How Do You Test Megger Insulation Resistance?

What does a reading of 0 ohms mean?

Resistance is measured in ohms with no current flowing through the circuit.

It indicates zero ohms when there is no resistance between the test points.

This shows continuity of current flow in a closed circuit.

It indicates infinity when there are no connections in the circuit that is as in an open circuit..

How do you read a Megger?

Select 500 volts DC or 1000 volts DC as the test voltage on your Megger, depending on the model you are using. Check whether your model has an integrated voltage tester for live circuits. If it doesn’t, check the circuits to be tested with a voltage tester to make sure they are not live.

Can you test insulation resistance with a multimeter?

An insulation resistance meter can measure into the gigohm or hundreds of gigohm range; some models reach into tera-ohms! The reason a multimeter cannot measure such extremely high resistance is because the measurement is performed with a low voltage (often a 9V battery inside the multimeter).

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 you test a 3 phase motor insulation resistance?

Phase Resistance: Take the insulation tester and set it to 500V. Take each end and place it on different permutations of L1, L2 and L3 and record each reading. Phase to Earth Resistance: Take the insulation tester, using the same setting, and check each lead from phase to the frame of the motor.

Why do you Megger a motor?

It specifically tests the motor windings insulation. Depending on the insulation class of the motor, a good motor could measure well into Tera Ohms or 1,000,000,000,000 ohms! This is an insulation test of motor windings, commonly referred to as megging, to megger, or to meg a motor.

Can a Megger damage insulation?

Using a megger meter is not destructive. When insulation has been damaged, a megger tester is used in determining the cause by testing. The test is typically conducted at rates that are low as compared to the insulation. The insulation tests may range from as low as 40 V dc to 10 kV.

How can I increase my Megger value?

Example-1: For 11KV, Three Phase Motor. IR Value =0.415+1=1.41 MΩ but as per IEEE43 It should be 5 MΩ….IR Value of Motor as per NETA ATS 2007. Section 7.15.1.Motor Name Plate (V)Test VoltageMin IR Value1000V1000V DC100MΩ2500V1000V DC500MΩ5000V2500V DC1000MΩ8000V2500V DC2000MΩ5 more rows•Apr 29, 2012

Can a Megger kill you?

The megger supplies over 500 volts, and that is enough to give a fatal shock.

What reading should you get for insulation resistance?

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.

How do you perform an insulation resistance test?

After the connections are made, the IR test is done at a low voltage, say 500V. The test specimen then is discharged and the test is done again, this time at a higher voltage, say 2500V. If more than a 25% difference exists between the two IR readings, age deterioration or damaged insulation should be suspected.

How do you read Megger results?

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. Any reading above 1.25 is considered excellent.

What is a bad Megger reading on a motor?

This is how the test works: DC voltage of 500 or 1000 V is applied between the windings and the ground of the motor….A general rule-of-thumb is 10 Megohm or more.Insulation resistance valueInsulation level2 Megohm or lessBad2-5 MegohmCritical5-10 MegohmAbnormal10-50 MegohmGood2 more rows•Jun 9, 2014

How do you test Megger Insulation?

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. Insulation resistance quality of an electrical system degrades with time, environment condition i.e. temperature, humidity, moisture and dust particles.

What is a good reading on a Megger?

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.