Computer Modelling of Numerical Distance Protection on High Voltage Transmission Lines

Transmission power lines are a very important part of a modern electric power system. Transmission lines can also be exposed to different types of failures caused by different weather conditions, wind, birds, surge lightning and personnel working on them. Transmission lines are protected by special devices called distance numerical protection relays. The paper presents modelling and simulation of numerical distance protection relays using DIgSILENT software. The software enables computer design and modelling of distance protection relays, their 2D, time and impedance diagrams. Sample case of a small power system with several HV transmission lines is presented. A three phase fault is simulated on the HV transmission line and a time response of polygonal characteristic of SIEMENS numerical distance relay is presented.