Nitrogen-filled sealed oil-immersed transformer

Abstract

The present application belongs to the technical field of oil-immersed transformers, and particularly relates to a nitrogen-filled sealed oil-immersed transformer, which comprises an oil-immersed transformer body, an oil storage pillow, an oil pillow support and an oil pillow pipeline, the inner wall of the oil storage pillow is fixedly connected with a first high-temperature-resistant rubber separation layer, and the upper surface of the oil storage pillow is fixedly connected with a hollow outer cover. The present application solves the inherent defects of the traditional respirator, such as easy blockage, moisture absorption failure and moisture intrusion into the insulating oil, through a full-sealing nitrogen-filled pressure self-adaptive structure. The risk of oil tank explosion caused by internal short-circuit fault is completely eliminated from the root by the double explosion-proof protection of mechanical passive millisecond pressure relief and active volume expansion, the secondary fire accident is effectively avoided, the overall structure can be directly adapted to the modification and installation of the existing outdoor oil-immersed transformer, the transformer body does not need to be structurally reconstructed, the maintenance process is simple, and the present application has strong practicability, safety and popularization value.

Description

Technical Field

[0001] This invention belongs to the technical field of oil-immersed transformers, and in particular relates to a nitrogen-filled sealed oil-immersed transformer. Background Technology

[0002] Oil-immersed transformers are core voltage conversion devices in power transmission and distribution systems. They use mineral insulating oil as the core insulation and cooling medium, with the core components such as the iron core and high and low voltage windings completely immersed in a sealed oil tank. During operation, the heat generated by the windings and iron core is carried away by the circulation of the insulating oil. At the same time, the high insulation performance of the insulating oil ensures electrical insulation between windings and between windings and the grounding box. They are characterized by strong overload capacity, stable operation, and low cost. Currently, most oil-immersed transformers are designed for outdoor installation, possessing excellent waterproof, dustproof, and weather-resistant properties, and are widely used in outdoor substations, urban and rural distribution substations, industrial parks, and other scenarios.

[0003] In existing oil-immersed transformers, to balance the pressure difference between the oil tank and the conservator (oil tank) caused by oil temperature changes during operation, a breather is generally installed on the top of the conservator. The breather has a built-in dust filter and color-changing silica gel desiccant, which has air filtration and moisture-proof functions. However, during long-term outdoor operation, the breather is easily blocked by outdoor dust, willow catkins, and mosquitoes, causing obstruction of the breathing channel. This not only leads to pressure imbalance in the conservator, but also exacerbates the leakage of unfiltered humid air under negative pressure conditions. Secondly, if the silica gel in the breather is not replaced in time after it becomes saturated with moisture, the dehumidification function will completely fail, and external moisture will continue to invade the insulating oil, causing a significant drop in the insulation breakdown voltage, excessive dielectric loss, and accelerated oxidation and deterioration of the oil quality. This can lead to insulation breakdown between winding turns and layers, directly inducing internal short circuit faults. As a result, the long-term operation of oil-immersed transformers with defects is common.

[0004] Furthermore, the rated positive pressure withstand strength of a conventional oil-immersed transformer tank is approximately 98 kPa. When an insulation breakdown occurs inside the transformer, causing a short circuit, a short circuit current of several thousand to tens of thousands of amperes will be generated, forming a high-energy arc. The instantaneous temperature of the arc exceeding 3000°C will instantly evaporate the surrounding insulating oil, rapidly generating high-pressure vapor bubbles. The incompressibility of the liquid insulating oil will restrict the expansion of the bubble volume, causing the pressure inside the bubble to rise sharply, forming a dynamic pressure wave that propagates at high speed in the oil. Within 60–100 ms after the short circuit occurs, the pressure wave will repeatedly impact the inner wall of the tank, causing the static pressure of the tank to rapidly exceed the rated withstand strength. The conventionally configured gas relay has a slow response speed and can only respond to... For malfunctions involving slow changes in oil flow; although the pressure relief valve operates quickly, its flow capacity is limited. Faced with extreme pressure increases that occur in milliseconds, the pressure relief rate cannot keep up with the pressure rise. If the breather is blocked, the auxiliary pressure relief channel of the oil reservoir will completely fail, further exacerbating the pressure buildup in the oil tank. This can easily cause stress concentration and tearing at the right-angle weld of the oil tank, or even lead to the oil tank bursting. After the oil tank bursts, a large amount of high-temperature insulating oil will leak out. If it comes into contact with residual electric arcs or high-temperature components, it will instantly ignite, causing a large-scale fire accident. This will not only result in the complete scrapping of equipment and a large-scale power grid outage, but will also affect the safety of surrounding buildings and personnel. At the same time, it will significantly increase the cost of equipment maintenance and replacement and the difficulty of power grid operation and maintenance.

[0005] To address these issues, we propose a nitrogen-filled, sealed oil-immersed transformer. Summary of the Invention

[0006] The purpose of this invention is to address the above-mentioned problems by providing a nitrogen-filled, sealed oil-immersed transformer.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a nitrogen-filled sealed oil-immersed transformer, comprising an oil-immersed transformer body, an oil conservator, an oil conservator support, and oil conservator pipelines. A first high-temperature resistant rubber diaphragm is fixedly connected to the inner wall of the oil conservator. A hollow outer cover is fixedly connected to the upper surface of the oil conservator. Multiple ventilation holes are opened on the outer wall of the oil conservator located inside the hollow outer cover. A circular hole is opened on the upper surface of the hollow outer cover, and a connecting cylinder is fixedly connected to the wall of the circular hole. The bottom end of the connecting cylinder penetrates the inner wall of the top end of the oil conservator. A fixing hole is opened at the top end of the oil conservator, which mates with the outer wall of the bottom end of the connecting cylinder. An installation groove is opened on the inner wall of the bottom end of the connecting cylinder, and a high-temperature resistant sealing sleeve is fixedly connected to the groove wall. A connecting mechanism is slidably and sealingly connected to the inner wall of the high-temperature resistant sealing sleeve.

[0008] The upper surface of the oil-immersed transformer body is provided with a through hole, and an electronic pressure gauge is fixedly connected to the wall of the through hole.

[0009] The top outer wall of the connecting cylinder is fixedly connected to a normally closed solenoid valve, and the outlet end of the normally closed solenoid valve is fixedly connected to a nitrogen storage mechanism.

[0010] A cooling mechanism is fixedly connected to the bottom of the oil-immersed transformer body.

[0011] A control component is fixedly connected to the upper surface of the cooling mechanism.

[0012] In the aforementioned nitrogen-filled sealed oil-immersed transformer, the communication mechanism includes a movable cylinder that is slidably and sealingly connected to the inner wall of a high-temperature resistant sealing sleeve. The bottom end of the movable cylinder is fixedly connected to the bottom end of a first high-temperature resistant rubber partition. Two symmetrically distributed oil outlet holes are opened on the outer wall of the movable cylinder at the bottom end of the high-temperature resistant sealing sleeve. A placement groove is opened on the upper surface of the movable cylinder, and a hollow trigger rod is inserted into the groove wall. A connecting sleeve is movably sleeved on the top wall of the hollow trigger rod. A threaded cover is fixedly connected to the upper surface of the connecting sleeve. A sealing ring is movably sleeved on the outer wall of the threaded cover. A connecting thread that mates with the threaded cover is opened on the inner wall of the top end of the communication cylinder. A shaped metal tube is fixedly connected to the top end of the communication cylinder. A U-shaped heat insulation cylinder is fixedly sleeved on the wall of the shaped metal tube. The wall of the U-shaped heat insulation cylinder is fixedly connected to the outer wall of the top end of the oil-immersed transformer body. Fixed round holes that mate with the walls of the shaped metal tube are opened on the outer walls of the two side ends of the U-shaped heat insulation cylinder.

[0013] In the aforementioned nitrogen-filled sealed oil-immersed transformer, the nitrogen storage mechanism includes a heat-resistant gas pipe fixedly connected to the outlet end of a normally closed solenoid valve. A gas cylinder is fixedly sleeved at the outlet end of the heat-resistant gas pipe. The outer wall of the gas cylinder is fixedly connected to the outer wall of the heat dissipation fins of the oil-immersed transformer body. A fixing hole is opened at the bottom end of the gas cylinder, and an electric push rod is fixedly connected to the wall of the fixing hole. A sealing rubber piston is fixedly connected to the moving end of the electric push rod. The outer wall of the sealing rubber piston is slidably and sealingly connected to the inner wall of the gas cylinder. A threaded hole is opened at the top end of the gas cylinder, and an air injection nozzle is threadedly and sealingly connected to the wall of the threaded hole. A circular hole is opened at the top end of the gas cylinder, and a pressure sensor is fixedly connected to the wall of the circular hole.

[0014] In the aforementioned nitrogen-filled sealed oil-immersed transformer, the cooling mechanism includes a water tank fixedly connected to the bottom of the oil-immersed transformer body. A second high-temperature resistant rubber partition is fixedly connected to the inner wall of the top of the water tank, which divides the internal cavity of the water tank into a storage area and a water storage area. A threaded hole is provided on the upper surface of the water tank, and a threaded hollow ring is threadedly sealed to the hole wall. A connecting pipe is fixedly connected to the inner wall of the threaded hollow ring. The top of the connecting pipe is fixedly connected to the bottom of an air cylinder. An air hole matching the top of the connecting pipe is provided at the bottom of the air cylinder. The discharge end of the shaped metal pipe passes through the inner wall of the top of the water tank and communicates with the internal cavity of the storage area. A conveying pipe is fixedly connected to the outer wall of the bottom of the water tank. The water outlet end of the conveying pipe is fixedly connected to the outer wall of a U-shaped heat insulation cylinder. Multiple spray holes are provided on the outer wall of the bottom of the U-shaped heat insulation cylinder.

[0015] In the above-mentioned nitrogen-filled sealed oil-immersed transformer, the first high-temperature resistant rubber partition divides the internal cavity of the oil reservoir into an insulating oil area and an air-filling area. The cavity of the insulating oil area is connected to the internal cavity of the movable cylinder. The oil reservoir has an oil filling hole on the side wall of the insulating oil area, and the hole wall of the oil filling hole is threadedly sealed with a sealing plug.

[0016] In the above-mentioned nitrogen-filled sealed oil-immersed transformer, the control component includes a protective box fixedly connected to the upper surface of the water tank. The top opening of the protective box is sealed with a box cover by bolts. A PLC controller is fixedly connected to the inner wall of the protective box. A wire hole is opened on the side wall of the protective box, and a perforated rubber protective block is fixedly connected to the wall of the wire hole.

[0017] In the above-mentioned nitrogen-filled sealed oil-immersed transformer, an L-shaped pipe is fixedly connected to the upper surface of the water tank, the air inlet end of the L-shaped pipe is connected to the internal cavity of the storage area, and a pressure relief valve is fixedly connected to the top wall of the L-shaped pipe.

[0018] In the above-mentioned nitrogen-filled sealed oil-immersed transformer, two symmetrically distributed mounting brackets are fixedly connected to the lower surface of the water tank. Fixed through holes are opened on both sides of the outer wall of the mounting brackets. A water supply valve is fixedly connected to the outer wall of the water tank located in the water storage area.

[0019] Compared with existing technologies, the advantages of a nitrogen-filled sealed oil-immersed transformer are:

[0020] 1. By incorporating a first high-temperature resistant rubber partition, an oil reservoir, a normally closed solenoid valve, a nitrogen storage mechanism, a PLC controller, a pressure sensor, an electric push rod, and a sealed rubber piston, the interior of the oil reservoir is divided into an independent insulating oil zone and a gas filling zone. This creates a fully sealed nitrogen filling path, eliminating the need for a traditional breather. This effectively solves inherent defects such as breather blockage, moisture absorption failure leading to moisture intrusion, insulating oil deterioration, and insulation breakdown. Simultaneously, through real-time linkage between the PLC controller and the pressure sensor, the gas filling zone achieves adaptive adjustment of a 3-5 kPa micro-positive pressure, automatically compensating for the expansion and contraction of the insulating oil volume caused by oil temperature changes. The entire process requires no interaction with the outside air, effectively delaying insulating oil aging, preventing partial discharge and oil leakage faults in the seals, significantly extending the transformer's service life, greatly reducing the frequency of outdoor equipment inspections and daily maintenance costs, and ensuring the long-term stable operation of the transformer.

[0021] 2. By incorporating a connecting mechanism, a high-temperature resistant sealing sleeve, a hollow trigger rod, a moving cylinder, an oil outlet, a shaped metal tube, and an electronic pressure gauge, a purely mechanical passive millisecond-level pressure relief structure is constructed. This solves the significant safety hazard of existing oil-immersed transformers where, during a high-energy arc generated by an internal short circuit, the tank pressure surges rapidly within 60–100 ms. Traditional gas relays and pressure relief valves often exhibit delayed response, easily leading to tearing of the tank's right-angle welds and tank explosion. When the tank pressure reaches 60 kPa, the hollow trigger rod instantly disintegrates and releases pressure. The moving cylinder moves rapidly upward under the push of high-pressure oil, making the oil outlet fully open. The high-pressure oil-gas mixture is released into the storage area within 1-3ms. In conjunction with the nitrogen system, the negative pressure expansion of the charging area is realized simultaneously, forming a dual explosion-proof protection of passive pressure relief and active expansion. It can control the oil tank pressure within the rated withstand strength within the golden window of 60ms after a short circuit. The operation does not require an external power supply, and its reliability is better than that of traditional pressure relief valves. It effectively reduces the probability of oil tank rupture and greatly improves the safety redundancy under transformer fault conditions.

[0022] 3. By incorporating a cooling mechanism, water tank, second high-temperature resistant rubber partition, U-shaped heat insulation cylinder, spray nozzles, L-shaped pipe, and pressure relief valve, this system addresses the pain points of existing transformers: high-temperature oil and gas leakage after a fault can easily lead to fires, flammable gas accumulation can easily cause deflagration, significant waste of faulty insulating oil, and complex maintenance procedures. The high-temperature oil and gas generated during a fault enters the storage area through a specially shaped metal pipe, where forced heat exchange and cooling are achieved by the cooling water in the water tank, rapidly liquefying the vaporized insulating oil. This enables fully enclosed recovery and subsequent regeneration and reuse of the faulty insulating oil. It significantly reduces the waste of insulating oil consumables. The L-shaped pipe and pressure relief valve can safely and controllably release flammable gas diluted with nitrogen, preventing the flammable gas from accumulating to the explosion limit. Spray cooling is only activated after the transformer differential protection or instantaneous overcurrent protection is activated or the power is completely cut off, effectively avoiding the risk of electric shock and flashover from spraying water while the power is on. At the same time, it quickly reduces the temperature of the oil tank to suppress the occurrence of fire. The overall structure can be directly installed on existing outdoor oil-immersed transformers without the need to reconstruct the transformer body. It is convenient to maintain after a fault, reducing the difficulty of maintenance and the cost of operation and maintenance throughout the entire life cycle. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a nitrogen-filled sealed oil-immersed transformer provided by the present invention;

[0024] Figure 2 This is a partial cross-sectional structural schematic diagram of a nitrogen-filled sealed oil-immersed transformer provided by the present invention;

[0025] Figure 3 This is the present invention. Figure 2 Enlarged structural diagram of the central connecting mechanism;

[0026] Figure 4 This is the present invention. Figure 2 Enlarged structural diagram of the cooling mechanism;

[0027] Figure 5 This is the present invention. Figure 1 Enlarged structural diagram of the central oil storage tank section;

[0028] Figure 6 This is the present invention. Figure 1 A magnified structural diagram of the central control component;

[0029] Figure 7 This is a schematic diagram of the U-shaped heat insulation cylinder in a nitrogen-filled sealed oil-immersed transformer provided by the present invention.

[0030] In the diagram: 1. Oil-immersed transformer body; 2. Oil reservoir; 3. Oil reservoir support; 4. Oil reservoir piping; 5. First high-temperature resistant rubber partition; 6. Control components; 61. Protective box; 62. Box cover; 63. PLC controller; 64. Rubber protective block; 7. Connecting mechanism; 71. Moving cylinder; 72. Oil outlet; 73. Hollow trigger rod; 74. Connecting sleeve; 75. Threaded cap; 76. Sealing ring; 77. Irregularly shaped metal tube; 78. U-shaped heat insulation cylinder; 8. Nitrogen storage mechanism; 81. Heat-resistant gas pipe; 82. Gas cylinder; 83. Electric push rod; 84. Sealing rubber. Rubber piston, 85 air injection nozzle, 86 air pressure sensor, 9 cooling mechanism, 91 water tank, 92 second high-temperature resistant rubber partition, 93 storage area, 94 water storage area, 95 threaded hollow ring, 96 connecting pipe, 97 conveying pipe, 98 spray orifice, 10 connecting cylinder, 11 high-temperature resistant sealing sleeve, 12 electronic pressure gauge, 13 normally closed solenoid valve, 14 hollow outer cover, 15 insulating oil area, 16 air filling area, 17 L-shaped tube, 18 pressure relief valve, 19 mounting bracket, 20 water supply valve, 21 sealing plug, 22 vent hole. Detailed Implementation

[0031] 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.

[0032] like Figure 1 – Figure 7As shown, a nitrogen-filled sealed oil-immersed transformer includes an oil-immersed transformer body 1, an oil conservator 2, an oil conservator support 3, and an oil conservator pipeline 4. A first high-temperature resistant rubber layer 5 is fixedly connected to the inner wall of the oil conservator 2. A hollow outer cover 14 is fixedly connected to the upper surface of the oil conservator 2. Multiple ventilation holes 22 are opened on the outer wall of the oil conservator 2 located inside the hollow outer cover 14. A circular hole is opened on the upper surface of the hollow outer cover 14, and a connecting cylinder 10 is fixedly connected to the wall of the circular hole. The bottom end of the connecting cylinder 10 penetrates the inner wall of the top end of the oil conservator 2. A fixing hole is opened at the top end of the oil conservator 2, which mates with the outer wall of the bottom end of the connecting cylinder 10. An installation groove is opened on the inner wall of the bottom end of the connecting cylinder 10, and a high-temperature resistant sealing sleeve 11 is fixedly connected to the groove wall. A connecting mechanism 7 is slidably connected to the inner wall of the high-temperature resistant sealing sleeve 11. The connecting mechanism 7 includes a movable cylinder 71 that is slidably and sealingly connected to the inner wall of the high-temperature resistant sealing sleeve 11. The bottom of the movable cylinder 71... The end is fixedly connected to the bottom end of the first high-temperature resistant rubber partition 5. The outer wall of the movable cylinder 71 located at the bottom end of the high-temperature resistant sealing sleeve 11 has two symmetrically distributed oil outlet holes 72. The upper surface of the movable cylinder 71 has a placement groove, and a hollow trigger rod 73 is inserted into the groove wall. The top wall of the hollow trigger rod 73 is movably sleeved with a connecting sleeve 74. The upper surface of the connecting sleeve 74 is fixedly connected with a threaded cover 75. The outer wall of the threaded cover 75 is movably sleeved with a sealing ring 76. The inner wall of the top end of the connecting cylinder 10 has a connecting thread that matches the thread on the outer wall of the threaded cover 75. The top end of the connecting cylinder 10 is fixedly connected to a special-shaped metal tube 77. The wall of the special-shaped metal tube 77 is fixedly sleeved with a U-shaped heat insulation cylinder 78. The wall of the U-shaped heat insulation cylinder 78 is fixedly connected to the outer wall of the top end of the oil-immersed transformer body 1. The outer walls of the two cylinder sides of the U-shaped heat insulation cylinder 78 have fixed round holes that match the wall of the special-shaped metal tube 77.

[0033] An oil-immersed transformer body 1 has a through hole on its upper surface, and an electronic pressure gauge 12 is fixedly connected to the wall of the through hole. A normally closed solenoid valve 13 is fixedly connected to the outer wall of the top of the connecting cylinder 10. A nitrogen storage mechanism 8 is fixedly connected to the outlet of the normally closed solenoid valve 13. The nitrogen storage mechanism 8 includes a heat-resistant gas pipe 81 fixedly connected to the outlet of the normally closed solenoid valve 13. A gas cylinder 82 is fixedly sleeved at the outlet of the heat-resistant gas pipe 81. The outer wall of the gas cylinder 82 is connected to the diffuser of the oil-immersed transformer body 1. The outer wall of the hot fin is fixedly connected, and the bottom end of the air cylinder 82 is provided with a fixed hole, and an electric push rod 83 is fixedly connected to the wall of the fixed hole. The moving end of the electric push rod 83 is fixedly connected to a sealing rubber piston 84. The outer wall of the sealing rubber piston 84 is slidably connected to the inner wall of the air cylinder 82. The top end of the air cylinder 82 is provided with a threaded hole, and an air injection nozzle 85 is threadedly sealed to the wall of the threaded hole. The top end of the air cylinder 82 is provided with a round hole, and a pressure sensor 86 is fixedly connected to the wall of the round hole.

[0034] A cooling mechanism 9 is fixedly connected to the bottom end of the oil-immersed transformer body 1. The cooling mechanism 9 includes a water tank 91 fixedly connected to the bottom end of the oil-immersed transformer body 1. A second high-temperature resistant rubber partition 92 is fixedly connected to the inner wall of the top of the water tank 91. The second high-temperature resistant rubber partition 92 divides the internal cavity of the water tank 91 into a storage area 93 and a water storage area 94. A threaded hole is opened on the upper surface of the water tank 91, and a threaded hollow ring 95 is threadedly sealed to the hole wall. A connecting pipe 96 is fixedly connected to the inner wall of the threaded hollow ring 95. The top end of the connecting pipe 96 is fixedly connected to the bottom end of the air cylinder 82. An air hole is opened at the bottom end of the air cylinder 82 that matches the top end of the connecting pipe 96. The discharge end of the irregular metal pipe 77 A conveying pipe 97 is fixedly connected to the bottom outer wall of the water tank 91 and communicates with the internal cavity of the storage area 93. The water outlet end of the conveying pipe 97 is fixedly connected to the outer wall of the U-shaped heat insulation cylinder 78. Multiple spray holes 98 are opened on the bottom outer wall of the U-shaped heat insulation cylinder 78. An L-shaped pipe 17 is fixedly connected to the upper surface of the water tank 91. The air inlet end of the L-shaped pipe 17 is connected to the internal cavity of the storage area 93. A pressure relief valve 18 is fixedly connected to the top wall of the L-shaped pipe 17. Two symmetrically distributed mounting brackets 19 are fixedly connected to the lower surface of the water tank 91. Fixed through holes are opened on both sides of the outer wall of the mounting brackets 19. A water replenishment valve 20 is fixedly connected to the outer wall of the water tank 91 located in the water storage area 94.

[0035] A control component 6 is fixedly connected to the upper surface of the cooling mechanism 9. The control component 6 includes a protective box 61 fixedly connected to the upper surface of the water tank 91. The top opening of the protective box 61 is sealed with a box cover 62 by bolts. A PLC controller 63 is fixedly connected to the inner wall of the protective box 61. A wire hole is opened on the side wall of the protective box 61, and a perforated rubber protective block 64 is fixedly connected to the wall of the wire hole.

[0036] The first high-temperature resistant rubber partition 5 divides the internal cavity of the oil reservoir 2 into an insulating oil area 15 and an air-filling area 16. The cavity of the insulating oil area 15 is connected to the internal cavity of the moving cylinder 71. The oil reservoir 2 has an oil filling hole on the side wall of the insulating oil area 15, and the hole wall of the oil filling hole is threadedly sealed with a sealing plug 21.

[0037] The electric push rod 83 and the normally closed solenoid valve 13 are electrically connected to the output terminal of the PLC controller 63 via wires, and the air pressure sensor 86 and the electronic pressure gauge 12 are electrically connected to the input terminal of the PLC controller 63 via wires. The above electrical components and electrical connections are all existing technologies and will not be described in detail here.

[0038] The operating principle of this invention is described as follows: Before the oil-immersed transformer is put into operation, the insulating oil zone 15 in the oil conservator 2 is first connected to the oil tank of the oil-immersed transformer body 1 through the oil conservator pipeline 4, thus establishing a complete path for the circulation of insulating oil and pressure transmission, solving the problem of transmission and compensation of oil level changes during transformer operation; then, insulating oil is filled into the insulating oil zone 15 and the oil tank through the filling hole on the side wall of the oil conservator 2, so that the insulating oil surface is tightly attached to the lower surface of the first high-temperature resistant rubber partition 5 without residual air gaps, and then the filling hole is sealed with the sealing plug 21 to prevent air from entering the oil body during operation and causing partial discharge hazards, ensuring stable insulation performance. Then, the assembly of the connecting mechanism 7 is completed, and the hollow trigger rod 73 is inserted into the placement groove at the top of the moving cylinder 71 (the hollow trigger rod 73 is made of tempered glass or other brittle and fragile special materials, is a disposable component, and has a rated pressure threshold of about 10 kPa, which can stably withstand normal operation). (Pressure, capable of instantaneous shattering under instantaneous impact of 60 kPa or higher), then the top end of the hollow trigger rod 73 is fixed to the top end of the connecting cylinder 10 via the threaded cap 75 and connecting sleeve 74. At this time, the oil outlet 72 on the outer wall of the moving cylinder 71 is completely within the sealing range of the high-temperature resistant sealing sleeve 11, ensuring complete isolation between the insulating oil area 15 and the shaped metal tube 77, guaranteeing the full sealing performance of the transformer during normal operation. Then, the air filling area 16 at the top of the oil reservoir 2 is connected through the... The air vent 22, the hollow outer cover 14 inner cavity, the connecting tube 10, the normally closed solenoid valve 13 that opens when energized, the heat-resistant air tube 81 and the air cylinder 82 form a fully sealed air passage. High-purity nitrogen with a purity of ≥99.99% is injected into the air cylinder 82 and the inflation zone 16 through the air injection nozzle 85 at the top of the air cylinder 82, so that the initial pressure in the inflation zone 16 is stabilized at a slight positive pressure of 3-5 kPa. This completely replaces the structure of the traditional respirator that connects to the outside world, and fundamentally prevents outdoor dust and moisture from entering.

[0039] Meanwhile, the pressure threshold and protection logic parameters are set in the PLC controller 63 of the control component 6. The air pressure sensor 86 collects the pressure data in the air cylinder 82 in real time and transmits it to the PLC controller 63. The PLC controller 63 is placed in a protective box 61 with a sealed protection. The rubber protective block 64 on the side wall of the protective box 61 can realize the sealed protection of the cable, prevent outdoor dust and moisture from entering and damaging the control components, and ensure the long-term stable operation of the control system in the outdoor environment.

[0040] Finally, open the water supply valve 20 on the side wall of the water tank 91 to fill the water storage area 94 inside the water tank 91 with cooling water. The interior of the water tank 91 is divided into the upper storage area 93 and the lower water storage area 94 by the second high-temperature resistant rubber partition 92. The discharge end of the irregular metal pipe 77 is connected to the storage area 93, and the delivery pipe 97 connects the water storage area 94 to the U-shaped heat insulation cylinder 78 sleeved on the outer wall of the irregular metal pipe 77, thus constructing a path for oil and gas cooling and oil tank cooling under fault conditions. After completing all initialization preparations, the transformer can enter the normal operation state.

[0041] During normal operation of the oil-immersed transformer, the PLC controller 63 controls the normally closed solenoid valve 13 to remain energized and conducting. Through the fully sealed nitrogen filling system, the transformer's internal pressure is adaptively balanced, completely replacing the pressure compensation function of the traditional breather. The transformer can operate stably without interacting with the outside air.

[0042] The specific working process is as follows: When the load on the oil-immersed transformer body 1 increases and the windings and core heat up, causing the insulating oil temperature to rise, the insulating oil volume expands due to heat. The excess insulating oil flows into the insulating oil area 15 of the oil storage tank 2 through the oil tank pipe 4, pushing the first high-temperature resistant rubber partition 5 to deform upwards, compressing the nitrogen in the upper inflation area 16, causing the pressure in the inflation area 16 and the air cylinder 82 to rise synchronously. After the pressure sensor 86 transmits the pressure exceeding the standard signal to the PLC controller 63 in real time, the PLC controller 63 immediately controls the electric push rod 83 of the nitrogen storage mechanism 8 to move, driving the sealing rubber piston 84 along the air cylinder. The inner wall of cylinder 82 moves downward, expanding its storage volume. This allows excess nitrogen in the filling zone 16 to flow back into cylinder 82 through the heat-resistant pipe 81, maintaining the internal pressure of the system within a preset stable range of 3–5 kPa. This solves the problem of internal pressure overpressure caused by rising oil temperature and prevents oil leakage from the seals due to pressure imbalance. When the load on the oil-immersed transformer body 1 decreases and the insulating oil temperature drops, the insulating oil volume shrinks. The first high-temperature resistant rubber separator 5 deforms downward with the oil surface, expanding the volume and reducing the pressure in the filling zone 16. The pressure sensor 86 transmits the low pressure signal to the PLC control unit. After the actuator 63 is activated, the PLC controller 63 immediately controls the electric push rod 83 to move the sealed rubber piston 84 upward, compressing the nitrogen in the air cylinder 82 and replenishing the inflation zone 16 with nitrogen to compensate for the volume change caused by the shrinkage of the insulating oil. Throughout the process, the first high-temperature resistant rubber layer 5 is kept in close contact with the insulating oil surface to avoid the formation of air gaps above the oil surface that could cause partial discharge and ensure long-term stability of insulation performance. During this process, the hollow trigger rod 73, relying on its rated pressure-bearing rigidity (e.g., 10 kPa), can stably withstand the slight positive pressure of 3–5 kPa in the insulating oil zone 15 without cracking or deforming. It maintains the limiting constraint on the moving cylinder 71 at all times, ensuring that the oil outlet 72 is always within the sealing range of the high-temperature resistant sealing sleeve 11, maintaining the fully sealed operating environment of the transformer. It fundamentally eliminates the inherent problems of traditional breathers, such as outdoor dust, willow catkins, mosquitoes blocking the breathing channel, and external moisture intrusion after the silica gel becomes saturated, leading to a drop in insulating oil breakdown voltage, oil oxidation and deterioration, and winding insulation breakdown. At the same time, it avoids faults such as oil leakage from the seal and abnormal oil level caused by pressure imbalance, which greatly reduces the frequency of outdoor transformer inspections and daily operation and maintenance costs, and ensures the long-term stable operation of the transformer without the need for a breather.

[0043] When an insulation breakdown short-circuit fault occurs inside the oil-immersed transformer body 1, a short-circuit current of tens of thousands of amperes is generated, forming a high-energy arc with an instantaneous temperature exceeding 3000℃. The high temperature of the arc instantly evaporates the surrounding insulating oil, rapidly generating high-pressure vapor bubbles. The incompressibility of the liquid insulating oil restricts the expansion of the bubble volume, causing the pressure inside the bubble to rise sharply, forming a dynamic pressure wave that propagates at high speed in the oil. This causes the pressure inside the oil tank to surge rapidly within 60–100 ms. At this time, the electronic pressure gauge 12 on the top of the oil-immersed transformer body 1 collects the pressure data inside the oil tank in real time and transmits it synchronously to the PLC controller 63. When the pressure inside the oil tank surges to 60 kPa (60% of the rated withstand strength of the oil tank of 98 kPa, with sufficient safety margin reserved), the high-pressure insulating oil rushes into the insulating oil area 15 of the oil storage tank 2 through the oil conservator pipe 4, generating a huge upward impact force on the first high-temperature resistant rubber partition 5 and the moving cylinder 71. This impact force far exceeds the rated withstand strength of the hollow trigger rod 73 (e.g., 1...). The high pressure of the oil (0 kPa) causes the hollow trigger rod 73 to shatter instantly, completely releasing the limiting constraint on the moving cylinder 71. Under the push of the high-pressure oil, the moving cylinder 71 slides upward along the inner wall of the high-temperature resistant sealing sleeve 11. The oil outlet 72, which was originally sealed, slides out of the high-temperature resistant sealing sleeve 11 completely, allowing the insulating oil zone 15 to be fully connected through the inner cavity of the moving cylinder 71, the oil outlet 72, the connecting cylinder 10, and the special-shaped metal tube 77. The high-pressure oil-gas mixture is instantly released into the special-shaped metal tube 77 within 1–3 ms and transported along the special-shaped metal tube 77 to the storage area 93 of the cooling mechanism 9. This quickly releases the accumulated pressure in the oil tank of the oil-immersed transformer body 1. Its response speed is much faster than that of traditional pressure relief valves. It can complete the core pressure relief within the golden window of 60 ms after the short circuit occurs, fundamentally preventing the oil tank pressure from exceeding the rated withstand strength of 98 kPa. This solves the problems of slow pressure relief speed of traditional breathers and the inability of conventional protection devices to act in time, which lead to stress concentration tearing of the right-angle weld of the oil tank and the bursting of the tank body.

[0044] While the mechanical passive pressure relief action is in progress, the PLC controller 63 simultaneously triggers the normally closed solenoid valve 13 to remain fully open, and controls the electric push rod 83 to drive the sealing rubber piston 84 to move rapidly downward to its maximum stroke, so that a negative pressure environment is formed in the upper cavity of the air cylinder 82. The nitrogen in the inflation zone 16 is quickly drawn back into the air cylinder 82 through the heat-resistant air pipe 81, so that the inflation zone 16 forms a negative pressure cavity. The first high-temperature resistant rubber partition 5 can deform significantly upward along the inner wall of the oil reservoir 2, so that the effective volume of the insulating oil zone 15 is significantly expanded instantaneously, further absorbing the impact energy of the high-pressure oil and reducing the pressure peak in the oil tank. This forms a dual explosion-proof protection of mechanical relief and volume expansion, greatly improving the safety redundancy under fault conditions. Meanwhile, as the sealing rubber piston 84 moves downward, the air at the bottom of the air cylinder 82 is injected into the storage area 93 at the top of the water tank 91 through the connecting pipe 96 and the threaded hollow ring 95. When the pressure relief valve 18 has not reached the opening threshold, the high-pressure nitrogen injected by the air cylinder 82, together with the high-pressure oil and gas input by the shaped metal pipe 77, squeezes the second high-temperature resistant rubber partition 92, causing the second high-temperature resistant rubber partition 92 to bulge downward, squeezing the cooling water in the water storage area 94 to be transported along the conveying pipe 97 to the interior of the U-shaped heat insulation cylinder 78. At this time, the flowing cooling water can perform forced heat exchange and cooling on the high-temperature oil and gas mixture inside the shaped metal pipe 77, so that the high-temperature vaporized insulating oil is quickly liquefied and restored to a liquid state upon cooling, avoiding the leakage of gaseous insulating oil and increasing the fire risk around the oil-immersed transformer body 1. At the same time, the combustible gas in the oil and gas completes the sedimentation and separation in the sealed shaped metal pipe 77 and the storage area 93, preventing the combustible gas from contacting the outside air and forming a deflagrative mixture.

[0045] After a short circuit fault occurs in the oil-immersed transformer body 1, within a certain period of time (e.g., 5 seconds), the differential protection and instantaneous overcurrent protection of the oil-immersed transformer body 1 have completed their actions, confirming that the high-voltage side is completely de-energized. This duration is also the time required for the cooling water in the water tank 91 to be transported along the conveying pipe 97 to the U-shaped heat insulation cylinder 78. After the cooling water that has completed heat exchange inside the U-shaped heat insulation cylinder 78 is sprayed out through the spray nozzles 98, evenly spraying it onto the heat dissipation fins and outer wall of the oil-immersed transformer body 1, accelerating the reduction of the surface temperature of the oil-immersed transformer body 1. Since the outer shell of the oil tank of the oil-immersed transformer body 1 is made of metal, the sprayed cooling water is rapidly evaporated on the high-temperature tank surface. During the evaporation process, the residual heat of the insulating oil inside the oil-immersed transformer body 1 is further removed, providing convenience for subsequent maintenance work of the oil-immersed transformer. At the same time, it effectively avoids the risk of electric shock and flashover caused by spraying water while the circuit is energized, which complies with the requirements of power safety regulations.

[0046] Subsequently, when the pressure in the storage area 93 exceeds the preset threshold of 80 kPa of the pressure relief valve 18, the pressure relief valve 18 on the L-shaped pipe 17 connected to the storage area 93 automatically opens, safely and slowly releasing the combustible gas diluted with nitrogen in the storage area 93, preventing the combustible gas from accumulating in the sealed cavity to reach the explosion limit and causing a deflagration accident; the liquefied insulating oil is retained in the sealed storage area 93, realizing the fully enclosed recovery of the faulty insulating oil, which not only avoids the fire risk caused by the leakage of high-temperature oil, but also allows the recovered insulating oil to be filtered, degassed, and regenerated after the fault, and can be reused after passing the test, greatly reducing the waste of insulating oil consumables and reducing the material cost after the fault.

[0047] After maintenance personnel have completed troubleshooting the oil-immersed transformer, it can be quickly restored to operation through a simplified maintenance process. This eliminates the need for extensive disassembly and repair of the transformer body 1's oil tank and oil conservator 2. Simply open the threaded cap 75 at the top of the connecting cylinder 10, replace the broken hollow trigger rod 73, and reset the connecting mechanism 7 to its initial state, returning the oil outlet 72 to the sealing range of the high-temperature sealing sleeve 11. This significantly reduces the difficulty and cost of maintenance. Subsequently, the threaded hollow ring 95 is removed, and the insulating oil recovered from the storage area 93 is extracted, filtered, degassed, and regenerated. After processing and passing the inspection, the oil is re-injected into the oil reservoir 2 and the oil tank. Sufficient cooling water is added to the water storage area 94 through the water replenishment valve 20. Then, the electric push rod 83 and the normally closed solenoid valve 13 are energized and reset by the PLC controller 63. The electric push rod 83 pushes the sealing rubber piston 84 upward, so that the high-purity nitrogen in the air cylinder 82 returns to the filling area 16 along the heat-resistant air pipe 81, and the nitrogen pressure in the filling area 16 is replenished to the preset value of 3-5 kPa. After the insulation performance, sealing performance and pressure control performance are fully tested and qualified, the operation and maintenance cost of the equipment throughout its entire life cycle is significantly reduced.

[0048] 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, 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 nitrogen-filled sealed oil-immersed transformer, comprising an oil-immersed transformer body (1), an oil conservator (2), an oil conservator support (3), and oil conservator piping (4), characterized in that, The inner wall of the oil storage pillow (2) is fixedly connected to a first high-temperature resistant rubber partition (5), and the upper surface of the oil storage pillow (2) is fixedly connected to a hollow outer cover (14). The outer wall of the oil storage pillow (2) located inside the hollow outer cover (14) is provided with multiple ventilation holes (22). The upper surface of the hollow outer cover (14) is provided with a round hole, and the hole wall of the round hole is fixedly connected to a connecting cylinder (10). The bottom end of the connecting cylinder (10) penetrates the top inner wall of the oil storage pillow (2). The top end of the oil storage pillow (2) is provided with a fixing hole that matches the bottom outer wall of the connecting cylinder (10). The bottom inner wall of the connecting cylinder (10) is provided with an installation groove, and the groove wall of the installation groove is fixedly connected to a high-temperature resistant sealing sleeve (11). The inner wall of the high-temperature resistant sealing sleeve (11) is slidably connected to a connecting mechanism (7). The upper surface of the oil-immersed transformer body (1) is provided with a through hole, and an electronic pressure gauge (12) is fixedly connected to the hole wall. The top outer wall of the connecting cylinder (10) is fixedly connected to a normally closed solenoid valve (13), and the outlet end of the normally closed solenoid valve (13) is fixedly connected to a nitrogen storage mechanism (8). A cooling mechanism (9) is fixedly connected to the bottom end of the oil-immersed transformer body (1). The upper surface of the cooling mechanism (9) is fixedly connected to a control component (6).

2. The nitrogen-filled sealed oil-immersed transformer according to claim 1, characterized in that, The communication mechanism (7) includes a movable cylinder (71) that is slidably and sealingly connected to the inside of the high-temperature resistant sealing sleeve (11). The bottom end of the movable cylinder (71) is fixedly connected to the bottom end of the first high-temperature resistant rubber partition (5). The outer wall of the movable cylinder (71) at the bottom end of the high-temperature resistant sealing sleeve (11) has two symmetrically distributed oil outlet holes (72). The upper surface of the movable cylinder (71) has a placement groove, and a hollow trigger rod (73) is inserted into the groove wall. The top wall of the hollow trigger rod (73) is movably sleeved with a connecting sleeve (74). The upper surface of the connecting sleeve (74) is fixedly connected with a screw. The outer wall of the threaded cover (75) is movably fitted with a sealing ring (76). The inner wall of the top end of the connecting cylinder (10) is provided with a connecting thread that matches the thread on the outer wall of the threaded cover (75). The top end of the connecting cylinder (10) is fixedly connected to a shaped metal tube (77). The wall of the shaped metal tube (77) is fixedly fitted with a U-shaped heat insulation cylinder (78). The wall of the U-shaped heat insulation cylinder (78) is fixedly connected to the outer wall of the top end of the oil-immersed transformer body (1). The outer walls of the two cylinder sides of the U-shaped heat insulation cylinder (78) are provided with fixed round holes that match the wall of the shaped metal tube (77).

3. A nitrogen-filled sealed oil-immersed transformer according to claim 2, characterized in that, The nitrogen storage mechanism (8) includes a heat-resistant gas pipe (81) fixedly connected to the outlet end of a normally closed solenoid valve (13). A gas cylinder (82) is fixedly sleeved at the outlet end of the heat-resistant gas pipe (81). The outer wall of the gas cylinder (82) is fixedly connected to the outer wall of the heat dissipation fins of the oil-immersed transformer body (1). A fixed hole is opened at the bottom end of the gas cylinder (82), and an electric push rod (83) is fixedly connected to the hole wall. A sealing rubber piston (84) is fixedly connected to the moving end of the electric push rod (83). The outer wall of the sealing rubber piston (84) is slidably connected to the inner wall of the gas cylinder (82). A threaded hole is opened at the top end of the gas cylinder (82), and an air injection nozzle (85) is threadedly sealed to the hole wall. A round hole is opened at the top end of the gas cylinder (82), and a pressure sensor (86) is fixedly connected to the hole wall of the round hole.

4. A nitrogen-filled sealed oil-immersed transformer according to claim 3, characterized in that, The cooling mechanism (9) includes a water tank (91) fixedly connected to the bottom of the oil-immersed transformer body (1). A second high-temperature resistant rubber partition (92) is fixedly connected to the inner wall of the top of the water tank (91). The second high-temperature resistant rubber partition (92) divides the internal cavity of the water tank (91) into a storage area (93) and a water storage area (94). A threaded hole is provided on the upper surface of the water tank (91), and a threaded hollow ring (95) is threadedly sealed to the hole wall. A connecting pipe (96) is fixedly connected to the inner wall of the threaded hollow ring (95). The top end of the connecting pipe (96) is fixedly connected to the bottom end of the air cylinder (82). The bottom end of the air cylinder (82) is provided with an air hole that matches the top end of the connecting pipe (96). The discharge end of the irregular metal pipe (77) passes through the inner wall of the top end of the water tank (91) and is connected to the internal cavity of the storage area (93). The bottom outer wall of the water tank (91) is fixedly connected to the conveying pipe (97). The water outlet end of the conveying pipe (97) is fixedly connected to the outer wall of the U-shaped heat insulation cylinder (78). The bottom outer wall of the U-shaped heat insulation cylinder (78) is provided with multiple spray holes (98).

5. A nitrogen-filled sealed oil-immersed transformer according to claim 2, characterized in that, The first high-temperature resistant rubber partition (5) divides the internal cavity of the oil storage pillow (2) into an insulating oil area (15) and an air filling area (16). The cavity of the insulating oil area (15) is connected to the internal cavity of the moving cylinder (71). The oil storage pillow (2) has an oil filling hole on the side wall of the insulating oil area (15), and the hole wall of the oil filling hole is threadedly sealed with a sealing plug (21).

6. A nitrogen-filled sealed oil-immersed transformer according to claim 4, characterized in that, The control component (6) includes a protective box (61) fixedly connected to the upper surface of the water tank (91). The top opening of the protective box (61) is sealed with a box cover (62) by bolts. A PLC controller (63) is fixedly connected to the inner wall of the protective box (61). A wire hole is opened on the side wall of the protective box (61), and a perforated rubber protective block (64) is fixedly connected to the hole wall of the wire hole.

7. A nitrogen-filled sealed oil-immersed transformer according to claim 4, characterized in that, The upper surface of the water tank (91) is fixedly connected to an L-shaped pipe (17), the air inlet of the L-shaped pipe (17) is connected to the internal cavity of the storage area (93), and a pressure relief valve (18) is fixedly connected to the top wall of the L-shaped pipe (17).

8. A nitrogen-filled sealed oil-immersed transformer according to claim 4, characterized in that, The lower surface of the water tank (91) is fixedly connected to two symmetrically distributed mounting brackets (19). The outer walls of both sides of the mounting brackets (19) are provided with fixed through holes. The outer wall of the water tank (91) located in the water storage area (94) is fixedly connected to a water supply valve (20).

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