This research investigates the relationship between post fault transient overvoltages and the functionality of the digital distance protection. The study is conducted in a 66kV network with a neutral earth resistor as method to earth the power system. This paper begins by performing an extensive power system analysis on ground fault transient overvoltages. The study is conducted by using the PSCAD-EMTC software package. The results of this analysis are discussed to determine the impact of a disturbed voltage signal fed to the distance relay, with particular attention to the polarisation and CVT transient mitigation techniques as implemented by modern relays. This research analyses the characteristics of modern digital distance relays to determine if the transient overvoltages could affect the accuracy and operating time of the protection relay. In addition, this study aims to establish a method to predict the performance of the distance protection relay following a phase to ground fault. Finally, this thesis provides protection setting advices to support the implementation of modern digital distance protection relays on short lines, lines with ineffective grounding system and weak impedance source. The results of this study show that fault current limitation and consequent reduction of the thermal stress and aging of the equipment are successfully supported by modern distance relays.
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