What Is a Vacuum Breaker?

"Vacuum Circuit Breaker" gets its name because its arc-extinguishing medium and the insulation medium of the contact gap after arc-extinguishing are both high vacuum; it has the advantages of small size, light weight, suitable for frequent operation, and no maintenance for arc-extinguishing Applications in the power grid are relatively widespread. Vacuum circuit breaker is an indoor power distribution device in a 3 10kV, 50Hz three-phase AC system. It can be used for the protection and control of electrical equipment in industrial and mining enterprises, power plants, and substations. For maintenance and frequent use, the circuit breaker can be configured in the center cabinet, double-layer cabinet and fixed cabinet for controlling and protecting high-voltage electrical equipment.

1893 American

1. Vacuum circuit breakers are usually divided into multiple voltage levels. Low voltage type is generally used for explosion-proof electrical use. Like coal mines and so on.

2. The rated current reaches 5000A, the breaking current reaches a better level of 50kA, and has developed to a voltage of 35kV.

3. Before the 1980s, vacuum circuit breakers were in the initial stage of development, and they were constantly exploring the technology. It was not possible to formulate technical standards. It was not until 1985 that relevant product standards were made. ^[1]

   JB / T 3855-2008 "High Voltage AC Vacuum Circuit Breaker"

   DL / T 403-2017 High Voltage AC Vacuum Circuit Breaker

   It needs to be explained here that there is no special standard corresponding to China's JB 3855 in the IEC standard, but only the "IEC56 AC high-voltage circuit breaker" is applied. Therefore, China's vacuum circuit breaker standards are higher or stricter than the IEC standards in at least the following aspects:

   (1) Insulation level: Test voltage IEC China

   1min power frequency withstand voltage (kV) 28 42 (between poles, pole to ground) 48 (between fractures)

   1.2 / 50 Shock withstand voltage (kV) 75 75 (between poles, pole to ground) 84 (between fractures)

   (2) Withstand voltage level of the vacuum interrupter fracture after the end of the electrical life test: There is no stipulation in IEC56. China's JB3855-96 stipulates that: after the vacuum circuit breaker has completed the electrical life test, its insulation capacity between the fractures should not be less than 80% of the initial insulation level, that is, the power frequency is 13.63kV and the impact is 60kV.

   (3) Bounce time of contact closing: IEC has no regulations, but China's regulations require no more than 2ms.

   (4)

   The contact opening distance is small. The contact opening distance of the 10KV vacuum circuit breaker is only about 10mm, the operating power of the operating mechanism is small, the mechanical part stroke is small, and the mechanical life is long.

   The arcing time is short and has nothing to do with the switching current. Generally, it has only half cycle.

   After the arc is extinguished, the contact gap medium recovers quickly, and the fault performance in the near region of the interruption is better.

   Because the contact wear is small when breaking current, the electrical life of the contact is long, breaking capacity is 30-50 times at full capacity, rated current breaking is more than 5000 times, low noise is suitable for frequent operation.

   Small size and light weight.

   Suitable for breaking capacitive load current.

   Because of its many advantages, it is widely used in substations. The current models are: ZN12-10, ZN28A-10, ZN65A-12, ZN12A-12, VS1, ZN30 and so on. ^[2]

   Parameter name Unit model

   ZN28-12 / 1250-20 ZN27-12 / 1250-31.5 ZN27A-12 / 3150-40

   Voltage parameter

   Rated voltage kV 10

   Maximum voltage 11.5

   Insulation level

   Power frequency withstand voltage between poles, pole to ground 42

   Fracture 48

   Shock withstand voltage between poles, pole to ground 75

   Fracture 84

   Current parameter rated current A 1250 1250 3150

   Rated short-circuit breaking kA 20 31.5 40

   Rated peak withstand current kA 50 80 100

   4S short-time withstand current kA 20 31.5 40

   Rated short-time closing current (peak) kA 50 80 100

   Rated breaking current of a single capacitor bank A 630 800

   Rated breaking current of back-to-back capacitor bank A 400 400

   Number of times of rated short-circuit breaking current 50 50 30

   Mechanical life times 10000

   Other rated operating sequence points-0.5s-total points-180s-total points-180s-total points-180-total points

   The number of full breaks is not greater than 60

   Equipped with operating mechanism CD or CT mechanism ^[2]

   Reduced vacuum of vacuum circuit breaker

   1.1 Failure phenomenon

   The vacuum circuit breaker interrupts the current in the vacuum bubble and performs arc extinguishing. The vacuum circuit breaker itself does not have a qualitative and quantitative monitoring device for the vacuum degree characteristic. Therefore, the vacuum degree reduction fault is a hidden fault, which is far more dangerous than the dominant fault. .

   1.2 Cause Analysis

   The main reasons for the decrease in vacuum are as follows:

   (1) There is a problem with the material or manufacturing process of the vacuum bubble, and there is a small leak in the vacuum bubble itself;

   (2) There is a problem with the material or manufacturing process of the corrugated tube in the vacuum bubble, and the leakage occurs after repeated operations;

   (3) Split vacuum circuit breaker, such as a vacuum circuit breaker using an electromagnetic operating mechanism, during operation, the distance of the operating link is relatively large, which directly affects the characteristics of the switch such as synchronization, bounce, and overtravel, and reduces the vacuum Speed up.

   1.3 Failure hazard

   The reduction of vacuum will seriously affect the ability of the vacuum circuit breaker to break overcurrent, and cause the service life of the circuit breaker to decrease sharply, which will cause the switch to explode in severe cases.

   1.4 Processing method

   (1) During the regular power failure inspection of the circuit breaker, a vacuum tester must be used to perform a qualitative test of the vacuum degree of the vacuum bubble to ensure that the vacuum bubble has a certain degree of vacuum;

   (2) When the degree of vacuum decreases, the vacuum bubble must be replaced, and the characteristics tests such as stroke, synchronization, and bounce must be done.

   1.5 precautionary measures

   (1) When selecting a vacuum circuit breaker, you must choose a mature product produced by a reputable manufacturer;

   (2) Select a vacuum circuit breaker with an integrated body and operating mechanism;

   (3) During the inspection, the operator should pay attention to whether there is a discharge phenomenon outside the vacuum bubble of the circuit breaker. If there is a discharge phenomenon, the vacuum degree test result of the vacuum bubble is basically unqualified, and it should be replaced immediately after power failure;

   (4) Maintenance personnel must perform characteristic tests such as synchronization, bounce, stroke, and overtravel during power outage maintenance to ensure that the circuit breaker is in good working condition.

   Vacuum breaker opening failure

   2.1 Failure phenomenon

   Depending on the cause of the failure, the following symptoms exist:

   (1) The remote control of the circuit breaker can not be disconnected from a distance;

   (2) Manual opening at the local site cannot be closed;

   (3) Relay protection was activated during the accident, but the circuit breaker could not be separated.

   2.2 Cause analysis

   (1) The opening operation circuit is disconnected;

   (2) The opening coil is disconnected;

   (3) The operating power voltage is reduced;

   (4) The opening coil resistance increases and the opening force decreases;

   (5) The opening rod of the opening gate is deformed, and there is a jam phenomenon during opening, and the opening force is reduced;

   (6) The opening lever is severely deformed and stuck when opening.

   2.3 Failure hazard

   If the opening failure occurs at the time of the accident, it will cause the accident to be overstepped and expand the scope of the accident.

   2.4 Processing method

   (1) Check whether the opening circuit is disconnected;

   (2) Check whether the opening coil is disconnected;

   (3) Measure whether the resistance of the opening coil is qualified;

   (4) Check if the opening lever is deformed;

   (5) Check whether the operating voltage is normal;

   (6) Change the copper sub-brake top rod to steel to avoid deformation.

   2.5 precautionary measures

   If the operating personnel finds that the opening and closing indicator light is not on, they should check whether the opening and closing circuit is disconnected in time; the maintenance personnel should pay attention to measuring the resistance of the opening coil during power failure and maintenance, and check whether the opening lever is deformed; The material of the rod is copper and should be replaced with steel; a low-voltage opening and closing test must be performed to ensure reliable circuit breaker performance.

   Vacuum circuit breaker additional information

   Failure of spring operating mechanism closing energy storage circuit

   3.1 Failure phenomenon

   (1) Opening operation cannot be realized after closing;

   (2) The operation of the energy storage motor does not stop, even causing the motor coil to overheat and damage.

   3.2 Cause analysis

   (1) The installation position of the limit switch is too low, so that the closing spring has not yet stored energy, the contact of the limit switch has been converted, the power of the motor is cut off, and the energy stored in the spring is not enough to open the switch;

   (2) The installation position of the limit switch is too high, so that after the closing spring energy storage is completed, the contact of the limit switch has not been changed and the energy storage motor is still in working state;

   (3) The stroke switch is damaged, and the energy storage motor cannot stop running.

   3.3 Failure Hazard

   In the case that the closed-circuit energy storage is not in place, if a line accident occurs and the circuit breaker refuses to open, the accident will be overstepped and the scope of the accident will be expanded; if the energy storage motor is damaged, the vacuum switch cannot be opened and closed.

   3.4 Processing method

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

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

   3.5 precautionary measures

   When the operator is in the shutdown operation, he should pay attention to the closing energy storage indicator to judge the closing energy storage situation; after the maintenance work is over, the maintenance personnel should perform 2 opening and closing operations on site to confirm that the breaker Good condition.

   Vacuum circuit breaker failure phenomenon

   This fault is a hidden fault, which must be measured by a characteristic tester to get the relevant data.

   Cause analysis of vacuum circuit breaker

   (1) The mechanical performance of the circuit breaker is poor. After multiple operations, the bounce value is large in different periods due to mechanical reasons;

   (2) Due to the large distance of the operating lever of the split-type circuit breaker, when the opening force is transmitted to the contact, there is a deviation between the phases, resulting in a large amount of bounce in different periods.

   Vacuum circuit breaker failure hazard

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

   Vacuum circuit breaker processing method

   (1) On the premise of ensuring the stroke and over-stroke, adjust the length of the three-phase insulated pull rod to make the synchronization and bounce test data within the qualified range;

   (2) If adjustment cannot be achieved, the vacuum bubble of the data failure phase must be replaced and readjusted until the data is acceptable.

   4.5 Preventive measures

   Due to the many hidden troubles of the split vacuum circuit breaker, an integrated vacuum circuit breaker should be used when replacing the circuit breaker; the characteristic tester must be used for related characteristic testing during regular maintenance work, and problems should be found and solved in time.

   Vacuum circuit breaker (5 photos)

   Vacuum circuit breaker protection device

   Where a vacuum circuit breaker is used, a microcomputer protection device is necessarily used. The microcomputer protection device is a relay protection composed of a microcomputer, which is the development direction of power system relay protection. It has high reliability, high selectivity, and high sensitivity. The hardware of the microcomputer protection device includes a microprocessor (Single Chip Microcomputer) as the core, with input and output channels, man-machine interface and communication interface. This system is widely used in electric power, petrochemical, mining smelting, railway and civil buildings.

   Advantages of vacuum circuit breaker

   1) Microcomputer protection device is a high-tech power automation high-tech product integrating measurement, control, monitoring, protection, communication and other functions. It is an ideal electrical unit for intelligent switchgear

   2) Highly integrated multiple functions, flexible configuration, and friendly man-machine interface make this general-purpose microcomputer integrated protection device suitable for ungrounded systems, low-resistance grounding systems, and arc suppression coil grounding systems with voltage levels up to 35KV The protection, measurement and control of various types of electrical equipment and lines in direct grounding systems can also be used as the protection and measurement and control of the voltage and current of the system in some 66KV and 110KV voltage levels.

   3), using 32-bit digital signal processor (DSP) has advanced core structure, high-speed computing capabilities and real-time signal processing and other advantages.

   4) Support conventional RS485 bus and CAN (DEVICENET) fieldbus communication. CAN bus has error correction mechanisms such as automatic retransmission of errors and automatic disconnection of faulty nodes to protect the implementation and reliability of information.

   5) Perfect self-checking ability, automatic alarm when device abnormality is found; self-protection ability, effectively preventing permanent damage to the device caused by wiring errors and abnormal operation; maintenance-free design, no need to adjust sampling accuracy on site, measurement accuracy will not Increased error due to environmental changes and long-term operation!