In the distribution network with voltage levels of 10kV and below, high-voltage vacuum circuit breakers have gradually replaced oil circuit breakers. High-voltage vacuum circuit breakers have the advantages of being suitable for frequent operation, long electrical life, small maintenance workload, flameproof, explosion-proof, and high operational reliability. Due to different manufacturers, some high-voltage vacuum circuit breakers have poor performance, especially in the characteristics of circuit breakers, there are many problems. Some defects of circuit breakers are easy to cause major accidents, or cause accidents to leapfrog and lead to large-scale power outages.

Due to the use of advanced scientific instruments such as vacuum testers and characteristic testers in the overhaul and maintenance of high-voltage vacuum circuit breakers in recent years, the hidden problems have been revealed in the form of scientific data. In the process of dealing with these problems, some experience has also been accumulated, and comprehensive maintenance has been achieved to prevent problems before they occur, and to ensure the safe and reliable operation of high-voltage vacuum circuit breakers. 

1. The main reason for the decrease of vacuum degree of high-voltage vacuum circuit breaker

The high-voltage vacuum circuit breaker uses the physical factors that eliminate the arc to continue, so that the arc cannot be formed or sustained. The vacuum tube used in the high-voltage vacuum circuit breaker maintains a certain degree of vacuum - so that when the dynamic and static contacts of the switch are breaking the load current, the arc cannot be generated or continued because there is no or very little ionizable medium. achieve the purpose of extinguishing the arc. At present, the high-voltage vacuum circuit breakers produced in China are not equipped with medium pressure blocking and other protections like the more widely used sF6 circuit breakers, and there is no device for qualitative and quantitative monitoring of the vacuum degree characteristics. Therefore, the vacuum degree of the vacuum tube equipped with the circuit breaker is reduced in It is impossible to be found in the actual operation, the fault is a recessive fault, and its danger is far greater than the dominant fault.

1. Influence of contact stroke

At present, various types of 10kv high-voltage vacuum circuit breaker arc extinguishing chambers produced in China have a contact overtravel of about 4mm and an opening distance of about 11mm according to regulations. During the installation or maintenance of the high-voltage vacuum circuit breaker, the contact travel requirements in the product installation manual should be measured accurately, and the tie rod should be adjusted to prevent the travel from exceeding. , Overtravel and contact distance. In actual operation, there are many accidents caused by improper adjustment of the overtravel of the circuit breaker, resulting in the rupture of the arc extinguishing chamber and the deformation of the conductive rod caused by the mechanical shock during the closing process of the circuit breaker.

2. The effect of bouncing

The contacts of high-voltage vacuum circuit breakers are mostly flat butt-type structures, which inevitably produce different degrees of rebound phenomenon during the opening and closing operations. No matter the opening rebound or the closing rebound will bring harm to the operation: the bellows may have cracks when subjected to forced vibration, which may cause the arc extinguishing chamber to leak air; when opening and closing, the contact movement speed of the circuit breaker is high, and the impact force at the end of the action is relatively high. If it is too large, it will cause bouncing, which may cause deformation of contacts and conductive rods, or even cracks; if the vacuum high-voltage vacuum circuit breaker that fits the capacitor bank has a closing bouncing, it will also cause damage to the capacitor. Therefore, at present, some high-voltage vacuum circuit breaker manufacturers have noticed the harm caused by the bounce of high-voltage vacuum circuit breakers, and have introduced so-called "no bounce" high-voltage vacuum circuit breakers. mechanical shock.

3. Influence of opening and closing speed

The opening and closing speed of the circuit breaker plays a certain role in the arc extinguishing of the high-voltage vacuum circuit breaker, and also determines the service life of the high-voltage vacuum circuit breaker. Therefore, before the circuit breaker is put into operation, the opening and closing speed should be measured, and some problems in product quality and debugging can be found in time. On the one hand, it prevents the opening and closing speed from being too large, and the mechanical collision is violent when the contact action of the circuit breaker ends, which makes the arc extinguishing chamber produce more serious vibration.

4, the impact of the buffer

The buffer stroke should be carefully checked, there should be no deformation damage or excessive compression, and a buffer allowance must be left. For some oil-filled buffers, the oil level of the buffer should be checked regularly, and the oil should be replenished in time.

5. The influence of the capacity of the operating mechanism

The common operating mechanisms of high-voltage vacuum circuit breakers are mainly CD10 type, CD17 type, VSl type and the operating mechanism modified to adapt to different installation spaces on the basis of the above models. In recent years, some domestic circuit breakers have been equipped with "Permanent Magnet Operating Mechanism". Equipped with different types of operating mechanisms, during installation or transformation, attention should be paid to the action distance of the operating transmission rod. If the capacity is too large, it will cause serious impact on the arc interrupter, resulting in damage to the bellows of the vacuum interrupter, which will directly affect the high voltage. The service life of the vacuum circuit breaker makes the vacuum degree of the circuit breaker decrease faster. 

2. Judgment and determination of vacuum drop of high voltage vacuum circuit breaker

The reduction of vacuum degree will seriously affect the ability of high-voltage vacuum circuit breaker to interrupt overcurrent, and lead to a sharp decrease in the service life of the circuit breaker, and in severe cases, it will cause the switch to explode. The vacuum degree in the vacuum interrupter tube must usually be maintained at 10-4~10-6Pa. With the increase of the use time of the vacuum interrupter and the increase of the number of interruptions, as well as the influence of external factors, the vacuum degree gradually decreases. To a certain extent, it will affect its breaking capacity and withstand voltage level. Therefore, the high-voltage vacuum circuit breaker must regularly check the vacuum degree in the arc extinguishing chamber tube during the use process, and check and observe the action of the circuit breaker at any time during the actual operation.

For the glass shell vacuum interrupter, regular visual inspection can be performed during inspection. Under normal circumstances, the surface color of the internal shielding cover and other components should be bright, and a light blue arc will be emitted when the current is interrupted; when the vacuum degree drops seriously, the internal color will become gray, and a dark red arc will be emitted when the current is interrupted. . When the above situation occurs during operation, it can be preliminarily judged that the vacuum degree of the arc-extinguishing chamber of the high-voltage vacuum circuit breaker has dropped, and it should be determined by testing methods in time. When the operator patrols, they should pay attention to whether there is discharge phenomenon outside the vacuum interrupter of the circuit breaker. If there is a discharge phenomenon, the vacuum degree test result of the vacuum bubble is basically unqualified, and the power outage should be replaced in time. In order to ensure the safety of electrical equipment, electrical equipment must be guaranteed to be regularly repaired and tested. Through a series of test methods and by detecting the overall working condition of the circuit breaker, the hidden danger of the vacuum degree drop of the high-voltage vacuum circuit breaker can be found timely and accurately. The vacuum degree of the high-voltage vacuum circuit breaker can generally be detected by the following tests:

1. Check the vacuum degree tester: use the vacuum degree tester to measure the vacuum degree of the arc extinguishing chamber.

Make sure that the vacuum degree of the vacuum interrupter is kept in the range of 10-4~10-6Pa; if the vacuum degree drops beyond the value specified above or in the product manual, further pass the circuit breaker breaker in the case of the vacuum interrupter breaking. Frequency withstand voltage test for reconfirmation;

2. Power frequency withstand voltage test: According to the provisions of the "Preventive Test Regulations for Electric Power Equipment", for high-voltage vacuum circuit breakers of 12Kv and below, a power frequency withstand voltage test should be carried out at least once in about 1 to 3 years, and the test scope includes circuit breaker. phase-to-phase, circuit breaker phase-to-ground, circuit breaker fracture. Among them, the fracture withstand voltage test of the circuit breaker can detect whether the distance between the dynamic and static contacts of the circuit breaker is qualified. When the dynamic and static contacts of the high-voltage vacuum circuit breaker meet the rated distance conditions, if the withstand voltage is very low and fails to meet the specified withstand voltage standard, it means that the vacuum degree of the vacuum interrupter has been seriously reduced and cannot be used continuously. 

Third, the key points of maintenance of high-voltage vacuum circuit breakers

To a certain extent, high-voltage vacuum circuit breakers are broadly called "maintenance-free circuit breakers", but in fact inspection and maintenance must be carried out. ". In the actual operation of the high-voltage vacuum circuit breaker, in addition to regular preventive tests, the overall performance indicators of the circuit breaker must also be regularly tested to judge the status of its transmission system and eliminate the disadvantages that affect the operating life of the high-voltage vacuum circuit breaker. factor.

1. Detection of the action stroke of the connecting rod of the operating mechanism; prevent the action distance from being too large to cause violent impact on the vacuum interrupter;

2. Detect the moving contact stroke of the high-voltage vacuum circuit breaker;

3. Detect the opening and closing speed of the circuit breaker;

4. Detect the opening and closing synchronization of the circuit breaker;

5. Measure the opening and closing bounce value of vacuum circuit breaker;

6. Detection of vacuum degree of circuit breaker vacuum interrupter;

7. Power frequency withstand voltage test of circuit breakers.

Although the high-voltage vacuum circuit breaker does not need to be dismantled and overhauled regularly, by regularly testing the technical characteristics of the high-voltage vacuum circuit breaker, the hidden dangers of the circuit breaker can be found in time. The unqualified data in the test cannot be ignored, and the reasons should be carefully analyzed. Eliminate unfavorable factors of circuit breaker operation in time. The arc extinguishing chambers listed as unqualified after the test must be replaced in time to ensure the reliability and safety of the power system and power supply. 

4. Conclusion

High-voltage vacuum circuit breakers have been widely used, but there has been no uniform corresponding maintenance process standards, and the high-voltage vacuum circuit breakers of various manufacturers are not the same in structure, and the failure of high-voltage vacuum circuit breakers, such as the reduction of vacuum degree , different periods of opening and closing, large bounce, etc. are mostly hidden open obstacles. Therefore, relevant scientific instruments must be used for testing and measurement during maintenance work, and actual data are used to explain problems, and also use actual data to prove and solve problems. .