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Tuesday, February 22, 2011

Root Cause Analysis: Stuck-up Worm Gear for Spring Charge Mechanism of 69kV Power Circuit Breaker (part 2)

This is the continuation of my previous post. We did some extreme measures but after re-energization of the line, it was worth it.
II. ACTIONS TAKEN
1. At 1750H, temporarily bypassed the Power circuit breaker 1 so that the line could be energized.

2. Around 1827H, 69kV Customer Line was energized through closing of DS’s No. 3 and No. 5.
3. The substation personnel and maintenance groups continued to repair the stuck-up worm gear. The spring charging motor of the power circuit breaker was removed to have a better access area in retrieval of the worm gear.
4. Removed the stuck-up worm gear and its bushing upon releasing the tension on closing spring and loosening up the coupling rings, worm wheel and pull hook and removal of the coupling shaft.
5. Delivered the stuck-up worm gear and bushing to machine shop to loosen up the worm gear and its bushing
6. Opened the motor drive mechanism connected to the motor and found the gears inside are broken and worn out.
7. Lubricated the various parts of the mechanical operating mechanism of the breaker 69kV Power Circuit breaker. Sprayed penetrating oil and applied lubricating grease on various gears, cams and latches.
8. Reassemble back breaker operating mechanism except the damaged motor drive mechanism. Tested the tripping and closing operation of 69kV Power Circuit Breaker after assembly. The testing yielded satisfactory result.
9. Coordinated to control center for the emergency shutdown of 69kV Breaker.
10. After securing clearance from customer affected and concerned persons, 69kV Power Circuit Breaker was manually tripped to facilitate restoration of the affected line.
11. Successfully restored 69kV Circuit breaker.




III. ROOT CAUSE OF THE PROBLEM
The cause of the stuck-up worm gear is due to tiny specs of foreign material that was able to penetrate and hardened in between the worm gear and its bushing. This stuck-up of the worm gear resulted the wearing out of gear teeth inside the motor drive mechanism.



IV. RECOMMENDED ACTION PLAN
1. Implement monthly vacuuming and cleaning of circuit breaker panel. The said activity will be reflected on a logbook.
2. Include in the annual preventive maintenance activities the lubrication of worm gears.
3. Charging of spring will be done while the motor-drive mechanism is under repair.
4. Conduct bimonthly lubrication on all bushings of the Circuit Breaker operating mechanism.

1 comment:

  1. Great informative post! We are India based manufacturers and suppliers of all type gears offers all over the at competitive rates.

    ReplyDelete

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