1. Disconnect the low-voltage side circuit breaker of the box transformer for overhaul, remove the operation insurance of the control power supply, and hang the "No-Closing" sign at the switch handle.
2. Disconnect the circuit breaker on the high-voltage side of the transformer for overhaul, close the grounding switch, after fully discharging the transformer, lock the high-voltage cabinet and hang the "No-Closing" sign at the switch handle.
3. Maintenance of box transformer should first clean the porcelain bushing and casing, and then check whether the casing, gasket and ceramic bushing are cracked, discharged traces or rubber pad are ageing, whether the cable and busbar are deformed or not, and if they are broken, they should be replaced.
4. Check whether the bus contact surface is kept clean. The contact surface should be removed and coated with electric compound grease.
5. Check whether the grounding of the transformer is good or not, whether the ground wire is corroded, and if the corrosion is serious, it should be replaced.
6. Tighten lead terminals, pins, grounding screw and connecting bus screw. If loose, remove the screw, or use thin flat file to lightly file contact surface, or replace spring washer and screw until good contact.
7. Clean the dust around the transformer and its fittings and check whether the fire fighting facilities and ventilation system are in good condition.
8. Disconnect the grounding switch on the high-voltage side and lock the high-voltage switch bars. Measure the insulation resistance with 2500V shake table. Compared with the measured value before leaving the factory, the insulation resistance should not be lower than 70% of the original data when leaving the factory. If it is not qualified, it should be reported and processed in time.
9. Close the grounding switch on the high-voltage side again and let the transformer discharge.
10. Check whether the transformer chamber and transformer have any left-over tools and evacuate the site.
11. Connect the low-voltage side circuit breaker to control the operation insurance of the power supply, and re-hang the "no-closing" sign to prevent the reverse transmission of power to the transformer.
12. Disconnect the grounding switch on the high-voltage side, check the control line on the zhongyaocai.71ix.combaohuqi.07858.netzaoxingzd.37ix.com.cnlangfang.71ix.cntransformer site and the low-voltage side again. After that, close the high-voltage side circuit breaker of the transformer and let zhongyaodou.71ix.comkakou.37ix.com.cnthe transformer test run and remove the high-voltage side sign.
13. Make detailed maintenance and trial operation records.