Work Instructions for Megger Insulation Resistance Testers

Written by michelle hickman
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Work Instructions for Megger Insulation Resistance Testers
Manufacturers and machinery workers use insulation resistance testers for electrical maintenance. (Green Cables image by Charlie Rosenberg from

Megger insulation resistance testers determine the safety of electrical equipment by testing the condition of the insulation in power cables, generator windings and line transformers. This nondestructive test method shows the user the amount of moisture in the insulation, the winding deterioration and the leakage of current over dirty or moist surfaces of the insulation. You will have to decide upon the appropriate Megger unit to use in accordance with safety and health specifications when working with high-voltage equipment.

Skill level:


  1. 1

    Clip the test leads using the medium insulated clips to the item needing testing, such as transformers, motor/generator windings, voltage buses or power cables. Turn on the unit to start automatic testing. If you accidentally connect the unit to a live test line, the instrument will prevent the external voltage from going above 50 or 80 volts (depending on the Megger testing unit) and the display will automatically show the external voltage reading.

  2. 2

    Take readings of the insulation. The display panel will show that a DC voltage of 500 or 1,000 is being applied. Insulation testing measures the resistance to the voltage over time. You can preset a specific resistance level, where the unit will beep when the limit is exceeded.

  3. 3

    Record the insulation resistance data at 1-minute to 10-minute intervals along with other intermediate times. A built-in timer allows for accurate readings displayed as minutes and seconds. Conclude the test of the insulation resistance as the unit will automatically discharge the dangerous static voltage. You can download the test results to your computer using the USB connection.

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