| A multiprocessor-based intelligent distance relay with the capabilities of underground cable or overhead transmission line protection was successfully designed, developed and tested. The Kalman filtering techniques were implemented to extract the fundamental frequency components from the collapsed signals following the fault, two state for voltages and three state for currents. The distance protection of the pipe type underground cable, which is characterized by nonlinear impedance, has not been proven prior to this study. The error sources caused by load and arc resistance are taken into consideration and corrected by using software technique. Furthermore, the inherent flexibility of the user-defined convex window zone protection characteristics has been proposed to improve the operating performance of the power systems.; The advanced distributed processing proposed relay is based on an Intel-80196 microcontroller and a Texas Instrument TMS320C25 type digital signal processor. The complete Kalman filtering, fault type identification, fault location, etc. algorithms has been simulated using the C language to verify the feasibility of the software scheme and to study the performance of the proposed relay. The simulation results are found to have as high an accuracy as desired. The laboratory tests performed in the Energy Systems Research Center (ESRC) power system simulation laboratory have confirmed the software simulation results. |
