The typical test equipment for this is a megger. The megger is connected to two conductors at a time to test the insulation between the two.
A good number on a megger test should be around 2 megohms.
The value of insulation resistance varies according to the type of CT and manufacturer. It is best to check with the manufacturer for acceptable values. The word 'Megger' is a registered trademark of Megger Limited. Megger Limited's product range includes insulation testers, relay testers, battery testers and many other electrical test and measurement products. Tony Wills, Applications Engineer, Megger Ltd.
Megger tests are important because the test makes sure that your electrical insulation is safe and operating as intended. Megger tests are performed using a Meg-ohmmeter.
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It is the terminal on the megger that the ground cable connect to when testing a device to ground.
On a hand crank megger which is used to test insulation breakdown, use the 300V setting. If the megger does not have that setting use 500V as opposed to 1000V for the test. The output of the megger is a DC voltage.
The megger is used to find insulation resistance in any equipement. It will generate around 10kVA power to test.
While using megger we only have to see whether resistance breaksdown at the upper value mentioned. Since megger generates high voltage we can check whether breakdown takes place or not.Megger has a range from o to infinity.So it is not possible to find accurate resistance,hence it is used as an insulation tester
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The time duration for a megger test is as long as it takes to turn the handle of the megger about five times. Voltage is generated on the first turn and if there is an insulation breakdown on the device being tested it will show instantaneously. If the megger is an electronic megger hold the generate button down for about three seconds.