MegOhm testing question....

[cptviggi]

Normally when Megging a piece of electrical apparatus we just hook up our leads and go.... but there is an industry standard out there that tells us to hook up our Black lead to the insulated piece in question (wire/windings/ buss, etc) and our Red lead to ground( forget the guard for the question), counter intuitive as that may be.....

I thought the reason why was electrokinesis, but cannot remember, nor can I remember the industry standard.

Does anybody here have the industry standard reference and supporting information? Ty

 

[mbednarik]

it doesn't matter how you connect the leads. The meter is simply applying voltage and measuring the current, doing the math and giving you the resistance value at the voltage tested.

 

[garbo]

Normally when Megging a piece of electrical apparatus we just hook up our leads and go.... but there is an industry standard out there that tells us to hook up our Black lead to the insulated piece in question (wire/windings/ buss, etc) and our Red lead to ground( forget the guard for the question), counter intuitive as that may be.....

I thought the reason why was electrokinesis, but cannot remember, nor can I remember the industry standard.

Does anybody here have the industry standard reference and supporting information? Ty

 

[garbo]

All of the meggers that I have used from several hand crank versions to the battery operated meggers all put out a DC voltage and does not matter what lead goes where. Saw a Greenlee Megger that might have a note by test lead port saying to attach certain lead to ground. 2 Megger tips: for meggering motors you should double the voltage so a 480 volt motor should use a Megger that puts out 1,000 volts. It is critical when meggering motors that shaft us not rotating. Had a coworker condemn a ceiling mounted 75 HP return fan because of erratic Megger readings. I had to place both 150 HP supply fans on drives to Manuel and turn speed down to 20% to finally have return fan to come to an absolute stop. I have a Megger that puts out up to 5,000 volts DC that I have used to check insult in 4,160 volt motors.