We use a "megger" or "meg out" electrical wiring and equipment to see if it is shorted to ground in any way.
The megger uses much higher voltages to check resistance than a normal Volt-ohm meter.
Ideally, you want infinity resistance but I've installed 460 volt motors with 750 meg ohms resistance to ground and had no problem.
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.
As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
An insulation test is not performed on a megger, but using a megger.
A good number on a megger test should be around 2 megohms.
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.
It is the terminal on the megger that the ground cable connect to when testing a device to ground.
A Megger MFT1552 is used to test electrical installation. It is typically used by electricians. You can purchase a Megger MFT1552 online from websites such as eBay.
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.
Depending on your location, a megger tester should be easy to find. The website test equipment depot has a variety of megger tester and parts for sale and will ship them to your door.
The megger is used to find insulation resistance in any equipement. It will generate around 10kVA power to test.