Method of Measurement of Insulation Resistance
Q. State the method of measurement of insulation resistance and explain any one method.
Methods of measurement of Insulation Resistance (IR) :
- By using megger
- By voltmeter method
An insulation resistance meter is a megger which indicates the resistance directly. Disconnect the equipment from mains and then connect one terminal of megger to the winding and the other to the frame, move the handle of megger at normal speed, this will cause the pointer to move to position on the scale corresponding to the value of insulation resistance under test.
The recommended value of insulation resistance as per Is rules between windings, windings and ground at the working temperature of 70° C should be
Insulation resistance = (Rated voltage in volts / 0.01 x kVA rating + 1000) MΩ
The minimum value should be above 0.5 MΩ