Vacuum Circuit Breaker Troubleshooting

The advantages of indoor high voltage vacuum circuit breaker are not only oil-free equipment, but also long electrical life. It has mechanical life, large breaking insulation capacity, strong continuous breaking capacity, small volume, light weight, frequent operation, fire free, less operation and maintenance, etc. And they are quickly recognized by the operation, maintenance and technical personnel of the power department. The quality of some high voltage vacuum circuit breakers is not stable enough, the current carrying voltage is on the high side during operation and some vacuum interrupters still have air leakage. 

With the wide application of vacuum circuit breaker, faults also occur from time to time. In this article, we will analyze the common faults of vcb breaker in ATO automation and gives treatment methods.

• Common abnormal operation state of vacuum circuit breaker

1. The circuit breaker refuses to close or open. After the circuit breaker gets the closing (opening) command, the closing (opening) electromagnet acts, the iron core push rod pushes the closing (opening) button open, the closing (opening) spring releases energy and drives the circuit breaker to close (open), but the circuit breaker interrupter cannot close (open).
2. Wrong opening of circuit breaker. The performance is that the circuit breaker operates normally and trips under unknown reasons.
3. After the circuit breaker mechanism stores energy, the energy storage motor does not stop. After the circuit breaker is closed, the energy storage motor of the operating mechanism starts to work, but after the spring energy is full, the motor is still running.
4. The DC resistance of circuit breaker increases. The contact resistance of the contact in the interrupter increases after the circuit breaker runs for a certain period of time.
5. The closing bounce time of circuit breaker increases. After the vacuum circuit breaker runs for a certain time, the closing bounce time increases continuously.
6. Discharge of CT surface of circuit breaker intermediate box to support. During the operation of the vacuum circuit breaker, the surface of the current transformer discharges to the support of the intermediate box.
7. Circuit breaker interrupter cannot be disconnected. The performance is that the circuit breaker cannot be opened or partially opened after opening operation.

• Processing method                                                                                                                                               

1. The circuit breaker refuses to close or open. Check the clearance of all connecting parts of the operating mechanism, and replace the unqualified parts with new qualified parts with high hardness.
2. Wrong opening of circuit breaker. Check all possible rain leakage points and block them effectively; Install the sealant sleeve on the connecting rod of the output crank arm; Turn on the heating device in the mechanism box.
3. After the circuit breaker mechanism stores energy, the energy storage motor does not stop. Adjust the installation position of the travel switch so that the normally closed contact of the travel switch can be opened when the rocker arm is in the highest position.
4. The DC resistance of circuit breaker increases. Adjust the contact distance and over travel of the interrupter, and measure the contact resistance with the DC voltage drop method required by the regulations (the current should be more than 100a), otherwise replace the interrupter.

• The closing bounce time of circuit breaker increases                                                                                                         

1. Increase the initial pressure of the contact spring appropriately or replace the contact spring.
2. If the clearance between crank arm and axle pin exceeds 0.3mm, the crank arm and axle pin can be replaced.
3. By adjusting the transmission mechanism, using the characteristic that the transmission ratio of the mechanism is small when the closing position exceeds the dead point of the driving arm, the mechanism can be adjusted to the direction close to the dead point to reduce the contact closing bounce.
4. Discharge of CT surface of circuit breaker intermediate box to support. A layer of semiconductor glue is evenly coated on the surface of the transformer to make the surface electric field uniform.
5. Circuit breaker interrupter cannot be disconnected

For the treatment of vacuum interrupter which cannot reach the required value of vacuum degree, if the vacuum degree of vacuum interrupter has dropped below the required value through detection, the vacuum interrupter shall be replaced.

• Specific steps                                                        

1. The vacuum interrupter to be replaced must pass the vacuum degree test.
2. Remove the original vacuum interrupter and replace it with a new one. The installation should be vertical. Pay attention to the coaxially of the movable conducting pole and the arc extinguishing chamber, and do not suffer torsion during operation.
3. After installing the new vacuum interrupter, the opening distance and over travel (contact stroke) should be measured. If it does not meet the requirements, it should be adjusted accordingly: ① adjust the bolt of insulation pull rod to adjust the overtravel;② The opening distance of arc extinguishing chamber can be adjusted by adjusting the length of moving conducting pole.
4. The opening and closing speed, three-phase synchronization, closing bounce and other mechanical characteristics are measured by the power switch comprehensive tester. If they are unqualified, they should be adjusted.