Analysis of the Reasons for the Rejection of Vacuum Circuit Breakers

The vacuum circuit breaker is the main electrical equipment of the substation. Due to various reasons, the tripping fault of the vacuum circuit breaker often occurs during operation. The tripping failure of the vacuum circuit breaker has great harm to the safe operation of the system, because when the equipment fails, the circuit breaker refuses to trip, which will lead to leapfrog tripping, the loss of busbar voltage will cause the accident to expand, and even the system will collapse. Therefore, it is very important to quickly determine the reason and handling it correctly.

1. The operation items that should be carried out when the vacuum circuit breaker refuses to trip:

a.The refusing to trip vacuum circuit breaker is turned down to a separate section of busbar and runs in series with the bus tie circuit breaker, that is, the protection of the refusal-to-trip circuit breaker is replaced by the protection of the bus tie circuit breaker. After exiting the protection device of the refusal to trip circuit breaker, deal with its secondary circuit fault.

b.For users with dual power supply,vacuum cuicuit breaker should be checked and deal with after the power cut after changing load.

c.If there is a bypass bus, only after the load is changed to the bypass bus and the power failure can be checked and dealt with.

d.Power failure operation of refusal to trip circuit breaker If the electric trip cannot be disconnected, the method of operating the trip iron core of the motor mechanism or the tripping mechanism will disconnect it.

2. Analysis of the reasons of vacuum circuit breaker refusing to trip:

a.The vacuum circuit breaker trip iron core does not move. Turn the control switch to the "pre-trip" position, the indicator light does not flash, indicating that the trip circuit is blocked. It is possible to measure whether there is voltage at both ends of the trip coil during the new opening operation. If there is no voltage or the voltage is very low, the reasons are: the fuse of the control circuit is blown or the contact is poor, the contact of the control switch, the auxiliary switch of the circuit breaker, the contact of the micro-switch and the terminal of the hydraulic opening lock Bad: The voltage at both ends is normal, the reason is that the polarity of the vacuum circuit breaker trip coil is reversed, the trip iron core is stuck, etc.

b.The tripping iron core acts, and the tripping mechanism does not trip. The reasons are: the tripping mechanism is buckled too deeply, the meshing is too tight, the four-bar linkage mechanism passes too much "dead point": the tripping iron core travel is not enough, and the tripping coil has strong residual magnetism , so that the iron core is not reset, and the thrust of the ejector rod is insufficient: the trip coil is short-circuited; the tripping mechanism is improperly adjusted, and there is no return gap.

c.The tripping iron core has acted, although it trips, it cannot be opened. The reasons are: the operation, transmission, and lifting mechanism are jammed, and the friction force increases; the shaft pin of the mechanism moves or is poorly lubricated; the opening force of the circuit breaker operating mechanism is too small, the tension or compression size of the spring is too small, and the spring poor performance, etc.