Page 339 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

EXERCISE 116 : Practice on repair and maintenance of

circuit breaker

Objectives

At the end of this exercise you shall be able to
• follow the shutdown procedure
• refer to service and operating manuals of a given circuit breaker to identify the parts and their functions (R)
• refer to previous maintenance records for carrying out routine maintenance checks
• locate the faulty part and replace it
• follow the general maintenance procedure on the circuit breaker.

Requirements

Tools/Equipments/Instruments Equipment/Machines
• Insulated cutting pliers 150 mm - 1 No. • Circuit breaker of higher voltage
• Screwdriver 150 mm - 1 No. and current rating - 1 No.
• Heavy duty screwdriver 300 mm - 1 No. Materials
• Neon tester 150 mm 600V - 1 No. • Rubber or cork gasket as specified
• D.E. spanner set of 9 Nos. 5 mm and reqd.
to 20 mm - 1 Set. • Sand paper Grade “0” - 1 Sheet.
• Box spanner set of 9 Nos. 5 mm • Grease - 10 g.
to 20 mm - 1 Set. • Flexible cable 14/0.2 - 5 mts.
• Megger 500V - 1 No. • Dash pot oil of specific grade - 200 ml.
• Multimeter 20 kilo ohm/volt - 1 No. • Contact cleaner oil - CRC 2-26 - 1 bottle.
• Cleaning brush round 2.5 cm - 1 No. • Electro tube - 25 g.
• Plumb bob with thread - 1 No.
• Spirit level 300 mm - 1 No.
• Flat file bastard 250 mm - 1 No.

Procedure

As it is impracticable to get a switch gear of high voltage and current rating in a vocational institute,
it is recommended that the trouble shooting procedure is followed in a circuit breaker, having
similar facilities like the rotor resistance starter used in a slip ring induction motor. However, the
manufacturers instruction for the trouble-shooting should be followed for larger circuit breakers
when the trainee is employed in an industry. The working steps given there are of a generalized
nature and could be used with slight modification for any circuit breaker.
Caution: Before taking up the maintenance work on any circuit breaker which is in operation, it
is utmost necessary to take permission from the engineer in-charge. He only decides whether
alternative arrangement is required to maintain supply to the consumer or a shut down is to be
effected.
Permission for shut down is given by the engineer in the approval forms. Follow all the instructions
contained in the shut down form before taking up the maintenance work on the circuit breaker.
The concerned control switch of the circuit breaker should be switched OFF and locked and
caution boards should be displayed in the control panel. The key should be kept in the custody of
the engineer in-charge. A caution board should also be displayed predominantly near the circuit
breaker which is under maintenance.

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