Maintenance Work of Vacuum Circuit Breakers

The vacuum circuit breaker should undergo an annual power outage inspection and maintenance to ensure normal operation. 

Daily inspection and maintenance include the following aspects: 
1. Check for abnormal sounds and burnt odors.

2. Check the amount of electrical wear on the contact. If the accumulated wear thickness of the moving and stationary contacts exceeds 3mm, the vacuum tube needs to be replaced. Observe the overtravel indicator and check if its overtravel is normal to roughly determine the amount of electrical wear on the contact. For circuit breakers with overtravel indicators, the relative position change between vacuum interrupter moving guide rod and the moving end flange surface can be used to measure. When the overtravel does not meet the requirements, the contact should be readjusted to ensure the contact pressure of the contact, otherwise it will shorten the service life.

3. Check if vacuum interrupter is damaged and if its internal parts are bright, whether the glass bubble clear, whether there are any abnormalities in the appearance, and whether there are stains on the outer surface. If the surface of the insulation shell is contaminated, it should be wiped clean with a dry cloth. If oxidation or discoloration of the shielding cover is found, it indicates that the vacuum interrupter is leaking and should be replaced immediately. Check the contact condition of the contacts.

4. Observe the opening of the vacuum circuit breaker. When opening, it is normal for the arc light to appear blue, when the arc light is found to be orange red, it indicates a decrease in vacuum degree, and vacuum interrupter should be repaired or replaced in a timely manner. The vacuum degree is mainly checked through the power frequency withstand voltage method. When the vacuum circuit breaker is in the off state, apply the prescribed preventive power frequency test voltage between the contacts of the vacuum arc extinguishing tube for 1 minute, and there is no abnormality.

5. Regularly clean the vacuum circuit breaker, especially attention should be paid to removing dust adsorbed on conductive parts and insulators.

6. Every maintenance should check and adjust the contact distance, compression stroke, and three-phase synchronization of the vacuum circuit breaker.

7. Check if the contact of the auxiliary switch is good.

8. Check if the grounding wire of the secondary circuit is secure.

9. Check and tighten all fixing bolts.

10. Regularly measure the resistance value of each phase of the main circuit, the insulation resistance of the main circuit to ground, between phases, and the insulation lifting rod during testing should not be less than the specified value. The circuit breaker shall pass the AC voltage withstand test of main circuit relative, phase to phase and fracture respectively for 1min under the on-off and on-off state. The insulation lifting rod must undergo a voltage withstand test after replacement or drying. The contact resistance between the two ends of the vacuum interrupter and between the main circuit ends should not exceed the specified value.

11. Check the wear of the opening and closing parts of the circuit breaker operating mechanism, whether the fastening components are loose, and whether various components are rusty, deformed or damaged. If there are any abnormalities, they should be repaired in a timely manner; Replace unqualified components and apply anti rust oil.

12. Conduct multiple opening and closing operation tests, free tripping tests, and power on and closing operation tests, the circuit breaker should have no abnormalities.

13. When taking measures to limit overvoltage, the vacuum circuit breaker cuts off the small inductance current, the current carrying value is relatively high. Especially when cutting off the no-load current of a small capacity high-voltage motor, it will generate high operating overvoltage.

In the following situations, the vacuum circuit breaker should be shut down for temporary inspection.

1. When abnormal phenomena are found during patrol inspection.

2. When the number of actions reaches the service life specified by the technical conditions.

3. After opening and closing the short-circuit accident current.