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Thread: CT Connection

  1. #11
    Join Date
    Apr 2004
    Location
    Mission Viejo, CA
    Posts
    5,191
    Quote Originally Posted by FaradayFF View Post
    The CT is part of a differential scheme protection delta(L)-Y grounded(H) Transformer. The relays are Schweitzer relays. I'm thinking that unless the relay is programmed to account for the reverse polarity connection of the load site CT, it may mis operate.
    A delta-wye transformer will have a phase displacement. You will need to tell the relay about it and the CT configuration. Several Schweitzer models will have no problem.
    "Bob"
    Robert B. Alexander, P.E.
    Answers based on 2014 NEC unless otherwise noted.

  2. #12
    Join Date
    Jul 2009
    Location
    Ware Shoals, South Carolina
    Posts
    1,201
    Quote Originally Posted by FaradayFF View Post
    The CT is part of a differential scheme protection delta(L)-Y grounded(H) Transformer. The relays are Schweitzer relays. I'm thinking that unless the relay is programmed to account for the reverse polarity connection of the load site CT, it may mis operate.
    Here is a typical connection for an SEL 787. Looks very much like the scheme you posted.
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    Advise is a dangerous gift, even from the wise to the wise.

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