As vacuum circuit breakers are widely used in the power industry, due to different manufacturers, some vacuum circuit breakers have better performance, less overhaul and maintenance workloads, and high power supply reliability; some vacuum circuit breakers have poor performance and compare problems. Many; some vacuum circuit breakers have extremely serious defects, which can easily cause accidents to leapfrog and cause large-scale power outages. Let's walk into the site where electrical engineers deal with vacuum circuit breaker failures together, so that we can accumulate experience and do comprehensive maintenance.

1. The vacuum degree of the vacuum bubble is reduced

Failure phenomenon

The vacuum circuit breaker interrupts the current and extinguishes the arc in the vacuum bubble, but the vacuum circuit breaker itself does not have a device for qualitatively and quantitatively monitoring the characteristics of the vacuum degree, so the vacuum degree reduction fault is a hidden fault, and its degree of danger is far greater than the dominant fault .

Reason analysis:

• There is a problem with the material or manufacturing process of the vacuum bubble, and the vacuum bubble itself has small leaks;
• There are problems with the material or production process of the corrugated tube in the vacuum bubble, and there are leaks after repeated operations;
• Split vacuum circuit breakers, such as vacuum circuit breakers using electromagnetic operating mechanism, during operation, due to the relatively large distance of the operating link, directly affect the characteristics of the switch's synchronization, bounce, over-travel, etc., so that the speed of vacuum reduction is accelerated .

Failure hazard

The reduction of the vacancy will seriously affect the ability of the vacuum circuit breaker to break the overcurrent, and lead to a sharp decline in the service life of the circuit breaker. In severe cases, the switch will explode.

Approach

• When the circuit breaker is regularly powered off for maintenance, a vacuum tester must be used to qualitatively test the vacuum degree of the vacuum bubble to ensure that the vacuum bubble has a certain degree of vacuum;
• When the degree of vacuum decreases, the vacuum bubble must be replaced, and characteristic tests such as stroke, synchronization, and bounce must be done.

Precaution

• When selecting vacuum circuit breakers, mature products produced by reputable manufacturers must be selected;
• Choose a vacuum circuit breaker integrated with the main body and the operating mechanism;
• Operators should pay attention to whether there is a discharge phenomenon outside the vacuum bubble of the circuit breaker during the inspection. If there is a discharge phenomenon, the vacuum degree test result of the vacuum bubble is basically unqualified, and the power should be replaced in time;
• When the maintenance personnel perform power outage maintenance work, they must perform characteristic tests such as synchronization, bounce, travel, and over travel to ensure that the circuit breaker is in good working condition.

2. The vacuum circuit breaker fails to open

Failure phenomenon

• According to the different causes of the failure, the following failure phenomena exist:
• The circuit breaker cannot be opened remotely;
• Can not be opened manually on the spot;
• In the event of an accident, the relay protection operates, but the circuit breaker cannot be separated.

Cause Analysis

• The opening operation circuit is disconnected;
• The opening coil is broken;
• The operating power supply voltage is reduced;
• The resistance of the opening coil increases and the opening force decreases;
• The opening ejector rod is deformed, there is jamming phenomenon when opening, and the opening force is reduced;
• The opening ejector rod is severely deformed and stuck when opening.

Failure hazard

If the opening failure occurs in an accident, it will cause the accident to leapfrog and expand the scope of the accident.

Approach

• Check whether the opening circuit is broken;
• Check whether the opening coil is disconnected;
• Measure whether the resistance value of the opening coil is qualified;
• Check whether the opening ejector rod is deformed;
• Check whether the operating voltage is normal;
• Change the copper opening mandrel to steel to avoid deformation.

Precaution

If the on-site electrician finds that the opening/closing indicator light does not light up, they should check whether the opening/closing circuit is disconnected; the maintenance personnel should pay attention to measuring the resistance of the opening coil during power outage maintenance, and check whether the opening ejector rod is deformed; The ejector rod is made of copper and should be replaced with steel; a low-voltage opening and closing test must be carried out to ensure the reliable performance of the circuit breaker.

3. The spring operating mechanism closing energy storage circuit failure

Failure phenomenon

• The opening operation cannot be realized after closing;
• The energy storage motor does not stop running, and even causes the motor coil to overheat and damage.

Cause Analysis

• The installation position of the travel switch is lower, so that the closing spring has not been stored, the contact of the travel switch has been converted, the motor power is cut off, and the energy stored in the spring is not enough for opening operation;
• The installation position of the travel switch is on the upper side, so that after the closing spring is charged, the travel switch contact has not been converted, and the energy storage motor is still in working condition;
• The travel switch is damaged, and the energy storage motor cannot be stopped.

Failure hazard

In the case that the energy storage is not in place, if the line has an accident and the circuit breaker refuses to open, it will cause the accident to leapfrog and expand the scope of the accident; if the energy storage motor is damaged, the vacuum switch cannot be opened and closed.

Approach

Adjust the position of the travel switch to realize the accurate power off of the motor;

If the travel switch is damaged, it should be replaced in time.

Precaution

During the switching operation, the operator should pay attention to the closing energy storage indicator light to judge the closing energy storage situation; the maintenance personnel should perform 2 opening and closing operations on the spot to confirm that the circuit breaker is in Good condition.

4. Different periods of opening and closing, large bounce value

Failure phenomenon

This fault is a hidden fault, and the relevant data must be obtained through the measurement of the characteristic tester.

Cause Analysis

• The mechanical performance of the circuit breaker body is poor. After multiple operations, due to mechanical reasons, the bounce value is too large in different periods;
• Due to the large distance between the operating rods of the split type circuit breaker, when the opening force is transmitted to the contacts, there are deviations between the phases, resulting in different periods and large bounce values.

Failure hazard

If the period is different or the bounce is large, it will seriously affect the ability of the vacuum circuit breaker to break the overcurrent, affect the life of the circuit breaker, and cause the circuit breaker to explode in severe cases. Because this fault is a hidden fault, it is more dangerous.

Approach

• Under the premise of ensuring the stroke and overtravel, adjust the length of the three-phase insulation rod to make the synchronization and bounce test data within the qualified range;
• If it cannot be achieved through adjustment, the vacuum bubble of the data unqualified phase must be replaced and readjusted to the data qualified.

Precaution

• Since split vacuum circuit breakers have many hidden troubles of failure, the integrated vacuum circuit breaker should be used when replacing the circuit breaker; the characteristic tester must be used for characteristic testing during regular maintenance work, and problems can be found and solved in time.
• In addition, the hazards of the environment to the equipment cannot be ignored, providing a good working environment for the equipment to ensure the safe and reliable operation of the vacuum circuit breaker.