Economic Fault Current Limiter System Interaction

Along with the scale of electric power net expanding continually, the electric power system which runs safely and stably has been badly threatened by the nowaday level of short circuit current, so it is imperative under the situation to take a proper measure to limit the short circuit current. Fault Current Limiter (FCL) with a wide application foreground and a better comprehensive capability has become a popular researching focus in these years.This article gives emphasis in researching the mutual influence between ZnO-based FCL and electric power system.Firstly, the developing status in quo of FCL is introduced in this article. Result from comparing and analysing the capability of various of FCL indicates that ZnO-based FCL not only has a better capability in technology and economy but also a larger value in application. Then a overall design of ZnO-based FCL is given, whose function principle is presented.Two methods using basic frequency equivalent impedance and dynamic impedance are presented to analyse the influence of ZnO-based FCL on distance protection. The conception of dynamic impedance is presented, and its definition and strict mathematic expression is given. Regarding presence and absence of the gap in ZnO-based FCL, simulation models are constructed by PSCAD/EMTDC, and the influence of FCL on distance protection is researched carefully with new setting formulas gained. The results of simulation indicate that distance relay can act reliably by using the new setting formulas without shorten the protection length. In addition, two methods to confirm dynamic resistance of ZnO-based FCL are presented and the advantages and disadvantages are analysed.This article also research the influence of ZnO-based FCL on transient stability in electric power system. With respect to a typical one-machine infinite-bus installed with FCL, the power-angle characteristics of generators are studied in various cases, and the transient physical process is analyzed in detail using Equal Area Criterion. A series of parameters which can quantificationally describe transient stability aredefined based on the foregoing theoretical analysis. Regarding presence and absence of the ZnO-based FCL in power systems, simulation models are constructed with MATLAB for both one-machine and multiple-machine systems, based on which the transient stability characteristics of power systems are studied under different current-limiting factors, fault types and fault clearance time.