Reasons and handling methods for high-voltage circuit breaker refusal to trip

High-pressure circuit breakers operate very frequently and are often affected by mechanical and electrical factors, often resulting in refusal to trip. For circuit breakers already in operation, if a fault recurs on the load side of the circuit breaker, a refusal to trip will inevitably cause cascading tripping, expanding the scope of the accident and power outage, so it should be eliminated as soon as possible.

1. Reasons for Circuit Breaker Failure to Trip

There are usually two reasons for a circuit breaker to fail to trip: a mechanical failure of the operating mechanism, and an electrical failure of the operating circuit.

When a circuit breaker fails to trip, the duty personnel should determine whether the tripping circuit is intact according to the light indication. If the red light is not on, it indicates that the tripping circuit is not connected. At this time, check whether the operating fuse is blown or has poor contact, whether the contacts of the universal switching switch and the auxiliary contacts of the circuit breaker have poor contact, whether the coil of the anti-tripping relay is broken, whether the operating circuit is broken, whether the bulb and lamp are intact, etc.

If the operating power supply is good, and the tripping core is weak, it indicates that the tripping coil operating voltage is too high, or the operating voltage is too low, the tripping core is stuck or detached, or the tripping coil itself is faulty. If the tripping core top rod transport is good, and the circuit breaker still refuses to trip, it may be due to mechanism jamming or transmission connecting rod pin detachment.

2. Handling Methods for Circuit Breaker Failure to Trip

After the cause of the refusal to trip is identified, the duty personnel should remain calm and adopt different handling schemes according to the different nature of the fault. For example, during normal isolation operation, if the red signal light is not on, after confirming that the lamp is intact, the operating fuse should be quickly replaced and then the isolation operation should be performed. This should be done by two people, one remotely operating the switching switch, and the other observing the isolation core movement on site, while paying attention to maintaining a safe distance. If the core movement is weak, it is core jamming; if the isolation core movement is normal, but the circuit breaker cannot be tripped, it indicates mechanical reverse jamming. At this time, the circuit breaker should be interrupted using the on-site mechanical isolation device. For air circuit breakers and SF6 circuit breakers, the air pressure must be normal before the mechanism can be interrupted.

When it is necessary to perform isolation under emergency conditions, such as when the relay protection device operates or manual remote tripping fails, and may cause damage to the main equipment, the duty personnel should immediately manually open the upper-level circuit breaker, and then use the mechanical isolation device to interrupt the faulty circuit breaker; if the mechanical isolation device cannot open the circuit breaker, the isolating switches on both sides of the faulty circuit breaker should be quickly disconnected, and then the upper-level power supply should be restored, and the cause should be investigated before processing; if time permits under accident conditions, the duty personnel should quickly run to the faulty circuit breaker and use the mechanical isolation device to open the circuit breaker; if the mechanical isolation device cannot be opened, the operation mode should be immediately switched, or the busbar circuit breaker or the upper-level circuit breaker should be used to open it, and then the isolating switch should be used to isolate the faulty circuit breaker and restore the operation mode.

Therefore, it is recommended to regularly use the DGK-S high-voltage switch dynamic characteristic tester to test the high-voltage circuit breaker to eliminate faults in a timely manner. The DGK-S high-voltage switch dynamic characteristic tester is a special high-voltage switch dynamic characteristic tester developed and produced by the Dingsheng Electric Research and Development Center to adapt to the dynamic characteristics of various indoor and outdoor low-oil, high-oil switches, vacuum switches, and sulfur hexafluoride switches. The internal processing of the DGK-S high-voltage switch dynamic characteristic tester uses a single-chip microcomputer as the core for sampling, processing, and output. Its main functional features are the use of Chinese prompts and graphic display in a human-computer dialogue mode, which is simple and fast, suitable for all models and voltage levels of SF6 switches, GIS combined electrical appliances, vacuum switches, and oil switches produced domestically and internationally. Mechanical characteristic tests meet the conditions for accurate measurement of time, speed, and low voltage and other functional parameters under the test conditions of live bypassing busbars in 500KV substations. The DGK-S high-voltage switch dynamic characteristic tester has many advantages such as intelligence, strong anti-interference ability, and high precision, and is widely favored by customers.

However, it should be noted that because the circuit breaker itself is subject to the limitation of the interrupting capacity, when any of the following faults occur, it is forbidden to disconnect it to avoid explosion accidents.

(1) Oil circuit breaker without oil or seriously lacking oil or oil seriously carbonized.
(2) When the insulating rod of a low-oil circuit breaker is broken.
(3) Gas circuit breaker pressure is too low and cannot be maintained.
(4) Circuit breakers using hydraulic mechanisms, when the hydraulic system drops to zero.

Once the above phenomena occur, the duty personnel should immediately remove the operating fuse of the circuit breaker, so that the circuit breaker cannot be opened remotely, and even if the circuit breaker is faulty, the protection device will not trip it. At the same time, the duty personnel should hang a "Do Not Operate" warning sign on the operating handle and the operating mechanism of the circuit breaker, and then handle it according to the following principles.

(1) If a load circuit breaker fails in a plant (station), the load should be transferred according to the instructions of the director or dispatcher, and then the busbar connected to the faulty circuit breaker should be de-energized, the circuit breaker should be opened, and then the operation of the upper-level circuit breaker should be restored.
(2) If it is indeed a fault of the working power supply circuit breaker of a plant (station), the standby power supply circuit breaker should be put into operation, the upper-level circuit breaker of the working power supply should be cut off, and then the faulty circuit breaker should be opened.
(3) If a circuit breaker fault occurs and a busbar switching operation must be performed, when a busbar circuit breaker or bypass circuit breaker is used as a substitute, the relay protection specialist should be notified to adjust the setting, and then the relevant units should be notified to shut down for maintenance.

When the duty personnel are patrolling, if the following abnormal phenomena are found, decisive measures should be taken. First, measures should be taken to prevent the circuit breaker from automatically or remotely reclosing, and then remote operation should be used to quickly open the circuit breaker to de-energize it:

(1) Circuit breaker bushing cracked.
(2) Circuit breaker catches fire.
(3) Personal accidents that require the circuit breaker to be opened immediately.