A Design Method of Iron-cored CTs To Prevent Satruation

포화를 방지하기 위한 보호용 철심 변류기 설계 방법

  • Published : 1999.02.01

Abstract

Current transformer (CT) saturation may cause a variety of protective relays to malfunction. The conventional CT is designed that it can carry up to 20 times the rated current without exceeding 10% ratio error. However, the possibility of CT saturation still remains if the fault current contains substantial amounts of ac and/or dc components. This paper presents a design method of iron-cored CTs for use with protective relays to prevent CT saturation. The proposed design method determines the core cross section of the CT; it employs the transient dimensioning factor to consider relay's operating time (duty cycle) and dc component as well as ac components contained in the fault current, and symmetrical short-circuit current factor to consider as well as ac components contained in the fault current, and symmetrical short-circuit current factor to consider the biggest fault current. The method designs the cross section of CTs in cases of reclosure and no reclosure.

References

  1. Power System Relaying Stanley H. Horowitz;A. G. Phadke
  2. International Electrotechnical Commission Standard 44-6 International Electrotechnical Commission
  3. IEEE Trans. on PWRD v.9 no.1 Experimental Evaluation of EMTP -Based Current Transformer Models for Protective Relay Transient Study M. Kezunovic;Lj. Kojovic;A. Abur;C. W. Fromen;F. Phillips
  4. The Institute of Electrical and Electronics Engineers. C57.13 American National Standard Institute