shell (4) and the corrugated pipe liner (6). The pressurizing pipe (402) is connected to a nitrogen pipeline. The gas pressure of the nitrogen pipeline is the same as the gas pressure of the insulating gas in the corrugated pipe liner (6).

5. The long pipeline GIL thermal expansion corrugated pipe compensation structure according to claim 4, characterized in that: The bottom of the support part (1) is fixed with an anchor pile (2), which is fixed in the foundation pit.

6. The long pipeline GIL thermal expansion corrugated pipe compensation structure according to claim 5, characterized in that: The included angle between the two end faces of the fixed base (111) is 0° to 90°.

7. An optimization method for a long pipeline GIL thermal expansion corrugated pipe compensation structure, applied to the long pipeline GIL thermal expansion corrugated pipe compensation structure as described in claim 6, characterized in that: S1. Estimate the maximum temperature difference based on the ambient temperature difference at the location where the GIL is laid and the line load temperature. S2. Design compensation based on the maximum temperature difference, and add design margin on this basis; S3. Based on the length of the transmission line, the GIL is divided into several units, and the compensation amount is evenly distributed to each unit. S4. Test the sealing performance during installation. Judge the airtightness of GIL by the rate of gas pressure loss in the nitrogen pipeline. S5. Maintenance and optimization after long-term use.

8. The optimization method for the long pipeline GIL thermal expansion corrugated pipe compensation structure according to claim 7, characterized in that: S5 is for periodic air tightness testing and insulation performance testing. The pressure inside and outside the corrugated pipe liner (6) is monitored. The replacement time of the seals in the corrugated pipe liner (6) and the support part (1) is determined based on the pressure loss rate of the nitrogen pipeline and the pressure values ​​inside and outside the corrugated pipe liner (6). SF6 is replenished according to the concentration of insulating gas in the corrugated pipe liner (6).

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