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http://dx.doi.org/10.5370/JEET.2006.1.1.016

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)
Publication Information
Journal of Electrical Engineering and Technology / v.1, no.1, 2006 , pp. 16-22 More about this Journal
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.
Keywords
Adaptive time delay; mis-operation; phase angle deviation; selective ground relay; ungrounded system; zero-sequence current transducer;
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