Journal of Electrical Engineering and Technology

The Korean Institute of Electrical Engineers (대한전기학회)
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A Modified Selective Ground Relay for Ungrounded Distribution Systems

  • Nam Soon-Ryul (Next-Generation Power Technology Center(NPTC) and the Department of Electrical Engineering, Myongji University) ;
  • Kang Sang-Hee (Next-Generation Power Technology Center(NPTC) and the Department of Electrical Engineering, Myongji University) ;
  • Park Jong-Keun (School of Electrical Engineering, Seoul National University)
  • Published : 2006.03.01
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Abstract

Selective ground relays (SGRs) are useful fur distinguishing a faulted feeder from the sound feeders in ungrounded systems. However, they sometimes mis-operate due to human or device errors. Particularly, the reversed polarity of zero-sequence current transducers (ZCTs) is the most frequent cause of mis-operation. This paper presents a modified SGR for reducing the probability of mis-operations caused by the reversed polarity of ZCTs. The modification is achieved by introducing an adaptive time delay, which depends on the magnitude of the zero-sequence current and the phase angle deviation from the reference. The modified SGR was successfully demonstrated on a sample ungrounded system without mis-operation.

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References

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