Page 333 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

Table 1
Sl. TMS Tap set Multiplier Time in Total fault Pickup Actual trip
No. Position current (A) value seconds current current time

1 1 0.5 2 x 0.5 = 1A 10 Sec 1A <1A

2 1 1.0

3 1 1.5

4 1 2.0

9 Increase the current slowly, the disc of relay start to move that is the pickup current. Note down the value in
Table 1.
10 Change the tap set current to some other current value and repeat the step 5 to 9.

11 Change the tap set for other value and repeat the steps 6 to 10 and record the readings.
12 Try few more tap set values and check the pickup current.

Note: TMS position should not be changed while doing the exercise.

TASK 2 : Reduce the tripping time by setting time multiplier setting
1 Keep all the controls knobs at zero position.
2 Set the TMS disc at 0.5 position by rotating TMS disc fitted on the main spindle.
3 Repeat the steps 5 to 10 for the new TMS value of 0.5. Enter all the readings in Table
Note : It may be noted that when TMS set for 0.5 the actual trip time reduced by 50% of the trip time
actual in Task 1.

Table 2
Sl. TMS Tap set Multiplier Time in Total fault Pickup Actual trip
No. Position current (A) value seconds current current time

1 0.5 0.5 A 2 x 0.5 = 1A 10 Sec 1A <1A
2 0.5 1.0 A

3 0.5 1.5 A

4 0.5 2 A

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CITS : Power - Electrician & Wireman - Exercise 113