During the last few years, the electric industry has witnessed a growing interest in the limitation of fault currents in power systems, as evidenced by recent publications [1, 2, 3]. This interest is due mainly to increased generating capacity and interconnection of electrical networks, which has led to systems approaching or even exceeding short circuit current withstand capability. There is also interest in limiting fault currents to enhance power quality [4], particularly in reducing voltage sags to protect sensitive loads, like adjustable speed drives, PLC's, computer systems, etc. According to experts in this field [5, 6], a fault current limiter (FCL) should fulfill the following requirements: (1) Almost instantaneous operation (2) No overvoltages as a result of its operation (3) Steady state current flow without significant voltage drop (4) Reliable operation (5) Economically acceptable Of course, these are ideal requirements, and in reality, some compromises have to be made for each particular case, type, and design. This paper presents relevant aspects of a project to design and install a FCL of the resonant link type [7]. This device consists of a series reactor and capacitor, tuned to 60 Hz. The series capacitor is shunted by a saturable reactor when a fault occurs. An analytical section includes a summary of its design characteristics. Field tests performed to a prototype installed on a 23 kV feeder are reported, as well as construction flaws encountered in the saturation curve of the reactor. Due to the above, alternatives for substituting the saturable reactor are being sought. One of these alternatives is to use metal oxide varistors (MOV). Results of laboratory tests on a scale model are described.
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