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Rating plug removal prior to dielectric testing

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  1. SecondGen's Avatar
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    Rating plug removal prior to dielectric testing

    When dielectric testing power circuit breakers, specifically Square D w/ Micrologic, we sometimes may need to pull the rating plug to avoid damaging the trip unit.

    My question to the community is this: do you pull the plug before or after your trip test? I've been doing megger first and then trip testing because my concern is that after pulling the plug how do I know the trip unit will function?

    Sure, i could run another quick trip test but I want to avoid extra steps. The probability of something going wrong is low I'm sure but I was mainly looking to get some opinions from others on how they test.

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    Quote Originally Posted by SecondGen View Post
    When dielectric testing power circuit breakers, specifically Square D w/ Micrologic, we sometimes may need to pull the rating plug to avoid damaging the trip unit.

    My question to the community is this: do you pull the plug before or after your trip test? I've been doing megger first and then trip testing because my concern is that after pulling the plug how do I know the trip unit will function?

    Sure, i could run another quick trip test but I want to avoid extra steps. The probability of something going wrong is low I'm sure but I was mainly looking to get some opinions from others on how they test.

    Click image for larger version. 

Name:	rating-plug-warning.jpg 
Views:	82 
Size:	44.5 KB 
ID:	260
    I operate the same as you. The last thing I want to be certain of is that the trip unit works.

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    Quote Originally Posted by SecondGen View Post
    When dielectric testing power circuit breakers, specifically Square D w/ Micrologic, we sometimes may need to pull the rating plug to avoid damaging the trip unit.

    My question to the community is this: do you pull the plug before or after your trip test? I've been doing megger first and then trip testing because my concern is that after pulling the plug how do I know the trip unit will function?

    Sure, i could run another quick trip test but I want to avoid extra steps. The probability of something going wrong is low I'm sure but I was mainly looking to get some opinions from others on how they test.

    Click image for larger version. 

Name:	rating-plug-warning.jpg 
Views:	82 
Size:	44.5 KB 
ID:	260
    I worked with an individual years ago that refused to test a breaker until he performed insulation resistance test first. We tested a breaker and found out it failed on insulation resistance after some difficult set up to perform the trip tests. So, it rubbed off on me and I've adopted it as a norm. It makes sense because if the breaker fails resistance testing, then it spares me having to set up to perform trip test on a failed breaker. It never occurred to me to worry about the rating plug since we test in that order.
    That being said, I have seen numerous people bend the pins on the Micrologic rating plugs when performing this test also. This helps to identify when this happens.

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    Quote Originally Posted by Kalbi_Rob View Post
    I worked with an individual years ago that refused to test a breaker until he performed insulation resistance test first. We tested a breaker and found out it failed on insulation resistance after some difficult set up to perform the trip tests. So, it rubbed off on me and I've adopted it as a norm. It makes sense because if the breaker fails resistance testing, then it spares me having to set up to perform trip test on a failed breaker. It never occurred to me to worry about the rating plug since we test in that order.
    That being said, I have seen numerous people bend the pins on the Micrologic rating plugs when performing this test also. This helps to identify when this happens.

    The theory makes sense. We usually megger last to be sure the breaker is clear before putting it in the cell, this also allows the insulation and contacts to heat up during trip testing.

    I'd imagine a line to load megger test wouldn't affect anything in this case, only phase to phase? If so it would make sense to megger, trip test, ducter, and megger open again as a final safety check.

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