Earth Resistance test to be conducted on summer conditions to achieve the correct value by using an earth resistance tester (From Megger/ Sanwa/ Fluke). The value should be less than 1 Ohm for electrical earth pits and less than 10 Ohm for Lightning protection System. Procedure for testing should be as per the equipment.
the earth resistance should be less than 1 ohm. if we using
digital earth resistor, then one common method used as
three terminal type and the distance between these three
terminal should be 20 to 30 meters.
Switch on the multimeter, and using the dial on the front, select the resistance function. The multimeter will have two probes with metallic pointed ends. Place the probes on either side of the earth wire. The display on the multimeter should show a low resistance of approximately 0.5 Ohms. If the resistance is significantly higher than this, the wire is faulty and needs to be replaced.
When measuring the Insulation resistance of a motor winding
(winding to earth) using a megger meter, Applied
voltage(1000V) was automatically reduced to 500V. and the
measured insulation resistance values are also very low (in
Kohm range) Can anyone give me a reason???