Page 64 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

TASK 3 : Measure the earth resistance of Earthing point
1 Switch OFF the main supply of Electrical installation and disconnect phase, neutral and earth connection in
main distribution board.
2 Fix the one GI rod in the ground at distance of 5 ft (as per approx length of earth electrode) from earth pit.
3 Fix other GI rod in the ground at distance of 50 ft (10 x length of earth electrode) from earth pit.
4 Now make the connections of earth tester as shown in the diagram.
5 Now turn ON the earth tester and set the range of 10 Ω

6 Press the test button of earth tester note the resistance value recorded in earth tester.
7 Switch OFF the earth tester and fix the first GI rod at a distance of 10 ft from earth pit.
8 Press the test button of earth tester note the resistance value recorded in earth tester.
9 Repeat the procedure and take 3 to 5 readings of earth resistance and take average value which is measured
value of earth resistance.
10 Disconnect earth tester from earth pit, and restore the main supply of electrical installation.
Safety precautions

• Handle and operate the earth tester carefully.
• Do not test earth resistance with main supply ON
• Do not disconnect the earth connection without disconnecting mains which causes electric shock.
Table

Earth Spike 5ft 10ft 15ft 20ft Average Value of earth resistance (Ω)
Distance
Earth Resistance Ω Ω Ω Ω

Length of Earth Electrode: _____
Ideal Value of Earth Resistance: < 2 Ω
Measured Value of Earth Resistance: ______

4 point Digital Earth Tester

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CITS : Power - Electrician & Wireman - Exercise 24