When are megger testers used?

Answer 1

On the whole megger testing is a non destructive test. What happens is a DC voltage is applied to the device or winding under test. It is an insulation test to see is the insulation has been injured in any way to cause a short circuit when normal power is applied to it. On my megger there are 3 ranges 300V, 750V, and 1000 volts. Applying the proper voltage is essential to not damaging the device you are testing. Working voltages up to 240 volts should use the 300 range. Working voltages up to 600 volts use the 750 volt range and working voltages above 600 use the 1000 volt range. As you can see if you used the 1000 volt range on a device that had a working voltage of say 24 volts you could damage the insulation just by testing it. So meggering a device is non destructive if you use the tester as its instructions tell you to.

Answer 2

A megger test is used to check the insulation factor of wires or devices. This is to make sure that when the working voltage is applied, a short circuit to ground will not occur due to a problem with the insulation of the device or wire.

On the whole megger testing is non destructive. What happens is a DC voltage is applied to the device or winding under test. It is an insulation test to see is the insulation has been injured in any way to cause a short circuit when normal power is applied to it. On my megger there are 3 ranges 300V, 750V, and 1000 volts. Applying the proper voltage is essential to not damaging the device you are testing. Working voltages up to 240 volts should use the 300 range. Working voltages up to 600 volts use the 750 volt range and working voltages above 600 use the 1000 volt range. As you can see if you used the 1000 volt range on a device that had a working voltage of say 24 volts you could damage the insulation just by testing it. So meggering a device is non destructive if you use the tester as its instructions tell you to.

Answer 3

Megger is a brand of tester that measures the resistance to ground"earth" through a conductor that you can not visually check. The tester normally can put 500v-5000v on the conductor to check the ground resistance by measuring the induced current. R=I/V

Answer 4

Megger testers are used to test the resistance of wire, primarily in motor windings. A very high voltage is applied to the coils and a resistance is shown. If the resistance drops, that means there is a possible short to ground. Although the Megger is a "resistance tester", it is actually not used the measure the specific resistance, but to check for shorts.

Answer 5

Megger is an abbreviation of Megohmmeter, or an electric meter which measures high levels of electrical resistance in Ohms. One Megohm is one million Ohms, so a megger or Megohm-meter is intended to be used on electrical insulation e.g. the electrical resistance between a high voltage conductor and ground. Ensuring a high level of resistance in the millions of Ohms will protect the circuit from shorting to ground causing damage to equipment or people known as a ground fault. One additional application is to measure the resistance between phases of a poly-phase electrical device or circuit such as a 3-phase circuit breaker to ensure there are no line-to-line shorts which would also cause a dangerous short circuit condition. Low levels of resistance indicate that the electrical insulation is faulty, has failed, or otherwise needs correction by either debriding the insulation of dirt or other debris or dehydrating through the application of heaters. It is common in electrical switchgear to install heaters, especially in humid climates to keep condensation from moisture to a minimum which can cause low megger readings.

Typical field meggers produce up to 5 kV DC at low current and require proper training and safety considerations to operate ensuring that all electrical paths are isolated from personnel while in use.

To note, high voltage electrical cables are subjected to many times rated voltage during testing and if a failure occurs, the insulation is permanently damaged and the cable must be completely replaced or, if practicable, spliced, however, this is not often possible due to the inability to locate the damaged section of cable which could have just a tiny pinhole between conductor and ground shield inside of a durable outer coating.

The companion tool to the megger as used in the electrical industry is a ductor which measures very low levels of resistance to ensure good electrical conductivity between conductors such as two sections of bolted electrical bus bar or the stabs on a circuit breaker.

Answer 6

A megger test is an insulation test. It is used to find out if the insulation has been degraded and what the insulation resistance is in megohms. Low insulation factors can cause short circuits between conductors or between conductors and the metallic conduits the wires have been pulled into. This low insulation factor can be caused by poor workmanship when the conductors were pulled into conduits. On major construction projects the electrical engineers request a signed document stating that the conductors have been megged and are at a specific megohm value before any conduits runs can be energized.