What Is Megger Tester

April 21, 2024 Post a Comment

What is megger tester

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.

How is megger test measured?

Steps

Connect the circuit as described above.
Press the test button on megger, the megger will generate current.
This current flows through cable, the resistance in scale is noted which ranges between 35 to 100 Mega Ohms.
Note to maintain this contact for 30 to 60 seconds.

How does a megger test resistance?

The Megger insulation tester is essentially a high-range resistance meter (ohmmeter) with a built-in direct-current generator. This meter is of special construction with both current and voltage coils, enabling true ohms to be read directly, independent of the actual voltage applied.

What is megger in simple words?

/ (ˈmɛɡə) / noun. trademark an instrument that generates a high voltage in order to test the resistance of insulation, etc.

What is the minimum megger value?

Insulation resistance should be approximately one megohm for each 1,000 volts of operating voltage, with a minimum value of one megohm.

Why do you megger a cable?

The purpose of Megger test equipment for cables is to measure the integrity of your insulation in megaohms, similar to an ohmmeter. The device itself consists of three essential components such as an alligator clip, an analog or digital meter, and a small button that generates a test current.

What is IR value of cable?

Application	Test Voltage	Min IR Value
New cables – Sheath	1KV DC	100 MΩ
New cables – Insulation	10KV DC	1000 MΩ
After repairs – Sheath	1KV DC	10 MΩ
After repairs – Insulation	5KV DC	1000MΩ

How many types of megger are there?

There are two types of meggers, manual and electrical megger. The main concept of megger is to measure insulation resistance and machine windings.

How megger produce high voltage?

In hand operated megger electromagnetic induction effect is used to produce the test voltage i.e. armature arranges to move in permanent magnetic field or vice versa. Where as in electronic type megger battery are used to produce the testing voltage.

What is the unit of insulation resistance?

Insulation resistance is very high resistance. Hence it is expressed in Mega Ohm.

What causes low megger readings?

Longer runs will result in lower insulation resistance values. Two conductors have consistently lower values: Because the conductors adjacent to the ground conductor only have one layer of insulation, those conductors will have lower insulation resistance and the Megger values will be lower.

How do you measure insulators?

Insulation resistance measurement is done using an IR tester. This is a portable tool that is more or less an ohmmeter with a built in generator that's used to produce a high DC voltage. The voltage usually measures at least 500V, and causes a current to flow around the surface of the insulation.

What is the difference between Megger and multimeter?

Megger is used to test the insulation resistance of a conductor while multimeters are used to measure the voltage,current and resistance of a circuit.

What is the difference between Megger and ohmmeter?

The chief advantage of the megger over an ohmmeter is its capacity to measure resistance with a high potential or breakdown voltage. Impedence of insulation is very high. A megger is specifically designed to accurately measure high impedences. An ordinary multimeter is designed to measure lower, more finite impedences.

How do you Megger a motor?

How to Test a Motor using Megger?

Place one megger lead on the ground terminal or wire and place the other lead on one of the phase wires or terminals.
Press test on the megger.
A very high resistance reading (greater than 10 megohms) will indicate the motor insulation is good.

What is a good megger test result?

For a successful test, the insulation resistance measurement must be equal to or greater than 1 Gigaohm (1 Gigaohm = 1 G ohms = 1000 Mega ohms = 1000 M ohms). We recommend that you always check the megohmmeter instruction manual as each manufacturer can use different symbols or values for their testers.

Why IR test is required?

Insulation resistance (IR) is a measurement of how good or bad your insulation is, which can help give you an overall assessment of your electrical equipment's health. By the way, no insulation is perfect—with infinite resistance—but good insulation has a relatively high resistance to current.

How do you calculate IR value?

IR Value at HV Side= (1.5 x 20000) / √ 1600 =16000 / 40 = 750 MΩ at 20⁰C.
IR Value at LV Side = (1.5 x 400 ) / √ 1600= 320 / 40 = 15 MΩ at 20⁰C.
IR Value at 30⁰C =15X1.98= 29.7 MΩ

How do you test a wire with a megger?

Clamp the alligator clip on one of the megger probes to the wire or cable, touch the other probe to the exposed conductor and press the test button. The megger will generate a current between the probes, and the meter will record the resistance of the jacket to the flow of the current.