What are acceptable Megger test readings?

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.

Can Megger measure high resistance?

Megger is used to measure very high resistances, such as those found in cable insulation, between motor windings, in transformer windings. The Megger is essentially a portable ohmmeter with a built-in high voltage source. Meggers may read resistances of several hundred or even thousands of megaohms.

What is a bad insulation resistance reading?

The purpose of the IR test is to check for damaged insulation, this can be mechanical damage or damage by heat, (overloaded cables), readings less than 2 Mohm indicate damaged insulation, readings of 2-50 Mohm are indicative of long circuit lengths, moisture and contamination and do not indicate the insulation quality.

How do I test my insulation with a Megger?

If you are testing insulation resistance to ground, place the positive probe on the ground wire or the grounded metal junction box and the negative probe on the conductor or terminal. Energize the Megger for 1 minute. Read the value of the resistance at the end of the minute test and note it in your table.

What is a bad reading on a Megger test?

What is a bad Megger reading? If the megger reads a resistance under 1 (1,000 ohms) on your meter after the initial 60-second interval, the cable has failed and the cable should be removed. If the megger reads a resistance between 1-1.25 on your meter, then the cable passes.

What is a good insulation resistance reading?

Insulation resistance should be approximately one megohm for each 1,000 volts of operating voltage, with a minimum value of one megohm. In practice, megohm readings normally are considerably above this minimum value in new equipment or when insulation is in good condition.

What does a megger test tell you?

The Megger test is a method of testing making use of an insulation tester resistance meter that will help to verify the condition of electrical insulation. The IR gives a measure of the enduring power of an insulator to bear the service voltage without any current leakage path.

Can a megger kill you?

Usual megger voltage is 500 V, and our body resistance can be 1 M or little less. This means a maximum current of 1 mA or bit more, which is not safe, though not fatal (If we don’t count meter resistance).

What is a bad reading on a Megger?

What is considered a bad Megger reading?

Turn on and read the meter. Anything reading between 2 megohms and 1000 megohms is usually considered a good reading, unless other problems have been noted. Anything less than 2 megohms indicates an insulation problem.

What does the Megger insulation tester tell you?

The Megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. For good insulation, the resistance usually reads in the megohm range. The Megger insulation tester is essentially a high-range resistance meter (ohmmeter) with a built-in direct-current generator.

How to interpret a Megohmmeter reading for insulation?

Properly interpreting megohmmeter readings of an insulation-resistance test can help you identify faulty or damaged insulation that can lead to these problems. Perform a time-resistance testing method using a megger, and take successive readings at specific intervals. A time-resistance test is performed over five to 10 minutes.

Which is the best test for insulation resistance?

The insulation resistance test, a.k.a., the “Megger test”, is as relevant as ever and, in many applications, is preferred to other insulation test methods. Today Megger offers the finest line of 5 kV, 10 kV and 15 kV (dc) insulation resistance testers available anywhere.

What should the resistance of a Megger be?

If the megger reads a resistance between 1-1.25 on your meter, then the cable passes. Any reading above 1.25 is considered excellent. Continue to monitor the megger over 30-second intervals. If the resistance reading continues to increase, the cable insulation is in excellent condition.