×
Follow Us
Page 2 of 2 FirstFirst 12
Results 11 to 12 of 12

Megger testing technique questions

 Jump to latest post
Page 2 of 2 FirstFirst 12
    #11
  1. michaellabeit is offline Junior Member Pro Subscriber
    Join Date
    Apr 2020
    Posts
    5
    Reputation
    I listened in on a Megger webinar on insulation resistance testing by Jo Jewett, one of Megger's senior engineers. He said that the polarity doesn't matter for IR tests. Moreover, Megger's A Guide To Diagnostic Insulation Testing Above 1 kV states the following on page 6:


    "With modern insulating materials there is little, if any, difference in the reading obtained, regardless of which way the terminals are connected. However, on older insulation, a little known phenomenon called electroendosmosis causes the lower reading to be obtained with the positive terminal connected to the grounded side of the insulation being tested."

  2. #12
  3. Join Date
    Apr 2021
    Posts
    25
    Reputation
    Quote Originally Posted by Urangtt View Post
    When performing insulation resistance on equipment, does it matter which lead on a megger goes where? If Im testing insulation resistance from A to B, does it matter if the Red lead goes on A or B?
    I have personally used a Megger in both polarities just to test that, and from my experience I have found that there is no difference in reading. The way a resistance meter works(at least on something like a Fluke)is that it applies a small known voltage across the load, and then measures the current. Voltage times current gives you your resistance. A Megger is doing the same thing, only using a much larger known voltage.

    Now, if you test in one direction, then try to test again in the other, it will take some time for you to get the correct reading, since it will now be magnetized in the original direction, and need to be overcome to magnetize in the new direction. I have also seen some insulation testers that have separate voltage and current leads, and on those, I am not sure what reading you would get if the voltage and current polarities were opposite.

Page 2 of 2 FirstFirst 12
Subscribe

Login or register to leave a reply!


Share this thread

Related Topics

  1. Replies: 7
    Last Post: August 3, 2017, 03:38 PM
  2. Help me understand how a megger works
    By Sanjayo in forum Electrical Testing Talk
    Replies: 1
    Last Post: April 23, 2016, 11:35 AM
  3. Megger Offers Free Testing Tactics Webinar Series
    By testguy in forum News and Announcements
    Replies: 0
    Last Post: November 1, 2014, 06:00 AM

Tags for this Thread



Related Content


Follow us


Explore TestGuy


NETA Certification Training


NICET Electrical Power Testing


Help and Support