A modeling method of a high impedance fault in a distribution system using two series time-varying resistances in EMTP

More reliable algorithms for detecting a high impedance fault (HIF) require the voltage and current data at a relaying point instead of a faulted branch when HIF occurs. Thus, an accurate modeling method of HIF is essential for the development of a reliable detecting algorithm. The data should contain the complex characteristics of HIF such as buildup and shoulder as well as nonlinearity and asymmetry. This paper presents a modeling method of the above-mentioned HIF characteristics. Among the experiment data on a 22.9 (kV) distribution system conducted by Korea Electric Power Corporation (KEPCO), experiment data showing all the above characteristics is chosen in this paper. Two series time-varying resistances (TVRs) controlled by transient analysis of control systems (TACS) in EMTP are employed for modeling. One TVR is used for nonlinearity and asymmetry from the voltage-current characteristic for one cycle in the steady state after HIF, and then the other TVR for buildup and shoulder from the waveforms in the transient state after HIF. The comparison of the modeling results with the experiment data shows close correspondence. With the developed HIF model, the voltage and current at the relaying point are obtained with various load condition and fault condition such as fault distance and inception angle.