ACB (MAINTENANCE, TROUBLE SHOOTING TESTING OF RELEASES)

 

AIR CIRCUIT BREAKERS

COMPLAINT :- BREAKER IS NOT CLOSING

 

PROBABLE CAUSE a) Undervoltage release not connected with supply. b) Undervoltage release, Shunt release,  Magneto thermal release connecting link not adjusted properly.     c) Magneto thermal release removed from ACB, but trip bar of release kept free.  d) Latch of the mechanism spring not in proper position or misplaced. e) Under voltage release coil burnt out or open circuited. f ) Bimetal element of magneto thermal release bent permanently. g) After overload or short circuit fault, breaker not reset (ONLY FOR MANUALLY RESET TYPE ACB.) h) Sticking of tripping mechanism due to excess dust.

POSSIBLE SOLUTION a) Give rated voltage to under voltage release.   b) Adjust the connecting linkage of releases correctly.   c) Lock the trip bar at given position.   d) Fix the spring correctly.   e) Replace the under voltage release.   f ) Replace the magneto thermal release.   g) Reset the breaker by pressing OFF / RESET button.   h) Clean the tripping mechanism with CRC 2-26 & grease them, (refer section on greasing)

 

COMPLAINT :- BREAKER IS NOT TRIPPING WITH UNDERVOLTAGE OR SHUNT RELEASE.

 

PROBABLE CAUSE   a) Shunt release does not get supply.   b) Supply of under voltage release does not get cut off.   c) Link pins of Undervoltage or shunt release misplaced.   d) Due to dust release becomes sticky.

POSSIBLE SOLUTION   a) Check control wiring of shunt release & ensure that shunt release gets supply.   b) Check control wiring.   c) Ensure that pins are in position.   d) Remove the dust from the release & clean it with CRC 2-26

 

COMPLAINT :- BREAKER IS NOT TRIPPING BY MANUAL TRIP PUSH BUTTON

 

PROBABLE CAUSE   a) Trip push buttons connecting link is short. (Not adjusted properly.)   b) Latch of the mechanism. jammed because of dust.

POSSIBLE SOLUTION a) Adjust the push button link correctly.   b) Clean the latch of the mechanism with CRC 2-26.

 

 

COMPLAINT :-  ACB IS NOT TRIPPING IN CASE OF OVERLOAD OR SHORT CIRCUIT FAULT

 

PROBABLE CAUSE   a) Connection between C.T. and magneto thermal release is loose or open circuit.   b) Overload setting of magneto thermal release is more than actual load current.   c) Magneto thermal release linkage not adjusted properly.

POSSIBLE SOLUTION   a) Tighten the terminals of C.T. in case of open circuit.   b) Make the overload setting of ACB as per actual load current.   c) Connect the linkage of magneto thermal release to trip bar properly & ensure its tripping operation.

 

 

COMPLAINT :-  MAIN CONTACTS OF ONE OF THE POLE OF ACB NOT CLOSING

 

PROBABLE CAUSE   a) Excessive dust accumulated in the pole assembly.   b) Nylon rollers of the pole assembly are not rotating smoothly.   c) Pole connector setting disturbed.   d) Nylon rollers of the pole assembly are broken

POSSIBLE SOLUTION   a) Clean the pole assembly mechanism with CRC 2-26. Remove grease and dust with brush & apply fresh grease.   b) Clean the nylon rollers with CRC 2-26 and relubricate them. (refer section on greasing)   c) Consult the manufacturer of Circuit Breaker   d) Consult the manufacturer of Circuit Breaker

COMPLAINT :-  PITTING ON MAIN CONTACTS

 

PROBABLE CAUSE   a) Arcing contact gap is not adjusted properly.   b) Thickness of arcing contact is reduced below the specified limit. (> 0.5 mm)

POSSIBLE SOLUTION   a) Adjust the gap of arcing contacts, it should be 0.9 + or -0.1 mm   b) Replace both fixed and moving arcing contacts

 

COMPLAINT :-  EROSION ON ARCING CONTACTS

 

PROBABLE CAUSE   a) Rough deion plates of arc chutes.   b) Breaker is operated without arc chute in position

POSSIBLE SOLUTION   a) Clean the deion plates and side insulating strips of arc chutes with CRC2-26.   b) Always operate ACB with arc chute in position & keep the arc chutes clean

 

 

COMPLAINT :-  BREAKER IS NOT RACKING IN THE CRADLE FREELY

 

PROBABLE CAUSE   a) Threads of mechanical indicating assembly worn out.   b) Shutter assembly is not properly set in the cradle.   c) Secondary isolating contacts not matching properly.   d) Dovel pin broken.   e) Telescopic rail becomes jammed.

POSSIBLE SOLUTION   a) Replace the mechanical indicating assembly.   b) Fix the shutter assembly properly in the cradle.   c) Match the fixed and moving secondary isolation contacts properly.   d) Replace the dovel pin.   e) Clean the telescopic rail with CRC 2-26. Remove dust, grease & relubricate it.

COMPLAINT :- OVERHEATING

 

PROBABLE CAUSE   a) Poor termination (High Milli- Volt drop across termination on ACB.)   b) Dusty atmosphere.   c) Use of undersized cable or bus bars.   d) High ambient temperature

POSSIBLE SOLUTION   a) Clean the terminals with CRC 2-26 and do proper retermination. Ensure that milli volt drop within specified limits.   b) Do periodic cleaning of circuit breaker.   c) Use cables or bus bars of adequate rating.   d) Reduce load current or select & install correct rating of ACB

 

 

COMPLAINT :- BREAKER IS NOT CHARGING WITH MOTOR

 

PROBABLE CAUSE   a) Motor is not getting supply.   b) Loose connections in secondary isolating contacts.   c) Motor is burnt out.

POSSIBLE SOLUTION   a) Check the limit switch of motor. Replace it if it is damaged.   b) Fix the secondary isolating contacts properly,   c) Replace the motor.

 

 

COMPLAINT :- BREAKER IS NOT CLOSING REMOTELY

 

PROBABLE CAUSE   a) Breaker is not in service position   b) Closing coil is not getting supply,   c) Closing coil burnt out or open circuited.

POSSIBLE SOLUTION   a) Take the breaker in service position.   b) Check control circuit and ensure that coli gets supply.   c) Replace the closing coil,

 

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