| Title |
Study on the 2nd Harmonic Blocking Scheme and Setting Value of a Current Differential Relay for 154 kV Transformers to Prevent Maloperation |
| Authors |
손용범(Yong-Beom Son) ; 강상희(Sang-Hee Kang) |
| DOI |
http://doi.org/10.5370/KIEE.2018.67.1.29 |
| Keywords |
Current differential relay ; Inrush current ; 2nd harmonic ratio ; 2nd harmonic restraint/block |
| 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. |