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Grounding Riddle No.33 – Two source with their own NGR

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  • #865
    Roxy

      When two source have their own NGR ( Wye ground)- Zero sequence can not be detected correctly. …
      When two source have their own NGR ( Wye ground)- Zero sequence can not be detected correctly.
      What would be the CT arrangement on both neturals ( one is on gen step up transformer and other on Grid step down transformer) with communication to trip the right source. relay such as T60 ( MULTILIN) are used.

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    • #2813
      Hamid

        It seems your problem is discriminative earth fault detection in a multi grounded system in source and load side grounding. The selective and ideal earth fault protection in multi grounding systems is difficult. One recommended solution for discrimination of earth fault protection is polarized or directional earth fault current protection. As you see in following figure, suitable directional earth fault relay can be the best solution. Please correct me if I didn’t underestand your question.

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