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Analysis of circuit failure of vacuum circuit breaker

By:Nader Updated:September 09,2020 11:32AM

At present, many power companies, substations, and power distribution network industries in China have begun to use vacuum circuit breakers. This is mainly because the insulator and arc extinguishing medium of the circuit breaker are all vacuum, which has excellent insulation and arc extinguishing effects. Although the circuit breaker has the characteristics of small size, light weight and good arc extinguishing effect, it also has many problems. Next, we will conduct a detailed analysis and discussion on the circuit failure of the 10kV vacuum circuit breaker, and put forward corresponding maintenance measures at the end of the article to ensure the safe operation of the vacuum circuit breaker.

1. Circuit failure analysis of 10kV vacuum circuit breaker

As far as the actual situation of the current 10kV vacuum circuit breaker is concerned, the common circuit faults are mainly reflected in the following four aspects:

(1) The control circuit is disconnected due to the car entering the car not in place. Trouble phenomenon: For example, there is a 10kV vacuum circuit breaker in a substation. When inspecting its operating state, the maintenance personnel found that the staff need to spend a lot of energy and strength to push the rocking trolley. When the staff thinks that the trolley is in place Later, on the intelligent operating device, the “control circuit disconnection” light was on, and the switch could not be opened and closed. When the maintenance personnel used the same method to shake the booklet in, the above-mentioned fault also existed. After permission, the maintenance personnel opened the switch cabinet door and found that after the trolley entered the car and reached the stop position, there was no change in the insulation baffle in the switch cabinet. At this time, the maintenance personnel think that the entry of the car has not been completely completed, and it needs to continue to enter the car. As the maintenance personnel gradually increase their strength, after the car enters the car and continues to advance to a certain extent, the switch will be closed in the cabinet. The "click" sound, and the "control circuit disconnection" light on the intelligent control device also stops lighting, and the switch can be opened and closed, indicating that the fault has been resolved. Fault analysis: When the circuit breaker uses the swinging square rod to enter the car, it will jam, and the square rod will also show some deformation, which makes the staff feel very difficult during the propulsion process. In addition, the rated current of the 10kV vacuum circuit breaker is 3200A. Compared with the contact force of the rated current of 1260A of the three-phase six torx contacts, the contact force of the three-phase six torx contacts is greater, so when When the car enters the final stage, it needs more effort. In other words, when the trolley enters to the final stage, because the moving and static contacts are not inserted deep enough, the switches located in the trolley's stroke in the cabinet are not in good contact, which causes a disconnection fault in the control loop. Treatment measures: first restore the square pole to its original position, then add lubricating oil, and then apply petroleum jelly to the dynamic and static contacts of the circuit breaker, so as to ensure the smooth completion of the car entering the car.

(2) The auxiliary switch in the mechanism fails due to moisture and the control circuit is disconnected. Trouble phenomenon: During the process of debugging the circuit breaker, the staff of the substation found that the "control circuit disconnection" problem appeared in the background monitoring machine report. When the maintenance personnel opened the front cover of the mechanism box, they smelled the smell of burning. The maintenance personnel found that the auxiliary switch inside the organization was burnt obviously, and water droplets appeared on the wall of the organization box. Fault analysis: The reason for the occurrence of water droplets is that the area has been in rainy days in recent days, and the humidity in the air is very high, resulting in serious moisture in the mechanism box and water droplets. After the staff performs an opening and closing action, the motor The energy storage circuit starts to store energy, which in turn will enable the auxiliary switch of the energy storage to be energized and eventually burnt. Treatment measures: Replace the auxiliary switch in time, and then take corresponding measures to remove water droplets in the mechanism box. In addition, a heater can be added to the mechanism box to effectively prevent the problem of wet weather.

(3) The failure of the energy storage micro switch causes the control loop to disconnect. Trouble phenomenon: During the normal operation of the 10kV vacuum circuit breaker of the substation, the energy storage motor stops running fault suddenly, and the energy storage indicator light is off, and then the signal of "control loop disconnection" is sent out by the protection and control device , And the circuit breaker cannot be closed at the same time. After a detailed inspection by maintenance personnel, it is found that the energy storage contact has been in a disconnected state, so that the energy storage and closing circuits are in a disconnected state. Failure analysis: Because the quality of equipment and equipment is not up to standard, the micro switch equipment fails within the rated service life. Treatment measures: periodically check the energy storage micro switch, and replace the energy storage micro switch in time.

(4) The opening and closing coils are burnt and the control circuit is disconnected. Fault phenomenon: The 10kV vacuum circuit breaker of this substation often has a trip switch failure on rainy days, causing the control circuit to be disconnected, which in turn causes the automatic reclosing to fail. Fault analysis: After the 10kV vacuum circuit breaker has tripped, the closing circuit will be connected, so that current will flow through the closing coil. If the protective equipment has issued a closing command at this time, the closing electromagnet It is just in the off state, so that the closing coil will have current flowing for a long time, which will directly cause it to burn. Vibration will occur during the opening and closing of the circuit breaker, which will cause the electromagnet to disconnect. Treatment measures: regular inspections, timely reinforcement of the electromagnet and replacement of the closing coil, and at the same time do a good job of sanitation in the cabinet.

2. Daily maintenance measures for circuit breakers

(1) Daily maintenance of the circuit breaker. When the circuit fault of the 10kV vacuum circuit breaker in the actual operation process is of a general nature, the maintenance personnel can first conduct an in-depth analysis of the fault type to determine whether the fault is a secondary circuit, electrical or mechanical problem. You can proceed to the next step after the fault type is determined. The maintenance personnel can first put the mechanism in the stored energy state, and perform the manual opening and closing test of the circuit breaker. If the opening and closing can be carried out, it does not belong to the scope of mechanical failure; then the electric opening and closing test, if the electromagnet is electrically opening and closing Sometimes action occurs, and the switch fails to open and close, it can be judged as a loop fault. On the one hand, the staff should check and repair the circuit failure of the 10kV vacuum circuit breaker in time. On the other hand, they should also do routine maintenance work. For example, the internal structure of the circuit breaker should be cleaned regularly to effectively reduce the friction of rotation. Replace the lubricating oil to ensure the flexibility of operation.

(2) Matters needing attention. When repairing the 10kV vacuum circuit breaker, the maintenance personnel need to pay attention to the following three aspects: First, check whether the circuit breaker is in the open state before manual operation, and cut off the main circuit and the control circuit, and then Ground the main circuit according to the actual situation; second, when operating through the stored energy spring, you must first ensure that the closing spring is in a loose state before proceeding to the next step; third, the maintenance personnel must ensure that the nut is loose , Nuts and bolts should be tightened. At the same time, it should be noted that the spring washers and other related accessories can only be used once, and then they cannot be reused. This can avoid other failures caused by the aging of the spring washers and other accessories. Therefore, when repairing the 10kV vacuum circuit breaker, the maintenance personnel must pay more attention to the above three aspects to effectively avoid accidents during the maintenance process.

In summary, in the actual operation of 10kV vacuum circuit breakers, various problems often occur, which seriously affect the safe operation of the circuit breaker. Therefore, maintenance personnel must strictly follow relevant standards for maintenance. At the same time, maintenance personnel It is also necessary to sum up more experience and learn more professional maintenance techniques, so as to ensure that the circuit breaker maintenance work is in place and lay a good foundation for the safe and stable operation of the circuit breaker.