Microcomputer Distance Protection In Dynamic Simulation System

When a fault occurs in power system, the relevant relay will operate and send out trip order to clear the faulted transmission line or other parts. The principles adapted in protection are quite a lot, of which the distance protection is one of the most widely applied principles. Generally, during the operation of a distance relay, its inner process and data conversions cannot be observed from outside. In order to analyze the detailed characteristics of distance protection in all operational conditions and observe its dynamic process, this thesis studies the digital dynamic simulation system for microcomputer based distance relay thoroughly.The studied project includes three main parts: the transient simulation calculations of faults using PSCAD/EMTDC, the format transition program for the data of the transient simulation result based on MATLAB and the dynamic simulation program of distance protection based on LabVIEW.The design of the dynamic simulation program of distance protection is accordance with the real components of computer distance relay. This program calculates and deals with data in form of data flow, almost the same to the real protection procedure. After a format transition, the transient simulation results serve as the input for the dynamic simulation program. In the process of simulation the dynamic simulation program calculates the input data point by point and displays the measured impedance and other relevant results synchronously.Some typical simulation cases, which focus on the main factors affecting distance relay's correct operation, have been conducted in the designed simulation system. There are: the influence of transient components, the calculation precision level caused by full-cycle DFT or half-cycle DFT algorithm, the influence of differentsampling frequencies, the influence of fault resistance, the fault resistance and the load current jointly resulted steady-state over-reach and the influence of the system oscillation.The simulation results showed that this dynamic simulation system is able to not only simulate the behavior of distance protection under different operational conditions, provide with necessary evidence for the analysis of distance protection, but also be a useful software tool for the development and teaching in protective relaying area.