×
Follow Us
Results 1 to 2 of 2

Primary current injection 138kV breaker with bushing CT's

    #1
  1. Join Date
    Apr 2018
    Posts
    1
    Reputation

    Primary current injection 138kV breaker with bushing CT's

    I need to know how to conduct this type of test. I usually do secondary current injection, but I have the opportunity to do primary current injection using a CPC100. I will be testing CT's on a 138kV breaker with bushing CT's. I believe I need to connect the polarity side of the test lead to the bushing of the affected CT and the non-polarity lead to the other correlated bushing (i.e. if testing the ct for bushing one, polarity to it and non-polarity to bushing two), then short out the non-polarity ct's , ensure the breaker is closed, and push the current into the affected CT and verify correct magnitude and polarity at my relay. Don't mean to sound stupid, but I haven't done this test before. Thanks!

  2. #2
  3. ElectricalTestTech's Avatar
    ElectricalTestTech is offline NETA Level IV
    Affiliate Member
    Pro Subscriber
    Join Date
    Sep 2017
    Location
    Washington, DC
    Posts
    69
    Reputation
    Quote Originally Posted by david2458 View Post
    I need to know how to conduct this type of test. I usually do secondary current injection, but I have the opportunity to do primary current injection using a CPC100. I will be testing CT's on a 138kV breaker with bushing CT's. I believe I need to connect the polarity side of the test lead to the bushing of the affected CT and the non-polarity lead to the other correlated bushing (i.e. if testing the ct for bushing one, polarity to it and non-polarity to bushing two), then short out the non-polarity ct's , ensure the breaker is closed, and push the current into the affected CT and verify correct magnitude and polarity at my relay. Don't mean to sound stupid, but I haven't done this test before. Thanks!
    The way I would approach it is by breaking it down to individual devices. I would Test the CT’s using whichever specs you’re required to follow (NETA or NERC or FERC). Test the breaker, test the associated relays. Then once every device has been tested and verified to be within tolerance, do a functional trip. Inject primary current through A-phase bushings and watch for a trip. If you already tested relays you should know what the secondary trio amperage will be; just convert it to primary and your trip should occur somewhere close to it. Repeat the steps with B and C phases.

    This was a very dumbed down response. There are a lot of variables that were not explained. There are many ways to perform the testing. But my advice will always be, break down the system to individual components and test. Then follow through with a functional verification to ensure all wiring between devices are correct

    I hope this helps

Subscribe

Share this thread

Related Topics

  1. How to Test Breaker through Current Injection Tester ?
    By mask1290 in forum Electrical Testing Talk
    Replies: 8
    Last Post: September 19, 2017, 06:57 PM
  2. High Current Injection LTD Test Value
    By alexlounsbury in forum NETA Level 3 Exam
    Replies: 5
    Last Post: July 10, 2017, 11:38 AM
  3. Continuous current rating of a circuit breaker
    By mainmanmerc in forum NETA Level 2 Exam
    Replies: 4
    Last Post: October 22, 2016, 07:32 PM

Tags for this Thread

Follow us


Explore TestGuy


NETA Certification Training


NICET Electrical Power Testing


Help and Support




You are viewing the archives. Enjoy new features and join the conversation at wiki.testguy.net