Operation and maintenance of automatic air circuit breakers and other power distribution equipment

I. Maintenance of automatic air circuit breakers

Automatic air circuit breaker structure includes contact system, arc extinguishing device, free release mechanism, closing operation drive mechanism and release (loss of voltage release, shunt excitation release, overcurrent release), some are also equipped with locking device.

Contact system structure:The contacts consist of a main contact, a secondary contact and an arc contact, and an auxiliary contact. The main contact carries the normal operating current of the circuit. Arc contacts are provided to avoid burning of the main contacts by the arc generated when the circuit is broken. The secondary contact is set up to avoid arc damage to the main contact when disconnecting the circuit due to the instantaneous voltage drop of the current moving from the main contact to the arc contact.

Sequence of actions:
● When closing the gate: the arc contact is energized first, then the secondary contact, and finally the main contact.
● When opening a gate: the main contact is disconnected first, then the secondary contact, and finally the arc contact.

The function of the free release mechanism is to keep the contacts closed or to disconnect them quickly, and it is mainly set up for external short-circuit protection, overload protection, under-voltage protection and so on. Most automatic air circuit breakers use arc extinguishing grids to extinguish the arc.

Maintenance and overhauling points of note for frame type automatic air circuit breakers:

Automatic air circuit breaker before use should be each solenoid working surface (such as loss of pressure release valve solenoid suction table surface) of the anti-rust paint or grease wipe clean, so as not to affect the action value of the switch.
Every period of time (such as monthly or at least a quarter), should be removed from the surface of the circuit breaker and the parts of the dust and black smoke, pay attention to the surface of the insulating parts of the clean, in order to ensure that the circuit breaker insulation is good, to prevent deterioration of the insulation performance.
After a period of time (e.g., after each cleaning), the drive mechanism should be partially coated with lubricating grease to improve the wear and tear of the drive mechanism.
Screws and bolts of each part should be tightened without loosening. Worn or damaged parts should be replaced in a timely manner.
Arc extinguishing chambers should be cleared of metal particles and black soot on the walls and grids inside the arc extinguishing chambers after disconnection due to a short circuit or after a longer period of time (e.g., every six months) of use. Long unused interrupter room (such as accessories), before use to ensure that the insulation is good.
After a certain number of times of use of the circuit breaker main contacts, such as found on the surface of the contacts have burrs, metal particles, etc., or every six months should disassemble the main contacts, with 200 fine sandpaper grinding in order to ensure good contact, to prevent poor contact caused by overheating, such as grinding the thickness of the contacts into the original 1/3 or less, the contacts shall be replaced, and the dynamic contacts and fixed contacts shall be replaced at the same time.
Regularly check the action setting value and delay time of each disconnector (especially semiconductor disconnectors), and reset them when the parameters change.

Second, automatic air circuit breaker common faults and troubleshooting

Automatic air circuit breakers should be cleaned regularly during normal operation and greased if necessary. Because of the complex structure of automatic air circuit breakers, there are more types of faults, as shown in Table 5-1.

Table 5-1 Troubleshooting Table

fault phenomenon

Cause analysis

Treatment

(1) Electrically operated circuit breaker does not close

(1) The operating power supply voltage does not match;

(2) Insufficient power supply capacity;

(3) Insufficient solenoid puller travel;

(4) The motor operation positioning switch is dislocated;

(5) Rectifier tube or capacitor damage in the controller

(1) Switch the power supply;

(2) Increase the operating power supply capacity;

(3) Readjust or replace the tie rods;

(4) Realignment;

(5) Replacement of damaged components

(2) Manual operation of the circuit breaker cannot be closed.

(1) No voltage to the loss-of-voltage striker or damaged coil;

(2) The deformation of the energy storage spring results in a reduction of the closing force;

(3) The reaction spring force is too large;

(4) The mechanism cannot be reset and reclosed

(1) Check wiring, apply voltage or replace coil;

(2) Replace the energy storage spring;

(3) Readjust the spring reaction force;

(4) Rebuckle the contact surface to the specified value.

(3) Failure of the excitation detacher to break the circuit breaker.

(1) Coil short circuit;

(2) The supply voltage is too low;

(3) Rebuckling contact surface is too large;

(4) Loose screws

(1) Replace the coil;

(2) Switch the supply voltage;

(3) Realignment;

(4) Tightening

(4) The circuit breaker breaks immediately when the motor is started.

(1) The instantaneous setting value of the overcurrent detacher is too small;

(2) Some parts of the disconnector (e.g., semiconductor devices, rubber film, etc.) are damaged;

(3) Broken or detached detacher reaction spring

(1) Adjust the transient setting value;

(2) Replace the striker or replace damaged parts;

(3) Replace the spring or reattach the

(5) Loss-of-voltage detent does not break circuit breaker

(1) The reaction spring becomes smaller;

(2) If it is a stored energy release, the stored energy spring becomes smaller or breaks;

(3) Mechanism jamming

(1) Adjust the spring;

(2) Adjust or replace the energy storage spring;

(3) Eliminate causes of jamming (e.g. rust)

III. Reset operation after tripping of automatic air circuit breakers

After tripping the automatic air circuit breaker, wear insulated gloves, goggles and other personal protective equipment to cut off the power supply to the faulty circuit through the main switchboard to ensure safe operation. Verify that the circuit breaker is fully tripped (with the operating handle in the “TRIP” or center position). Check the switchboard for smoke, burning odor or traces of arcing.

1. Specific steps for the reset operation

Step 1: Determine the cause of the trip.Common reasons for tripping: overload, short circuit, under/over voltage, mechanical failure, protective device malfunction, etc.

Step 2: Troubleshooting.Disconnect part of the load and reduce the total current to below the rated value of the circuit breaker; use a multimeter or an insulation tester to identify the short-circuit point, repair it and re-insulate it; check whether the voltage of the grid is stable, and activate the voltage stabilizing device if necessary.

Step 3: Manual reset operation.Before resetting, make sure that the fault has been removed and that there is no abnormality in the circuit breaker body and wiring.

Standard reset:Trigger the operating handle in the direction of “OFF” to the limit position, and then in the direction of “ON” to the closed position, and then hear the “click” sound to indicate a successful reset.
With reset button type:Press the reset button (usually red or yellow), then trigger the handle to the “ON” position, observe the panel indicator or mechanical signs to confirm.

Step 4: Energize and test to gradually restore power.After closing the gate, first no-load energize, observe whether to trip again; if there is no abnormality, gradually access the load to the rated value, continuously monitor the current, voltage and temperature rise data.

2. Precautions

Forced reset is prohibited:Multiple reset attempts are prohibited until the cause of the trip has been identified, otherwise the fault may be amplified.
The power supply must be cut off before reset to avoid arcing injury caused by energized operation.
If the internal components of the circuit breaker (e.g., striker coil, contacts) are damaged, spare parts of the same type shall be replaced.
The overload and short-circuit protection functions need to be calibrated after reset (can be verified by simulation test).

IV. Breaking principle of circuit breakers with emergency cut-off signs

1. Overview of circuit breakers with emergency cut-off symbols

Circuit breakers with an emergency cut-off symbol (e.g. red button, pull lever or rotary switch) are safety protection devices used to quickly cut off the power supply in case of emergency (e.g. electrocution, short-circuiting of equipment, fire, etc.) to prevent the accident from expanding. Its core features are manual priority breaking and high response speed. They are mainly used in ships' main switchboards, emergency switchboards and key equipment control boxes, as well as in high-voltage power circuits where there is a risk of electric shock.

2. Construction of circuit breakers with emergency cut-off signs

The core structure includes: Mechanical emergency breaking mechanism (through the spring energy storage mechanism or lever linkage to achieve rapid release); Electromagnetic emergency breaking mechanism (triggered by the electromagnetic coil to release the mechanism, need to be connected to the emergency power supply). Emergency cut-off symbol design is eye-catching, and some models are equipped with anti-touch interlocking device. Display “OFF” or red warning sign after opening the gate.

3. Principles of emergency disconnection

Normal tripping:The control loop signal (e.g. overload, short circuit protection) triggers the striker and the mechanical mechanism breaks the contacts.
Emergency tripping:Manual triggering, direct operation of the emergency button/pull lever, bypasses the control loop and forces the release of the striker spring or activates the electromagnetic striker.

Action Process:
(1) Emergency operation part is stressed → Mechanical interlock is triggered.
(2) The energy storage spring releases energy instantaneously → the movable contact separates quickly.
(3) The arc is extinguished by the arc extinguishing chamber → The circuit is completely disconnected (less than 50 ms).

4. Differences between emergency tripping and conventional tripping

Table 5-2 Differences between emergency tripping and conventional tripping

characterization	emergency sluice gate	Conventional Split Gates
trigger method	Manual priority, direct physical operation	Automatic or remote electrical signal control
response time	≤100 ms	200~500 ms (dependent on protective device response)
prioritization	Maximum (can interrupt other protection logic)	Controlled by preset protection parameters