Analysis Of Common Abnormal Problems Of Circuit Breakers

Electrical circuit failure

1. Control power supply failure: The closing circuit loses power or the voltage is too low.

2. Closing coil burnout: The coil is damaged due to overheating caused by prolonged power-on or a stuck mechanism.

3. Auxiliary switch contact failure: The auxiliary switch contacts used to cut off the closing circuit current are in poor contact or improperly positioned, resulting in a blockage of the closing circuit.

4. Closing button/relay failure: The operating element itself is damaged.

5. Lockout circuit activation: These protection contacts, such as those caused by low SF6 gas pressure, spring depletion, or relay lockout, are open, preventing closing.

Mechanical failure

1. Operating mechanism stuck: Lack of lubrication, foreign matter, or worn or deformed components prevent smooth operation.

2. Energy storage mechanism failure (for spring-operated mechanisms): The energy storage motor is damaged, gears are slipping, or the chain is broken, resulting in the closing spring not storing energy.

3. Free trip mechanism not resetting: The trip mechanism has not fully reset after the last trip.

Malfunction of protective device

1. Relay protection device failure: A protection plug-in error or improper setting may cause a trip signal to be issued even when no fault conditions exist.

2. Trip unit failure (for molded case/miniature circuit breakers): The electronic release or thermal-magnetic trip element may malfunction.

Electrical circuit failure

1. Trip power supply or coil failure: Similar to the control power supply and closing coil, the trip circuit may lose power or the trip coil may burn out.

2. Trip circuit contact problem: Poor contact between the trip button, protective relay contacts, and auxiliary switch contacts.

3. The local/remote selector switch is in the wrong position.

Mechanical failure

1. Severely stuck operating mechanism: This is the most common cause. Rust, deformation, or foreign matter may be trapped, preventing the mechanism from tripping.

2. Failure of the trip spring: Spring fatigue or breakage.

3. Deformation or damage to transmission components such as the main shaft and connecting rod.

Protection system malfunction

1. Relay protection missetting: The protection setting is set too low, or the coordination with the upper and lower levels is inadequate.

2. Secondary circuit fault: This can cause false fault signals due to, for example, an open secondary circuit in the current transformer (CT), interference caused by a double ground connection, or a short circuit caused by damaged cable insulation.

3. Fault in the protection device: This can be caused by a hardware or software failure in the plug-in.

Malfunction of operating mechanism

Human error

Poor insulation, causing flashover or explosion

Overheating

Poor contact in the main conductive circuit: Excessive contact resistance between the moving and static contacts, loose terminals, and prolonged load current flow can lead to severe heating.

Consequences: Accelerated insulation aging, potentially causing phase-to-phase short circuits or equipment burnout.

Abnormal operating mechanism (for different types)

1. Spring mechanism: The energy storage motor keeps running, automatically releases energy after storage, and produces unusual noise.

2. Hydraulic mechanism: Abnormal pressure increase or decrease, frequent pump activation, oil line leaks, and unusual noise.

3. Pneumatic mechanism: Abnormal pressure, air leaks, or air compressor failure.

SF6 gas leakage (for SF6 circuit breakers)

Cause: Deterioration of the seal ring, valve leakage, etc.

Consequences: Decreased arc extinguishing capability and insulation performance, triggering a low-pressure lockout or alarm.

abnormal noise