What do Megger readings mean?

What do Megger readings mean?

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 Megger range?

For this purpose, megohmmeters, which can provide high DC voltages (typically in ranges from 500 V to 5 kV, some are up to 15 kV) at specified current capacity, are used. Acceptable insulator resistance values are typically 1 to 10 megohms, depending on the standards referenced.

What are different ranges of resistance in Megger?

The new range of Megger insulation resistance testers consists of three models: two 5 kV units (MIT515 and MIT525) and a 10 kV unit (MIT1025). Resistance measurement is available up to 10 TΩ for the 5 kV models and 20 TΩ for the 10 kV model.

How is Megger measured?


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

What is a good insulation test reading?

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. In practice, megohm readings normally are considerably above this minimum value in new equipment or when insulation is in good condition.

What should be Megger value?

A general rule-of-thumb is 10 Megohm or more.

Insulation resistance value Insulation level
5-10 Megohm Abnormal
10-50 Megohm Good
50-100 Megohm Very good
100 Megohm or more Excellent

Is a Megger AC or DC?

Therefore, if we apply AC voltage during IR test then there will always be a flow of current through the capacitor and thus a leakage current to the ground. This is the reason, an Insulation Tester or Megger have DC voltage generator.

What is the normal speed of Megger?

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How do you megger a 3 phase motor?

  1. Turn off the power supply to the motor, usually accomplished by switching the circuit breaker.
  2. Place one megger probe to the any mounting bolt on the breaker box to test for grounding continuity, then touch the other probe to a motor terminal.
  3. Crank the handle for about a minute, and notice the resistance reading.

What is earth megger?

The earth megger is essentially a direct reading ohmmeter and it has a hand driven generator which supplies the testing current. The ohmmeter essentially consists of two coils (current coil and pressure coil) mounted at a fixed angle to each other on a common axis.