Maintenance Methods For Box-type Transformers

1. Disconnect the low-voltage side circuit breaker of the transformer under maintenance, remove the operating fuse for the control power supply, and hang a "Do Not Close" sign at the switch handle.

2. Disconnect the high-voltage side circuit breaker of the transformer under maintenance, close the grounding switch, fully discharge the transformer, lock the high-voltage cabinet, and hang a "Do Not Close" sign at the switch handle.

3. For maintenance of the transformer, first clean the porcelain bushings and casing. Then check the casing, gaskets, and porcelain bushings for cracks, discharge marks, or aging of rubber gaskets. Check the cables and busbars for deformation; replace any cracked parts.

4. Check that the busbar contact surfaces are clean. Remove the oxide layer from the contact surfaces and apply electrical compound grease.

5. Check that the transformer grounding is good and that the ground wire is corroded. Replace any severely corroded wires.

6. Tighten the lead terminals, pins, grounding screws, and busbar screws. If any are loose, remove the screws, or lightly file the contact surfaces with a fine flat file, or replace the spring washers and screws until good contact is achieved.

7. Clean the area around the transformer and its accessories of dust. Check the fire-fighting facilities and ventilation system for proper functioning.

8. Disconnect the high-voltage side grounding switch and lock the high-voltage switch block. Use a 2500V megohmmeter to measure the insulation resistance. Compare this resistance with the value measured before the transformer left the factory. The insulation resistance should not be lower than 70% of the original factory data. If it fails to meet the standard, report it immediately.

9. Reconnect the high-voltage side grounding switch to allow the transformer to discharge.

10. Check the transformer room and transformer for any tools left behind, and evacuate the site.

11. Connect the low-voltage side circuit breaker control power supply operating fuse and re-hang the "Do Not Close" sign to prevent backfeeding to the transformer.

12. Disconnect the high-voltage side grounding switch, and check the control lines of the transformer site and the low-voltage side again. After confirming that everything is correct, close the high-voltage side circuit breaker of the transformer and allow the transformer to run for trial operation. Remove the high-voltage side sign.