How significant is Insulation Resistance Testing?
Since over 80% of electrical maintenance testing involves evaluating insulation integrity, the answer is Yes, it’s a very important test. This is because electrical insulation begins to age as soon as it’s manufactured and aging causes deterioration in the performance of the insulation. Harsh operating environments will also cause further deterioration, especially where the electrical insulation is exposed to extreme operating temperatures, moisture, and chemical contamination. As a result, personnel safety and operating reliability can both be compromised. It’s extremely critical to always know the electrical condition (IR) of the insulation in your equipment at all times.

What is an Insulation Resistance Test?
The Insulation Resistance (IR) test, commonly known as a “Megger” test, is normally used as a “Spot type” test to measure the insulation’s dielectric condition at a given moment in time. The test is performed by applying a current limited DC test voltage between the conductors (Windings) and the chassis of the equipment (Ground), and then measuring any current leakage across the insulation’s dielectric materials. The current may be measured in Milli-amps or Micro-amps and then calculated into Meg-ohms of resistance. The lower the current level measured, the greater the insulation resistance.