Maintenance Methods Of Dry-type Transformers

1. Put in the spare transformer, disconnect the circuit breaker on the low-voltage side of the transformer for maintenance, remove the operating fuse of the control power supply, and hang a "no closing" sign on the switch handle.
2. Disconnect the circuit breaker on the high-voltage side of the maintenance transformer, close the grounding switch, fully discharge the transformer, lock the high-voltage cabinet, and hang a "No closing" sign on the switch handle.
3. To maintain the dry-type transformer, first clean the porcelain bushing and shell, and then check whether the shell, gasket, and porcelain bushing are cracked, discharge traces, or the rubber pad is aging, and whether the cables and busbars are deformed or cracked. It should be replaced.
4. Check whether the busbar contact surface is kept clean. The oxide layer should be removed from the contact surface and coated with power compound grease.
5. Check whether the grounding of the transformer is good and whether the ground wire is corroded. If the ground wire is seriously corroded, replace it.
6. Tighten the lead terminals, pins, grounding screws, and busbar screws. If any are loose, remove the screws, or lightly file the contact surface with a fine flat file, or replace the spring washers and screws until the contact is good.
7. Clean the dust around the transformer and accessories, and check whether the fire protection facilities and ventilation system are in good condition.
8. Disconnect the grounding switch on the high-voltage side, lock the high-voltage switch joint, and measure the insulation resistance with a 2500V megger. And compared with the value measured before the transformer leaves the factory, the insulation resistance should not be less than 70% of the original data when it leaves the factory. If it is unqualified, it should be reported in time.
9. Close the grounding switch on the high-voltage side again and let the transformer discharge.
10. Check whether there are any tools left behind in the transformer room and transformer, and evacuate the site.
11. Connect the low-voltage side circuit breaker control power supply operation fuse, and re-hang the "No closing" sign to prevent reverse power transmission to the transformer.
12. Disconnect the high-voltage side grounding switch and check the control lines at the transformer site and low-voltage side again. If correct, close the high-voltage side circuit breaker of the transformer and allow the transformer to be put into trial operation. Remove the high-voltage side sign.
13. Keep detailed maintenance and trial operation records.