What should be the insulation resistance value between phases?

The rule may be stated: Insulation resistance should be approximately one megohm for each 1,000 volts of operating voltage, with a minimum value of one megohm. For example, a motor rated at 2,400 volts should have a minimum insulation resistance of 2.4 megohms.

Why does insulation resistance increase with time?

As the voltage builds up, the absorption level in the insulation decreases. This gradual change reflects the storage of potential energy in and along the insulation. Incidentally, absorption current is an important part of the time resistance method of insulation testing. Leakage current.

Which factors can affect the insulation time resistance test?

Factors that affect insulation resistance measurements include such things as temperature, humidity, previous conditioning, test voltage, charging current and duration of the test voltage (electrification time).

What are the factors affecting insulation resistance?

The factors that commonly affect the insulation resistance are:

Surface condition. For example oil or carbon dust on the equipment’s surface that can lower the insulation resistance.
Moisture.
Temperature.

Why does the resistance of insulation change over time?

In the real world, however, actual resistance values can be higher or lower due to the effects of factors such as temperature, humidity, the moisture content of the insulation, even the person doing the testing. And, IR readings can be very different for the same motor tested on three different days.

What is the purpose of the insulation resistance test?

The Insulation Resistance Test is the second test required by the electrical safety testing standards. The Insulation Resistance Test consists in measuring the Insulation resistance of a device under test, while phase and neutral are short circuited together.

How is the insulation resistance of a transformer measured?

Connect the test leads (avoid joints). Apply the test voltage and note the reading. The IR. Value at 60 seconds after application of the test voltage is referred to as the Insulation Resistance of the transformer at the test temperature. The transformer Neutral bushing is to be disconnected from earth during the test.

What’s the difference between a dielectric and an insulation test?

Then there’s insulation resistance test, or just simply insulation test, which measures the resistance of the insulation. The insulation test is done prior to high-potential tests in order to eliminate any contamination in the electrical insulation.