20 D-04 Q |
Checking of Heater Function :
- Do as described in Sub-Para 20 C-04Q.
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20 D-05 Q |
Visual Inspection of Breaker and Operating Mechanism :
- Do as described in Sub-Para 23C-05 Q.
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20 D-06 Q |
Checking of Breaker Operation and Removal of Coatings Developed on Current Carrying Parts of the Breaker, Remains for Long Time in the Closed Position :
- Do as described in Sub-Para 23 C-06Q.
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20 D-07 Q |
Checking of Oil Leaking From Oil Dash Pot in Operating Mechanism :
- In the closed position the oil surface should not be more than 15 mm below the edge of the filling hole.
- Do as described in in Sub para 20 C-07 Q
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20 D-08 Q |
Checking of Gas Vent :
- Ensure vent pipe is free of obstructions like insects, wasp, rusting etc. The vent pipe is be checked with the help of thin rod to remove obstructions.
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20 D-09 Q |
Lubrication :
- Check whether gears, latches and springs etc. are properly lubricated. Do, if not
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20 D-10 Q |
Cleaning of The Breaker :
- Clean the circuit breaker with non fluffy cloth with special attention to porcelain insulators. Cotton waste is unsuitable not recommended.
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20 D-11 Q |
Checking of Dielectric Strength of Oil :
- Do as described in sub para 20 C-08 T.
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NOTE : The circuit breaker should be overhauled regularly, the first time after one year operation and there after every third year unless operational experience motivates other periods. |
Tripping Based Maintenance :
- Record no. of short circuit tripping if any and identify the pole which has cleared the short circuit fault current.
- Following maintenance work is to be carried out after 3 tripping at rated short circuit current or 8 tripping at 50%breaking capacity or 400 tripping at rated normal current. If faults are occurring in one particular phase, shorter trip based overhauling may be necessary.
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20 D-12 T |
Checking of Dielectric Strength of Oil :
- Do as described in 20 C-08 T.
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20 D-13 T |
Checking of Plug Contacts Burning :
- Contact plugs are to be examined for burning :
Check contact measurement as described in the manual. If burning is very slight, removing of burn heads and polishing the surface insufficient. Replace the tips and arcing ring when burning is heavy. The degree of burning of the plug contact should be checked when the circuit breaker is in closed position. Correct measurement of distances as per BHEL manual reference no. BHE/IM/SEG/005/5000/3.79'a1' to 'a2' from the ruler DA-10 to the plug contact DA-13 and the surface DA-12 is to be done. If the degree of burning approaches the value given for used tip, remove the plug contact from the interrupter for more careful measurement of the contact tip.
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Dimensions at a1 and a2 in mm. new tip a1 – a2 = 50 mm. used tip a1 – a2 = 56 mm. |
20 D-14 T |
Checking of Extinguishing Chamber :
- Do as described in 20 C-10 T and see the manual. It is important that the chamber is kept free from contamination and that contacts and insulating parts are not burnt/damaged. Valve and piston should not be sluggish or hindered in their movement.
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