Page 340 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

1 Collect the service and operating manuals of the circuit breaker and read them carefully.
2 Collect the maintenance record sheet of the circuit breaker.

Note: It is desirable that you read the service and operating manuals carefully and thoroughly
before starting the actual maintenance work.

3 Note the name-plate details of the circuit breaker in Table 1.
Note: Example of work permit and shut down

4 Switch ‘OFF’ the incoming and outgoing bus bars, and then disconnect the circuit breaker from the bus bars.
5 Follow the instructions contained in the service manual to open the top covers of the circuit breaker.
6 Identify the parts and compare with the service manual.
7 Identify and trace the tripping circuits.

8 Carefully inspect the parts for burnt smell, visible indication of burns, pittings and discolouring.
9 Interpolate your finding with the maintenance record sheet information to pin point the faulty part.
10 Identify the part number from the service manual and collect the parts from the stores.
11 Check the correctness of the part received from the stores and then replace the part in the circuit breaker.

General maintenance procedure
12 Check the mounting bolts/studs for correct tightness.
13 Check the verticality of the circuit breaker with the help of a plumb bob, and horizontality with the help of spirit
level.

Note: If necessary correct them by mounting bolts.
Table 1
Technical data of the circuit breaker
i Type of the circuit breaker ......
ii Type designation ......

iii No. of phases/poles ......
iv Rated voltage ......
v Maximum voltage ......
vi Rated frequency ......

vii Rated current ......
viii Rated symmetrical breaking capacity ......
ix Rated making current ......
x Rated short time current ......
xi Quantity of oil per pole ......
xii One minute try withstand voltage ......

xiii Impulse withstand voltage ......
xiv Type of closing device ......
xv Trip free/fixed trip ......
xvi Weight of the oil ......

xvii Quantity of oil in litres ......

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CITS : Power - Electrician & Wireman - Exercise 116