Universal circuit breaker operation failure analysis and processing

There are a large number of universal circuit breakers in the high-rise building's power supply and distribution equipment. It is generally used as a low-voltage main switch or a large-capacity branch circuit switch, which plays a decisive role in the power supply of the building. Caused a large area power outage.

1. The universal circuit breaker trips and fails to re-close.

1. First determine if the circuit breaker is a non-accident trip

Non-accident trip refers to tripping without a short circuit or overload fault. There are many reasons why the circuit breaker cannot be closed. First, it is necessary to determine whether the circuit is short-circuited or tripped due to overload, or whether the circuit breaker itself or the control circuit is faulty. The following block diagram is used to illustrate the steps and methods for finding and determining whether a line fault or a circuit breaker fault.

After determining that the circuit breaker is faulty, pull out the circuit breaker (refer to the drawer circuit breaker) for inspection.

2. Universal troubleshooting of universal circuit breakers

(1) The failure of the circuit breaker to close the voltage due to the loss of power of the undervoltage release or the failure of the undervoltage release coil coil will cause the circuit breaker to trip and cause the switch to fail to be reclosed. The following four conditions can cause the undervoltage release coil to lose power.

1 The protection circuit fuse is blown, such as RT14, causing the loop to fail, and the trip coil of the undervoltage release is de-energized;

2 If the closed button, relay contact, and auxiliary contact of the circuit breaker are in poor contact, the components may be damaged, which may cause the loop to be unreachable and the trip coil to lose power;

The disconnection of the connecting wire in the 3 circuit and the loosening of the crimping screw may also cause the loop to be unreachable and the trip coil to lose power;

4Because the coil of the undervoltage release is in the energized working state for a long time, the environmental pollution and the armature are not flexible or the air gap between the iron core and the armature is too large, so that the current is too large and the trip coil is heated and burned. Loss of the function of the trip coil.

The above faults can be correctly judged by observation and simple inspection test, so if the fault point is found, it should be eliminated in time. If the joint is loose, it should be tightened, and the component damage and coil burnt need to be replaced.

(2) The mechanical system is faulty, causing the circuit breaker to fail to close

After the circuit breaker operating mechanism has been tripped and closed several times, the mechanism is seriously worn and the following faults may occur.

1 The motor drive mechanism is worn out. If the worm gear and the worm of the ME switch are damaged, the operating mechanism of the circuit breaker cannot be driven to buckle and close. The replacement of the worm gear and the worm is more complicated and requires professional maintenance.

2 The free tripping mechanism wears out, making the circuit breaker difficult to buckle again, and the tripping is easy. Sometimes it is barely buckled. When it is vibrated, it will trip off by itself; sometimes, after the buckle is released, the closing will be buckled. At this time, the adjusting screw should be rotated to adjust the relative position of the trip half shaft and the jumper so that the contact area is about 2.5 square millimeters, and if necessary, replace the corresponding parts.

3 operating mechanism energy storage spring failure. The breaking energy storage spring of the operating mechanism relaxes or loses elasticity after multiple stretching, and the closing force becomes small. When closing, the four-bar linkage of the circuit breaker cannot be pushed to the dead position, and the mechanism cannot be kept in the closing position. Therefore, the circuit breaker also cannot be closed normally. The energy storage spring must be replaced.

4 The operating mechanism is not flexible and has a stuck phenomenon. Since the circuit breakers are not fully enclosed, if the foreign objects such as screws and nuts are accidentally left in the operating mechanism, the circuit breaker operation is stuck, which will affect the closing; in addition, the rotating and sliding parts lack lubricating grease. The breaking energy storage spring of the operating mechanism is slightly deformed, and the circuit breaker will not close the brake. Therefore, in the case of the above-mentioned failure, in addition to checking whether there is foreign matter in the operating mechanism, it is necessary to inject lubricating grease into the rotating and sliding portions.

Second, press the trip button, the circuit breaker refuses to break

Circuit breaker rejection may have the following types of failures.

1. Button failure

If the button is mechanically faulty or the contact of the wire contact is poor, the trip circuit will be blocked, resulting in no power to the shunt trip coil, the armature cannot be closed, and the circuit breaker cannot be disconnected.

2. Shunt release fault

The shunt trip coil is open or shorted, and there is an obstacle in the armature pull-in, which affects the tripping of the circuit breaker. Therefore, it is necessary to regularly check the shunt release to remove the obstacles that affect the armature pull-in. It is found that the coils with open or short circuit should be replaced in time to ensure that the circuit breaker can be quickly disconnected when the circuit needs to be disconnected.

3. Free trip mechanism failure

The contact surface of the trip half shaft of the free trip mechanism and the jumper is too large (generally should be 2~3mm2), which will make the circuit breaker refuse to break. Therefore, the adjustment screw is used to rotate the trip half shaft by a certain angle to reach 2~ 3mm2 contact surface requirements, and coating low temperature extreme pressure grease on the contact surface to reduce friction and facilitate tripping.

Third, other faults

1. Undervoltage release noise

After the undervoltage release device works for a period of time, it will often produce abnormal noise. If it is disturbed, it will burn the coil. Therefore, the oil and dust on the working surface of the core should be cleaned regularly, and the short-circuit ring should be replaced. The spring pull of the undervoltage release should also be adjusted until the core and armature air gaps meet the requirements.

2. Micromotor burned

Failure of the travel switch will cause the micromotor in the electric operating mechanism to burn out. For example, when it is necessary to close the circuit breaker with the electric operating mechanism, press the closing button, the power supply circuit of the motor is turned on, and the motor rotates. After the energy storage or closing of the mechanism is completed, the power supply circuit of the micro motor should be disconnected by the travel switch. However, due to the failure of the travel switch, the motor will be overheated for a long time and burned.

3. Short circuit caused by poor insulation

The long-term use of the circuit breaker will gradually deteriorate the insulation performance. If the maintenance is improper, the dust on the surface of the insulation parts will accumulate, and the moisture will cause the insulation to accelerate and age. It may cause phase-to-phase or relative grounding during the power distribution operation or when the short-circuit current is cut off. Short circuit. Therefore, it is necessary to keep the insulation surface clean and prevent the insulation performance from deteriorating to extend the service life of the circuit breaker.

Fourth, the circuit breaker after the breaking short-circuit current measures

After each short-circuit current is disconnected, the circuit breaker should be inspected once. The contents of the inspection and the troubleshooting methods are as follows.

1. Contact system

(1) The smoke marks on the main and arc contacts are wiped off with alcohol;

(2) If small particle metal chips are formed on the contact surface of the contact, it should be cleaned and smoothed;

(3) If the thickness of the silver alloy contact layer on the main contact (moving and static contact) is less than 1 mm due to electrical wear, it must be replaced, and the moving and static contacts should be replaced at the same time;

(4) Check the contact pressure spring, if it is overheated, it should be replaced in time;

(5) Check the soft joint for fracture. If there is a small part of the fracture, the broken belt layer should be removed. If most of the belt layer breaks, the soft joint should be exchanged.

2. Arc extinguishing system

(1) Clean the metal particles and soot on the inner wall of the arc extinguishing chamber and the grid. If the grid is welded or burnt, it should be replaced;

(2) If the arc chamber is damaged, it is not allowed to be used again and must be replaced;

(3) The newly replaced arc extinguishing chamber should be dried before use to ensure good insulation.

3. Operating mechanism and free trip mechanism

(1) The lubricant may be properly added first;

(2) Close the operation with the electric operating mechanism and the manual handle, the operating mechanism should be flexible, and the circuit breaker should be closed reliably; when the opening button is pressed, the circuit breaker should be tripped and disconnected in an instant.