A Megger insulation tester can be used to perform three different types of insulation resistance tests, short-time or spot-reading, time-resistance and dielectric absorption ratio. Each test varies with results and is used for particular purposes.
To help you get a better understand of what each test is and how a Megger test can be used. We have created a brief guide below.
THREE TYPES OF RESISTANCE TESTS
SHORT-TIME OR SPOT-READING TEST
A short-time or spot-reading test is performed by simply connecting a Megger insulation tester across the insulation that is being tested. It is then to be operated for a short, specific time period, usually 60 seconds. During this test, it’s important to remember that temperature, humidity and the condition of the insulation are affecting the reading.
A time-resistance method is fairly independent of temperate and often gives conclusive information without records from prior tests. This method is based on absorption effect of good insulation compared to contaminated insulation. During this test, the Megger insulation tester will take successive readings at specific times and note the differences. This test should display a continual increase in resistance over a period of time if insulation is good.
DIELECTRIC ABSORPTION RATIO
A dielectric absorption ratio is the ratio of two time-resistances readings. For example, a 60-second reading divided by a 30-second reading, A Megger insulation tester makes a dielectric absorption ratio test easier and is known for giving best results. For example, a Megger insulation tester can run for 60 seconds; however, it allows you to record readings at the 30-second interval and at the 60-second interval.