Development of a fault current limiter for 22.9 kV distribution power line

A 25.8 kV/600 A/12.5 kA fault current limiter (FCL) for 22.9 kV distribution power line has successfully designed, manufactured, and field tested at KEPCO Power Testing Center for the protection coordination. FCL is composed of fast fault detector (FFD) developed as a key component, mechanical fast switch (FS), and current limiting resistor (CLR). The FFD plays a role in sensing a fault current, which is recognized when it passes over the certain fault current level. The FFD has 5 fault current levels between 0.9 kA and 3 kA, and the fault current levels can be selected according to the electrical power systems. This function makes FCL more simple, economical, manageable and useful in various electrical power systems in comparison with a superconductor of a superconducting FCL. The FS has a function of a current commutation from main circuit to the CLR when fault occurs by using of a vacuum interrupter (VI). The CLR's role is to reduce the fault current by its impedance, which is decided based on the power system analysis of an application site. The whole process is perfectly completed within 1 cycle after the fault occurs. Recently, short circuit test, impedance test, and the electrical insulation test are passed. And also the field test is performed on the 1.5 kA and 5.0 kA faults, which are made by connecting the Artificial Fault Generator (AFG) to the distribution line in test grid at KEPCO Power Testing Center. Various demonstration tests of the FCL have proved that the current limiting performance is satisfactory and the protection coordination with conventional relays is realized.