Page 63 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

EXERCISE 24 : To measure the earth resistance by earth

tester

Objectives

At the end of this exercise you shall be able to
• test the earth continuity of earthing point
• check the terminals & connections of earth tester
• measure the earth resistance of earthing point.

Requirements

Tools/Equipments Materials
• Combination Plier 165mm, • Connecting wire 1.0 sq.mm - 90 meter
insulated - 1 No. • Insulation tape PVC, 19mm - 1 role
• Neon tester 75mm, insulated - 1 No. • Test lamp 60 W, 230V - 1 No.
• Screw driver, insulated 150mm - 1 No. • Salt water - as reqd.
• Spanner Adjustable - 1 No.
• Ball peen hammer 0.5 Kg - 1 No.
• Digital Multi meter 3 digit - 1 No.
1/2
• Earth tester 4 point, Digital - 1 No.
• GI rods 10mm dia, 1.5 ft - 2 Nos.
• Resistance 100 Ω - 1 No.

Procedure

TASK 1 : Identify & test the earthing point
1 Identify the earthing point to be tested and clean the earth fit and its surrounding.

2 Check the earth conductor, earth connector strip for rigid connection, and damage / breakage If any.
3 Test the earth continuity with test lamp.
(The test lamp should glow bright, if lamp glows dim the earth connectivity is poor)
4 Pour the salt water sufficiently through funnel with mesh into the earth pit.

TASK 2 : Check the earth tester

1 Draw the circuit diagram of measurement of earth resistance.
2 Read the specifications, scale of earth tester and check its terminals.
3 It is necessary to calibrate the earth tester before testing of earth resistance.
4 For calibration, short the terminals C1 P1 & P2 C2 of earth tester and connect resistance of 100 Ω across
shorted terminals.
5 Now turn ON the digital earth tester and test button, the earth tester should read 100 Ω
6 Disconnect the shorted wire on terminals of earth tester, and it is ready for measurement of Earth resistance.

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