Insulation Resistance (IR)

Insulation Resistance (IR) Test

Understanding the fundamentals of electrical insulation testing will help you keep your power system running smoothly and maintenance is taking insulation resistance (IR) readings. This is done to verify the integrity of the insulating material, be it wire and cable insulation or motor/generator winding insulation. Any electrical insulation must have the opposite characteristic as the conductor: It should resist the flow of current, keeping it within the conductor.


Purpose of insulation resistance testing:
  • A quality control measure at the time a piece of electrical equipment is produced;
  • An installation requirement to help ensure specifications are met and to verify proper hookup;
  • A periodic preventive maintenance task; and  A troubleshooting tool.