When the transformer is overhauled, the on-load tap-changer undergoes the process of disassembly, inspection and reloading. The overhaul items are as follows:
What should be paid attention to in the "technical" transformer on-load tap-changer?
1. Inspection, maintenance and commissioning of the core of the tap changer core.
2. Cleaning, leak detection and maintenance of the tap-changer oil compartment.
3. Drive mechanism inspection, cleaning, refueling and maintenance
4. Inspection and maintenance of oil storage cabinets and their accessories
5. Inspection, maintenance and verification of oil flow control relays (or gas relays), over-pressure relays and pressure relief devices.
6. Inspection of automatic control device.
7. Treatment of insulating oil in oil conservator and oil room
8. Inspection, maintenance and commissioning of motor-drive mechanisms and other devices.
9. Seal inspection of all parts and oil leakage treatment.
10. Inspection, maintenance and commissioning of electrical control circuits.
11. Connection verification and debugging of the tap changer and motor-drive mechanism.
First, the main operating points of the on-load tap-changer
1, combined on-load tap-changer installation
(1) Unscrew the bolts that secure the switch head cover, and then remove the switch head cover, taking care to protect the seal gasket.
(2) Check if the notch on the drive shaft of the diverter switch and the triangular mark on the support plate are aligned.
(3) Remove the locking tab of the position indicator disc and then remove the tap position indicator disc.
(4) Remove the nut that connects the main body of the diverter switch to the support plate. Hang the wire on the suspension line of the diverter switch and carefully lift the diverter switch body vertically. After lifting out the oil chamber, place it on a platform covered with plastic sheets or on a flat surface.
(5) Remove the suction pipe and take it out of the oil compartment.
(6) Check if the diverter switch oil compartment is clean. If it is not clean, it should be cleaned up.
(7) Use a special hanging plate to traverse the oil chamber, so that the support flange is focused, so as to hang the tap changer. Then unscrew the connecting bolts of the intermediate flange and the support flange to separate the two.
(8) Gently lower the hanging plate until the supporting flange will attach the tap-changer bracket to the bracket mounted on the body, and then the fuel-saving tank can be lifted.
(9) After lifting the mailbox of the previous section, do the following checks on the selector:
1) Check if the connecting wire (copper rod) of the selector and the switch is loose.
2) Check if the contact between the tap wire and the selector static contact is good and the pressure equal cover is complete.
3) Check that the tap leads are subjected to horizontal tension (the horizontal pull should be close to zero).
4) Check if the contact line of the selector moving contact is located in the cylindrical part of the static contact and not less than 2 mm from the spherical part of the fixed contact.
(10) Connect the bridge on the fixed main arc contact and the fixed transition contact or use a multimeter to measure the resistance value of the transition resistance. The measured value shall deviate from the nominal value on the nameplate within ±10%.
(11) After the upper fuel tank is reinstalled, the oil chamber of the diverter switch should be inspected and cleaned again, rinsed with clean oil, and then the suction pipe is installed.
(12) Lift the tap changer with a special lifting plate to restore the connection between the intermediate flange and the support flange, and make the seal good.
(13) Lift the diverter switch and carefully drop it into the oil chamber. In order to ensure the fit of the coupling, the switch insulation shaft should be gently rotated to embed the coupling and bring the diverter switch into position.
(14) Reload the nut of the fixing bolt on the support plate to fix the switch to the support plate.
(15) Reload the position indicator plate and attach the shaft lock piece.
(16) Reinstall the switch head cover, tighten all the bolts on the switch head cover to make it firmly connected with the switch head flange, and ensure a good seal.
(17) A bypass pipe is arranged on the pipe joint of the switch head flange and the pipe connecting the transformer tank, so that the diverter switch oil chamber communicates with the inside of the transformer tank, so that the oil chamber and the oil tank are simultaneously vacuum-filled. When the vacuum is filled into the venting plug on the switch head cover, the bypass pipe should be removed, the sealing plate should be added, and then the vacuum filling should be continued.
(18) Install the worm gear box and the bevel gear box, install the horizontal shaft and the vertical drive shaft with the coupling chuck, and install the rain cover.
(19) Switch between the positive and negative directions by manual operation to check the symmetry of the transmission mechanism. If it is asymmetrical, the vertical drive shaft should be loosened and adjusted until the number of rotations of the forward and reverse switches does not differ by more than one revolution.
(20) First, manually switch the operation, and then use the motor-drive mechanism to perform the switching operation. Check that at each tap position, the tap indicator and the motor-drive mechanism position indicator are in the same position.
2, composite on-load tap-changer installation
The utility model is characterized in that the direct switching selection switch and the switching switch are integrated into one body, the oil of the tap change switch oil tank is isolated from the oil of the transformer body, and the switching operation is completed at the same time of tapping selection, so the volume is large, since the pressure regulation is completed once, the structure Simple, low cost, simple operation process, suitable for transformers with low current and low voltage. It is generally used on on-load voltage regulating transformers with fewer voltage tapping stages (more than 7 levels). The steps to install the composite on-load tap-changer are as follows:
(1) Adjust the tap position to the rated tap position.
(2) Remove the switch head cover and drain or deflate before disassembling
(3) Loosen the joint nut of the suction pipe elbow.
(4) Move the matching body of the counter into the switch head.
(5) Remove the lock screw of the gear mechanism from the switch head and loosen the spring.
(6) Remember the position mark of the gear mechanism, remove the fixing screw of the gear mechanism, and then pull up the gear mechanism. Record the position of the support rail.
(7) Disassemble the suction pipe. When pulling, first insert the screwdriver into the previous slot, pick up the suction pipe, then grab the second slot by hand and pull out the suction pipe.
(8) Fix the special spreader with the 3 screws to the end face of the joint of the selector switch. The stop plate of the spreader must be inserted into the intersection between the support rails.
(9) Turn the spreader clockwise so that the movable contact of the selector is located between the two phases, that is, at the lifting position.
(10) Hang the hanging object on the spreader and slowly and carefully pull out the selector switch body. During the drawing process, pay attention to the gap between the moving contact and the equalizing ring and the oil chamber to avoid collision.
(11) Place the selector switch body at the inspection site for inspection and cleaning.
(12) Screw the four M8 screws on the special tool of the lifting oil chamber into the screw holes of the support flange. Suspend the oil chamber, remove the bolt with the locking pad that connects the support flange to the head flange of the switch, and then place the oil chamber on the support plate on the wire. At this point, the upper fuel tank can be lifted.
(13) After cleaning the oil compartment, follow the reverse procedure described above. But should pay attention to the following points:
1) After inserting the suction pipe, firmly press the top end of the suction pipe so that the main body of the selector switch is coaxial with the oil chamber.
2) Use a spreader to twist the switch to the calibration position.
3) The gear mechanism should be adjusted to the position where it can be inserted and coupled to the selector body.
4) Before placing the switch head cover, first place the sealing rubber pad to ensure the head cover is sealed.
5) Finally, inspect the window from the switch head cover to check if it is the calibration position.
(14) Install the bypass pipe so that the oil chamber and the fuel tank simultaneously fill the oil, and install the transmission shaft and the rain cover at the same time.
(15) Check the symmetry of the transmission mechanism.
(16) Trial operation
Second, the installation check and adjustment of the tap changer
(1) Check the components of the tap changer, including the switch or selector switch, the tap selector, the change selector, etc. for damage and deformation.
(2) Check the insulation of the tap-changer without cracking, creepage and moisture.
(3) Check that the fasteners in each part of the tap-changer should be well fastened.
(4) Check that the contacts of the tap-changer and its connection should be intact, good contact, and the connection is correct and firm. If necessary, measure the contact resistance and the contact pressure and stroke of the contact. Check that the copper braided wire should be free of strands.
(5) Check the transition resistance for breakage and looseness, and measure the value of the transition resistance. The resistance value should meet the requirements.
(6) Check the insulation distance of each part of the tapping lead.
(7) The length of the tapping lead should be appropriate so that the tap changer is not pulled.
(8) Check that the valve between the disintegration switch and its oil conservator should be opened.
(9) The tap changer seal inspection. In the case of oil filling of the transformer body and its oil storage cabinet, the insulating oil in the oil chamber of the tap-changer is exhausted, and the leakage in the oil chamber is checked. Finally, the overall sealing inspection, including the accessories and all the pipes, should be Leakage of oil.
(10) Clean the oil chamber and core of the tap-changer and inject it into the standard insulating oil. The oil level of the oil storage tank should be adapted to the ambient temperature.
(11) When the transformer is vacuumed, the tap-changer oil chamber should be connected to the transformer. When the tap-changer is used for vacuum oiling, the transformer body and the tap-changer oil chamber must be vacuumed at the same time. The tap changer with the explosion-proof membrane shall be removed from the explosion-proof membrane and replaced with a sealing plate. If the tap-changer oil conservator cannot withstand this vacuum value, remove the tubing that leads to the conservator and close all valves and venting plugs that affect the vacuum. When the tap-changer is used for normal-pressure oil injection, an air outlet should be left to prevent the pressure release device from swelling.
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