A Study on the Over Current Relay Misoperation in Power System with Distributed Generations

분산전원 연계 계통에서의 과전류계전기 오동작에 관한 연구

  • Park, Jong-Il ;
  • Lee, Kyebyung ;
  • Park, Chang-Hyun
  • 박종일 ;
  • 이계병 ;
  • 박창현
  • Received : 2018.10.26
  • Accepted : 2018.11.23
  • Published : 2018.12.01


This paper deals with an analysis of the causes of over current relay(OCR) misoperation in power system with distributed generations(DG). In general, Y-D and Y-Y-D transformer connections are used for grid interconnection of DG. According to the interconnection guideline, the neutral point on Y side should be grounded. However, these transformer connections can lead to OCR misoperation as well as over current ground relay(OCGR) misoperation. Several researches have addressed the OCGR misoperation due to the interaction between transformer connections and zero-sequence voltage of distribution system. Recently, a misoperation of OCR at the point of DG interconnection to the utility system has been also reported. With increasing the interconnections of DG, such OCR as well as OCGR misoperations are expected to increase. In this paper, PSCAD/EMTDC modeling including DG interconnection transformer was performed and various case studies was carried out for identifying the cause of OCR misoperation.


Over current ground relay(OCGR);Over current relay(OCR);Voltage unbalance;Yg-Yg-D transformer;Zero-sequence harmonic


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Supported by : 한국전력공사