1： Reason

Theoretical analysis shows that during the process of opening and closing, the coil is only energized instantaneously, and the heat generated when the coil is energized is not enough to cause a temperature rise. Even if it is opened and closed multiple times in a row, the phenomenon of burning out the coil will not occur. However, there have been multiple incidents of burnout of the opening coil on site, mostly due to poor contact of the auxiliary contacts or obstruction of the armature movement during the closing process of the opening coil, mechanical jamming, etc., which caused the coil to be energized for a long time without completing the opening operation. The usual handling method is to replace the auxiliary switch, adjust the mechanical transmission components for opening and closing, or polish the auxiliary contacts. Sometimes adjusting the installation position of the auxiliary switch and adjusting the pressure and stroke of the operating link on the auxiliary switch can also ensure good contact.

2： Handling method

To provide a basis for fault diagnosis and analysis, regular inspections should be conducted on vacuum circuit breakers after they are put into operation. Vacuum circuit breakers used in substations or power plants with personnel on duty should be inspected at least once a day, while unmanned substations can be determined according to specific circumstances, usually at least once every ten days. The inspection items are as follows:

1. Whether the opening and closing indicators indicate correctly, and their indications should be consistent with the actual operating conditions at that time.

2. Support whether the insulator has cracks or damage, and whether the surface is smooth.

3. Check for any abnormalities in the vacuum arc extinguishing chamber (including abnormal sounds), and if it is a glass shell, observe whether there is a significant change in the color of the shielding cover.

4. Whether the metal frame or base is severely corroded or deformed.

5. Check whether the connecting bolts of the observable parts are loose, and whether the shaft pins are loose or deformed.

6. Whether the grounding is good.

7. Check whether there is overheating at the contact area of the lead or the area with temperature indicating wax, and whether the lead sag is appropriate.