Reduction and modification of equivalent networks for transient fault simulation in power transmission systems

This paper is concentrated on the optimization of equivalent reduced networks for power system relaying purposes. For the parameter identification of reduced networks in time domain the EMTP program is applied. Moreover, the sensitiveness criterion has been used for the optimum choice of reduced network parameters. The accurate model is based on the precise representation of the transmission lines using distributed parameters. For such a model simple faults, i.e. single-phase, double-phase and threephase faults as well as simultaneous and nonsimultaneous faults have been simulated and reference current and voltage waveforms determined. Afterwards, various reduced models of subsystems connected to the investigated transmission line have been analysed and deviations from the reference quantities evaluated. In consequence an optimum reduced model has been selected for power sytem protection purposes, enabling for example the analysis of line protection performance during various faults.