The Transactions of The Korean Institute of Electrical Engineers (전기학회논문지)

The Korean Institute of Electrical Engineers (대한전기학회)
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A Study on the 2nd Harmonic Blocking Scheme and Setting Value of a Current Differential Relay for 154 kV Transformers to Prevent Maloperation

154 kV 변압기 보호용 비율차동계전기 오동작 방지를 위한 2고조파 억제 방식의 적용방법 및 정정값에 관한 연구

  • Son, Yong-Beom (Dept. of Electrical Engineering, Myongji Univ, Korea Electric Power Corporation) ;
  • Kang, Sang-Hee (Dept. of Electrical Engineering, Myongji Univ.)
  • Received : 2017.10.25
  • Accepted : 2017.12.11
  • Published : 2018.01.01
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Abstract

Inrush current and fault current in a transformer need to be distinguished from one another. In order to do this, KEPCO uses a 2nd harmonic restraint/block method. We use two setting values for 2nd harmonic restraint; 15% and 10%. We also apply per-phase blocking method among various harmonic restraint methods. If the transformer is located at the radial system, we adjust 10% in the 2nd harmonic restraint, but this method is not enough to prevent mal-operations of the current differential relay and let us spend more time to change setting value again as the power system changes. In this paper, a more reasonable setting value for a 2nd harmonic blocking scheme in KEPCO is proposed. To present a proposed method, the fault data of the current differential relays which have occurred since 2009 are analyzed. To evaluate the performance of the proposed method, the results of the RTDS test for the current differential relay of the transformer by KEPCO are analyzed.

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References

  1. S. P. Patel, "Fundamentals of transformer inrush," in 2011 64th Annual Conference for Protective Relay Engineers, pp. 290-300, 2011.
  2. Power System Protection Department, KEPCO, "Setting Guide of the Relay to Protect the Power System", pp. 1, 2016.
  3. R. Hamilton, "Analysis of Transformer Inrush Current and Comparison of Harmonic Restraint Methods in Transformer Protection," IEEE Transactions on Industry Applications, vol. 49, pp. 1890-1899, 2013. https://doi.org/10.1109/TIA.2013.2257155
  4. Yong-Beom Son, "Practical Use of the Fault Record Analysis Software, SIGRA by Editing the Data of a Comtrade File", Korean Institute of Electrical Engineers Summer Conference journal, pp. 555-557, 2017. 7.