A method for replacing the neutral point bushing of a converter transformer with a small oil drain

Abstract

The invention discloses a method for replacing the neutral point bushing of a converter transformer with small oil drainage; it relates to the technical field of substation maintenance; the method uses an oil level maintaining tool and a guide rod limiting tool, the guide rod limiting tool includes two limiting rods, the limiting rods are provided with a semicircular notch, the two limiting rods can be spliced, and the two notches are spliced ​​together to form a through hole; the oil level maintaining tool includes a cylinder, the bottom surface of the cylinder is provided with a mounting flange, the bottom side wall is provided with an oil filling and draining valve, the middle side wall is provided with an oil level maintaining valve, and the top is provided with a hanging point; the application uses the setting of the oil level maintaining tool to ensure that the "straw hat" structure of the grid-side high-voltage bushing is always wrapped by the converter transformer oil when the bushing is disassembled, thereby avoiding the exposure of the straw hat structure; therefore, in the subsequent bushing replacement process, there is no need to drain the oil of the converter transformer as a whole and then perform full vacuum oil filling, which saves a lot of time; at the same time, when replacing the bushing, the guide rod limiting tool is used, and when replacing the bushing, the guide rod copper rod is fixed to prevent the lead from being damaged by downward pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of substation maintenance, in particular to a method for replacing a neutral point bushing of a commutator transformer with a small oil drain. Background Art

[0002] Many converter transformer neutral point bushings use ABB glue-impregnated paper dry bushings. Obvious cracks have been found on the dry bushing's silicone rubber sheds and the corresponding internal epoxy resin tubes on several occasions, necessitating replacement of the neutral point bushings.

[0003] observe Figure 1 When the converter transformer is operating normally, the left neutral point bushing is full of oil, and the body is also full of oil. At this time, the "straw hat" structure of the grid-side high-voltage bushing is soaked in oil; when replacing the neutral point bushing of the converter transformer, since the paper insulation grading ring of the grid-side high-voltage bushing "straw hat" structure is higher than the neutral point bushing mounting flange surface, the straw hat structure will inevitably be exposed. However, according to the requirements of the ABB manufacturer, after the insulating parts of the converter transformer are exposed, the oil must be drained as a whole before full vacuum oil filling; at the same time, since the current-carrying guide rod of the neutral point bushing is heavy, it is necessary to enter to assist in the disassembly and assembly of the bushing. Therefore, the converter transformer is drained as a whole and then oiled. The whole process takes about 15 days; not only is the replacement efficiency slow, but there are also safety hazards. Summary of the Invention

[0004] In order to speed up the replacement of the neutral point bushing of a converter transformer, the present application provides a method for replacing the neutral point bushing of a converter transformer by draining oil.

[0005] The present application provides a method for replacing the neutral point bushing of a converter transformer by draining oil, which adopts the following technical solution:

[0006] A method for replacing a small oil drain on a neutral point bushing for a converter transformer is provided, which includes a guide rod limiting tool and an oil level maintaining tool. The oil level maintaining tool is used to prevent a straw hat structure from being exposed, and the guide rod limiting tool is used to prevent the guide rod from falling. The guide rod limiting tool includes two limiting rods, each having a semicircular notch formed thereon. The two limiting rods can be spliced ​​together by a screw rod, and the two notches are spliced ​​together to form a through hole.

[0007] The oil level maintaining tooling comprises a cylinder, the bottom surface of which is provided with a mounting flange, the bottom side wall is provided with an oil filling and draining valve, the middle side wall is provided with an oil level maintaining valve, and the top side wall is provided with a hanging point;

[0008] Replacing the casing involves the following steps:

[0009] S1. Clean the machines and work sites;

[0010] S2. Install the oil level monitoring device: Close the gate valve on the pipeline from the main body to the oil pillow, and install a transparent tube at the gas position next to the pressure regulating switch to the elevated seat on the side of the network;

[0011] S3. Remove the casing general cap, install the casing professional lifting device, install the oil level maintaining tooling, and inject a certain amount of oil into the cylinder;

[0012] S4. Lift the casing. When the guide rod leaks out, install the guide rod limit fixture.

[0013] S5. Continue to slowly lift the casing until the top of the guide rod is completely exposed, then remove the guide rod traction rope, lift off the old casing, and place a sealing gasket in the casing flange hole;

[0014] S6. Lift the new casing and install the traction rope;

[0015] S7. Slowly lower the new casing. When it reaches a certain height, remove the guide rod limit fixture.

[0016] S8. Hold the traction rope tightly, install the new casing and copper rod, and complete the exhaust of the new casing;

[0017] S9. After draining the oil, remove the oil level maintaining tooling and complete the cleaning work; then open the oil pillow to the main body valve and restore the converter to the operating state.

[0018] Optionally, the step S1 specifically includes: cleaning the tooling, hooks and slings, sleeves and flange surfaces with alcohol and cotton gauze; and cleaning the tools that need to be used in oil with oil.

[0019] Optionally, connect the mounting flange on the oil level maintaining fixture to the flat-top flange surface with bolts, connect the oil filling and draining valve to the flange of the gas relay next to the converter transformer voltage regulating switch, and connect the oil level maintaining valve to the oil tank; fill oil into the cylinder. If the height difference between the straw hat structure and the flat top of the converter transformer is h, the oil level in the cylinder is 1.5h; after the oil filling is completed, shake the casing slightly, and proceed to the subsequent steps after the oil level stabilizes.

[0020] Optionally, the casing lifting in step S4 is specifically as follows: keep the oil pillow pipeline valve slightly open to allow the oil to slowly overflow from the casing flange, and slowly lift the neutral point casing; after the bottom of the casing leaves the flat top, close the oil pillow pipeline gate valve, lift the bottom of the casing until the sealing plate is completely separated from the flat top, check the oil level status in the tooling again, and use the flange mouth sealing plate to seal the casing flange hole.

[0021] Optionally, the installation of the guide rod limiting tooling in step S4 is specifically as follows: assembling two limiting rods, both limiting rods are mounted on the cylinder, allowing the guide rod to pass through the through hole on the limiting rod, and installing a clamp on the guide rod.

[0022] Optionally, step S6 specifically includes: hanging the new casing to the upper part of the guide rod, passing one end of the traction rope through the guide rod hole of the new casing, connecting the other end with a special bolt, and screwing the special bolt into the threaded hole at the top of the guide rod.

[0023] Optionally, step S7 is specifically as follows: slowly lower the casing, and when it reaches a height of 600 mm, tighten the traction rope to prevent the guide rod from being pressed down, remove the guide rod limit tooling and flange hole sealing plate, install the sealing gasket, and pay attention to the oil level to maintain the oil level in the tooling and the oil level of the mesh side riser.

[0024] Optionally, step S8 specifically includes: after the casing is lowered into place, installing the flange bolts and tightening them evenly; then slowly opening the oil pillow to the main body valve, observing that oil is flowing out from the guide rod at the top of the neutral point casing, closing the oil pillow to the main body valve, and installing the general cap of the new casing.

[0025] In summary, this application has the following beneficial technical effects:

[0026] The present application sets up an oil level maintaining tool so that the "straw hat" structure of the grid-side high-voltage bushing is always wrapped by the converter transformer oil when the bushing is removed, thereby preventing the straw hat structure from being exposed; therefore, in the subsequent bushing replacement process, there is no need to drain the oil of the converter transformer as a whole and then perform full vacuum oil filling, which saves a lot of time; at the same time, when replacing the bushing, a guide rod limiting tool is used, and when replacing the bushing, the guide rod copper rod is fixed to prevent the lead from being damaged by downward pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a rough overall structural diagram of the current converter transformer;

[0028] Figure 2 This is an overall structural diagram of the tooling used in a method for replacing a small oil drain on a neutral point bushing for a converter transformer according to the present application;

[0029] Figure 3 This is the overall structural diagram of the oil level maintenance tooling of this application;

[0030] Figure 4 This is the overall structural diagram of the guide rod limiting tooling of this application.

[0031] Description of reference numerals:

[0032] 1. Guide rod; 2. Oil level holding fixture; 201. Cylinder; 202. Mounting flange; 203. Oil filling and discharge valve; 204. Oil level holding valve; 205. Lifting point; 3. Guide rod limit fixture; 301. Limit rod; 302. Clamp; 303; Screw. DETAILED DESCRIPTION

[0033] The following is combined with Figure 1-4 This application is described in further detail.

[0034] An embodiment of the present application discloses a method for replacing the small oil drain of the neutral point bushing of a converter transformer. The method uses an oil level maintaining tool 2 and a guide rod 1 limiting tool. The guide rod 1 limiting tool includes two limiting rods 301. The limiting rods 301 are provided with a semicircular notch. The two limiting rods 301 can be spliced ​​by a screw 303, and the two notches are spliced ​​together to form a through hole; the oil level maintaining tool 2 includes a cylinder 201, and the bottom surface of the cylinder 201 is provided with a mounting flange 202, the bottom side wall is provided with an oil filling and drain valve 203, the middle side wall is provided with an oil level maintaining valve 204, and the top is provided with a hanging point 205.

[0035] The method includes the following steps:

[0036] S1. Clean the machines and work sites;

[0037] S11. Tool cleaning: Use alcohol and cotton gauze to wipe the inner wall and flange surface of the tool to ensure that it is clean and free of impurities; use alcohol and cotton gauze to wipe the crossarms, clamps, fixing bolts, etc.

[0038] S12. Cleaning of equipment: Wipe hooks, slings, etc. with alcohol, and wrap the surfaces of large and small hooks with plastic cloth; use clean lifting ropes and pull ropes; use oil to clean tools that need to be used in oil.

[0039] S13. Casing cleaning: Wipe the silicone rubber shed of the casing with alcohol and cotton gauze, and wrap the surface of the casing with plastic cloth.

[0040] S14. Flange Cleaning: To prevent impurities and rust on the screw holes, screws, and nuts from dissolving in the oil after the casing flange bolts are removed, replace the bolt set and clean the screw holes before oiling the installation tool. First, replace the diagonal bolts #1 and #5, #3 and #7, and the grounding bolt, followed by the diagonal bolts #2 and #6, and #4 and #8 to prevent oil leakage. After removing the old bolts, blow out the screw holes with high-pressure air and then clean them with dough to ensure they are clean and free of impurities. After replacing the bolts, tighten them securely.

[0041] Since the gap between the sleeve flange surface and the CT flange surface is small and difficult to clean, it is necessary to blow the gap with high-pressure air during the removal of the bolts; then use cotton gauze to clean the sleeve and CT flange surface, and then use dough to stick the flange surface to ensure that there are no tiny impurities remaining on the flange surface.

[0042] S15. Cleaning after the tooling is reinstalled: Remove 8 bolts from the CT flange surface at the following intervals, hoist the tooling, install it with a long screw, and clean the sealing gasket; after the tooling is installed, clean the internal parts of the tooling with oil, rinse twice, and drain the oil to ensure that there are no impurities at the work point.

[0043] S2. Install an oil level monitoring device: Close the gate valve on the pipeline from the main body to the oil pillow, and install a transparent tube at the gas point next to the pressure regulating switch to the mesh side riser to observe the oil level in the mesh side riser to prevent the "straw hat" structure from being exposed.

[0044] S3. Remove the casing general cap to prevent the oil seeping here from flowing into the tooling along the casing surface, install a clean casing special hoist to prevent impurities from contaminating and install the casing professional hoist, install the oil level maintaining tooling, connect the mounting flange on the oil level maintaining tooling to the flat-top flange surface with bolts, connect the oil filling and draining valve to the gas relay flange next to the converter transformer pressure regulating switch, connect the oil level maintaining valve to the external oil tank, and then inject a certain amount of oil into the cylinder; considering that the "straw hat" structure is 200mm higher than the converter transformer flat top, during the casing replacement process, in order to ensure the normal work, prevent the oil level fluctuation from causing the oil level of the grid side riser to drop, resulting in the "straw hat" being exposed, and set the oil level in the tooling to 300mm. During the casing replacement process, a dedicated person is assigned to monitor the oil level throughout the process, and the oil level is adjusted through the pressure regulating switch gas relay valve and the tooling oil level control valve to always keep the oil level in the tooling at 300mm.

[0045] After filling the tooling with oil to 300mm, remove the six bolts on the neutral point bushing flange (leave two diagonally), then slowly remove the two diagonally bolts and slightly shake the bushing to prevent a large amount of insulating oil from gushing out. Wait until the oil level in the tooling remains stable before starting to lift the bushing.

[0046] S4. Lift the casing. When the guide rod leaks, install the guide rod limit fixture, keep the oil pillow pipe valve slightly open, and allow the oil to slowly overflow from the casing. Slowly lift the neutral point casing to ensure that the external insulating oil of the converter transformer will not flow back into the main body oil tank during the casing lifting process, affecting the cleanliness of the main body insulating oil. During the lifting process, assign dedicated personnel to operate the casing guide rod traction device and monitor the traction status to prevent the guide rod from sliding down. When the bottom of the casing is lifted until the sealing plate is completely separated from the flat top, check the oil level in the fixture again, and use the flange hole sealing plate to cover the casing flange hole.

[0047] Then assemble the two limit rods, both of which are mounted on the cylinder, so that the guide rod passes through the through hole on the limit rod, and at the same time install a clamp on the guide rod; continue to slowly lift the casing until the top of the guide rod is completely exposed, remove the guide rod traction rope, lift off the old casing, and place a sealing gasket on the casing flange.

[0048] S5. Continue to slowly lift the casing until the top of the guide rod is completely exposed, then remove the guide rod traction rope, lift off the old casing, and place a sealing gasket in the casing flange hole;

[0049] S6. Lift the new casing and install the traction rope. Lift the new casing to the top of the guide rod. Pass one end of the traction rope through the guide rod hole of the new casing and connect the other end to the special bolt. Screw the special bolt into the threaded hole at the top of the guide rod.

[0050] S7. Slowly lower the casing. When it reaches a height of 600mm, tighten the traction rope to prevent the guide rod from being pressed down. Remove the guide rod limit fixture and flange hole sealing plate, install the sealing gasket, and pay attention to the oil level in the fixture and the oil level in the riser on the mesh side.

[0051] S8. After the casing is lowered into place, install the flange bolts and tighten them evenly. Then slowly open the oil pillow to the body valve. After observing oil coming out from the guide rod at the top of the neutral point casing, close the oil pillow to the body valve to complete the casing exhaust. Then install the new casing's general cap.

[0052] S9. After draining the oil, remove the oil level maintaining tooling and complete the cleaning work; then open the oil pillow to the main body valve and restore the converter to the operating state.

[0053] In an embodiment of the present application, a method for replacing the neutral point bushing of a converter transformer with a small amount of oil is used. Due to the provision of an oil level maintaining tooling, the "straw hat" structure of the grid-side high-voltage bushing is always wrapped by the converter transformer oil when the bushing is removed, thereby preventing the straw hat structure from being exposed; therefore, in the subsequent bushing replacement process, there is no need to drain the oil of the converter transformer as a whole and then perform full vacuum oil filling, which saves a lot of time; at the same time, when replacing the bushing, a guide rod limiting tooling is used, and when replacing the bushing, the guide rod copper rod is fixed to prevent the lead from being damaged by downward pressure.

[0054] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A method for replacing the neutral point bushing of a converter transformer by draining oil, characterized by: The application includes a guide rod limiting tool and an oil level maintaining tool. The oil level maintaining tool is used to prevent the straw hat structure from being exposed, and the guide rod limiting tool is used to prevent the guide rod from falling. The guide rod limiting tool includes two limiting rods, each of which has a semicircular notch. The two limiting rods can be spliced ​​together by a screw rod, and the two notches are spliced ​​together to form a through hole. The oil level maintaining tooling comprises a cylinder, the bottom surface of which is provided with a mounting flange, the bottom side wall is provided with an oil filling and draining valve, the middle side wall is provided with an oil level maintaining valve, and the top is provided with a hanging point; Replacing the casing involves the following steps: S1. Clean the machines and work sites; S2. Install the oil level monitoring device: Close the gate valve on the pipeline from the main body to the oil pillow, and install a transparent tube at the gas position next to the pressure regulating switch to the elevated seat on the side of the network; S3. Remove the casing general cap, install the casing professional lifting device, install the oil level maintaining tooling, and inject a certain amount of oil into the cylinder; S4. Lift the casing. When the guide rod leaks out, install the guide rod limit fixture. S5. Continue to slowly lift the casing until the top of the guide rod is completely exposed, then remove the guide rod traction rope, lift off the old casing, and place a sealing gasket in the casing flange hole; S6. Lift the new casing and install the traction rope; S7. Slowly lower the new casing. When it reaches a certain height, remove the guide rod limit fixture. S8. Hold the traction rope tightly, install the new casing and copper rod, and complete the exhaust of the new casing; S9. After draining the oil, remove the oil level maintaining tooling and complete the cleaning work; then open the oil pillow to the main body valve and restore the converter to the operating state.

2. A method for replacing the neutral point bushing of a converter transformer according to claim 1, characterized in that The step S1 specifically includes: cleaning the tooling, hooks, slings, sleeves and flange surfaces with alcohol and cotton gauze; and cleaning the tools that need to be used in oil with oil.

3. A method for replacing the neutral point bushing of a converter transformer with a small oil drain according to claim 2, characterized in that Step S3 specifically includes: connecting the mounting flange on the oil level maintaining tool to the flat-top flange surface with bolts, connecting the oil filling and draining valve to the flange of the gas relay next to the converter transformer voltage regulating switch, and connecting the oil level maintaining valve to the oil tank; filling oil into the cylinder; if the height difference between the straw hat structure and the flat top of the converter transformer is h, the oil level in the cylinder is 1.5h; after the oil filling is completed, slightly shake the casing, and proceed to the subsequent steps after the oil level stabilizes.

4. A method for replacing a neutral point bushing for a converter transformer according to claim 3, characterized in that The specific steps for lifting the casing in step S4 are as follows: keep the oil pillow pipeline valve slightly open to allow the oil to slowly overflow from the casing flange, and slowly lift the neutral point casing; after the bottom of the casing leaves the flat top, close the oil pillow pipeline gate valve, lift the bottom of the casing until the sealing plate is completely separated from the flat top, check the oil level status in the tooling again, and use the flange hole sealing plate to seal the casing flange hole.

5. A method for replacing the neutral point bushing of a converter transformer with a small oil drain according to claim 4, characterized in that The specific steps of installing the guide rod limiting tooling in step S4 are as follows: assembling two limiting rods, both of which are mounted on the cylinder, passing the guide rod through the through hole on the limiting rod, and installing a clamp on the guide rod.

6. A method for replacing the neutral point bushing of a converter transformer with a small oil drain according to claim 5, characterized in that Step S6 specifically includes: hanging the new casing to the upper part of the guide rod, passing one end of the traction rope through the guide rod hole of the new casing, connecting the other end with a special bolt, and screwing the special bolt into the threaded hole at the top of the guide rod.

7. A method for replacing the neutral point bushing of a converter transformer according to claim 6, characterized in that Step S7 is specifically as follows: slowly lower the casing, and when it reaches a height of 600 mm, tighten the traction rope to prevent the guide rod from being pressed down, remove the guide rod limit fixture and flange hole sealing plate, install the sealing gasket, and pay attention to the oil level to maintain the oil level in the fixture and the oil level of the mesh side riser.

8. A method for replacing the neutral point bushing of a converter transformer with a small oil drain according to claim 7, characterized in that Step S8 specifically includes: after the casing is lowered into place, the flange bolts are installed and tightened evenly; then the oil pillow is slowly opened to the main body valve, and after oil is observed to flow out from the guide rod at the top of the neutral point casing, the oil pillow is closed to the main body valve, and the general cap of the new casing is installed.

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