Distance relay - impedance characteristic question

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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]

Thanks,
Pauls
 
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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.
 
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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]
 
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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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