Vacuum breaker is the main electrical equipment in substations. It may trip due to various reasons during operation. When the vacuum breaker fails to trip, it poses a great threat to the safe operation of the system. This is because when a fault occurs in the equipment and the circuit breaker refuses to trip, it can cause cascading tripping, leading to busbar voltage collapse, accidents expansion, and even system collapse. Therefore, it is very important to quickly identify the cause and handle it correctly.
Place the refused-to-trip vacuum breaker on a separate busbar section after closing the bus tie circuit breaker, i.e., use the protective function of the bus tie circuit breaker instead of the refused-to-trip circuit breaker's protection. After withdrawing the protection device of the refused-to-trip circuit breaker, handle its secondary circuit fault.
For dual power users, shut down the power after reducing the load and check and handle it.
For those with a bypass busbar, shift the load to the bypass busbar before shutting down and checking and handling it.
If the refused-to-trip circuit breaker cannot be shut down by electric operation, use the method of tripping the iron core or disengaging mechanism of the operating mechanism to disconnect it.
The tripping iron core does not operate. Turn the control switch to the "pre-trip" position. If the indicator light does not flash, it indicates that the tripping circuit is not connected. You can measure whether there is voltage at the two ends of the tripping coil during the disconnection operation. If there is no voltage or the voltage is very low, the reasons may include: the control circuit fuse is blown or the contact is poor, the control switch contact, the auxiliary switch of thevacuum breaker, the micro switch of the hydraulic parting lock of the circuit breaker, the contact of the terminal, etc.; If the voltage at both ends is normal, the reasons may include the polarity of the tripping coil being reversed or the tripping iron core being jammed.
The tripping iron core operates, but the disengaging mechanism does not disconnect. The reasons may include: the tripping mechanism is inserted too deep and the meshing is too tight, the four-link mechanism exceeds the "dead point" too much; the travel of the tripping iron core is not enough, and there is residual magnetism in the tripping coil, causing the iron core not to reset, and the thrust of the top rod is insufficient; there is a short-circuit between turns of the tripping coil; the disengaging mechanism is improperly adjusted without reset clearance, etc.
The tripping iron core has operated, but the circuit breaker cannot be disconnected even though it is disengaged. The reasons may include: the operating, transmission, and lifting mechanisms are jammed, and the friction force increases; the shaft of the mechanism slides or is poorly lubricated;the disconnection force of the circuit breaker operating mechanism is too small, and the related spring tension or compression size is too small, and the spring performance deteriorates, etc.