Closed-Form Determination of the Impedance Locus Plot of Fault Current Limiters: Asymmetrical Faults

Shayan Behzadirafi, Francisco De Leon

Research output: Contribution to journalArticlepeer-review


Closed-form determination of fault current limiter (FCL) impedance for symmetrical faults was reported previously using a mathematically rigorous method. In this paper, extensions of the method to asymmetrical faults are presented. Single line-to-ground faults and line-to-line faults are studied. As shown in this paper, although the material corresponding to asymmetric faults use the same basic concepts described before, the different nature of asymmetrical faults and application of symmetrical components theory lead to a different formulation. Also, the graphical representation of asymmetrical faults is as contour plots instead of the circle diagrams for three-phase faults. A three-bus and the IEEE 39-bus systems are used to illustrate the virtues of the method for the proper selection of FCLs impedance. Results demonstrate that the FCL designed, as shown in this paper, works properly for asymmetrical faults. The new formulation and graphical representation for asymmetrical faults are compatible with traditional power system short-circuit analysis software. An example with both symmetrical and asymmetrical faults is presented to illustrate how a full FCL impedance design can be achieved with the method.

Original languageEnglish (US)
Article number8747430
Pages (from-to)754-762
Number of pages9
JournalIEEE Transactions on Power Delivery
Issue number2
StatePublished - Apr 1 2020


  • Asymmetrical faults
  • contour plots
  • fault current limiters (FCLs)
  • impedance plot
  • power systems
  • short circuit calculation

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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