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Distance relay - impedance characteristic question

  1. Dec 24, 2014 #1
    Dear all!

    I have a question about the impedance characteristics in the distance relay used for transmission line protection. I understand that in the first quadrant we have a inductive load and in the fourth quadrant we have a capacitive load. I, however, do not understand what we measure in the second quadrant that I marked red. We would have a negative resistance. Can someone please help me with that?

    https://dl.dropboxusercontent.com/u/3809800/impedance_characteristics.jpg [Broken]

    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Dec 24, 2014 #2

    jim hardy

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  4. Dec 26, 2014 #3
    Thanks for your answer.

    That's what I thought and I also saw the paper. That means, however, that the relay is bi-directional. For me that's contradicting since the diagonal shown in my picture marks the operating direction of the relay. So when you want to detect both directions you would need 2 relays anyways. That means the -R and +X area would be redundant.
  5. Dec 26, 2014 #4

    jim hardy

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    i think they're saying the math works out to a function that'd be bidirectional

    there's discussion later on about adding restraint coils

    i'm not a relay guy, just have watched over the shoulders of some genuine ones.

    i'd resort to a genuine industrial training manual for in-depth discussions of how it's done in the real world..
    http://www.pdfslibfree.com/applied-protective-relaying-westinghouse.pdf [Broken]
    http://www.osinerg.gob.pe/newweb/uploads/GFE/eventos/EVENTO%207/TEXTO%207A.pdf [Broken]
    Last edited by a moderator: May 7, 2017
  6. Dec 26, 2014 #5
    This should help you.
    It gets right at the heart of your question in a relay technician/relay engineer sort of way.


    I would download the entire book, but in particular you will want chapters 3 & 4.
    Post again if you need further help.
  7. Dec 27, 2014 #6

    jim hardy

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    Since the torques are in proportion to RMS currents squared, it looks to me like the basic device would be bidirectional...
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